Early versus late GD-DTPA MRI enhancement in experimental glioblastomas.

To compare early versus late enhancement in two glioblastoma models characterized by different infiltrative/edematous patterns.Three weeks after inoculation into nude mice of U87MG and U251 cells, T1-weighted images were acquired early (10.5 min), intermediate (21 min) and late (30.5 min) after a bolus injection of Gd-DTPA at 300 μ mol/kg dosage. EARLY(TH) and LATE(TH) were the corresponding volumes with an enhancement higher than a threshold TH, defined by the mean (μ) and standard deviation (σ) on a contralateral healthy area. ADD(TH) was the enhancing volume found in LATE(TH) but not in EARLY(TH) . T2 imaging of both tumors was performed, and T2 mapping of U251.In all tumors, LATE(TH) was significantly higher than EARLY(TH) for TH ranging from μ+σ to μ+5σ. The ADD(TH) /EARLY(TH) ratio was not significantly different when U251 and U87MG tumors were compared. In the U87MG tumors, some enhancement was observed outside the regularly demarcated T2-hyperintense area. In the U251 tumors, irregularly T2 demarcated, a large portion of ADD(μ+3σ) had normal T2 values. At histology, U251 showed a higher infiltrative pattern than U87MG.In these models, the increase over time in the enhancing volume did not depend on the different infiltrative/edematous patterns and was not closely related with edema. J. Magn. Reson. Imaging 2011;33:550-556. © 2011 Wiley-Liss, Inc.