Illustrations on MRI Techniques Using Matlab - Digital Signal Processing for Medical Imaging Using Matlab - page 66

Fig. 3.9 Illustration of the increase in the magnitude of the resultant longitudinal magnetic moment
at every pixel (of the 11 × 11 image slice) due to natural longitudinal relaxation (spin-lattice

interaction based)

figure
imagesc(abs(B))
C2=abs(ifft2(B));

figure
colormap(gray)
subplot(3,1,1)
imagesc(n)
title('Original')
subplot(3,1,2)
imagesc(C1(1:1:25,1:1:25))
title('With zero interpolation in frequency domain')
subplot(3,1,3)
title('With Linear interpolation in frequency domain')
imagesc(C2(1:1:25,1:1:25))

3.4 Illustration on the Steps Involved in Obtaining the T 1 MRI
Image

The following steps are followed to obtain the T 1 image.
1. Select the image slice using z-gradient. Apply refocussing gradient to compen-
sate the phase introduced due to z-gradient.
2. Apply 90 ◦ pulse to obtain the transverse component.
3. The transverse component at different pixel starts dephasing due to spin-spin
interaction (described by the factor T 2 ( x , y ) ).