Lecture 1- Intro to Radiology Imaging Flashcards
Terminology
CXR
chest xray = chest radiograph = chest plain film
Terminology
image
any singular image (doesn’t matter type)
Terminology
study/examination
collection of images
Terminology
wet reading
archaic term for immediate or “stat” intercreptation
Terminology
PACS
Picture Archiving, Communications, and Storage System (the system that archives and stores images for later retrieval)
Terminology
Films vs Computed Radiography
- films: printed
- computed: electronic (almost everything now)
Radiographs/CT
what are the 5 radiographic densities
- air (least dense, black)
- fat
- water
- bone
- metal (most dense, white)
Radiographs/CT
differentiate radiolucent and radiopaque
- radiolucent: least dense (air); black
- radiopaque: most dense (bone); white
Film Quality
3 factors that affect quality of CXR?
- penetration
- inspiration
- rotation
Film Quality
differentiate underpenetrated and overpenetrated
- underpenetrated: too white
- overpenetrated: too black
Film Quality
how to know if CXR is penetrated correctly?
you can see the thoracic spine faintly through the heart shadow
Film Quality
how to evaluate for rotation
- R & L clavicle heads are equally distant from the spinous process
why are 2 views often required for xrays
because they are 2D pictures of 3D objects
describe silhouette sign
when 2 structures of the same density are in anatomical contact, their margins cannot be seen on film
* ex: the heart rests on the diaphragm, so you cannot see where one starts and the other ends.
describe CTs
- digital image generated by multiple xrays which are generated into a slice of the body
- generated to be axial, coronal, sagittal, and 3D images
CT
denser structures have higher what?
measurement
hounsfield units (more white)
CT
describe windowing
manipulating images to maximize the display of different densities (ex: bone windowing, soft tissue windowing)
CT
why is contrast administered
to increase density differences between tissues
CT
describe IV Iodinated contrast
- opacifies tissues and organs w/ high blood flow
- excreted by the kidneys
CT
potential adverse effects of iodine contrast
- mild reaction: n/v, itching, hives, irritation at injection site
- rare: severe anaphylaxis, death
CT
which patients are at a higher likelihood of a contrast rxn?
3
- asthma
- severe atopy
- hx of prior rxns
CT
which renal conditions should contrast be used in caution with?
renal insufficiency (diabetes, multiple myeloma)
CT
what tests do you order to clear someone with renal insufficiency for contrast?
- BUN (> 21)
- Creatinine (> 1.5 mg/dL)
CT
what to do with patients taking metformin?
stop metformin for 48 hrs after contrast dye due to increased risk of lactic acidosis
CT
describe barium contrast
- oral or enema contrast used to visualize GI tract
- this is not absorbed by the body
CT
contraindication of barium contrast
- suspected bowel perforation
- before bowel surgery
CT
what is a double contrast study (GI)
air + barium
MRI
differentiate T1 and T2 imaging
- water is dark on T1
- water is bright on T2
MRI
contraindications
- pregnancy
- presence of ferromagnetic object
MRI
most common contrast agent for MRI?
gadolinium
MRI
contraindications of gadolinium?
- severe renal disease
- caution in moderate renal disease
due to risk of nephrogenic systemic fibrosis (rare)
CT vs MRI
- CT more readily available, faster, cheaper
- MRI has better soft tissue contrast, no radiation, no iodinated contrast, but can be problematic for pts with claustrophobia
US
advantages
6
- low cost
- tolerable
- readily available
- safe (no rad)
- portable
- real time imaging
US
disadvantages
4
- operator skill dependent
- more difficult to interpret
- not good for bone or lung imaging
- may be difficult to see in obese patients
US
types of US
- gray scale (B mode)
- color doppler (blood flow in vessels)
- spectral doppler (determines direction, velocity, and acceleration of blood flow in vessels)
