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761 Cards in this Set
- Front
- Back
How many NEX are needed to maintain the SNR at 100% if the matrix is changed from 256 x 256 to 512 x 512?
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16
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On two dimensional acquisition the k-space is filled:
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All k-spaces are filled at the same time
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What would be the correct action to take if you realize that the patient inside the magnet has a ferromagnetic aneurism clip?
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Call the radiologist and emergency services and then slowly move the patient out of the magnet
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From the following parameters combination, which one will result in square pixels?
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256 x 512 matrix, 12 x 24 FOV
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Gradient recall echo is caracterized by:
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Using a gradient to rephase the protons
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In MRI, thin slices are achieved by applying a ______ gradient slope or a _____ bandwidth.
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Steep, Narrow
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Which of the following intrinsic contrast parameters is responsible for the contrast in a MR image?
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T1 relaxation
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Artifacts can cause:
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Unreadable images
Poor quality images Readable images, but mimicking or masking pathology |
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Isotopes are atoms that gain or loose:
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Neutrons
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Image data along both the phase and frequency axis with the lowest signal amplitude is stored in which area of the K space?
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Outer lines
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The process that uses mathematical conversions to calculate the amplitude of individual frequencies is known as ______
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Fast fourier transformation
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Which method is the most accurate when trying to rule out metal foreing bodies in the patient eyes?
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CT
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As the slice thickness increases the TOF phenomenon:
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Decreases
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Which gradients could be used for phase encoding in sagital image?
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Y or Z
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Gradient recall echo technique rephases the transverse magnetization ______ than the spin echo.
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faster
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What is the Farday's cage?
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used to prevent external RF to enter the MR suite
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Halving the receive bandwidth increases the SNR by:
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40%
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Which is the precessional frequency of hydrogen protons when are under a .2T magnet?
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8.6 MHz
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In a dual echo pulse sequence two different echoes are obtained. The early echo will produce an image with _______ contrast, and the late echo will produce an image with ______ contrast.
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PD, T2
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Cross talk and cross excitation can be reduce by:
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Using gaps between the slices
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FLAIR sequences are used to saturate:
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Free fluid
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What will be the effect of increasing the TR in the SNR?
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Increase
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Some of the advantages of the SE technique include:
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Good image quality
Very versatile True T2 weighting |
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RF shielding is achieved by:
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Lining the MR suite with cooper
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Gradient amplitude is:
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Strength of the gradient.
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What parameter combination will be the best to increase saturation effects (T1) in gradient echo pulse sequences?
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Decrease TR and increase flip angle
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acquires data from an entire volume of tissue, then uses a method called slice encoding to separate the images
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3D volumetric
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The frequency encoding gradient is also known as the ______ because it is turned on during the sampling of signal.
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Readout gradient
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pulse sequences will produce an image with higher SNR
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SE
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The main Source of magnetic field inhomogeneities are:
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Eddy currents
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In order to maximize T1 differences in GRE pulse sequences the best flip angle will be?
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90
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The gradient that is turned on just before the 180 degree rephasing pulse is known as the ______
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Phase encoding gradient
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The horizontal axis of K space represents which axis of the image?
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Frequency encoding
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Flow produced by a stenosis or stricture of the blood vessel is known as:
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Vortex flow
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The phase encoding gradient is turn on:
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Depending on the pulse sequence some time between the 90 RF and the collection of the echo
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How increasing the TE will affect the effects magnetic susceptibility on the image?
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Increase
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When the phase encoding gradient is activated, steep slopes produce what type of signal amplitude?
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Low
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What is the name of the equipment used to measure the strength of the magnetic field?
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Gauss meter
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STIR sequences are characterized by using:
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Short TI
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The gradient use for slice selection is the one that:
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Runs perpendicular to the slice
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In T2 weighted images free fluid appears _______ compared to fat tissues.
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Hiperintense
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The top portion of the k-space is a mirror of:
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Bottom
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Which of the following coil is used to improve the magnetic field homogeneity?
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Shim coil
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The process of filling only a percentage of K space with acquired data and filling the rest with zeros is known as _______
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Partial averaging
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In a 2DFT technique, the phase encoding gradient is used to change the phase along the:
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Short axis of the anatomy
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In what type of FOV and matrix combination is intravoxel dephasing is more prominent?
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Large FOV and low matrix
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During the acquisition of axial images of the body with the phase direction AP, frequency encoding is performed by which physical gradient?
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X gradient
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During half Fourier Technique:
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Only half of the k-space is fill
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Which is the carotid artery that arises straight from the aortic arch?
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LT common carotid artery
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The main source of degrading fat sat sequences is:
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Eddy currents
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EPI fills the k-space by rapidly switching the:
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Readout gradient from positive to negative
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Aliasing in the slice selection direction is seen in:
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3D acquisition
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GRE pulse sequences will allow to obtain bright signal from flowing protons. This is because:
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The rephasing gradient is not slice selected
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The time varying magnetic field is produce by:
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Gradients coils
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The magnitude of the phase shifts between two points within a patient is determined by which factor?
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Slope of the phase encoding gradient
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Compare to narrow transmitter bandwidth, a broader transmitter bandwidth will produce:
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Thicker slices
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Keeping all other parameters constant. Decreasing the slice thickness will ________ SNR.
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Decrease
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When the phase encoding gradient is activated, steep slopes produce data with what type of spatial resolution?
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High
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The degree of the net magnetization vector inversion is called:
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Flip angle
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Gradient slew rate is measured in:
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mT/m/s
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What will be the best choice in order to maximize T2 contrast on an image?
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Long TE
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The MR signal is recorded in:
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Transverse plane
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In MRS no images are obtained, the main reason for this is:
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Low number of hydrogens present on the aminoacids
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Possible conductors of Eddy currents include:
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Cryoshields
RF coils Shim coils Patient |
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To minimize differences in T2 relaxation the best parameter selection will be:
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Short TE
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Doubling the NEX will increase SNR by:
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1.41
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Ernst angle
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The flip angle which produces the best SNR, for a given TR and tissue type
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The type of Shielding that uses metal isolation is call:
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Passive
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When imaging the wrist, the optimal plane in which to visualize the carpal tunnel is the:
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Axial
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Intra-voxel dephasing decreases as the TE :
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Decreases
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The range of frequencies that is sampled during frequency encoding is known as the ______
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Receive bandwidth
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Some characteristics of superconductive magnets include:
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High field homogeneity
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B1 is another name for:
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Radio frequency field
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The FDA allows the manufacturer to either maintain the SAR level less than or equal to:
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4 W/Kg
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The main purpose of reducing the fringe field is:
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Ancillary electronic equipment, credit cards and computer disks can be brought closer to the magnet
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Tissues that return faster to the longitudinal plane are said to have:
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Short T1 relaxation time
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T1 relaxation is a process characterized by:
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Energy been released
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When evaluating the female pelvis, the plane that best demonstrates the uterine anatomy is the:
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Sagittal
|
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used to cool down the superconductive magnets
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Helium
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In order to produce a T2* weighted images. What parameters combination will you select?
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Long TR, long TE, and small flip angle
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There are two ways of achieving homogeneity of the main magnetic field. What is the name for the one that uses electricity?
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Active
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The theorem that states that a frequency must be sampled at least twice in order to reproduce it reliably is known as the _______
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Nyquist theorem
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Intrinsic contrast parameters are those:
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Can not be manipulated by the MR technologist
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Quadrature coil can provide a __ % improvement in signal to noise ratio (SNR) when used to receive the MR signal.
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40
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As the strength of the main magnetic field increases the T1 relaxation time of the tissues:
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Increases
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What is the best way of reducing chemical shift artifact?
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Increasing receiver band width
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What will be the sequence of choice to detect Multiple Sclerosis?
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FLAIR
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Flow that is faster in the center of the blood vessel is known as:
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Laminar flow
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increasing the sampling time will force to:
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Increase the minimum TE
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The sequence of choice in order to detect small hemorrhages will be:
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GRE (gradient echo sequence)
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The best option to increase SNR and not affect other factors that influence image quality will be:
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Use the smallest possible coil that covers the anatomy of interest.
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SNR
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(signal-to-noise ratio)
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In MR, small electrical potentials have been observed in:
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Large blood vessels that flow perpendicular to the static magnetic filed
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Compare to narrow transmitter bandwidth, a broader transmitter bandwidth will produce:
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Thicker slices
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Between T1 and T2 relaxation. Which one happens faster?
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T2
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During T1 relaxation:
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Protons return to longitudinal magnetization
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If the slice thickness is increase from 5 to 10 mm:
Signal will? |
increase
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The islets of Langerhans are found in:
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Pancreas
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Fast gradient echoes pulse sequence have the advantage of:
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Reduce motion on the image
Acquire images where temporal resolution is required Scan faster |
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Increasing the FOV from 10 to 20 will increase SNR by:
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4
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The coil selected for a procedure will have a direct impact in the SNR of the image. The coil that will provide better SNR is:
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- The one that have more channels
- The one with the smallest size that covers the area of interest - The one that is closer to the anatomy |
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The sampling rate can be calculated with:
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Nyquist theorem
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The optimal plane to use when evaluating patients for cruciate ligament tears of the knee is the:
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Sagittal
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In Gradient Echo Pulse sequence which parameter combination will produce a T2* weighted image?
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Long TR, Long TE, 10 Flip Angle
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Gradient slew rate is:
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Strength of the gradient over distance
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In SE pulse sequence which parameter combination will produce a PD weighted image?
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2500 TR, 20 TE, 90 Flip Angle
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Tissues with short T2 relaxation time will appear__________ on T2 weighted images.
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Dark
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Keeping all other parameters constant, decreasing the slice thickness will ________ SNR.
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Decrease
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The conus medularis and the cauda equina in adult patients are best demonstrated by a:
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Sagittal image of the lumbar spine
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In a T2* image of the abdomen the liver will show ________ compared to the spleen.
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Hipointense
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The strength of the signal depends on:
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The degree of magnetization in the transverse plane
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The FDA limits the acoustic noise to a maximum of:
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140dB/dt
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Some of the major concerns with EPI (Echo-planar Imaging) pulse sequences are:
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Increase acoustic noise
Increase peripheral nerve stimulation Increase image artifacts |
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The FDA limits the effect of RF absorption to an increase in core body temperature of:
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1°C
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Chemical saturation can be used to saturate signal from:
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Fat
Water Silicone |
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Chemical saturation technique is achieved by applying:
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A 90° RF pulse at the beginning of the sequence to the tissues being saturated.
