1. Chapter 11 Lecture
Mark D. Herbst, M.D., Ph.D.

2. Acquistion Time and Protocol Optimization
Time of scan = (# phase encoding steps xTR x NEX)/ETL

3. Ways to save time Reduced matrix
always done in phase direction (why do it if it doesn’t save time?)
No change in frequency matrix
Reduces number of phase encoding steps

4. Ways to save time Rectangular FOV
Done in phase enc direction, to match reduced matrix size to make square pixels

5. Ways to save time Half acquistions Half scan or half Fourier
Uses the phenomenon of Hermitian Symmetry to make up the empty part of k-space with known info
Equal to ½ NEX
Results in decreased S/N
Incorrect in book---says increases noise…not really, it decreases S

6. Signal Averaging
Decreases noise, but increases time (NEX)

7. Protocol Design
Usually all are optimized by manufacturer or techs that are working at that center
Consider contrast sensitivity
For example, uterus is shown well with T2WI, not so well with T1WI
Image detail – rule of thumb is to make the slices half the size of the thing you want to see, or less.

8. Protocol Design Consider rectangular FOV and matrix
Don’t overdo detail, since small voxels will give you decreased S/N
Consider “3D” MR, which gives more signal
Artifact reduction (see ch 14)
Speed factor = turbo factor = ETL for Fast Spin Echo (FSE, TurboSE)