Evaluation of human brain tumor heterogeneity using multiple T1‐based MRI signal weighting approaches

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Abstract
Vascular‐space‐occupancy (VASO) MRI without contrast injection was explored for imaging cerebral blood volume (CBV) and tissue heterogeneity in gliomas (n = 10). VASO contrast complemented contrast‐enhanced T1‐weighted (GAD‐T1w), FLAIR and T1w magnetization‐prepared‐rapid‐gradient‐echo (MPRAGE) images. High‐grade gliomas showed a VASO‐outlined hyperintense zone corresponding to long‐T1 regions in MPRAGE and to nonenhancing regions in GAD‐T1w images. FLAIR, MPRAGE, and VASO data were used to segment tumors into multiple zones of different T1. After removal of known resection areas using pre‐ and postsurgical MRI, the volume of overlap between the hyperintense VASO‐zone and the long‐T1 MPRAGE zone correlated with that of GAD‐T1w enhancement (R2 = 0.99) and tumor grade. Based on these correlations, this remaining long T1 overlap area was tentatively assigned to necrosis. In one promising case the collective T1‐weighted approach accurately identified a low‐grade glioma despite the presence of contrast enhancement in GAD‐T1w images consequential to chemoradiation‐associated treatment effect. The results suggest that this collective T1‐weighted approach may provide useful information for regional assessment of heterogeneous tumors and for guiding treatment‐related decisions in patients with gliomas. Magn Reson Med, 2008.