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The line of the k-space to be filled with data in a given TR is determined by:
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The polarity and slope of the phase gradient
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Balance gradient echo are utilize to reduce
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Phase dephasing due to flow
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Another name for Torque force is:
|
Alignment force
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If the slice thickness is reduce by half, how many times do we need to increase the NEX to maintain the original SNR?
|
4
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The slice thickness can be determine by:
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Transmitter bandwidth and slope of slice select gradient
|
|
How many NEX are needed to maintain the SNR at 100% if the matrix is changed from 256 x 256 to 256 x 512?
|
4
|
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Which method of image acquisition fills one line of K space for each slice in the sequence before it moves to the second line of K space?
|
2D volumetric
|
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Which of the following pulse sequences will you select in order to reduce susceptibility artifact in patient that has a metallic implanted device in the area of interest?
|
FSE (Fast Spin Echo)
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The renal arteries drain to:
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IVC (Inferior vena cava)
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The term used to describe a picture element is known as a ____
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Pixel
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What tissue will transfer energy faster?
|
The one were molecules are closely pack
|
|
Halfling the receive bandwidth increases the SNR by:
|
40%
|
|
In a spin echo pulse sequence which parameter combination will produce a T1 weighted image?
|
500 TR, 10 TE, 90 Flip Angle
|
|
T2 relaxation time is defined as when:
|
63% of the transverse magnetization has decayed
|
|
The MR signal is recorded in:
|
Transverse plane
|
|
Possible conductors of Eddy currents include:
|
Patient
Shim coils RF coils Cryoshields |
|
the limit of the static magnetic field strength of clinical images
|
80 000 G for children and adults = 8 teslas
|
|
Proper patient screening should include which of the following?
|
- The elimination of any loose metal objects and personal items
- The identification of any possible contraindications - The identification of any biomedical implants |
|
For optimum operation of the MR system, the ambient temperature should be between:
|
65° to 75°F
|
|
The coil that will provide the best image quality is the one:
|
More number of receiver channels
Closer to the anatomy of interest |
|
Hydrogen protons in high energy state are oriented in:
|
Anti-parallel orientation
|
|
When protons recieve a 90 RF pulse they are located:
|
In the transverse plane in phase
|
|
High field magnets are consider to be in a range of:
|
1.5 to 3.0 T
|
|
will increase Chemical shift effects
|
Increasing the strength of the magnetic field
|
|
Array coils:
|
Use more than one coil to gather imaging data simultaneously
|
|
In a horizontal magnet the X axis is located:
|
Left to Right
|
|
The main Source of magnetic field inhomogeneities are:
|
Eddy currents
|
|
an induced spurious electrical current produced by time-varying magnetic fields. Eddy currents can cause artifacts in images and may seriously degrade overall magnet performance.
|
Eddy currents
|
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Which of the following coil is used to improve the magnetic field homogeneity?
|
Shim coil
|
|
B1 is another name for:
|
Radio frequency field
|
|
the ratio of signal intensity differences between two regions, scaled to image noise. Improving CNR increases perception of the distinct differences between two clinical areas of interest.
|
CONTRAST-TO-NOISE RATIO (CNR
|
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an artifact introduced into images by interference between adjacent slices of a scan. This artifact can be eliminated by limiting the minimum spacing between slices.
|
CROSSTALK
|
|
a series of 180° RF rephasing pulses and their corresponding echoes for a Fast Spin Echo (FSE) pulse sequence.
|
ECHO TRAIN
|
|
a cooling agent, typically liquid helium or liquid nitrogen used to reduce the temperature of the magnet windings in a superconducting magnet.
|
CRYOGEN
|
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the utilization of rapid gradient reversal pulses of the readout gradient resulting in a series of gradient echo signals to reduce fast dephasing or signal loss.
|
ECHO PLANAR IMAGING (EPI)
|
|
an electrically conductive screen or shield that reduces or eliminates interference between outside radio waves and those from the MRI unit.
|
FARADAY SHIELD (Faraday Cage)
|
|
Fluid Attenuated Inversion Recovery
|
FLAIR
|
|
Fast Low-Angle Recalled Echoes
|
FLARE
|
|
a mathematical procedure used in MRI scanners to analyze and separate amplitude and phases of the individual frequency components of the complex time varying signal.
|
FOURIER TRANSFORM (FT)
|
|
the process of locating an MR signal in one dimension by applying a magnetic field gradient along that dimension during the period when the signal is being received.
|
FREQUENCY ENCODING
|
|
a term usually relating to the extents of the magnetic field surrounding the magnet.
|
FRINGE FIELD
|
|
is a non-toxic paramagnetic contrast enhancement agent utilized in MR imaging.
|
GADOLINIUM
|
|
three paired orthogonal current-carrying coils located within the magnet which are designed to produce desired gradient magnetic fields which collectively and sequentially are superimposed on the main magnetic field (Bo) so that selective spatial excitation of the imaging volume can occur.
|
GRADIENT COILS
|
|
a constant for any given nucleus that relates the nuclear MR frequency and the strength of the external magnetic field.
|
GYROMAGNETIC RATIO (g)
|
|
uniformity of the main magnetic field.
|
HOMOGENEITY
|
|
an equation that states that the frequency of precession of the nuclear magnetic moment is directly proportional to the product of the magnetic field strength (Bo) and the gyromagnetic ratio (g).
|
LARMOR EQUATION
|
|
the frequency at which magnetic resonance in a nucleus can be excited and detected. The frequency varies directly with magnetic field strength, and is normally in the radio frequency (RF) range.
|
LARMOR FREQUENCY
|
|
number of excitations.
|
NEX
|
|
a loss of resolution due to excessively large voxels, typically caused by slices that are too thick.
|
PARTIAL VOLUMING
|
|
a term describing the degree to which precessing nuclear spins are synchronous.
|
PHASE COHERENCE
|
|
acronym for a picture element, the smallest discrete two-dimensional part of a digital image display.
|
PIXEL
|
|
a method of scanning in which the data is collected simultaneously from an entire layer.
|
PLANAR IMAGING
|
|
a positively charged particle located in the nucleus of an atom
|
PROTON
|
|
the concentration of mobile Hydrogen atoms within a sample of tissue.
|
PROTON DENSITY
|
|
magnetic field gradient applied during the period when the receiver components are on. The application of this gradient, which is active during the period when the echo is being formed, results in the frequency encoding of the object being imaged.
|
READOUT GRADIENT
|
|
a signal-to-noise improvement method that is accomplished by taking the average of several FIDs made under similar conditions. This is also referred to as the number of excitations (NEX) or the number of acquisitions.
|
SIGNAL AVERAGING
|
|
relates to the addition of phase encoding steps for 3D volumetric imaging.
|
SLICE ENCODING
|
|
the ability to define minute adjacent objects/points in an image, generally measured in line pairs per mm (lp/mm).
|
SPATIAL RESOLUTION
|
|
SPIN-LATTICE RELAXATION TIME
|
T1 or Longitudinal Relaxation Time.
|
|
SPIN-SPIN RELAXATION TIMe
|
T2 and Transverse Relaxation Time.
|
|
an image created typically by using short TE and TR times whose contrast and brightness are predominately determined by T1 signals.
|
T1 WEIGHTED
|
|
spin-spin or transverse relaxation time. The time constant for loss of phase coherence among spins oriented at an angle to the static magnetic field due to interactions between the spins. Results in a loss of transverse magnetization and the MRI signal.
|
T2
|
|
the time constant for loss of phase coherence among spins oriented at an angle to the static magnetic field due to a combination of magnetic field inhomogeneities and the spin-spin relaxation.
|
T2* ("T-two-star")
|
|
an image created typically by using longer TE and TR times
|
T2 WEIGHTED
|
|
a specialized imaging technique that uses computer processing to combine individual slice acquisitions together to produce an image that represents length, width and height. TI (Inversion Time) - the time between the initial (inverting) 180° pulse and the 90° pulse used in inversion recovery pulse sequences.
|
THREE DIMENSIONAL IMAGING (3DFT)
|
|
and MRA technique relying solely on the flow of unsaturated blood into a magnetized presaturated slice.
|
TIME OF FLIGHT (TOF)
|
|
an MRI surface coil that acts as both transmitter and receiver
|
TRANSCEIVER COI
|
|
the Fourier transformation process reconstructs the detected frequency and phase encoded image information (which are rotated 90° from each other) into a usable image.
|
TWO-DIMENSIONAL IMAGING (2DFT)
|
|
volume element; the element of the three-dimensional space corresponding to a pixel, for a given slice thickness.
|
VOXEL
|
|
the phenomenon resulting from digitizing fewer than two samples per period in a periodic function.
|
ALIASING (WRAP AROUND ARTIFACT)
|
|
the signal height.
|
AMPLITUDE
|
|
an all-inclusive term referring to the preselected band or range of frequencies which can govern both slice select and signal sampling.
|
BANDWIDTH (BW)
|
|
a series of rapidly recorded multiple images taken at sequential cycles of time and displayed on a monitor in a dynamic movie display format. This technique can be used to show true range of motion studies of joints and parts of the spine.
|
CINE
|
|
a large network of interconnecting blood vessels at the base of the brain that when visualized resembles a circle.
|
CIRCLE OF WILLIS
|
|
Magnetic suceptibility is:
|
Ability of a substance to become magnetized
|
|
Between T1 and T2 relaxation. Which one happens faster?
|
T2
|
|
During thermal equilibrium the magnetization is located in:
|
In the longitudinal orientation
|
|
Which pulse sequence increases the RF deposition the most?
|
Fast Spin Echo
|
|
In MRI Vector M is used to indicate
|
Patient magnetization
|
|
advantage of Spin Echo
|
Reduce magnetic suceptibility
|
|
What is used to prevent external RF to enter the MR suite
|
Farday's cage
|
|
T1 relaxation time is defined as when:
|
63% of the longitudinal magnetization has regrow
|
|
One of the advantages of the transmit-receive coil is:
|
Decrease SAR (RF deposition on the patient)
|
|
Bo is used in MRI to indicate:
|
Main Magnetic Field
|
|
Which of the followings is a characteristic of a magnet?
