Research progress in dosimetry with MRI-Linac

The integration of MRI and linac has realized real-time MRI-guided radiotherapy and accelerated the progress of precision radiotherapy. Electrons are subjected to Lorentz force in the magnetic field, especially the electron cyclotron effect occurs at the tissue-air interface, which changes the original electron equilibrium state and brings challenges to dosimetry with MRI-Linac. In recent years, a series of studies carried out through Monte Carlo simulation and experimental measurement have suggested that the conventional dosimetry devices can be used for the dosimetry with MRI-Linac after replacing the magnetic materials, but corresponding correction factors should be introduced according to the magnetic field intensity, placement angle of the measuring device, type of the measuring device. The standardization, streamlining, and real-time dosimetry with MRI-Linac need to be further studied. (authors)