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108 Cards in this Set
- Front
- Back
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what is radiation biology
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the study of how ionizing radiation affects tissue
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1R =
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10 mGy = 10 mSv
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what are the 2 types of biologic effects that are seen with radiation
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stochastic
non-stochastic (deterministic) |
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stochastic
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lifetime dose determines probability of having sx, there is no threshold that determines when sx will occur
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deterministic effects
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dose determines severity of sx, must cross a threshold before effects are seen
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example of a stochastic effect
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radiation induced cancer and genetic effects
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example of a deterministic effect
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cell is killed --> degenerative changes in exposed tissue
cataracts, erythema, fibrosis, hematopoietic damage |
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when will a deterministic effect be seen in radiology
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during a long lengthy fluoroscopic procedure
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when will a deterministic effect be seen in radiology
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from lots of imaging studies, threshold required
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describe the interaction between radiation and tissue
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ionizing radiation energy is deposited randomly and rapidly via excitation, ionization, and thermal heating
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what are the direct effects of ionizing radiation
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DNA, RNA ettc is directly ionized or excited
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what are the indirect effects of ioniziation radiation
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radiation interacts within the medium (ex cytoplasm) --> free radicals production
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where, in the cell, are radiosensitive targets located
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in the nucleus
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what is the mechanism behind cell death from radiation
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damage to DNA, single strand breakage from low dose radiation, double-strand breakage from high dose radiation
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which cells are most radiosensitive
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cells with:
high mitotic rate long mitotic future undifferentiated |
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when in the cell cycle are cell most sensitive to ionizing radiation
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during metaphase and G2 (RNA synth)
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when in cell cycle is cell least susceptible to radiation
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during DNA synth (S)
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what role does o2 play in radiation
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presence of o2 --> more damage (free radicals)
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what are the 2 types of healing that can occur with radiation damage
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regeration and repair
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examples of repair seen in radiation damage
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replacement of damaged tissue by different type of tissue (ex fibrosis)
organ is not returned to its pre-radiated state |
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examples of regeneration seen in radiation damage
what tissue does this occur in |
replacement of damaged cells by the same cell type
organ is retunred to original state occurs in radiosensitive tissue (brain, skin, GIT, bone marrow) |
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what is the dose --> temporary sterility in women
permanent sterility |
1.5 Gy acutely
6.0 Gy acutely |
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what is the dose --> temporary sterility in men
permanent sterility |
2.5 Gy
5.0 gy |
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what is the dose --> cataracts acutely
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2 gy in small % of ppl exposed
>7 Gy will always --> cataracts |
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what is the dose --> cataracts over protracted amount of time
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2 months: 4Gy
4 months: 5.5 Gy |
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what is the difference between senile cataracts and radiation induced cataracts
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senile cataracts typically develop in anterior pole of the lens
radiation induced begins with a small opacity in the posterior pole and migrate anteriorly |
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what is acute radiation syndrome
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charateristic clinical response when whole body is subjected to large acute external radiation exposure
in order of occurrence with increasing radiation dose: 1st: hematopoietic syndrome 2nd: GI 3rd: neurovascular syndrome |
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sequence of events in acute radiation syndrome
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prodromal symptoms w.i 6 hrs of exposure
no sx during latent pd (up to 6 wks) manifest illness stage = onset of organ system damage lasting 2-3 wks higher risk of ca and genetic abnormalities in future progeny if pt survives |
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when should acute radiation syndrome be treated
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within the first 6-8 wks
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which is the risk estimation model generally used to evaluate radiation --> ca
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multiplicative risk
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what is multiplicative risk
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after a latent period, excess risk is a multiple of teh natural age-specific ca risk for the population in question
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additive risk model
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not raelly used anymore
fixed or constant increae in risk unrelated to spontaneous age specific ca risk |
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latency pds of leukemia
solid tumor |
10 yrs
25 yrs |
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what is the best estimate of radiation induced mortality at low exposure
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4%/ Sv/yr
5%/ Sv/yr if children are included |
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estimation of radiation induced mortality at high doses at high dose rate
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8% per Sv
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what are the 3 phases in gestational pd and what role does radiation play
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pre-implantation stage (day 0-9), cells will either live or die
extended pd of major organogenesis (9-56 days), if >1 Gy --> CNS abn, growth retardation after >100 mGy fetus |
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recommendations for abortion and radiation exposure to fetus
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not indicated if exposed <14 d
between 2nd - 8th week, not advised if dose <150 mGy, if >150 mGy, may be indicated all in all, the probability of giving birth to a normal child is very likely |
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what are the HU for a blood clot
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65HU
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HU for air?
