Clinical simulations of prostate radiotherapy using BOMAB-like phantoms: Results for photons

• Published in: Radiation measurements 2013-10, Vol.57, p.35-47
• Main Authors: Miljanić, Saveta, Bessieres, Igor, Bordy, Jean-Marc, d'Errico, Francesco, Di Fulvio, Angela, Kabat, Damian, Knežević, Željka, Olko, Pawel, Stolarczyk, Liliana, Tana, Luigi, Harrison, Roger
• Format: Article
• Language: English
• Subjects: Bioengineering; Cancer; Dosimeters; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochronology; IMRT; Irradiation; Isotope geochemistry. Geochronology; Life Sciences; Nuclear Experiment; Nuclear medicine; OSL; Out-of-field doses in radiotherapy; Photon dosimetry; Photons; Physics; Radiotherapy; Risk; RPL; Simulation; Therapy; TLD; Tomotherapy; VMAT; Water tanks
• ISSN: 1350-4487; 1879-0925
• DOI: 10.1016/j.radmeas.2012.12.012

In this part of work carried out by Working Group 9 (Radiation Protection Dosimetry in Medicine) of the European Radiation Dosimetry Group (EURADOS), water tank experiments described in this issue (Bordy et al., 2013) were extended to a BOMAB-like phantom. This phantom is more clinically realistic than a water tank, sufficiently to allow the simulation of some clinical treatments. In the experiments to be described, four types of prostate treatment were simulated: Volumetric Modulated Arc Therapy (VMAT, 6 MV), Tomotherapy (6 MV), IMRT (6 MV and 18 MV), 5-field conformal radiotherapy (15 MV) and 4-field conformal radiotherapy (6 MV and 18 MV). Irradiations were performed in two centres, University Hospital of Santa Chiara, Pisa, Italy and Centre of Oncology M. Skłodowska-Curie Memorial Institute, Krakow, Poland. Whatever the difficulties and uncertainties in risk estimation, its foundation lies in the knowledge of the absorbed dose to the irradiated organs. Thus the measurement of out-of-field doses is a crucial pre-requisite for risk estimation and is the subject of the EURADOS Working Group 9. For photon out-of-field dose measurements TLD, OSL and RPL dosimeters were used. Comparison of dosimeters under the same irradiation conditions showed that dosimeters generally agreed to within 3% compared with ion chamber reference measurements. Other comparisons were possible with these data. They include a comparison of doses (beam profiles) in different positions in the BOMAB phantom, a comparison of different treatment modalities in the two contributing clinical centres (Pisa and Krakow) and a comparison of dose profiles resulting from the different treatment techniques and the corresponding doses calculated by the treatment planning systems used to generate the treatment plans. Finally, preliminary measurements of surface doses at selected points on the trunk of the BOMAB phantom were made using diode detectors. Comparison of out-of-field doses for different modalities in the two clinical centres shows that differences in out-of-field doses for the same Planning Treatment Volume (PTV) can be even a factor of 4. For sparing adjacent organs-at-risk the best results were obtained for IMRT. On the other hand the lowest out-of-field doses were for MLC conformal therapy. ► Dosimeters used (TLD, OSL and RPL) are suitable for out-of-field dosimetry. ► Generally agreement is within 3% compared with ion chamber reference measurements. ► Peripheral doses for the same PTV