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computed tomography (CT)
produces axial and coronal views
image is reconstructed by computer and recorded as:
matrix of individual blocks called voxels
each square of image is a pixel
each pixel is assigned a CT number (proportion to attenuation of x-ray beam)
CT range:
-1000 - +1000
air is -1000
water is 0
dense bone is +1000
advantages and disadvantages of CT
advantages:
eliminates superimposition of structures
higher contrast resolution
can differentiate soft tissues
disadvantages:
metallic artifact
higher radiation dose
CT applications
diagnosis of maxillofacial complex (tumor, trauma, inflammation)
salivary gland disease
TMJ
cone-beam computed tomography (CBCT)
produces 3D imaging of jaws and teeth
uses pulsed cone-shaped x-ray beam that produces 150-600 "basis" images
composed of voxels:
superior dimensional accuracy in reconstruction process of raw data
image can be viewed in axial, sagittal, coronal, and cross-sectional planes
CBCT applications
oral and maxillofacial diagnosis
ortho and endo planning
TMJ abnormalities
3rd molar extractions
airway assessment (sleep apnea)
bone graft assessments
dental implants:
assess bone quantity and quality, shape and anatomy
virtual implant placement to form surgical template
NOT recommended for caries detection
identifies bone defects and furcation involvements
magnetic resonance imaging (MRI)
T1-weighted image:
short TR and TE
high signal in fat and bone marrow
intermediate signal in muscle
low signal in air, cortical bone, fibrocartilage, ligament
good for anatomic detail structures
T2-weighted image:
long TR and TE
high signal in water (edema, cystic lesions, CSF)
good for pathology
MRI applications
internal derangements of TMJ (ADD with/without reduction)
diagnosis of soft tissue neoplasms
infectious diseases
pathology related to cranial nerves
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