Homework-6: Basic Imaging Techniques

  1. How many slices could you image with a gradient echo sequence that uses a 20 ms slice selection gradient, 10 ms phase encoding gradient, 10 ms dephasing frequency gradient, 100 ms frequency encoding gradient, and TR = 1 s?

  2. Draw a timing diagram for an inversion recovery imaging sequence which uses a gradient echo sequence rather than a spin-echo sequence to detect the signal present TI after the inversion (180 degree) pulse.

  3. There are two adjacent tissues in an image with T1a = 300 ms, T2a* = 20 ms, ra = 50 ASDU, and T1b = 150 ms, T2b* = 20 ms, rb = 50 ASDU. (ASDU = arbitrary spin density units.) You wish to produce a 90 o gradient echo image of the tissues such that the contrast between the tissues is maximized. What TR should be used?

  4. You wish to image an oblique slice that makes an angle of 45o between the +Z-axis and +y-axis, and an angle of 45o between the +Z-axis and +x-axis. Since gradients can only be produced with the three gradient coil systems located around the x, y, and z-axes, what combination of the three gradients should be applied to produce a slice selection, phase encoding, and frequency encoding gradient?