Improved accuracy for Australian radiotherapy

Advances in measurement standards at ARPANSA mean that radiotherapy clinics can now measure radiation more accurately.

The success of cancer treatment depends on the radiation dose. While delivering the radiation involves relatively large uncertainties due to patient setup and delivery methods, the treatment is aided by improvements in the ability of the hospital to measure dose at the most fundamental level. ARPANSA has developed a calibration service for hospital dose meters which uses a linear accelerator as the source of radiation. Because this radiation source is so similar to that used to deliver the therapy, the dose meters can be calibrated much more accurately. In order to make this service possible, ARPANSA scientists adapted a graphite calorimeter (the most accurate instrument for measuring radiation dose) to work with megavoltage X-rays produced by the linear accelerator.

International consistency of dose measurements is critically important in radiotherapy treatments, where dose prescriptions are frequently based on clinical trials and dose measurements made overseas. A recent comparison between ARPANSA and the international primary standards laboratory (the Bureau International des Poids et Mesures) in France confirmed the level of agreement of ARPANSA’s new calibration service with those overseas.

Key comparison BIPM.RI(I)-K6 of the standards for absorbed dose to water of the ARPANSA, Australia and the BIPM in accelerator photon beams

S Picard, DT Burns, P Roger, PD Harty, G Ramanathan, JE Lye, T Wright, DJ Butler, A Cole, C Oliver, DV Webb, Metrologia 2014 51 Tech. Suppl. 06006.

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Using synchrotron radiation to treat cancer is now one step closer to reality

The Australian Synchrotron has a research project into the potential of synchrotron microbeams for cancer treatment. These finely divided, intense X-ray beams promise to be able to damage tumours without harming normal tissue. Before they move to treating human patients, there are three key criteria to satisfy. The first concerns how much dose is being delivered to the patient, the second patient positioning, the third is to understand and predict the biological response to doses of 100’s of Gy in very small volumes of tissue. ARPANSA’s work has helped with the first piece of the dose puzzle, and brings clinical use of the Australian Synchrotron’s microbeams one step closer to reality.

Members of ARPANSA’s Medical Radiation Services Branch used a graphite calorimeter to assist the synchrotron’s Imaging and Medical Beam Line (IMBL) group in measuring the high dose rate from their intense x‑ray beam. This is a significant breakthrough, since no previous dose rate measurements using a graphite calorimeter on similar beams have been reported in the scientific literature. The journal Medical Physics has accepted the manuscript for publication.

Absolute X-ray dosimetry on a synchrotron medical beam line with a graphite calorimeter

PD Harty, JE Lye, G Ramanathan, DJ Butler, CJ Hall, AW Stevenson, PN Johnston, Medical Physics 41, 052101 (2014).