Application of diamond detectors to the dosimetry of 45 and 100 kVptherapy beams: comparison with a parallel-plate ionization chamber and MonteCarlo

Abstract

Diamond detectors have become an increasingly popular dosimetric method whereeither high spatial resolution is required or where photon or electron spectraare likely to change with depth or field size. However, little work has beenpreviously reported for superficial energies. This paper reports the responseof a commercially available diamond detector (PTW Freiburg/IPTB Dubna) at45 kVp (0.55 mm Al first HVL) and 100 kVp (2.3 mm Al first HVL) including doseand dose-rate linearity, percentage depth-dose and output factors as afunction of applicator size. Comparisons are made with Br. J. Radiol.supplement 25 data, measurements using a PTW parallel-plate chamber and MonteCarlo simulations based on spectra determined from transmission measurementsin aluminium. Excellent agreement was obtained for percentage depth-dosecurves between Monte Carlo and diamond after correcting for sublinearity ofthe dose-rate response and energy dependence of the diamond detector. However,significant differences were noted between diamond/Monte Carlo and theparallel-plate chamber, which is attributed to the perturbation caused by thepolyethylene base of the chamber.