metal? water fat? muscle |
-1000
+1000 0 -120 +40 |
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imaging findings of epidural hematoma
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lentiform
mass effect look for fx blood can cross falx, tentorium will not cross sutures mass effect |
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tx of epidural hematoma
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emergent evacuation
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imaging findings of acute subdural hematoma
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hyperdense
crescent shaped can cross sutures does not cross falx or tentorium does not enter sulci mass effect |
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tx of acute subdural hematoma
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evacuate if large
f/u scans |
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appearance of chronic subdural hematoma
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can get fluid-fluid levels
hyodense and hyperdense blood |
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isodense subdural hematoma appearance
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isodense
sulci do not extend all the way outward |
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person who will get an isodense subdural hematoma
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coagulopathy
anemia evolution fo blood products |
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appearance of SAH
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enters sulci, cisterns, and ventricles
trauma shows lateral convexities |
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most sensitive site for sah
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interpeduncular cistern is most sensitive
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appearance of cerebral contusion
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coup is ipsilateral
countrecoup is contralateral hyperdense surrounded by hypodense edema |
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appearance of subcortical injury
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disruption of penetrating bv
gray-white interface blurring |
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presentation of subcortical injury (diffuse axonal damagee)
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ct doesn't look so bad, but pt is comaose... suspect subcortical injury and get mri (diffues axonal damage)
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location of vasogenic cerebral edema
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extracellular
white matter > gray matter |
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location of cytotoxic cerebral edema
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intracellular
gray matter > white matter |
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appearance of cerebral edema
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gray white interface obscured
sulcal effacement |
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whcih bv are most involved with traumatic dissection
morphology of bv s/p dissection |
cervical arteries
hemorrhage within arterial walls (intimal flap, crescentic shape) |
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which bv is involved if aneurysmal sah is interhemispheric
sylvian |
anterior communicating
mca |
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what is the location if there is an ICH from htn?
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deep grey structures
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how should a lobar ICH be handled
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must SEARCH for underlying cause
do MRI, MRA, MRV, etc repeat imaging if - |
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complications of ICH
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hematomas can expand
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what are the 2 most common type of ca in women
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skin
breast |
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ratio of women diagnosed with breast ca in their lifetime
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1:8
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a primary tumor >2 cm has what risk of LN spreaed
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>20%
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most common distant location for breast ca mets
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lung
liver bone |
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what population has an increase in estrogen and progesterone - breast ca
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aa
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what group of women has the highest mortality from breast ca?
why? |
aa
?more aggressive dz, increased stage at presentation, psychosocial factors? |
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what reduction in mortality from breast ca did mammo result in in early studies
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30%
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now: what is the mortality reduction seen in screening mammos in 50-69 yo?
40-49 yo? |
16-35%
15029% |
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why is the mortality reduction less in younger women with screening mammos
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dense breasts
rapidly growing tumors lower incidence |
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cause of mortality reduction related to mammo
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due to detection of ca at smaller size, earlier stage
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how much earlier can a mammo detect breast ca compared to sbe/cbe
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3-5 yrs before it is palpable
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definition of a screening test
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screening is used to evaluate a population of asx ppl at risk for a dz
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goals of a good screening test
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high sensitivity
lower specificity is ok low false - rate |
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how sensitive is a screening mammo in a woman >50
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98% if fatty breasts
84% in dense breasts |
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specificity of screening mammo
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82-98%
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who gets a diagnostic mammo
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pts with si/sx
pts wtih abnormality detected on screening mammo |
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views seen on screening mammo
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cc
mlo |
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popcorn calcs seen on mammo: benign/malig?
