Handbook Of MRI Tecnique: Ch 2

Question 1

What is SNR?

Answer 1

Signal to noise ratio is the amplitude of signal received by the coil to the amplitude of noise.

Question 2

How can SNR be increased?

Answer 2

1. Using SE and FSE pulse sequences
2. Long TR and short TE
3. Flip angle of 90°
4. Well tuned and correctly sized coil
5. A coarse matrix
6. Large FOV
7. Thick slices
8. Using narrowest receive bandwidth
9. As many excitations and signal averages as possible

Question 3

What is CNR?

Answer 3

Contrast to noise ratio is the difference in the SNR b/w two adjacent areas

Question 4

How can the CNR between pathology and other structures be increased?

Answer 4

1. Administration of contrast
2. Utilization of T2 weighted sequences
3. Selection of magnetization transfer (MT) sequences
4. Suppression of normal structures via sat bands or sequences that null signal from certain tissues (FLAIR, STIR)

Question 5

What is spatial Resolution?

Answer 5

Spatial resolution is the ability to distinguish between two points as separate and distinct. It is controlled by voxel size.