|
Attract ferromagnetic material
Has a north and a south pole Has magnetic lines |
|
The strenght of the signal depends on:
|
The degree of magnetization in the transverse plane
|
|
The T wave of the ECG represents which phase of the cardiac cycle?
|
Ventricular diastole
|
|
Gradient echo pulse sequences that eliminate leftover transverse magnetization are said to be what?
|
Incoherent
|
|
Noise that degrades image quality in a specific location within an MRI image is known as what?
|
Discrete noise interference
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for water is what?
|
2500 ms
|
|
Image data along both the phase and frequency axis with the highest signal amplitude is stored in which area of K space?
|
Central lines
|
|
The effects of time of flight and entry slice phenomena can be minimized by which method?
|
Pre-saturation RF pulse
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for CSF is what?
|
300 ms
|
|
Noise that generally degrades overall quality of an MRI image is known as what?
|
Random noise interference
|
|
During the sampling of signal, the sampling rate is directly proportional to what?
|
Receive bandwidth
|
|
The type of MRA that produces image contrast based on the differences in phase shifts between blood flow and stationary tissue is known as what?
|
PC MRA
|
|
The pulse sequence that performs a series of 180 degree rephasing pulses and echoes is known as what?
|
Fast spin echo
|
|
When image matrix increases, acquisition time ________
|
Increases
|
|
On a T1 weighted image of the brain, white matter appears________ to grey matter.
|
Hyperintense
|
|
The vascular imaging method that maximizes vascular contrast while also suppressing stationary tissue is known as what?
|
Magnetic resonance angiography
|
|
On a T1 weighted image of the knee, cortical bone appears to all other tissues.
|
Hypointense
|
|
When the number of excitations is increased, spatial resolution _______
|
Stays the same
|
|
Gradient moment nulling is most effective on which type of flow?
|
Slow laminar flow Correct
|
|
In a proton density weighted image, tissues with a high number of hydrogen nuclei appear _______
|
Hyperintense
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time of fat is
|
40 ms
|
|
In a T2 weighted image, tissues with long T2 relaxation times appear ______
|
Hyperintense
|
|
The horizontal axis of K space represents which axis of the image?
|
Frequency encoding
|
|
Image data with high spatial resolution is stored in which area of K space?
|
Outer lines
|
|
As the echo time increases, the effects of time of flight phenomenon _______
|
Increase
|
|
The number of 180 degree rephasing pulses performed in a fast spin echo pulse sequence is known as its what?
|
Turbo factor
Echo train length |
|
The number of picture elements used to make up an image is known as ______
|
Matrix
|
|
During the acquisition of axial images of the body with the frequency direction L/R, phase encoding is performed by which physical gradient?
|
Y gradient
|
|
When slice thickness is decreased, the effects of entry slice phenomenon _____
|
Increase
|
|
The depth of a volume element is determined by what parameter?
|
Slice thickness
|
|
The magnitude of intra-voxel dephasing is dependent upon which factor(s)?
|
Degree of disruption in the flow
|
|
Three characteristics commonly used to define the quality of an MRI image are ______
|
Resolution, Contrast, Signal to noise
|
|
When voxel size decreases, signal to noise ratio________
|
Decreases
|
|
The P wave of the ECG represents which phase of the cardiac cycle?
|
Atrial systole
|
|
In a T1 weighted image, tissues with long T1 relaxation times produce what type of signal?
|
Low
|
|
At a field strength of 1.0 Tesla, the approximate T2 relaxation time for blood is what?
|
180 ms
|
|
During cardiac gating, which of the following is the formula used to calculate available imaging time?
|
Time = R-R interval - (trigger window + trigger delay)
|
|
During cardiac gating, the waiting time between the R wave and the start of the data acquisition is known as what?
|
Trigger delay
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for spleen tissue is what?
|
480 ms
|
|
The gradient echo pulse sequence that is characterized by an echo time that is longer than its repetition time is known as what?
|
Steady state free precession
|
|
When the amplitude of the phase encoding gradient increases, the amount of phase shift along the gradient _________
|
Increases
|
|
The T wave of the ECG represents which phase of the cardiac cycle?
|
Ventricular diastole
|
|
Blood flow that has consistent velocities within a vessel is known as what type of flow?
|
Laminar flow
|
|
The area within the array processor where spatially located information is stored is known as _______
|
K space
|
|
In MRI, thick slices are achieved by applying a ______ gradient slope or a _____ bandwidth.
|
Shallow, Broad
|
|
During cardiac gating, one R-R interval and a short TE is used to produce what type of image?
|
T1 weighting
|
|
When the direction of blood flow is opposite the direction in which slices are acquired, the effects of entry slice phenomenon
|
Increase
|
|
The condition that occurs in a gradient echo pulse sequence when the TR is shorter than the T1 and T2 relaxation times of tissue is known as what?
|
Steady state
|
|
The type of signal that is created after a gradient is used to refocus the dephasing net vector is known as what?
|
Gradient echo signal
|
|
The theorem that states that a frequency must be sampled at least twice in order to reproduce it reliably is known as the _______
|
Nyquist theorem
|
|
the conventional technique used to produce a black appearance in vascular structures
|
Short TE, Short TR, Pre-saturation pulse
|
|
The effects of entry slice phenomenon are dependent upon which factor(s)?
|
Repetition time
Slice thickness Velocity of flow |
|
As blood flow velocity increases, the effects of time of flight phenomenon _____
|
Increase
|
|
The smaller the net magnetic vector in the transverse plane the ____the signal that is produced.
|
Weaker
|
|
The area of K space filled with the shallowest phase encoding slopes is known as ______
|
Central lines
|
|
Blood flow that receives a 90 degree excitation pulse but not a 180 degree rephasing pulse produces what type of signal?
|
No signal
|
|
The letters FID in an FID signal stand for what?
|
Free induction decay
|
|
Which of the following type of MRA uses a bipolar gradient to enhance vascular structures?
|
Phase contrast MRA
|
|
The method of acquiring more than one echo that are multiples of each other to reduce intra-voxel dephasing is known as what?
|
Even echo rephasing
|
|
Gradient echo pulse sequences that have incoherent residual transverse magnetization are primarily used to create what type of image weighting?
|
T1 weighting
Proton density weighting |
|
As blood flow velocity decreases, the effects of time of flight phenomenon _____
|
Decrease
|
|
When field of view is increased, signal to noise ratio________
|
Increases
|
|
In TOF MRA, which method is used to suppress signal from stationary tissue?
|
Saturation
|
|
The type of pulse sequence that fills all lines of K space per TR is known as what?
|
Echo planar
|
|
The height and width of a picture element is determined by what parameter(s)?
|
Number of phase encoding steps
Size of the FOV Number of frequency encoding steps |
|
Which of the following is the formula for determining scan time for a 3D FT pulse sequence?
|
TR x NEX x phase steps x number of slices
|
|
On a T2 weighted image of the brain, CSF appears _______ to grey matter.
|
Hyperintense
|
|
The gradient that is turned on just before the 180 degree rephasing pulse is known as the ______
|
Phase encoding gradient
|
|
Typical peak velocities of the vertebral and basilar arteries are usually within what range?
|
30-50 cm/sec
|
|
Blood flow velocity is measured in what type of unit?
|
cm/sec
|
|
Which of the following is a parameter that directly affects signal to noise ratio?
|
Voxel size
Number of excitations Repetition time |
|
The type of MRA that uses gradient echo pulse sequences and gradient moment nulling to enhance flow is known as
|
TOF MRA
|
|
During the sampling of signal, the sampling time is inversely proportional to what?
|
Sampling rate
Receive bandwidth |
|
In a T2 weighted image, fat has a _______ T2 relaxation time and therefore appears_______
|
Short, Dark
|
|
The number of times each signal is sampled with the same value of the phase encoding gradient is known as ______
|
Number of signal averages
Number of excitations Number of signal quotients |
|
During a fast spin echo pulse sequence, which lines of k space are filled by the gradients performed closest to the effective TE?
|
Central lines
|
|
When TR is increased, acquisition time ________
|
Increases
|
|
Which Parameter(s) effect total scan time?
|
Repetition time
Number of phase encoding steps Number of excitations |
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for CSF is what?
|
2000 ms
|
|
The X gradient alters the magnetic field strength along which axis?
|
Horizontal axis
|
|
Which of the following is a method used in MRA to increase signal from vascular structures?
|
Gradient moment nulling
Bipolar gradient |
|
In a gradient echo pulse sequence, blood flow that receives the initial RF pulse produces what type of signal?
|
High
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for water is what?
|
2500 ms
|
|
MRI images that are based on the differences in the amount of hydrogen nuclei in tissues are known as what?
|
Proton density weighted images
|
|
On a T2 weighted image of the brain, grey matter appears _______ to white matter.
|
Hyperintense
|
|
Which of the following is an advantage of TOF MRA?
|
Increased sensitivity to flow
Relatively short scan times Decreased sensitivity to intra-voxel dephasing |
|
The type of spin echo pulse sequence that begins with a 180 degree inversion RF pulse and is followed by a 90 degree excitation pulse is known as what?
|
Inversion recovery
|
|
In a RARE pulse sequence, the multiple number of echo times that create image weighting are averaged together to produce what is known as the what?
|
Effective TE
|
|
During the acquisition of axial images of the brain with the phase direction L/R, frequency encoding is performed by which physical gradient?
|
Y gradient
|
|
The ability to distinguish one structure from another on an image is known as ______
|
Spatial resolution
|
|
Which of the following is the formula that is used to calculate blood flow velocity?
|
Flow volume + vessel area
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time of liver tissue is what?
|
50 ms
|
|
Typical peak velocities of the distal aorta and iliac vessels are usually within what range?
|
100 - 160 cm/sec
|
|
The spin echo pulse sequence that performs more than one phase encoding step per TR is known as what?
|
Fast spin echo
RARE |
|
The series of 180 degree rephasing pulses in a fast spin echo pulse sequence is known as what?
|
Echo train
|
|
The signal produced after the 180 degree RF pulse is applied is known as what?
|
Spin echo signal
|
|
Bright pixels on an MRI image represent what type of signal?
|
High
|
|
The center of the magnet where the magnetic field strength remains unchanged even during the application of gradient magnetic fields is known as the_______.
|
Isocenter
|
|
The use of an additional gradient to correct the effects of intra-voxel dephasing is a technique known as what?
|
Gradient moment rephasing
Gradient moment nulling |
|
With the parameters given, which protocol gives the highest spatial resolution?
