First demonstration of arterial spin labeling on a 1.5T MR-Linac for characterizing glioblastoma perfusion dynamics

Motivation: Glioblastoma is a highly vascularized brain tumor. Changes in perfusion could guide treatment adaptation, but the dynamics of blood flow changes in glioblastoma during radiotherapy are poorly understood. Goal(s): We sought to characterize changes in glioblastoma cerebral blood flow during radiotherapy. Approach: We acquired twice-weekly arterial spin labeling (ASL) MRI in 22 glioblastoma patients during radiotherapy on a 1.5T MRI-linear accelerator (MR-Linac) and evaluated changes in cerebral blood flow. Results: We provided the first demonstration of MR-Linac ASL. Tumor cerebral blood flow tended to decrease during radiotherapy. Highly-perfused tumor regions showed the greatest change. Impact: We showed that frequent perfusion imaging on MRI-linear accelerators is feasible and that blood flow in highly-perfused regions of human glioblastoma tends to decrease during radiotherapy. Radiotherapy with dose escalation to highly perfused tumor regions likely requires target adaptation.