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benign, probably calcified fibroadenoma
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how should calcs be handled on mammo
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most are benign and can be dismissed
goal is to look for new or increasing calcs, or ones with suspicious morphology |
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what are the limitations of mammo
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5-15% of breast ca are not detected on mammo
a negative mammo should not deter w/u of a clinically suspicious abnormality |
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what type of ca is occult on mammo
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lobular ca
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recommendations for mammos and cbe
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annual mammo >40 yo will reduce mortality by 30-50%
cbe annually if >40 yo |
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imaging features of OA
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distal and mp joints most commonly involved
no osteopenia +osteophytes asymmetric joint space narrowing subchondral sclerosis |
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imaging features of SLE arthritis
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osteopenia
+ subluxation no osteophytes no erosions no periostitis |
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what are the main diseases that cause joint subluxation, features of each
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sle (no erosions)
RA (+ erosions), osteopenia (periarticular at first), fusiform swelling, diffuse joint space narrowing |
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features of psoriatic arthritis
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cap in pencil
carpals show erosions and increased joint space narrowing sausage digits DIP, PIP, carpals: asymmetric joint space widening and erosions minor subluxation periostitis "mouse ears" |
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descriptions of the different salter fx
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I (S): Superior to physis
II (A): Above metaphysis to physis nto through epiphysis III (L): Lower (epiphysis --> physis) IV (T): Through V (R): Rams... crushes the physis |
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4 types of seronegative arthritides
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reiter's syndrome
psoriatic sacroiliitis ibd |
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causes for posterior dislocation of shoulder
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electric shock
sz trauma |
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when is u/s indicated for evaluating a palpable mass
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<30 yo, lacating, and to determine if cystic vs. solid
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clinical indications for breast mri
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pt w newly dx breast ca
+ BRCA 1/2 prior chest radiation li-fraumeni, cowden syndrome, bannajan-riley-ruvalcala syndrome |
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why should a pt w newly dx breast ca get a breast mri
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to determine the extend of dz in breast
additional unsuspected dz in 16% (ipsilateral breast) 5% have dz in bilateral breasts evaluate tx response |
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which xr study delivers the most radiation
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lateral spine *(lots of bone to absorb radiation)
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what % of radiation exposure is inhaled
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70%
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what is the dose limit exposure
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5 rem/yr
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how to decrease radiation exposure if you are in a room near radiation
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1/D^2 (decreases by distance squared)
shielding (although still has some xr penetration) |
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1 R = 1 rem = .01 Sv
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1R = 1 rem = .01 Sv
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when is MR most likely to occur if a fetus is exposed to radiation
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8-15 wks
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causes of free intra-abdominal air with acute abdomen
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perforating gastric/duodenal ulcer
diverticuli perforation appendix perf colon ca |
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location of bv in hila (L to R0
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97% r and l are equal in height
3% l higher than right |
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things that cause cavitary lesions in the lung
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necrotizing infx (tb, abscess)
necrotizing tumors (squamous cell, most common) necrotizing vasculitis (wegeners, etc) |
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causes for sbo
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adhesions most common
hernia mass intussusception/volvulus |
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what is a crookes tube
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energized by high voltage, electrons move from cathode to anode
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occupational limitis of annual radiation dose
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.05 Sv to whole body, .5 Sv to individual organ, skin, extremities
eye lens, .15 Sv |
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how much radiation can an fetus get if mom is radiation worker
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5 mSv
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radiation limit for general public
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1 mSv
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how to calculate dose equivalent
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DE = absorbed dose x quality factor
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which type of particles have the highest quality factor
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alpha and heavy charged particles (20)
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which type of particles has the lowest quality factor
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x, gamma, or beta rays (1)
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