Endo-microdosemeters for the control of radiation effectiveness in therapy applications

New instrumentation utilising microdosimetry in the condensed phase is being developed with the aim of providing improved methods for quality assurance in radiotherapy. The main applications for the device will include assessing and monitoring photoneutron hazards around high energy accelerators, and in vivo determination of the dose and quality of the radiation field in brachytherapy. The endo-microdosemeter instrument is essentially a miniature scintillator (<500 μm in diameter) coupled to an optical fibre which is connected by its other end to a photomultiplier tube. Pulse-height spectra from the instrument are processed with conventional microdosimetric algorithms. The initial measurements using this instrument were made in the beam and the penumbra of the beam of a high energy (6 and 10MW) therapy LINAC. Spectral changes have been found to occur for different operating modes of the machine. (Author)