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year 2 > radiology 1 > Flashcards

radiology 1 Flashcards

1
Q

Bayesian analysis

A

posttest odds = pretest odds * likelihod ratio

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2
Q

degree of attenuation of xray beams based on 3 things

A
  1. density
  2. thickness
  3. energy of xray beam
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3
Q

radiolucency -> radiodensity of common materials (6)

A
  1. air = most radiolucent- looks black
  2. fat
  3. water
  4. bone
  5. contrast
  6. heavy metals= most radiodense - looks white
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4
Q

digital storage systems for info

PACS

DICOM

RIS

HIS

A

PACS= picture archiving and communication systems

DICOM= digital imaging and communication in medicine

RIS= radiology information system

HIS= hospital information system

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5
Q

orienting an image on xray

AP/PA view

lateral

hands/feet

A

hang anatomically- like u are looking at the person

laterals are hung in same direction they are taken

hands and feet hand so you are looking at dorsal surface and digits face up

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6
Q

satisfaction of search (2)

A

can lead to false negative

when detection of 1 radiologic finding interferes w/ that of another

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7
Q

hounsfied units

def

3 common #s to know

A

def: measure of how much attenuation occurs in each pixel of CT scan

air = -1000

water = 0

bone = 1000

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8
Q

artifacts in CT

why they are caused

3 things that can cause them

A

caused by partial volume average of each voxel (less of a problem with new machines with thinner slices)

caused by:

  1. motion (eg cardiac motion)
  2. metal artifacts- distorts tissue around it
  3. beam hardening = algorithm filters out areas of low energy - which is high density places
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9
Q

risks of CT contrast (3)

A
  1. allergic reactions

can be mild (rash ) => severe -HTN, swelling, CV collapse*

  1. renal failure (creatinine >1.5-1.8)**

diabetics, dialysis pts, multiple myelomas

  1. contrast extravasation = contrast in soft tissue instead of vein
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10
Q

what type of contrast is okay for pts on dialysis?

what type of contrast is not okay for pts on dialysis?

A

OKAY: IV CT contrast

NOT OKAY: MRI contrast

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11
Q

3 advantages of CT

A
  1. fast
  2. high resolution
  3. multiplanar reformatting (3D)
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12
Q

3 disadvantages of CT

A
  1. radiation**
  2. possible risks
  3. possible artifacts
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13
Q

ionizing radiation

def

why we care

A
  1. electromagnetic waves that have the potential of creating an ion by knocking an electron out of its valence shell
  2. can damage DNA
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14
Q

radiation safety

acronym

trade-off

A

ALARA- as low as reasonably achievable

trade off btwn dose and quality of image

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15
Q

2 biological effects of radiation

examples of each

linear no threshold model (assumption)

A
  1. deterministic effects - means its dose dependent and there is threshold below which there is no effecteg; epilation, permanent sterility, cataracts
  2. stochastic effects= random = not dose dependent and no lower threshold
    a. k.a. cancer from radiation (leukemia, breast, thyroid)

** linear no threshold model (assumption)= risk is directly proportional to dose at all levels. sum of several small exposures can = 1 large exposure

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16
Q

MRI pulse sequences

A
17
Q

what is MRI contrast material?

risks of MRI contrast (3)

A

material = gadolinium

risks:

  1. nephrogenic systemic fibrosis = fibrosis of skin, joints, eyes, organs (= fatal)
  2. pts with severe kidney failure or on HD - contraind EGFR <30
  3. contraI for pregnant women
18
Q

advantages of MRI (6)

A
  1. no ionizing radiatio
  2. lots of info on soft tissue
  3. sensitive to contrast enhancement
  4. ability to obtain 3d dataset
  5. get angiograms w/o contrast
  6. gadolinium is not as allergenic as iodinated compounds (CT)
19
Q

disadvantages of MRI (6)

A
  1. long scan times
  2. motion artifacts
  3. artifacts- eg surgical hardware
  4. expsensive
  5. many pts have contra I
  6. claustrophobia
20
Q

MRI safety

4 zones

A

the magnet is always on full strength*

zone 1: public accessible

zone 2: supervised access, where screening by MRI staff occurs

zone 3: restricted area, prescreened pts and staff

zone 4: magnet room

21
Q

MRI dangers (7) (first 4 are **)

A
  1. missile effect*
  2. field interatcion w/ medical devices*
  3. torque on implanted devices*
  4. gadolinium risks*
  5. thermal effect
  6. cryogens
  7. acoustic noise
22
Q

MRI safety signage

A

MR in a box = MR safe

device/ implant non-magnetic, non-electrically conductive, non-RF reactive = safe for MRI

MR in a triangle= MR conditional

device/implant may contain magnetic, electrically conductive or RF reactive components- but is safe in the proximity of the MR

MR circle w/ line= unsafe

device/implant significantlly ferromagnetic

23
Q

general rules to follow for ordering films (1)

for fx: order

soft tissue

infection

A

always order plain films first

fx: 1. plain films
2. CT
3. bone scan and MRI

soft tissue injury

  1. MRI
  2. US

infection

  1. xray
  2. MRI w/ & w/o contrast
  3. bone scane
  4. indium WBC scan

year 2 (24 decks)

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