Intercomparison of dosimeters for non-targe dose measurements in radiotherapy - Activity of EURADOS WG 9: Radiation protection in medicine

It has been known for a long time that patients treated with ionizing radiation carry a risk of developing radiation induced cancer in their lifetimes. It is recognized that cure/survival rates in radiotherapy are increasing, but so are secondary cancers. These occurrences are amplified by the early detection of disease in younger patients. These patients are cured from the primary disease and have long life-expectancies, which increase their chances of developing secondary malignancies. The motivation of the EURADOS Working Group 9 (WG 9) “Radiation protection dosimetry in medicine” is to assess undue non-target patient doses in radiotherapy and the related risks of secondary malignancy with the most accredited available methods, with the emphasis on a thorough evaluation of dosimetry methods for the measurements of doses remote from the target volume in phantom experiments. The development of a unified and comprehensive dosimetry methodology for non-target dose estimation is the key element of the WG9 current work. The first scientific aim is to select and review dosimeters suitable for photon and neutron dosimetry in radiotherapy and to evaluate the characteristics of dosimeters at CEA LIST Saclay in reference clinical LINAC beam. Dosimeters were irradiated in a matrix of measurements points within a 30 x 30 x 60 cm3 water phantom. 2 Gy was delivered to a point on the central axis of the horizontal beam at a depth of 10 cm in water. The irradiation size field was 10 x 10 cm2. For photon dosimetry, irradiations were carried out at three radiation qualities corresponding to 6, 12 and 20 MV, giving a total of 204 measurements per dosimeter type. For neutron dosimetry only 12 and 20 MV were used. Dosimeters used in the intercomparison were a) For photons: Radiophotoluminescence (RPL) – Ruđer Bošković Institute (RBI) Zagreb, Optically stimulated luminescence (OSL) – Commissariat à l’ Ėnergie Atomique (CEA), Paris, Thermoluminescence (TLD) – Instytut Fizyki Jadrowej (IFJ), Krakow and RBI, Zagreb and b) For neutrons: Track etch detector (CR39) – Universitat Autònoma de Barcelona (UAB) and Bubble detector – Università di Pisa (UP). In this work the results obtained by RPL and TLD dosimeters measured by RBI will be presented for in phantom dose measurements.