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

Abstract

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 measurements. 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 30×30.15emcm2. 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 14×14.15emcm2 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 6×6.15emcm2, 14×14.15emcm2, and 20×20.15emcm2. Within a tolerance 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 microDiamond 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% highe...

Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate 192Ir brachytherapy sources

“…MC calculated beam quality correction factors, which were 1.003, 1.005 and 1.013 for 1.5, 2.5 and 5.5 cm SDD irradiation plans, respectively, also indicate low absorbed‐dose energy dependence of microDiamonds calibrated in 60 Co beam. These findings are also in line with other studies on microDiamond response in high‐energy photon beams which indicate low energy‐dependence of the detector at the tail regions of percentage depth‐dose curves where low‐energy scattered photons are present …”

“…Furthermore, the standard deviation of averaged detector readings did not exceed 0.2%, and no drift was observed in detector readings over time in long‐term stability measurements, again indicating no radiation‐induced damage and long‐lasting preirradiation effects during the measurement period. These findings show a major advantage of microDiamonds over natural diamond detectors and are in line with other studies where negligible dose‐rate dependence and deviations in signal stability within ±0.5% were observed for preirradiation doses below 3 Gy . Nevertheless, several authors observed individual behavior among microDiamond detectors and unusually high preirradiation doses of up to 12 Gy …”

“…To assess this hypothesis, three microDiamond detectors were used to determine absorbed dose to water using two clinical HDR 192 Ir BT treatment delivery systems. The results presented in this paper will contribute to the development of HDR BT dosimetry and also complement the current characterization of microDiamond detectors …”

“…A detailed description of its structure and detection properties can be found elsewhere . Characterization in high‐energy photon beams showed that it has linear response to dose from 0.5 to 15 Gy, good stability, negligible dose‐rate dependence, uniform energy response (including low‐energy scattered photons) and low angular and temperature dependences . Since dosimetry of HDR 192 Ir BT sources is similar to that of small photon fields in terms of high dose gradients and high dose rates, these findings, coupled with near water‐equivalence of carbon, direct readout and convenience of use, suggest that the microDiamond would be suitable for the determination of absorbed dose to water in HDR 192 Ir beams.…”

Toward Pulse by Pulse Dosimetry Using an SC CVD Diamond Detector

“…The microDiamond system was connected to a PTW UNIDOS dosimeter to measure the charge generated by the photon beams. Several studies on the use of this system in therapeutic dosimetry have been reported [17]- [20].…”