Radiology for the PA Student Flashcards
why is it called an Xray?
it was unknown what was causing the glow
why it is called a wet read?
X-rays had to be developed with chemicals
how are X-rays recorded now?
photo-sensitive cassette stored on PACS (picture archiving communications storage)
what 6 images can be stored in PACS?
- conventional radiography (xray)
- CT
- MRI
- ultrasound
- fluoroscopy
- nuclear medicine
what are 2 advantages and 2 disadvantages of xrays?
inexpensive
convenient
ionizing radiation
just 5 basic densities in b/w
what are the 5 basic densities seen in X-ray?
- air
- fat
- soft tissue/fluid
- both have same density on plain films so can’t tell difference between heart muscle and blood
- calcium
- metal
- absorbs all x-rays and appears the whitest
what is the most common X-ray support structure?
ceiling support system
what is the effect of radiation?
- cumulative over lifetime
- deposits energy on its path thru body
- free radicals produced
- ↑ likelihood cancer
how long does abdominal CT radiation linger in the body?
4 years
how long does extremity radiation linger in the body?
1.5 days
how do health professionals protect themselves from radiation?
lead apron +/- thyroid shield
where is the safest place to stand in relation to the xray machine?
90degrees to incident beam
what is the initial imaging study of choice following skeletal trauma?
xrays
what are the 4 commonly evaluated disorders with xray?
chest
abdomen
pelvis
musculoskeletal system
what are the 3 positions people are in for xray?
seated
standing
supine
what is lateral placement?
what is decubitus placement?
Lateral decubitus placement/purpose?
- 90 degrees to the AP or PA
- recumbent (lying down) to horizontal beam
- laying on side
- to see air/fluid levels
- up side shows air
- down side shows fluid
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All extremity x-rays should be ordered with how many views?
Most extremity projections involve how many views?
- 2
- 3
what is an oblique view?
half way between lateral and ap/pa views–> at an angle
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why are heart xrays taken PA?
xray projection magnifies as it goes through so keeping the heart closest to the screen helps to give accurate size
patient fell on ice on butt, do you xray coccyx?
no
- radiation to gonads
- doesn’t impact treatment, still sit on donut
under penetrated xrays are what color?
white
What is the most important question ask female patients if they are around 12-50 before giving x-ray?
are you preggers
What views should you always order when getting an xray?
AP/Lateral usually suffice, but get oblique if able
- In 5% of fractures, the fracture line is only visualized on one of the two orthogonal projections
Overpentrated films will be to? why
dark because too much energy went through-because button was held for too long
what is the most important study of musculoskeletal evaluation?
taking a patients history
what are the ABCS of reading an xray?
- Adequacy (penetration, alignment)
- Bones (Lucent lines, deformities)
- Cartilage (joint space, defects)
- Soft tissue (swelling, effusion)
what orientation is extremity xray viewed?
fingers/toes up
what are the 4 geometric qualities of xrays?
magnification (size)
distortion (misrepresentation size, shape)
elongation (shape)
foreshortening (shape)
what is body habitus?
objects at different levels projected onto image as different sizes (large object near screen same size as small object farther from screen)
when is shape distortion beneficial?
to move overlying anatomy out of the way or see farther between disc spaces
what is foreshortening?
magnifying one side of a long bone by keeping the area of interest closer to source
what is a CT scan?
rapidly spinning array of xrays to ↑ sensitivity
CT is the study of choice for?
abdominal trauma
what 3 things is CT better at identifying than xray?
- fracture extension
- articular step off/gap
- aortic injuries in chest trauma
What does MRI imaging use to make an image?
energy derived from hydrogen atoms pulsing in magnetic field
what is a pro and con of MRI?
pro: no ionizing radiation
con: expensive
MRI is better than Xray and CT at identifying what?
- occult fractures-(A fracture is a broken bone. Occult means hidden. An occult fracture is one that does not appear well on an X-ray.)
- also useful for tendon, muscle, ligament eval
what is the cornerstone of neuroimaging?
MRI
MRI is the modality of choice for what?
- disc herniation
- & internal derangement of joints (ACL tear)
how does ultrasound work?
produces images using acoustic properties of tissue
what are 3 pros for ultrasound? what is it useful for?
pros: no ionizing radiation, safe in children, pregnancy, less expensive and portable
useful for soft tissue & blood flow eval, locate foreign body in soft tissue, guide joint injections
ultrasound is commonly used in trauma to asses which 2 soft tissue injuries?
Achilles tendon rupture
quad tendon rupture
what is a FAST exam? what does it identify?
focused abdominal sonography for trauma
to identify free peritoneal fluid
what is fluoroscopy?
- real time xray constant low dose ionizing radiation
- but radiation doses are GREATER than plain x-ray as so many more images acquired for every minute of fluoro time
- When you swallow the contrast and doctors can see it moving through your GI system in real time
which 3 things are commonly evaluated with fluoroscopy?
motion of joints
visualize GI/GU with contrast
fracture reduction visualization or placement of pins/hardware
what is nuclear medicine? what 3 things is it used to detect?
- patient is source of ionizing radiation (given source)
- used to detect: mets, occult/stress fractures, insufficiency fractures
- Insufficiency fracture is a subgroup of stress fracture. Unlike the other subtype (ie, fatigue fracture), insufficiency fracture is caused by normal or physiologic stress upon weakened bone. Loss of bone trabeculae decreases the bone’s elastic resistance.
what is the timeline for nuclear medicine bone scan results?
80% positive within 24hrs injury
95% within 72hrs
“that 95% of scans are positive within 72 hours. The half life of technetium (Tc-99m) half-life is 6 hours. So within 72 hours, the radiotracer is excreted from the body. So doing a nuclear medicine bone scan in 3 days is not ideal because there would be not enough tracer in the body to do the scan.” The ideal time then to read them is right away.
what are the 3 most common indications for ordering an imaging study?
- traumatic injuries
- sports/overuse
- arthritis
- arthritis affects approx 10% of men and 18% of women over 60 years old worldwide
what studies should you start with?
simplest/least expensive
necessary for diagnosis & guiding treatment
what resource is useful for determining which studies to preform?
American College of Radiology (ACR) appropriateness criteria
suggested xray views for AC joint?
AP with and without weights
suggested xray views for chest?
PA, lateral (full inspiration)
suggested xray views for clavicle?
AP, axial (20 deg cephalad)
Suggested xray views for humerus?
AP, lateral
suggested xray views for ribs?
AP, obliques (bilateral)
upper: inspiration
lower: expiration
suggested xray views for SC (sternoclavicular) joint?
AP, obliques (bilateral)
suggested xray views for shoulder?
AP, Grashey, Y-scapular view
suggested xray views for elbow?
AP, lateral, external oblique
suggested xray views for fingers?
AP, lateral affected finger, oblique of hand
suggested xray views for hand?
AP, lateral, oblique
suggested xray views for thumb?
AP, lateral, oblique
suggested xray views for hip?
AP pelvis, frog leg later, lateral affected hip
suggested xray views for femur?
AP, lateral
suggested xray views for foot?
AP, oblique, lateral
suggested xray views for knee over and under 40 yo?
under 40: AP, lateral, tunnel, sunrise
over 40: bilat PA weight bearing (30 degree PA flexed view), bilateral tunnel, lateral of affected knee, bilateral sunrise
suggested xray views for tib-fib?
AP, lateral
suggested xray views for ankle?
AP, mortise, lateral
suggested xray views for heel?
axial, lateral calcaneus
What is the Rosenberg view ? Why is it useful?
45 degree flexion, PA, WB with patella touching image receptor
- useful for for arthritis