Contrast-enhanced magnetic resonance imaging was used to monitor tumor growth in the brain. In these studies, the rats were anesthetized with isoflurane and maintained at a surgical anesthesia plane through the procedure. A Phillips Achieva 3.0T X-series MRI with a modified rodent coil (Philips Research Europe, Hamburg, Germany) was used . T1- and T2-weighted turbo-spin echo images were acquired prior to intravenous administration of 0.1 mmol of gadolinium Gd-DTPA (Magnevist®) and the post-contrast T1W image sequence was collected 10 min following gadolinium injection. The T2W image sequence was collected during the contrast uptake. The MRI images were processed and analyzed using NIRFAST Software (Version 1.12) [28, 29].