Preview

PDF, English Download (28MB) | Terms of use

Abstract

Magnetic resonance guided radiotherapy (MRgRT) uses MR Linacs combining an MR scanner with a linac. This thesis aimed at the characterisation of the alanine dosimeter in the magnetic fields of MRgRT, i.e. the static magnetic main field continuously present at an MR Linac and radiofrequency pulses and gradient fields occuring in addition during MRI. Alanine pellets were irradiated in static magnetic fields at an Elekta Unity MR Linac and at a conventional linac with an electromagnet positioned in front of it. Alanine pellets were also exposed to MRI at the MR Linac and at a conventional MR scanner. The dose information was read out using an EPR spectrometer. The magnetic field correction factors to be applied for dose assessments with the alanine dosimeter at the Elekta Unity and at the ViewRay MRIdian MR Linac were determined. Their agreement with unity within the standard uncertainty indicates no measurable effect of the static magnetic fields on the alanine dosimeter. Furthermore, no measurable impact of MRI was found. The alanine dosimeter is, hence, an excellent choice for dose assessments at MR Linacs. It is further suited for end-to-end tests in MRgRT involving MRI after or during irradiations.