Characterisation of a synthetic diamond detector for end-to-end dosimetry in stereotactic body radiotherapy and radiosurgery

Maddison Shaw; Jessica Lye; Andrew Alves; Stephanie Keehan; Joerg Lehmann; Maximilian Hanlon; John Kenny; John Baines; Claudiu Porumb; Moshi Geso; Rhonda Brown

doi:10.1016/j.phro.2021.10.002

Characterisation of a synthetic diamond detector for end-to-end dosimetry in stereotactic body radiotherapy and radiosurgery

Phys Imaging Radiat Oncol. 2021 Oct 19:20:40-45. doi: 10.1016/j.phro.2021.10.002. eCollection 2021 Oct.

Authors

Maddison Shaw^{1

2}, Jessica Lye^{1

3}, Andrew Alves¹, Stephanie Keehan¹, Joerg Lehmann^{4

5

6

7}, Maximilian Hanlon¹, John Kenny⁸, John Baines⁹, Claudiu Porumb¹⁰, Moshi Geso², Rhonda Brown¹

Affiliations

¹ Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia.
² School of Health and Biomedical Science, RMIT University, Melbourne, VIC, Australia.
³ Olivia Newtown John Cancer Wellness & Research Centre, Heidelberg, VIC, Australia.
⁴ Department of Radiation Oncology, Calvary Mater Newcastle, Newcastle, Australia.
⁵ School of Science, RMIT University, Melbourne, Australia.
⁶ School of Mathematical and Physical Sciences, University of Newcastle, Australia.
⁷ Institute of Medical Physics, University of Sydney, Australia.
⁸ Medical Physics Specialists, Health Stem Solutions, Melbourne, VIC, Australia.
⁹ Radiation Oncology, Townsville Cancer Centre, Townsville, QLD, Australia.
¹⁰ Alfred Health Radiation Oncology, Melbourne VIC, Australia.

Abstract

Background and purpose: Synthetic diamond detectors offer real time measurement of dose in radiotherapy applications which require high spatial resolution. Additional considerations and corrections are required for measurements where the diamond detector is orientated at various angles to the incident beam. This study investigated diamond detectors for end-to-end testing of Stereotactic Body Radiotherapy (SBRT) and Stereotactic Radiosurgery (SRS) in the context of dosimetry audits.

Material and methods: Seven individual diamond detectors were investigated and compared with respect to warm up stability, dose-rate dependence, linearity, detector shadowing, energy response, cross-calibration, angular dependence and positional sensitivity in SBRT and SRS.

Results: Large variation in the cross calibration factors was found between the seven individual detectors. For each detector, the energy dependence in the cross calibration factor was on average <0.6% across the beam qualities investigated (Co-60 Gamma Knife, and MV beams with TPR_20,10 0.684-0.733). The angular corrections for individual fields were up to 5%, and varied with field size. However, the average angular dependence for all fields in a typical SRS treatment delivery was <1%. The overall measurement uncertainty was 3.6% and 3.1% (2σ) for an SRS and SBRT treatment plan respectively.

Conclusion: Synthetic diamond detectors were found to be reliable and robust for end-to-end dosimetry in SBRT and SRS applications. Orientation of the detector relative to the beam axis is an important consideration, as significant corrections are required for angular dependence.

Keywords: Dosimetry audit; Quality assurance; SBRT; SRS; Small field dosimetry; microDiamond.