Imaging (Willett) 080916

Question 1

 List the commonly available imaging modalities

Answer 1

X-Ray
Ultrasound
Angiography, contrast
Nuclear medicine
CT +/- contrast
MRI +/- gadolinium

Question 2

 For each, list mechanism, common uses, utility,
and toxicity

X-Ray

Answer 2

Two dimensional

Can visualize down to 2-4 mm

Differentiate air, fat, fluid/solid organ, bone

Toxicity - radiation, minimal

Common uses - chest, abdomen, bones

Question 3

 For each, list mechanism, common uses, utility,
and toxicity

Ultrasound

Answer 3

Sound wave reflection, two-dimensional

Can visualize down to 2-4 mm, fluid vs. solid

Sound: reflected back by air and hard objects (bones and stones), travels unimpeded through FLUID, partially reflected by SOLID ORGANS

Toxicity - thought to be nil (no radiation)

Common uses - heart, gallbladder, pregnancy

Problem - areas with bone (brain) and lots of air (lungs/abd) can be hard to visualize

Question 4

 For each, list mechanism, common uses, utility,
and toxicity

Angiography

Answer 4

Basically same as X-ray except using an intravascular contrast dye, two-dimensional or 3-D

Can visualize to

Question 5

 For each, list mechanism, common uses, utility,
and toxicity

CT +/- contrast

Answer 5

X-ray - 3-D

Can visualize to 1mm

Differentiates tissues of differing Hounsfield unites (many more gradations than plain X-ray)

Contrast shows areas of increased blood flow or inflammation, can do angiography

Toxicity - radiation (much higher), contrast

Common uses - trauma, brain, tumors

Fairly expensive ~$1,000

Question 6

 For each, list mechanism, common uses, utility,
and toxicity

Nuclear Medicine

Answer 6

Administration of radiation-emitting material, with subsequent scanning for emission

2- or 3-D

Visualization often less fine than other modalities (esp the 2-D)

Differentiates tissues with more vs. less uptake

Toxicity - radiation (often less than CT)

Common uses - myocardium (i.e. stress test), pulmonary embolism, cancer/inflammation

Fairly expensive, variable ~$500-$1,500

Question 7

 For each, list mechanism, common uses, utility,
and toxicity

MRI

Answer 7

3-D MR

Can visualize

Question 8

 Estimate the magnitude of the risk of

malignancy from radiation and list its influences

Answer 8

Link of cancer and other outcomes to low/moderate radiation exposures

Levels of common radiation exposures

Cancer risk based on age, gender (breast), site, underlying risk (e.g. BRCA)

Increased cancer risk often delayed by decades, so very hard to track/prove

Question 9

 Identify populations at higher risk from imaging

Answer 9

Young

Female (breast)

Pregnant

Renal dysfunction (b/c of contrast, gadolinium)

Question 10

 Define and describe importance of

incidentaloma

Answer 10

Many imaging studies show abnormalities having nothing to do with the reason the test was ordered.

Sensitivity tends to correlate negatively with specificity

More “incidentalomas” the finer the visualization

Try to use cheaper, less sensitive, and less toxic imaging if adequate for the task