Intro To Imagery - Self Exam Questions

The vast majority of clinical diagnosis come from through these two non-imagery tasks?

History and Physical Exam

What type of radiation do X-rays use?

Ionizing radiation

Name three imaging methods that utilize ionizing radiation.

Radiographic film, CT, nuclear medicine scan

What are two examples of imaging modalities that use non-ionizing radiation?

Ultrasound and MRI

What are the four types of imaging densities and provide two examples of each?

Air/gas: lungs, gas in intestine

fat: adipose tissue, breasts

soft tissues/water density: blood, solid organs, full bladder

bone & metal: ribs, calcified bones, teeth, metal caps, bullet fragments.

What percentage of all radiographic studies are chest X-rays?

Approximately half

In which two views are chest X-rays taken, and why?

PA & lateral views to better localize any density found on the films.

What are three methods/substances used to enhance film radiography images?

Contrast iodine solution (angiogram), barium swallow/enema (GI series), Technetium-99M (nuclear bone scan).

Describe the process of angiography.

An iodine solution is introduced into a vessel (artery or vein) by a catheter. Film Xray and/or CT are taken at timed intervals. The Iodine metal absorbs xrays rendering a radiopacity (white on negative film) at the location of the iodine - hopefully enhancing the vessels of interest.

What is the advantage of CT over classical film imagery?

3D rendering of large anatomical regions with increased resolution of soft tissues, also especially good for visualizing fine bone structure.

What methods enhance CT imagery?

Oral, intravenous, or intra-arterial contrast material.

What is typically seen on a normal nuclear medicine bone scan?

Bone is a living tissue and is constantly being remodeled so a light background of tracer deposition is normal over all the bones of the skeleton. In areas of high impact and constant movement such as joints a greater amount of deposition of tracer is seen. Tracer is also excreted from the kidney so the kidneys and urinary bladder also shows "normal" enhancement on bone scan.

What processes would show enhanced uptake of tracer on a nuclear bone scan?

Deposition of tracer at the site of increased metabolic activity and osteoblast activity (rapid turnover and formation of new bone). This is found at sites of metastatic lesions of the bone and at sites of bone healing after injury.

What are the advantages and limitations of ultrasound (US)?

Advantages: no ionizing radiation exposure, fast, inexpensive, reliable for screening.

Disadvantages: lower resolution than CT, limited use on areas blocked by bone or filled with air.

What are some indications for the use of MRI?

Brain diseases (infarction & tumors), body cavity tumors, soft tissue injuries with edema, spinal cord injuries.

What are some contraindications for MRI?

Ferrous objects (metal surgical staples & aneurysm clips), pacemakers, implanted medication pumps, some IUDs, nerve stimulator devices.

On T1 weighted MRI, what tissue appears bright white?

Fat

What is best visualized as bright white on T2 weighted MRI?

CSF and edema

What is interventional radiology?

A subspecialty of modern imaging that directly treats disease through minimally invasive percutaneous access to internal structures.