|
Thin slice/Small FOV/High matrix
|
|
Which of the following is a disadvantage of fast spin echo pulse sequences?
|
Increased effects of flow motion
Bright fat on T2 weighted images |
|
Which of the following is a method used in MRA to suppress stationary tissue?
|
Tissue subtraction
Tissue saturation |
|
Which of the following logical gradients is known as the phase encoding gradient?
|
Y gradient
|
|
the conventional technique used to produce a bright appearance in vascular structures
|
Gradient moment nulling
|
|
When slice thickness is increased, the effects of entry slice phenomenon _____
|
Decrease
|
|
The image parameter that primarily affects T1 weighting is known as what?
|
Repetition time
|
|
Which method of image acquisition fills one line of K space for each slice in the sequence before it moves to the second line of K space?
|
2D volumetric
|
|
The gradient that is turned on during signal sampling is known as the ______
|
Frequency encoding gradient
|
|
The clarity with which different areas of an image are distinguished is known as _______
|
Spatial resolution
|
|
When TE is decreased, the spatial resolution.
|
Stays the same
|
|
Volume averaging artifact can be reduced by
|
Decreasing slice thickness
|
|
The method of MRI field containment that uses additional magnets outside the cryogenic area of the magnet is known as what?
|
Active shielding
|
|
In MR imaging, the inter slice gap is determined by which factor(s)?
|
Slice selection gradient slope
Slice thickness |
|
The artifact that is produced when anatomy that is outside the FOV is mapped within the FOV is known as what?
|
Aliasing
|
|
The time it takes for a tissue's bulk longitudinal magnetization to return to 63% of its original value is known as what?
|
T1 relaxation time
|
|
The type of signal that is created after a gradient is used to refocus the dephasing net vector is known as what?
|
Gradient echo signal
|
|
The wire used in the main magnetic field of a superconducting magnet has its resistance removed by cooling it to a temperature of what?
|
-452 degrees Fahrenheit
|
|
Dephasing of the net vector in the transverse plane is caused by two factors, imperfections in the external magnetic field and what?
|
Interaction between surrounding nuclei
|
|
The proportion of signal actually used to construct an image relative to the amount of background noise is known as what?
|
Signal to noise ratio
|
|
Which of the following is an advantage of using a resistive magnet for clinical MRI?
|
Low capital cost
|
|
With the exception of hydrogen, all matter is composed of three components. They are what?
|
Neutrons, Electrons, Protons
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time of fat is what?
|
180ms
|
|
During the acquisition of coronal images with the frequency direction S/I phase encoding is conducted by which physical gradient?
|
X gradient
|
|
The RF pulse used to move nuclei into a higher energy state is at a frequency known as what?
|
Resonance frequency
|
|
Which of the following three characteristics are commonly used to define the quality of an MRI image?
|
Resolution, Contrast, Signal to noise
|
|
There are how many pairs of gradient coils in a standard MRI system?
|
3 pairs
|
|
To decrease the chances of cross excitation there should be at least what percentage of interslice gap?
|
30%
|
|
Image data with high spatial resolution is stored in which area of K space?
|
Outer lines
|
|
In biological tissue, which type of relaxation occurs the quickest?
|
T2* relaxation
|
|
Which method of image acquisition acquires all of the data from one slice before acquiring data from the next slice?
|
Sequential
|
|
Another name for T1 relaxation is what?
|
Longitudinal relaxation
|
|
The difference in brightness between two regions of an image is known as what?
|
Image contrast
|
|
Magnetic susceptibility artifact can be used to help diagnose what pathology?
|
Hemorrhage
|
|
After being placed in an external magnetic field, low energy hydrogen nuclei point in which direction?
|
Parallel
|
|
When the phase encoding gradient is activated, steep slopes produce data with what type of spatial resolution?
|
High
|
|
Which imaging parameter affects the amount of chemical misregistration that will be seen on an image?
|
TE
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for white matter is what?
|
390 ms
|
|
The vertical axis of K space represents which axis of the image?
|
Phase encoding
|
|
The process during prescan that fine tunes the resonant frequency is known as what?
|
Center frequency adjustment
|
|
A 180 degree RF pulse is used to ______ the dephasing net vector in the transverse plane.
|
Refocus
|
|
The smaller the net magnetic vector in the transverse plane, the ____ the signal that is produced.
|
Weaker
|
|
Material that is slightly repelled from a magnetic field is said to be what?
|
Diamagnetic
|
|
What type of molecule makes up 50% to 90% of a person's total body weight?
|
Water
|
|
The thickness of an MRI image can be changed by which of the following methods?
|
Altering the gradient slope
Altering the RF bandwidth |
|
In a T2 weighted image, tissues with short T2 relaxation times appear_______.
|
Hypointense
|
|
Chemical misregistration artifact is most likely to affect which type of pulse sequence?
|
Gradient echo pulse sequences
|
|
The process during the prescan that determines the amount of signal that is received is known as what?
|
Receive attenuation adjustment
|
|
In a T2 weighted image, CSF has a ________ T2 relaxation time and therefore appears _______.
|
Long, Bright
|
|
Image data with low spatial resolution is stored in which area of K space?
|
Central lines
|
|
The area of K space that is filled with the steepest phase encoding gradient slopes is known as what?
|
Outer lines
|
|
The image parameter that primarily affects T1 weighting is known as what?
|
Repetition time
|
|
The artifact that is caused due to the difference in precessional frequencies between fat and water is called what?
|
Chemical shift
|
|
The device used to store and transport cryogenic liquids is known as a what?
|
Dewar
|
|
A volume element that has the same height, width, and depth is known as what?
|
Isotropic
|
|
An artifact caused by faulty receiver attenuation settings during prescan is known as what?
|
Data clipping
|
|
The time that both fat and water are in phase with each other is known as what?
|
Periodicity
|
|
The center of the magnet where the magnetic field strength remains unchanged even during the application of gradient magnetic fields is known as what?
|
Isocenter
|
|
An image artifact caused by anatomical motion along a gradient is known as what type of artifact?
|
Phase mismapping
|
|
Materials reach their highest magnetic potential when their atoms are grouped in areas known as what?
|
Domains
|
|
Chemical shift artifact occurs in which direction of the MR image?
|
Frequency encoding direction
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for muscle tissue is what?
|
600 ms
|
|
The number of times each signal is sampled with the same value of the phase encoding gradient is known as what?
|
Number of signal averages
Number of excitations Number of signal quotients |
|
This materials is most commonly used to produce a permanent magnet
|
Aluminum-Nickel-Cobalt alloy
|
|
The signal produced after the 180 degree RF pulse is applied is known as what?
|
Spin echo signal
|
|
Cross excitation artifact can be eliminated by which of the following methods?
|
Increasing interslice gap
Using a digital RF pulse Interleaving |
|
The type of magnet that is produced by permanently magnetizing a ferromagnetic substance is known as a what?
|
Permanent magnet
|
|
Coils used to imperfections in the magnetic field are known as what?
|
Shim coils
|
|
A voxel that is unequal in height, width, and depth is known as what?
|
Anisotropic
|
|
The ability to distinguish one structure from another on an image is known as what?
|
Spatial resolution
|
|
Another name for aliasing artifact is what?
|
Foldover artifact
Wraparound artifact |
|
Wraparound artifact caused by undersampling of frequencies in the readout direction is known as what?
|
Frequency wrap
|
|
During the acquisition of axial images of the brain with the frequency direction A/P, phase encoding is performed by which physical gradient?
|
X gradient
|
|
The law that is used in MRI to describe how a magnetic field is induced by flowing current is known as what?
|
Faraday's Law
|
|
During slice selection, the Y gradient is used to select slices in which plane?
|
Coronal
|
|
The computer that performs the complex calculations necessary to reconstruct MRI images is known as the what?
|
Array processor
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for grey matter is what?
|
100 ms
|
|
The height and width of a picture element is determined by what parameter(s)?
|
Size of the FOV
Number of phase encoding stepsw~ Number of frequency encoding steps |
|
The time it takes for a gradient coil to reach its peak strength is known as its what?
|
Rise time
|
|
Which of the following logical gradients is known as the slice selection gradient?
|
Z gradient
|
|
MRI images that are based on the differences in the transverse relaxation characteristics of tissues are known as what?
|
T2 weighted images
|
|
The ratio that describes the constant at which any magnetic nucleus will precess in a 1 tesla magnet is known as what?
|
Precessional ratio
Gyromagnetic ratio |
|
When a patient is placed in an external magnetic field, the number of unmatched hydrogen protons usually equals how many?
|
Few per million
|
|
During the acquisition of axial images of the brain with the phase direction L/R, frequency encoding is performed by which physical gradient?
|
Y gradient
|
|
The stronger the magnetic field the ________ the precessional frequency.
|
Higher
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for renal cortex tissue is what?
|
360 ms
|
|
Three types of ferromagnetic material are include which of the following?
|
Iron, Cobalt, Nickel
|
|
The equation that is used to determine the precessional frequency of magnetic nuclei is known as what?
|
Larmor equation
|
|
Coils that are used to transmit and receive radio frequencies are known as what?
|
RF coils
|
|
The homogeneity of the external magnetic field is measured in what type of unit?
|
Parts per million
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for spleen tissue is what?
|
80 ms
|
|
The process of filling only a percentage of K space with acquired data and filling the rest with zeros is known as what?
|
Partial averaging
|
|
When the radio frequency is turned off, precessing nuclei begin to display what type of behavior?
|
Relax
Lose energy Dephase |
|
Gradient moment nulling is most effective in reducing flow related motion in which type of flow?
|
Slow flow
Inplane flow |
|
In an inversion recovery pulse sequence, the time between the 180 degree RF pulse and the 90 degree RF pulse is known as what?
|
Inversion time
|
|
A spin echo image with a long TR and a long TE is known as what type of image?
|
T2 weighted image
|
|
The wire used to create the main magnetic field in a superconducting magnet is known as what?
|
Niobium-Titanium
|
|
The precessional frequency of magnetic nuclei is determined by which of the following?
|
The strength of the external magnetic field
The gyromagnetic ratio of the specific nuclei |
|
Which of the following is an example of phase mismapping artifact?
|
Cardiac motion
Flow motion Respiratory motion |
|
When the proper radio frequency is applied, the precessing hydrogen nuclei begin to display which type of behavior?
|
Resonate
|
|
In plane pixel size can be determined by which of the following methods?
