Multicompartment analysis of gadolinium chelate kinetics: Blood-tissue exchange in mammary tumors as monitored by dynamic MR imaging

The blood-tissue exchange kinetics of gadopentetate were studied in 49 mali gnant and benign mammary tumors. Signal enhancement was monitored simultane ously in the aorta and in tumor for 10.5 minutes after the beginning of a 1 minute i.v. infusion of the contrast medium (CM), Kinetic analysis was bas ed on a model with two compartments for systemic pharmacokinetics and up to three kinetically distinct compartments for tumor. Kinetic heterogeneity, ie, two or more compartments with different exchange rate constants in a gi ven tumor, was found in 85% of carcinomas, 38% of fibroadenomas, and 14% of mastopathic tumors. The within-tumor average of CM exchange rates was 1.22 (0.62-1.65) min(-1) in carcinomas, 0.38 (0.26-0.60) min(-1) in fibroadenom as, and 0.16 (0.12-0.20) min(-1) in mastopathies (median and interquartile distances). The area under the signal enhancement-time curve of the aorta v aried 4.5-fold between individuals. It is concluded that individual CM kine tics in arterial blood should be taken into account when CM exchange rates between blood and tumor are to be determined and that a kinetic model for p otentially malignant tumors should allow for kinetic heterogeneity. (C) 199 9 Wiley-Liss, Inc.