ORIGINAL PAPER Clinical investigations of a CVD diamond detector for radiotherapy dosimetry G.T. Betzel a, *, S.P. Lansley a,b , F. Baluti a,c , L. Reinisch d , J. Meyer a a Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand b The MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, New Zealand c Oncology Service, Christchurch Hospital, Christchurch, New Zealand d Department of Physical and Earth Sciences, Jacksonville State University, Jacksonville, AL, USA Received 14 August 2010; received in revised form 14 April 2011; accepted 18 April 2011 KEYWORDS CVD diamond; Radiation therapy; Detector; Dosimetry Abstract X-ray detectors based on single crystal diamond film made via chemical vapor deposition were investigated to evaluate their performance under clinically relevant condi- tions for radiotherapy dosimetry. Studies focused on repeatability, dose rate dependence, tissue phantom ratios, output factors and beam profiling. Repeatability experiments revealed a temporary loss in sensitivity due to charge detrapping effects following irradiation, which was modeled to make corrections that improved short-term precision. Dose rate dependence was observed (Fowler fitting parameter D Z 0.96 Æ 0.2) using dose rates up to w2 Gy min^À1. The detector statistically distinguished (n Z 5, P < 0.05) between dose values separated by 7.7 Â 10^À3 Gy (1 MU). Depth dose measurements from 1 to 15 cm and output factors using 3 Â 3 to 10 Â 10 cm^2 field sizes compared well with a Farmer ion chamber (<1.3% difference). Output factor measurements indicate encouraging results for fields sizes <4 Â 4 cm^2. Off-axis measurements showed that perturbation of the beam could be reduced when the detector is used in the edge-on orientation due to its thin-film sandwich configuration and w200 nm thick Ag contacts. This relatively inexpensive detector has potential to be used for routine dosimetry using conventional radiotherapy instrumentation. ª 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved. * Corresponding author. Present address: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA. Tel.: þ1 410 328 3485; fax: þ1 410 328 2618. E-mail address: gbetzel@umm.edu (G.T. Betzel). available at www.sciencedirect.com journal homepage: http://intl.elsevierhealth.com/journals/ejmp Physica Medica (2011) xx,1e9 + MODEL Please cite this article in press as: Betzel GT, et al., Clinical investigations of a CVD diamond detector for radiotherapy dosimetry, Physica Medica (2011), doi:10.1016/j.ejmp.2011.04.003 1120-1797/$ - see front matter ª 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ejmp.2011.04.003