|
Dividing the FOV by the number phase and frequency steps
|
|
The depth of a volume element is determined by what parameter?
|
Slice thickness
|
|
Dephasing of the net vector in the transverse plane is known as what?
|
Spin-Spin relaxation
|
|
The rule that is used to determine the direction of the magnetic field in an electromagnet is known as what?
|
Right hand thumb rule
|
|
The range of frequencies that is sampled during frequency encoding is known as what?
|
Receive bandwidth
|
|
How many milliseconds are there in a minute?
|
60,000
|
|
The technique used to eliminate cross excitation artifact that acquires data in two separate acquisitions from alternating slices is known as what?
|
Interleaving
|
|
Gradient strength is measured in what form of unit?
|
Gauss per centimeter
Millitesla per meter |
|
The time it takes for transverse magnetization to decay to 37% of its original value is known as what?
|
T2 relaxation time
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for CSF is what?
|
2000 ms
|
|
Magnetization in the transverse plane can also be known as what?
|
Mxy
Mo |
|
In clinical MRI, the homogeneity of the magnet should be at least what?
|
10 parts per million
|
|
Alignment of the net magnetic vector in the direction of the external magnetic field is known as what?
|
Longitudinal magnetization
Equilibrium |
|
In an MR image, the degree of chemical shift artifact depends upon which parameter?
|
Receive bandwidth
Size of the FOV Magnetic field strength |
|
The amplitude of the phase and frequency encoding gradients determines the dimension of what parameter?
|
FOV
|
|
In a proton density weighted image, tissues with a high number of hydrogen nuclei appear _______.
|
Hyperintense
|
|
Which Parameter(s) effect total scan time?
|
Repetition time
Number of phase encoding steps Number of excitations |
|
The area within the array processor where spatially located information is stored is known as what?
|
K space
|
|
15,000 gauss is equal to what?
|
1.5 tesla
|
|
Which of the following logical gradients is known as the phase encoding gradient?
|
Y gradient
|
|
In fat, the hydrogen atom is bound with what other type of atom?
|
Carbon
|
|
Prior to each scan, the process of prescanning performs which type of calibration?
|
Adjusts the transmit gain
Adjusts the receive attenuation Sets the center frequency |
|
During the acquisition of sagittal images with the frequency direction S/I, phase encoding is conducted by which physical gradient?
|
Y gradient
|
|
The Z gradient alters the magnetic field strength along which axis?
|
Long axis
|
|
When the phase encoding gradient is activated, shallow slopes produce what type of signal amplitude?
|
High
|
|
On a T1 weighted image of the knee, bone marrow appears to meniscal tissues.
|
Hyperintense
|
|
A saturation pulse is a technique used to reduce what type of motion artifact?
|
Blood flow motion
Respiratory motion Swallowing motion |
|
Which method of image acquisition acquires data from an entire volume of tissue, then uses a method called slice encoding to separate the images?
|
3D volumetric
|
|
The time between the 90 degree RF pulse and the spin echo signal in a spin echo pulse sequence is known as what?
|
Echo time
|
|
The area of K space filled with the shallowest phase encoding slopes is known as what?
|
Central lines
|
|
The precessional frequency of hydrogen nuclei that experience increased magnetic field strength due to gradient coils ________.
|
Increases
|
|
The type of coils used to change the strength of the magnetic field inside the bore of the magnet are known as what?
|
Gradient coils
|
|
Another name for a proton density weighted image is what?
|
Spin density
Intermediate |
|
The process of filling K space by sampling only half of the echo and interpolating the rest is known as what?
|
Fractional echo
Partial echo |
|
Data loss due to gradient instability, excessive noise, or tuning errors can cause an artifact with what type of appearance?
|
Herringbone
|
|
The strength of a magnet is measured by its what?
|
Flux density
|
|
The range of frequencies that is transmitted by the RF pulse is known as what?
|
Transmit bandwidth
|
|
The gradient that is turned on during signal sampling is known as what?
|
Frequency encoding gradient
|
|
The sum of all of the unmatched parallel protons in an external magnetic field makes up what is called the what?
|
Net magnetic vector
|
|
The device in the MRI system that supplies power to the gradient coils is known as the what?
|
Gradient amplifier
|
|
Isolating the RF transmitter from the RF receiver is known as what?
|
Decoupling
|
|
The term used to describe a volume element is known as what?
|
Voxel
|
|
Another name for phase mismapping artifact is what?
|
Ghosting
|
|
Chemical misregistration artifact most commonly occurs in which direction of the MR image?
|
Phase encoding direction
|
|
the movement of molecules in the extra-cellular space due to random thermal motion.
|
Diffusion
|
|
an imaging technique that displays a frequency spectrum of differences between various elements within tissues. This techniques is commonly utilized to measure the amount of a specific element that is within the tissue.
|
Spectroscopy
|
|
In diffusion weighted imaging, tissues with a low apparent diffusion coefficient have what type of signal intensity?
|
Hyperintense
|
|
The term _____________ is defined as the volume of blood that flows into one gram of tissue.
|
Perfusion
|
|
While ligaments, membranes, and macromolecules are all common boundaries that restrict motion within the extra-cellular space, _________ is not one of these boundaries.
|
Microfibers
|
|
In diffusion weighted imaging, tissues with a high apparent diffusion coefficient have what type of signal intensity?
|
Hypointense
|
|
Which of the following terms is used to describe the net displacement of molecules diffusing across an area of tissue per second?
|
Apparent Diffusion Coefficient
|
|
Which MR imaging techniques creates image contrast by enhancing magnetic susceptibility differences between various tissues?
|
Susceptibility Weighted Imaging
|
|
In MR spectroscopy, which of the following is an element commonly found in the proton spectra of human tissue?
|
Creatine
Glutamine Choline |
|
Which MR imaging techniques is utilized to image activity within the brain caused by stimulus?
|
Functional
|
|
Which of the following is a method utilized in MR spectroscopy to locate a spectrum of elements?
|
Multi-Voxel
Single Voxel |
|
Which is a diffusion weighted imaging technique that is utilized to map the white matter tracks within the brain?
|
Diffusion Tensor Imaging
|
|
In diffusion weighted imaging, the b-value is expressed in what unit of measurement?
|
s/mm2 ( seconds per millimeters squared)
|
|
In functional MRI, which physiological effects is utilized to measure variations in signal intensity between areas of the brain experiencing stimuli versus areas at rest?
|
Blood Oxygenation Level Dependent or (BOLD)
|
|
During the acquisition of sagittal images with the phase direction A/P, frequency encoding is performed by which physical gradient?
|
Z gradient
|
|
Typical peak velocities of the ascending aorta are usually within what range?
|
150-175 cm/sec
|
|
The speed at which blood flows through an excited slice and only receives one RF pulse is known as what type of phenomenon?
|
Time of flight phenomenon
|
|
When TR is decreased, the effects of entry slice phenomenon ______
|
Decrease
|
|
In a T2 weighted image, a long TE is used to do what?
|
Maximize T2 effects
|
|
The process of filling K space by sampling only half of the echo and interpolating the rest is known as _______
|
Fractional echo
Partial echo |
|
MRI images that are based on the differences in the transverse relaxation characteristics of tissues are known as what?
|
T2 weighted images
|
|
A 180 degree RF pulse is used to ______ the dephasing net vector in the transverse plane.
|
Refocus
|
|
In a gradient echo pulse sequence, the process of eliminating residual transverse magnetization is known as what?
|
Spoiling
|
|
In which of the following types of flow can intra-voxel dephasing be compensated for?
|
Laminar flow
|
|
The area of K space that is filled with the steepest phase encoding gradient slopes is known as _______
|
Outer lines
|
|
Which of the following methods can reduce blurring in a fast spin echo pulse sequence?
|
Reduce echo train length
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for renal cortex tissue is _______
|
70 ms
|
|
The flow phenomenon that is characterized by phase differences between flowing and stationary nuclei within a voxel is known as ______
|
Intra-voxel dephasing
|
|
TOF MRA is most sensitive to blood flow that flows in what direction in relation to the slice?
|
Perpendicular
|
|
In conventional spin echo pulse sequences, how many phase encoding steps are achieved per TR?
|
1
|
|
When the number of excitations is decreased, acquisition time________
|
Decreases
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time for muscle tissue is what?
|
600 ms
|
|
During slice selection, the X gradient is used to select slices in which plane?
|
Sagittal
|
|
In conventional spin echo pulse sequences, how many lines of K space are filled per TR?
|
1
|
|
The time between the 90 degree RF pulse and the spin echo signal in a spin echo pulse sequence is known as what?
|
Echo time
|
|
The signal created after applying a 90 degree RF pulse is known as what?
|
FID Signal
|
|
In an echo planar pulse sequence, proton density weighting can be produced by which of the following techniques?
|
Using a short TE
|
|
The three primary functions that gradients perform during MR scanning are known as what?
|
Slice selection, Phase encoding, Frequency encoding
|
|
A spin echo image with a long TR and a long TE is known as what type of image?
|
T2 weighted image
|
|
At a field strength of 1.0 Tesla, the approximate T1 relaxation time for blood is what?
|
800 ms
|
|
The time between two successive 90 degree RF pulses is known as what?
|
Repetition time
|
|
Entry slice phenomenon is most prominent in what slice of the area scanned?
|
Affects all the same
|
|
Advantages of phase contrast MRA
|
Increased stationary tissue suppression
Sensitive to flow in all directions Sensitive to flow with various velocities |
|
In MRI, thin slices are achieved by applying a ______ gradient slope or a _____ bandwidth.
|
Steep, Narrow
|
|
Blood flow velocity at a given point is dependent upon which factor?
|
Phase of patient's cardiac cycle
|
|
Blood flow that has high velocities in the center of the vessel but spirals near walls of a vessel due to a stricture is known as what type of flow?
|
Vortex flow
|
|
As bandwidth increases, sampling time ______
|
Decreases
|
|
Which method of image acquisition acquires all of the data from one slice before acquiring data from the next slice?
|
Sequential
|
|
In MR imaging, the inter slice gap is determined by which factor(s)?
|
Slice selection gradient slope
Slice thickness |
|
In conventional spin echo sequences, how many phase encoding steps must be selected to fill 256 lines of K space?
|
256
|
|
Which method of image acquisition acquires data from an entire volume of tissue, then uses a method called slice encoding to separate the images?
