SAQs - Chapter 12
1. What term is used to describe the net displacement of diffusion spins across a tissue?
Apparent diffusion coefficient (ADC).
2. What are the units of this parameter?
mm2/s.
3. What is the extrinsic parameter that controls the amount of diffusion seen in an image?
b factor or value.
4. How is this parameter defined?
The duration, amplitude and interval of the sensitizing gradients.
5. What signal intensity is an area of abnormality likely to have on an ADC map?
Hypointense.
6. What signal intensity is an area of abnormality likely to have on a trace image?
Hyperintense.
7. What sequence should be used in perfusion imaging when the transient change in T2* is measured?
GE-EPI perhaps with echo shifting where the TE is longer than the TR.
8. Why is this sequence appropriate?
For speed and to accentuate T2* effects with a gradient echo.
9. What does BOLD stand for?
Blood oxygenation level dependent.
10. What are the single voxel techniques used in MR spectroscopy?
STEAM and PRESS.