Clinical studies of optimised single crystal and polycrystalline diamonds for radiotherapy dosimetry

Abstract

Natural diamond based ionisation chambers commercialised by PTW are used in several hospitals, and their dosimetric properties have been reported in many papers. Nevertheless their high costs and long delivery times are strong drawbacks. Advancements in the growth of synthetic diamonds offer new possibilities. This paper presents the dosimetric analysis in terms of stability and repeatability of the signal, background signal, detector response dynamics, linearity of the signal with the absorbed dose and dose rate dependence of synthetic optimised polycrystalline and single crystal diamonds. Both were elaborated at the CEA-LIST using the chemical vapour deposition (CVD) growth technique. The first dosimetric evaluation of single crystal diamond detector, reported here, shows a repeatability better than 0.1%, a good sensitivity around 70 nC/Gy compared to 3 nC/Gy for optimised polycrystalline diamond, very fast response with rise time around 1 s. Moreover, the signal linearity vs absorbed dose and energy dependence are very satisfactory. This preliminary dosimetric study with medical linear accelerators proves that diamond, and more precisely synthetic single crystal diamond, appears as a good alternative to air ionisation chambers for quality beam control and could be a good candidate for intensity modulated radiation therapy (IMRT) beams dosimetry.