|
3D volumetric
|
|
Image data along both the phase and frequency axis with the lowest signal amplitude is stored in which area of the K space?
|
Outer lines
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for renal medulla tissue is what?
|
140ms
|
|
Another name for a proton density weighted image is ______
|
Spin density
Intermediate |
|
The Y gradient alters the magnetic field strength along which axis?
|
Vertical axis
|
|
The magnitude of time of flight phenomenon effects is dependent upon which factor(s)?
|
Velocity of flow
TE Slice thickness |
|
Which of the following TOF MRA sequences is most likely to saturate slow flow?
|
3D TOF
|
|
Which of the following is a disadvantage of phase contrast MRA?
|
Long scan times
Increased sensitivity to turbulence |
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time of liver tissue is what?
|
390 ms
|
|
When image matrix is decreased, spatial resolution _______
|
Decreases
|
|
The type of pulse sequence that uses only 90 degree RF pulses is known as what?
|
Partial saturation pulse sequence
Gradient echo pulse sequence |
|
During cardiac gating, the time between two consecutive R waves is known as what?
|
R-R interval
|
|
The amplitude of the phase and frequency encoding gradients determines the dimension of what parameter?
|
FOV
|
|
On a T1 weighted image of the spine, the intervertebral disk appears to spinal cord.
|
Hypointense
|
|
During an inversion recovery pulse sequence, the time between the 180 degree inversion pulse and the 90 degree excitation pulse is known as what?
|
Inversion time
|
|
As slice thickness increases, the effects of time of flight phenomenon _______
|
Decrease
|
|
Image data with low spatial resolution is stored in which area of K space?
|
Central lines
|
|
The precessional frequency of hydrogen nuclei that experience decreased magnetic field strength due to gradient coils_______
|
Decreases
|
|
During slice selection, the Y gradient is used to select slices in which plane?
|
Coronal
|
|
The vertical axis of K space represents which axis of the image?
|
Phase encoding
|
|
In plane pixel size can be determined by which of the following methods?
|
Dividing the FOV by the number phase and frequency steps
|
|
The Z gradient alters the magnetic field strength along which axis
|
Long axis
|
|
SSFP
|
Steady-state free precession
|
|
FFE
|
Fast Field Echo
|
|
A spin echo image with a long TR and a short TE is known as what type of image?
|
Proton density weighted image
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for white matter is what?
|
90 ms
|
|
In a proton density weighted image, tissues with a low number of hydrogen nuclei appear ______
|
Hypointense
|
|
When the velocity of flow increases, the effects of entry slice phenomenon _____
|
Increase
|
|
The inversion recovery pulse sequence that is used to suppress CSF in proton density and T2 weighted images is known as what?
|
FLAIR
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for muscle tissue is what?
|
40 ms
|
|
In MR imaging, slice thickness is determined by which factor(s)?
|
Gradient slope slice select
Transmit bandwidth |
|
used to describe parameters that affect each other inversely.
|
Trade-off parameters
|
|
At a field strength of 1.0 tesla, the approximate T1 relaxation time of fat is what?
|
180ms
|
|
Which of the following conventional MRI techniques can be used to produce contrast differences between vascular structures and stationary structures?
|
Gradient moment nulling
Pre-saturation pulse |
|
In an echo planar pulse sequence, pre-inverting tissue with a 180 degree RF pulse before excitation produces what type of image weighting?
|
T1 weighting
|
|
When the phase encoding gradient is activated, steep slopes produce data with what type of spatial resolution?
|
High
|
|
The frequency encoding gradient is also known as the ______ because it is turned on during the sampling of signal.
|
Readout gradient
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for spleen tissue is ________
|
80 ms
|
|
When the direction of blood, flow is the same as the direction in which slices are acquired, the effects of entry slice phenomenon _______
|
Decrease
|
|
The difference in brightness between two regions of an image is known as______
|
Image contrast
|
|
Spatial resolution
|
determines how "sharp" the image looks.
|
|
Blood flow that has randomly different velocities is known as what type of flow?
|
Turbulent flow
|
|
In a gradient echo pulse sequence, the use of an RF pulse to eliminate residual transverse magnetization is known as what?
|
Digital RF spoiling
|
|
The magnitude of the phase shifts between two points within a patient is determined by which factor?
|
Slope of the phase encoding gradient
|
|
During cardiac gating, the waiting time before each R wave is known as what?
|
Trigger window
|
|
The term used to describe a volume element is known as ______
|
Voxel
|
|
When pixel size increases, signal to noise ratio________
|
Increases
|
|
Gradient echo pulse sequences that preserve left over transverse magnetization are said to be what?
|
Coherent
|
|
As bandwidth decreases, sampling time ______
|
Increases
|
|
During cardiac gating, TR is dependent upon which factor(s)?
|
The patient's heart rate
The R- R interval |
|
When the phase encoding gradient is activated, steep slopes produce what type of signal amplitude?
|
Low
|
|
A spin echo pulse sequence is characterized by which of the following?
|
90 degree excitation pulse followed by a 180 degree rephasing pulse
|
|
The method that is most commonly used to reduce artifact produced by cardiac motion when scanning the chest is known as ______
|
Cardiac gating
|
|
When image matrix is increased, spatial resolution______
|
Increases
|
|
Gradient echo pulse sequences that eliminate leftover transverse magnetization are said to be what?
|
Incoherent
|
|
In an echo planar pulse sequence, using a long TE produces what type of weighting?
|
T2 weighting
|
|
In a T2 weighted image, CSF has a ________ T2 relaxation time and therefore appears _______
|
Long, Bright
|
|
Which of the following logical gradients is known as the frequency encoding gradient?
|
X gradient
|
|
The proportion of signal actually used to construct an image relative to the amount of background noise is known as ______
|
Signal to noise ratio
|
|
Noise that degrades image quality in a specific location within an MRI image is known as what?
|
Discrete noise interference
|
|
Blood flow that travels in the same direction in which the slices are acquired is known as what type of flow?
|
Co-current flow
|
|
When TR is increased, the effects of entry slice phenomenon _______
|
Increase
|
|
The range of frequencies that is transmitted by the RF pulse is known as the
|
Transmit bandwidth Correct
|
|
The precessional frequency of hydrogen nuclei that experience increased magnetic field strength due to gradient coils ________
|
Increases
|
|
The inversion recovery pulse sequence that is used to suppress fat in a T1 weighted image is known as what?
|
STIR
|
|
During the acquisition of sagittal images with the frequency direction S/I, phase encoding is conducted by which physical gradient?
|
Y gradient
|
|
As slice thickness decreases, the effects of time of flight phenomenon ______
|
Increase
|
|
The type of cardiac gating that detects the increase in blood volume in the capillary bed during systole is known as what?
|
Peripheral gating
|
|
MRI images that are based on the differences in longitudinal relaxation characteristics of tissues are known as what?
|
T1 weighted images
|
|
When the phase encoding gradient is activated, shallow slopes produce what type of signal amplitude?
|
High
|
|
In a T1 weighted image, a short TR is used to do what?
|
Maximize T1 effects
|
|
In a gradient echo pulse sequence, transverse magnetization that is leftover from a previous excitation pulse is known as what?
|
Residual transverse magnetization
|
|
Typical peak velocities of the middle and anterior cerebral arteries are usually within what range?
|
40-70 cm/sec
|
|
The gradient that is turned on during the application of the 90 degree excitation pulse and the 180 degree RF pulse is known as ______
|
Slice selection gradient
|
|
The spatial location of signal according to its precessional frequency is known as ______
|
Frequency encoding
|
|
The ECG wave with the highest electrical amplitude is known as the what?
|
R wave
|
|
Because the nucleus of the hydrogen atom acts much like a bar magnet it is said to have what?
|
Magnetic moment
|
|
An example of aperiodic motion is what?
|
Peristalsis motion
|
|
Material that is strongly attracted to a magnetic field is said to be what?
|
Ferromagnetic
|
|
paramagnets
|
Unlike ferromagnets, paramagnets do not retain any magnetization in the absence of an externally applied magnetic field because thermal motion randomizes the spin orientations.
|
|
Which of the following is the equation that is used to determine precessional frequencies?
|
Wo=yBo
F=Boy |
|
Another name for transverse relaxation is what?
|
Spin-Spin relaxation
|
|
The X gradient alters the magnetic field strength along which axis?
|
Horizontal axis
|
|
During the acquisition of axial images of the body with the frequency direction L/R, phase encoding is performed by which physical gradient?
|
Y gradient
|
|
Chemical shift artifact can be minimized by which of the following methods?
|
Minimizing the FOV
Increasing the receive bandwidth Utilizing chemical saturation |
|
After being placed in an external magnetic field, high energy hydrogen nuclei point in which direction?
|
Anti-parallel
|
|
The return of longitudinal magnetization to equilibrium is known as what?
|
T1 relaxation
Spin-Lattice relaxation Longitudinal relaxation |
|
The gradient that is turned on during the application of the 90 degree excitation pulse and the 180 degree RF pulse is known as what?
|
Slice selection gradient
|
|
The artifact that is produced when many structures with different signal intensities are averaged together within a pixel is known as what?
|
Partial volume averaging
|
|
The spatial location of signal according to its precessional phase is known as what?
|
Phase encoding
|
|
Wraparound artifact occurs in which direction of an MR image?
|
Phase direction
Frequency direction |
|
During slice selection, the Z gradient is used to select slices in which plane?
|
Axial
|
|
Gibbs artifact can be decreased by ______ the number of phase encoding steps.
|
Increasing
|
|
The number of picture elements used to make up an image is known as what?
|
Matrix
|
|
In MRI, thin slices are achieved by applying a ______ gradient slope or a _____ bandwidth.
|
Steep, Narrow
|
|
Image data along both the phase and frequency axis with the lowest signal amplitude is stored in which area of the K space?
|
Outer lines
|
|
Another name for truncation artifact is what?
|
Gibbs artifact
Ringing artifact |
|
Peripheral gating is a technique used to decrease what type of motion artifact?
|
CSF pulsation motion
|
|
The type of RF coil configuration that uses a series of independent coils to create one image is known as a what?
|
Phased array coil
|
|
The spin of the proton of the hydrogen atom is known as what?
|
Hydraulic spin
|
|
The magnitude of the phase shifts between two points within a patient is determined by which factor?
|
Slope of the phase encoding gradient
|
|
During the sampling of signal, the sampling rate is directly proportional to which of the following?
