Dose dependency of MRI changes following pre-operative radiotherapy in glioblastoma; volumetric, ASL and APT changes

Motivation: Prognosis for people with glioblastoma remains poor, pre-operative radiotherapy may improve outcome. Goal(s): Determine early changes after pre-operative radiotherapy using T1w+contrast, FLAIR, Arterial Spin Labelling (ASL) and Amide Proton Transfer-weighted (APTw) MRI to better understand early impact of radiotherapy on tumours. Approach: Assess hyperintense-FLAIR, enhancing and necrotic volume change, and change in perfusion and MTRasym after pre-operative radiotherapy. Assess association with radiotherapy dose received. Results: Hyperintense-FLAIR volume decreases in 8 out of 9 patients 1-2 days after radiotherapy in a dose-dependent manner. Perfusion showed dose-dependent increase in both the enhancing and hyperintense-FLAIR regions and MTRasym showed dose-dependent decrease in the hyperintense-FLAIR region. Impact: This study assesses early changes after pre-operative brain irradiation in glioblastoma. We show that hyperintense-FLAIR volume reduces, perfusion increases and MTRasym decreases in a dose-dependent manner within 1-2 days of radiotherapy, providing potentially valuable measures to track radiotherapy response.