Cerebral abnormalities: use of calculated T1 and T2 magnetic resonance images for diagnosis.

The potential clinical importance of T1 and T2 relaxation times in distinguishing normal and pathologic tissue with magnetic resonance (MR) is discussed and clinical examples of cerebral abnormalities are given. T1 and T2 values may be used in three ways: (a) Relative values, obtained by an analysis of intensity images with varying dependence on T1 and T2, may be used if absolute values for T1 and T2 are not required for diagnosis. (b) If an absolute value is desired, the numerical values for the relaxation times may be generated using a region of interest on the intensity images. (c) In cases in which both T1 and T2 change may require a calculated image to indicate the contribution of each to the signal intensity, the numerical value may be used to generate analogue images of T1 or T2 calculations. Five patients with cerebral infarction, 15 with multiple sclerosis, two with Wilson disease, and four with tumors were imaged. Hemorrhagic and ischemic cerebrovascular accidents were distinguished using the spin echo technique. In the patients with multiple sclerosis, lesions had prolonged T1 and T2 times, but the definition of plaque was limited by spatial resolution. No abnormalities in signal intensity were seen in the patient with Wilson disease who was no longer severely disabled; abnormal increased signal intensity in the basal ganglia was found in the second patient with Wilson disease. Four tumors produced abnormal T1 and T2 relaxation times but these values alone were not sufficient for tumor characterization.