|
Receive bandwidth
|
|
The image parameter that primarily affects T2 weighting is known as what?
|
Echo time
|
|
The nucleus of the hydrogen atom carries what type of charge?
|
Positive
|
|
On a T1 weighted image of the knee, cortical bone appears __________ to all other tissues.
|
Hypointense
|
|
The clarity with which different areas of an image are distinguished is known as what?
|
Spatial resolution
|
|
The larger the net magnetic vector in the transverse plane the _____ the signal that is produced.
|
Stronger
|
|
The artifact produced by the transfer of spin lattice energy from one slice to its adjacent slice is known as what?
|
Cross talk artifact
|
|
The artifact that is characterized by a loss of signal intensity in one area of an image is known as what?
|
Shading artifact
|
|
An artifact that is caused by an external radio frequency leak is known as what?
|
Zipper artifact
|
|
Image data along both the phase and frequency axis with the highest signal amplitude is stored in which area of K space?
|
Central lines
|
|
At a field strength of 1.0 tesla, the approximate T2 relaxation time for water is what?
|
2500 ms
|
|
Hydrogen nuclei begin to precess in phase when which of the following occurs?
|
The proper RF is turned on
|
|
During the acquisition of coronal images with the phase direction L/R, frequency encoding is conducted by which physical gradient?
|
Z gradient
|
|
On a T1 weighted image of the brain, fat appears ________ to white matter.
|
Hyperintense
|
|
When placed in an external magnetic field, the hydrogen nuclei that are of clinical interest are known as what?
|
Parallel unpaired
|
|
In a T1 weighted image, a short TR is used to do what?
|
Maximize T1 effects
|
|
The time between two successive 90 degree RF pulses is known as what?
|
Repetition time
|
|
The external magnetic field in a superconducting magnet is said to be what type of magnetic field?
|
Static
|
|
Metal in the patient, in the area that is being scanned, will most likely create what type of artifact?
|
Magnetic susceptibility
|
|
The frequency encoding gradient is also known as the ______ because it is turned on during the sampling of signal.
|
Readout gradient
|
|
When the phase encoding gradient is activated, medium slopes produce what type of signal amplitudes?
|
Medium
|
|
The type of secondary rotation that is displayed by hydrogen nuclei in an external magnetic field is known as what?
|
Precession
|
|
In a T1 weighted image, tissues with short T1 relaxation times produce what type of signal?
|
High
|
|
When the amplitude of the phase encoding gradient increases, the amount of phase shift along the gradient _________.
|
Increases
|
|
The nucleus of the hydrogen atom is made up of one ______.
|
Proton
|
|
The type of RF coil that encompasses the entire anatomy to be scanned is known as what?
|
Volume coil
|
|
A spin echo image with a short TR and a short TE is known as what type of image?
|
T1 weighted image
|
|
The calibration of transmit gain during the prescan process determines which factor?
|
RF output necessary to produce a 90 degree flip angle
|
|
The artifact that is produced by overlapping radio frequency pulses in adjacent slices is known as what?
|
Cross excitation artifact
|
|
The image parameter that primarily affects T2 weighting is known as what?
|
Echo time
|
|
When slice spacing increases, signal to noise ratio________
|
Increases
|
|
When repetition time is increased, signal to noise ratio ________
|
Increases
|
|
When the velocity of flow decreases, the effects of entry slice phenomenon ____
|
Decrease
|
|
The vertical axis of K space represents which axis of the image?
|
Phase encoding
|
|
the following terms is defined as the volume of blood that flows into one gram of tissue
|
Perfusion
|
|
the following MRI imaging techniques displays a frequency spectrum of differences between various elements within tissues
|
Spectroscopy
|
|
There are two image types associate with diffusion weighted imaging
|
Trace Images
and ADC Maps |
|
In MR spectroscopy, the following is an element commonly found in the proton spectra of human tissue
|
Creatine, choline, and glutamine are all common elements found in the proton spectra of human tissue.
|
|
A diffusion weighted imaging technique that utilizes multi-directional gradients to map the anatomy of white matter tracks within the brain.
|
Diffusion Tensor Imaging
|
|
Used to describe the movement of molecules in the extra-cellular space due to random thermal motion.
|
Diffusion
|
|
In diffusion weighted imaging, which parameter controls the amount of a tissue’s apparent diffusion coefficient (ADC) that is utilized to weight the image?
|
b-Value - The b value controls the amount of a tissue's apparent diffusion coefficient (ADC) that is utilized to weight an image. Image weighting on images with a b value of 0 are controlled by other timing parameters such as TR and TE.
|
|
Specific absorption rate is expressed in units of what?
|
Watts/kg
|
|
The rate at which a patient can safely dissipate excess heat caused by RF energy is known as what?
|
Specific absorption rate
|
|
The chemical compounds used to bind the metallic ion in MRI contrast agents are known as what?
|
Chelates
|
|
The recommended SAR limit for safely imaging the head is what?
|
3.2 Watts/kg.
|
|
The recommended whole body SAR limit for MR imaging is what?
|
4.0 Watts/kg
|
|
The first use of a paramagnetic agent on a human subject was in what year?
|
1981
|
|
The term used to describe freedom from infection or infectious material is known as what?
|
Asepsis
|
|
Contrast agents most commonly used in MRI today have what type of effect on tissue?
|
Decrease T1 relaxation times
|
|
The effect of MRI contrast media on tissue relaxation rates is known as what?
|
Relaxivity
|
|
The amount of a drug required to cause death in half of a sample of laboratory mice is known as what?
|
LD50
and Median lethal dose |
|
Which of the following is a biological effect unique to echo planar imaging?
|
Muscular twitches in face and back
|
|
Heating that is directly associated with the RF pulse sequence should not increase the core body temperature greater than what?
|
1 degree Celsius
|
|
The first material used by Felix Bloch to change magnetic relaxation times was known as what?
|
Ferric Nitrate
|
|
Substances that adhere to and transmit infectious material are known as what?
|
Fomites - A fomite is defined as an inanimate object or substance that is capable of transmitting infectious organisms from one individual to another.
|
|
The first oral MRI contrast agent used in a human subject was known as what?
|
Ferric Chloride
|
|
To minimize MRI contrast agent's toxicity, the agent should be what?
|
Excreted intact by the kidneys
and Excreted intact by the gallbladder and intestines |
|
Which of the following describes the two major types of asepsis?
|
Medical and Surgical
|
|
The first intravenous MRI contrast agent that was used on a human subject was known as what?
|
Gadopentetate dimeglumine
|
|
Infections that originate within the healthcare setting are known as what?
|
Nosocomial infections, healthcare associated infections, and HAI's are all terms that describe infections that originate within the healthcare setting.
|
|
The recommended SAR limit for safely imaging small volumes is what?
|
8.0 Watts/kg
|
|
Which of the following is the median lethal dose of Gadopentetate dimeglumine?
|
10-20 mmol/kg
|
|
The image parameter that primarily affects T2 weighting is known as what?
|
Echo time
|
|
On a T2 weighted image of the brain, grey matter appears _______ to white matter.
|
Hyperintense
|
|
On a proton density weighted image of the brain, CSF appears_______ to grey matter.
|
Hypointense
|
|
When slice thickness is increased, signal to noise ratio________
|
Increases
|
|
The T wave of the ECG represents which phase of the cardiac cycle?
|
Ventricular diastole
|
|
When TR is decreased, the effects of entry slice phenomenon ______
|
Decrease
|
|
The QRS wave of the ECG represents which phase of the cardiac cycle?
|
Ventricular systole
|
|
When image matrix is increased, spatial resolution______
|
Increases
|
|
Which of the following type of MRA uses a bipolar gradient to enhance vascular structures?
|
Phase contrast MRA
|
|
Gradient echo pulse sequences that preserve left over transverse magnetization are said to be what?
|
Coherent
|
|
When the number of excitations is decreased, acquisition time________
|
Decreases
|
|
the volume of blood that flows into one gram of tissue
|
Perfusion
|
|
term used to describe the net displacement of molecules diffusing across an area of tissue per second.
|
Apparent Diffusion Coefficient
|
|
artifact specifically associated with diffusion weighted imaging
|
T2 Shine Through
|
|
In diffusion weighted imaging, the b-value is expressed in what unit of measurement?
|
s/mm2
|
|
controls the amount of a tissue's apparent diffusion coefficient (ADC) that is utilized to weight an image.
|
b-Value
|
|
In diffusion weighted imaging, tissues with a low apparent diffusion coefficient have what type of signal intensity
|
Hyperintense
|
|
In diffusion weighted imaging, tissues with a high apparent diffusion coefficient have what type of signal intensity?
|
Hypointense
|
|
Which of the following is an image type associated with diffusion weight imaging?
|
trace images and ADC maps
|
|
Creatine, choline, and glutamine are all common elements found in the
|
proton spectra of human tissue.
|
|
________________ is a term describing the containment of the static magnetic fringe field through the use of secondary coils attached around the MRI scanner
|
Active shielding
|
|
_______________ is a term used to describe the adjustment of the current within the shim coils on a per/patient or per/sequence basis, for the purposes of achieving uniform fat suppression or optimal prescan calibrations.
|
Active shimming
|
|
__________images are reconstructed from diffusion weighted images with multiple b-values, and correspond to the spatially distributed diffusion coefficients of the target tissues
|
ADC
|
|
________ artifact occurs when tissue outside the Field of View is undersampled, causing a misregistration of anatomical location, in the phase direction, but on the opposite side of the anatomical location, also known as wrap-around artifact
|
Aliasing
|
|
_________ – equates to signal height or strength; the larger the amplitude, the larger the number of protons
|
Amplitude
|
|
________ – being continuous, or having a continuous range of values
|
Analog
|
|
The ____________ converter (ADC) is part of the computer system that converts the analog acquired MR signal into a digital signal
|
Analog-to-digital
|
|
An ________ voxel is a voxel with uneven measurements, with regards to the phase, frequency and slice thickness dimensions
|
anisotropic
|
|
An ______ processor comprises a multiprocessor that is switched in sequence and in parallel while simultaneously performing a computing task
|
array
|
|
_________ are signal misrepresentations that do not correspond to the spatial location of the specific tissue imaged
|
Artifacts
|
|
_________ is defined as the range or spectrum of frequencies (minimum to maximum processed frequency) of a pulse sequence acquired by an RF system
|
Bandwidth
|
|
The _____ coil is an integrated part of the magnet design that acts as its own transceiver coil, with large FOV capabilities, but lacking the high SNR of localized coils
|
body
|
|
The ______ is defined as a factor in diffusion weighted imaging; the higher the factor, the stronger the diffusion weighting
|
b-value
|
|
The ____ field is defined as the static main magnetic field of an MR system
|
B0
|
|
_____________ prevents or reduces motion artifacts in the MR image caused by the heartbeat or pulsating blood flow and enables the images to be acquired synchronized to cardiac movement
|
Cardiac triggering
|
|
________________ artifact is due to the difference in resonant frequencies between fat and water, causing a phase shift in voxels containing fat and water.
