Evaluation of human brain tumor heterogeneity using multiple T ₁-based MRI signal weighting approaches

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 T₁ 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 (R ² = 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.