Measurement of radiofrequency emissions from a medical linac

The integration of a medical linear accelerator (linac) with a magnetic resonance imaging (MRI) system requires the measurement and shielding of radiofrequency (RF) noise produced by linac pulsing. Near field RF measurement techniques and their suitability for measurement of RF emissions of a medical linac are investigated in this thesis. A measurement technique using commercial field probes is proposed and investigated by measurement of the radiation pattern of a dipole emission source. The results indicate the field probes appropriately measure the electric and magnetic field components of the dipole source. The measurement technique is then applied to measure the RF emissions of a medical linac. The results of these preliminary measurements show that the RF emissions of a medical linear accelerator contain substantial field strengths in the range of DC -- 50 MHz. Finally, future directions for the isolation and shielding of the sources of RF emission are suggested.