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Fig. 5B. —Calculated tissue signal levels at fixed TE (14 msec) for 1.5
and 3.0 T using measured relaxation times. Signal levels at 1.5 T (A)
and 3.0 T (B) were divided by square root of TR and plotted versus TR
with maximum signal level at 3.0 T normalized to 1.0. Difference between
signal levels at any given TR determines contrast between tissues.
Subcutaneous fat and bone marrow are plotted together as fat for simplicity.
Note that at 3.0 T (B), because of increased T1 relaxation times, TR of
1,600 msec is required to achieve same signal level (zero contrast) of
cartilage and fluid, which requires TR of only 1,200 msec at 1.5 T (A).
At TR of 4,000 msec, fluid-to-cartilage contrast is greater at 3.0 T (0.12 vs
0.7) because of increase in magnetization.
