Clinical radiation therapy measurements with a new commercial synthetic single crystal diamond detector.

A commercial version of a synthetic single crystal diamond detector (SCDD) in a Schottky diode configuration was recently released as the new type 60019 microDiamond detector (PTW-Freiburg, Germany). In this study we investigate the dosimetric properties of this detector to independently confirm that findings from the developing group of the SCDDs still hold true for the commercial version of the SCDDs. We further explore if the use of the microDiamond detector can be expanded to high-energy photon beams of up to 15 MV and to large field measure- ments. Measurements were performed with an Elekta Synergy linear accelerator delivering 6, 10, and 15 MV X-rays, as well as 6, 9, 12, 15, and 20 MeV electron beams. The dependence of the microdiamond detector response on absorbed dose after connecting the detector was investigated. Furthermore, the dark current of the diamond detector was observed after irradiation. Results are compared to similar results from measurements with a diamond detector type 60003. Energy dependency was investigated, as well. Photon depth-dose curves were measured for field sizes 3 × 3, 10 × 10, and 30 × 30 cm2. PDDs were measured with the Semiflex type 31010 detector, microLion type 31018 detector, P Diode type 60016, SRS Diode type 60018, and the microDiamond type 60019 detector (all PTW-Freiburg). Photon profiles were measured at a depth of 10 cm. Electron depth-dose curves normalized to the dose maximum were measured with the 14 × 14 cm2 electron cone. PDDs were measured with a Markus chamber type 23343, an E Diode type 60017 and the microDiamond type 60019 detector (all PTW-Freiburg). Profiles were measured with the E Diode and microDiamond at half of D90, D90, D70, and D50 depths and for electron cone sizes of 6 × 6 cm2, 14 × 14 cm2, and 20 × 20 cm2. Within a tol- erance of 0.5% detector response of the investigated detector was stable without any preirradiation. After preirradition with approximately 250 cGy the detector response was stable within 0.1%. A dark current after irradiation was not observed. The microDiamond detector shows no energy dependence in high energy photon or electron dosimetry. Electron PDD measurements with the E Diode and micro- Diamond are in good agreement. However, compared to E Diode measurements, dose values in the bremsstrahlungs region are about 0.5% lower when measured with the microDiamond detector. Markus detector measurements agree with E Diode measurements in the bremsstrahlungs region. For depths larger than dmax, depth-dose curves of photon beams measured with the microDiamond detector are in close agreement to those measured with the microLion detector for small fields and with those measured with a Semiflex 0.125 cc ionization chamber for large fields. Differences are in the range of 0.25% and less. For profile measurements, microDiamond detector measurements agree well with microLion and P Diode measurements in the high-dose region of the profile and the penumbra region. For areas outside the open field, P Diode measurements are about 0.5%-1.0% higher than microDiamond and microLion measurements. Thus it becomes evident that the investigated diamond detector (type 60019) is suitable for a wide range of applications in high-energy photon and electron dosimetry and is interesting for relative, as well as absolute, dosimetry.