Quantitative Magnetization Transfer Imaging in Glioblastoma Patients using Balanced Steady-state Free Precession on a 1.5 T MR-Linac

Quantitative magnetization transfer (qMT) imaging could be used to assess tumor response on an MR-Linac. However, qMT protocols which use an off-resonance saturation pulse are slow and does not have the 3D coverage necessary to assess tumor response. We implemented a fast 3D balanced steady-state free precession qMT protocol on the MR-Linac. Six glioblastoma patients were scanned on the MR-Linac at weekly intervals during treatment. qMT parameter maps derived using non-linear least square fitting show similar contrast to other qMT protocols. Within-subject coefficient of variation was higher than values found in literature for off-resonance qMT protocols.