We will make a simple digital phantom to study the Nyquist ghosting artifacts and the blurring effect
due to relaxation. The following object is to be imaged with an FOV of 128\times 128mm and a scan
resolution of 64\times 64. A and B have uniform magnetization of 60 and 20 , respectively. Both objects A and
B are centered at the FOV. A single-shot gradient echo EPI sequence is used for imaging. The flat portion
of the readout gradients is 3.2 ms each.
Show the magnitude and the phase of the k-space data if relaxation is ignored, with a proper
colorbar.
Ignore relaxation, due to some errors during the scan there was a delay of 0.2 ms on all the even
echoes compared to the odd echoes:
a. Show the new k-space data with such delays (show both magnitude and phase images,
use colorbar);
b. Reconstruct the image (show both magnitude and phase images, use colorbar);
Starting from Prob. 1, now consider relaxation times T2* =600ms and 200 ms for A and B,
respectively. The ky lines are collected from bottom up, e.g., ky=-32,-31,dots,0,1,2,dots,31ky=-32 t=6ms. (Hint:
you only need to consider the relaxation between different ky lines and ignore the relaxation
within the acquisition in each ky line.)
a. Show the new k-space data collected (show both magnitude and phase images, use
colorbar);
b. Reconstruct t DON"T WORK ON THIS QUESTION... ACCCIDENTALLY UPLOADED