Use of cerebrospinal fluid gating to improve T2-weighted images. Part II. Temporal lobes, basal ganglia, and brain stem.

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Abstract
Ungated and gated magnetic rsonance images of the temporal lobes, basal ganglia, and brain stem acquired with the use of long repetition times (TRs) and long echo-delay times (TEs), were compared quantitatively. Twenty-five pairs of images (TR = 2,000 msec, TE = 80 msec) were acquired in the same manner as gated images except for TR, which, for gated studies, was determined by a patient''s heart rate and generally fell into the 1,500-1,800-msec range. Three image parameters were assessed: signal-to-noise ratio (S/N), object contrast, and resolving power. In both normal and abnormal brain tissue, gated images were superior to ungated images in object contrast and resolving power and equivalent in S/N. More so than in comparable studies of the spinal cord, ungated studies were susceptible to both false-positive and false-negative interpretations. As in spinal cord studies, the major benefit of gating was the elimination of phase shift images arising from basal cisterns and the third ventricle.