Perfusion MRI of U87 brain tumors in a mouse model.

Continuous arterial spin labeling (CASL) was used to obtain an index of cerebral blood flow (ICBF) in the normal mouse brain and in an orthotopic mouse model of human U87 high-grade glioma at 8.5 T. Under the assumption of a constant tissue:blood partition coefficient for water in different tissues, the mean ICBF (n = 14) was found to be 50 +/- 9 mL/100g/min for tumor core and 209 +/- 11 mL/100g/min for normal tissue. The apparent T(1) (T(1app)) was 2.01 +/- 0.06 sec for tumor core and 1.66 +/- 0.03 sec for normal tissue. The ICBF and the T(1app) values were significantly different (P < 0.001) between these two regions. The detailed changes of ICBF and T(1app) in the transition from the tumor core through the tumor periphery to surrounding tissue were studied. Immunohistochemistry indicated that tumor vascularity was not uniform, with microvessel density highest in normal brain and the tissue surrounding the tumor and lowest in the tumor core. The large difference in ICBF between the tumor core and normal tissue suggests that this index might be useful for the assessment of the efficacy of antiangiogenic therapy.