TIME-DEPENDENCY IN BRAIN LESION ENHANCEMENT WITH GADODIAMIDE INJECTION

Purpose: To determine the effective time window for MR imaging of tumo rs with blood-brain barrier (BBB) damage after injection of Gd-contain ing contrast media. Material and Methods: Eleven patients with 15 brai n lesions (metastasis, glioma, abscess) were studied with a T1-weighte d spin-echo sequence repeated over periods of up to 43 min after contr ast injection. A quotient was calculated between the signals in the le sion and in the gray matter, and plotted against time. Results: All le sions reached 70% of the maximum RATIO within 3.5 min. After 25 min 12 out of 15 lesions showed persistent enhancement within 15% of the max imal RATIO. Conclusion: The peak enhancement of BBB damage occurs arou nd 3.5 min after injection. The effect does not change during the next 25 min. Scanning should not be started until 2-5 min after injection of the contrast medium. and there is no advantage in waiting longer as no major increase (or decline) of contrast can be expected.