19: MSK Imaging Flashcards
Why is ionizing radiation dangerous?
Disrupts molecular bonds -> produces damage to tissues/DNA
What happens if pt receives a high dose of radiation (not possible from imaging)
Radiation sickness
Interpreting X-rays: high, intermediate and low density
High density: white; bone/metal
Intermediate density: grey; soft tissue, fluid-filled organs
Low density: black; air-filled organs
Magnification artifact in X-ray
Structures closest to the projector will appear larger
What does DEXA stand for?
Dual-energy X-ray absorptiometry
Two ways to increase resolution in CTs
- Combine multiple images in a single plane
2. Take “thinner” slices (more images in the same amount of time)
CT Angiography
Using iodine-based contrast to improve context between structures
Two possible risks of using contrast dye in CTA
- Processing by kidneys can cause injury
2. Rare but possible allergic reaction
How MRIs work: 4 steps
- Magnetic field lines up randomly aligned protons
- Radiofrequency pulse -> changes proton alignment
- Radiofrequency pulse deactivates -> protons realign with magnetic field, release energy -> read by MRI machine
- Can use variations of this sequence to produce different types of images
Common reading convention of MRI
Sagittal plane slices (same as CT)
What type of material is present in the transducer of an Ultrasound?
Piezoelectric material
Low vs high frequency transducer in US
Lower frequency: more penetration + lower resolution
Higher frequency: less penetration + higher resolution
What is nuclear medicine used for?
To measure physiology, not anatomy
How does nuclear medicine work?
Radioactive radiotracers injected -> bind targeted physiological process -> produce gamma radiation, which is visualized by camera