|
Chemical shift
|
|
____ function scrolls through the entire sequence's images, giving the appearance of CSF flowing or cardiac movement, from the cycling of the images acquired; a “movie” function of scrolling images
|
Cine
|
|
_________ – maintaining a constant state of “in-phase” relationships between protons; located at the same phase cycle simultaneously
|
Coherent
|
|
________ can be defined as the signal strength differences between two adjacent tissue types
|
Contrast
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__________________ utilizes the reduced T1 relaxation time of blood through the use of an intravenously injected Gadolinium contrast agent
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CE MRA (Contrast-enhanced MR angiography)
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_________ – Circularly polarized transmission or receiver coil with two orthogonal transmission and/or receiver channels, also known as a quadrature coil. This yields better signal-to-noise than a linear coil
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CP coil
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_______ artifact occurs when slices are positioned too close together, causing signals from adjacent slices to affect one another. This affects T1 contrast, and is remedied by utilizing an interleaved slice profile or by increasing slice gap
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Cross-talk
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______ – Formula for the temporal change of the magnetic field, especially important with regards to patient safety in relation to gradients.
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dB/dt
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__________ occurs after initial RF application, causing phase differences to appear between precessing spins, resulting in decay of transverse magnetization
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Dephasing
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____________ is an effect resulting in a slightly weakened magnetic field when a substance is introduced into it. This material is considered to have a negative magnetic susceptibility
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Diamagnetism
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_______ – the movement of atoms or molecules from an area of higher concentration to an area of lower concentration. (Brownian motion)
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Diffusion
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______________ – displays the mobility of water molecules in all three coordinates
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Diffusion tensor
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_________ – A technique utilizing the differences in resonant frequencies of fat and water separating the two tissues, acquiring each separately, then adding the two to yield a water-only image (fat suppression), then subtracting the two to yield a fat-only image
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Dixon
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_________ – A spin echo sequence with two echoes, two generated images per slice location
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Double Echo
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_________ – The time which the gradient system can be run at maximum power
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Duty cycle
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______________________________ refers to DCE, or Basic T1 perfusion imaging (pituitary or prostate dynamic sequences, longer acquisition times/dynamic compared to DSC)
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Dynamic Contrast Enhancement
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___________________ -- refers to DSC, or better known as T2* gradient echo Perfusion imaging, utilized in Brain Perfusion studies
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Dynamic Susceptibility Contrast
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_____ – The MR signal generated by an RF or a gradient pulse
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Echo
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_______________ – Very fast MR imaging technique where the complete image is acquired using a single selective excitation pulse, field gradients are periodically switched to generate a series of gradient echoes
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Echo Planar Imaging
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____________ – Distance between two echoes, as in Fast Spin Echo or EPI sequences. The shorter the echo spacing, the more compact the sequence timing and few artifacts result
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Echo Spacing
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___________ – The time between the excitation pulse of a sequence and the resulting echo used as the MR signal
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Echo Time (TE)
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___________– Multiple echoes in sequence, each obtaining rows of k-space, shortening overall scan time, also reducing SNR with each additional echo train
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Echo Train
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_________ – In a pulse sequence, the contrast and overall SNR of an image is determined by the position of the echo when the phase encoding gradient has the smallest amplitude.
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Effective TE
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__________ – referring to prospective cardiac triggering techniques, the patient’s heart rate controls the TR, or termed the effective or available TR (TReff), according to the beats per minute (BPM) factor
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Effective TR
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_________________ – The electrical voltage created in a receiver coil as a result of a temporal change in the magnetic field
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Electromagnetic Induction
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________ –the medical term used to describe vomiting
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Emesis
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_________– Number of gradient echoes in an Echo Planar sequence acquired after the initial excitation pulse; equating to the scan time acceleration factor
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EPI factor
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______________ – The radiofrequency (RF) pulse used to disturb the equilibrium of the Net Magnetization Vector; the higher the energy of excitation, the greater the flipped angle of magnetization
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Excitation pulse
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________ – the cause or origin of a disease
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Etiology
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____________ – An MR technique used to suppress signal from fat protons, yielding a “water-only” image, utilizing a chemically selective presaturation pulse
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Fat Saturation
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________ – the process of utilizing specific sequence parameters to null signal from fat in the MR sequence, as in STIR, for example
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Fat Suppression
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_____________ – the property of being strongly attracted to either pole of a magnet.
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Ferromagnetism
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________________ – A technique used to suppress fluids, utilizing a long echo time (TE) coupled with a long Inversion Time (TI)
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FLAIR – FLuid Attenuated Inversion Recovery
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_________ – the angle to which the longitudinal magnetization is tipped into the transverse plane, following the initial RF excitation pulse
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Flip Angle
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______________ – an MR technique used to reduce artifacts from spin phase effects through the use of additional gradient pulses. Also known as Gradient Moment Nulling
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Flow Compensation
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_______ – the invisible lines of force that extend around a magnetic field, with the greatest strength/force being at the two poles/ends of the magnet
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Flux
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_______________ – the mathematical process of converting raw data into an image suitable for display
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Fourier Transform
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__________ -- a time-based electrical signal that is detected in a nuclear magnetic resonance spectrometer, that is produced by induction from the motion of the magnetic moments of nuclei, that decays with time (T2*), that can be converted to a more conventional frequency-based signal using analysis by Fourier transforms;
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Free Induction Decay
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________ – the number of times that a periodic function or vibration repeats itself in a specified time. It is usually measured in hertz (Hz),
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Frequency
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_________ – the process of locating an MR signal in one dimension by applying a magnetic field gradient along that dimension during the period when the signal is being received, utilizing differences in frequencies along the same row in order to spatially differentiate one location from another
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Frequency Encoding
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_________ – A non-toxic paramagnetic contrast agent used in MR imaging. The infusion of gadolinium based paramagnetic contrast agents (GBCA’s) shortens the T1 (and T2) times of tissue, dependent upon concentration
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Gadolinium
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_________ – Due to the symmetry of the matrix to be sampled, a little more than half of the raw data is necessary to be acquired, reconstructing the remaining data to complete the image, greatly reducing scan time
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Half-Fourier
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___________ – Mathematical computation converting the collected raw data signals into images using Fourier Transform
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Image Reconstruction
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_______________ – MR sequence that begins with 180º RF inverting pulse followed by 90º RF excitation pulse, then 180º RF refocusing pulse
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Inversion Recovery
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_________ – The time between the initial 180º RF and the 90º RF excitation pulse in an Inversion Recovery sequence
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Inversion time (TI)
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______ – Atomic nuclei that contain the same number of protons but differ in the number of neutrons in the nucleus of the atom
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Isotope
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_________– data acquisition matrix containing raw image data prior to image processing.
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k-space
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_______– the magnetic and thermal environment through which nuclei exchange energy in longitudinal (T1) relaxation
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Lattice
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____________ – MR technique utilized to image flowing blood and specific vasculature structures
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Magnetic resonance angiography (MRA)
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_______________________ – MR technique which quantitatively assesses the mechanical properties of tissues, based on the propagation of shear waves
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Magnetic resonance elastography (MRE)
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_____________ – MR technique generating a spectrum of metabolites in a specific volume of interest
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Magnetic resonance spectroscopy (MRS)
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____________ – an MR technique using a series of echoes following a single excitation pulse, usually in the form of 180º RF pulses that generate images
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Multi-echo imaging
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________ how many times each line of k-space data is acquired during the scan, or how many times each slice is repeated to gain signal and reduce noise, improving SNR
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NEX
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____________ – A scan time acceleration technique which requires the use of a phased array coil to reconstruct an image in less time than conventional imaging
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Parallel Imaging
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_________ – property of magnetism signifying weak magnetic properties due to its unpaired electrons. IV Gadolinium contrast is an example of a paramagnetic substance
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Paramagnetic
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____________ – a loss of resolution due to excessively large voxels, typically caused by slices that are too thick
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Partial volume averaging
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__________ – a term describing the degree to which precessing nuclear spins are synchronous
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Phase coherence
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_______ – an MRA technique based on the speed of the vessels of interest, utilizing velocity encoding (VENC)
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Phase contrast
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_____________ – the process of locating an MR signal along the phase axis, directly correlating spatial resolution and scan time with the number of phase encodings in an MR image
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Phase encoding
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_______________ – an image minimizing T1 and T2 effects, with contrast primarily dependent upon the density of protons in the imaging volume
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Proton Density weighting
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__________ – magnetic field gradient applied during the moment when the echo is formed, and is responsible for frequency encoding in the image
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Readout gradient
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_______ – the process of returning out-of-phase magnetic moments to phase coherence, instigated by applying a 180º RF pulse (spin echo) or reversing a magnetic gradient (gradient echo)
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Rephasing
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_________ – is the speed rate of ascent or descent of a gradient from zero to its maximum amplitude, either positive or negative
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Slew rate
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_____________– the ability to define adjacent points in an image
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Spatial resolution
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________ – An MRI pulse sequence whose signal is an echo resulting from the refocusing of magnetization after the application of 90º and 180º RF pulses
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Spin echo
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_____________________ – A gradient echo sequence in which a non-zero steady state develops for both transverse and longitudinal components of magnetization
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Steady-state free precession
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_______– Short TI Inversion Recovery: a version of the Inversion Recovery pulse sequence where the inversion time (TI) is set to 0.69 times the T1 of fat, nulling the signal from fat at the specific field strength in which it’s being acquired
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STIR
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_________ – the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone
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Syncope
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________________ – MRA technique relying on flow related enhancement to distinguish between stationary spins and flowing spins
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Time of Flight (TOF)
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_____________ – MRA technique used for encoding flow velocities
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Velocity Encoding (VENC)
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