Pilot dose intercomparisons of 3D and 4D advanced lung radiotherapy

s / Physica Medica 30 (2014) e16ee44 e26 Contemporary therapeutic radiation oncology treatments require the de- livery of highly localized doses of radiation to well defined target regions inside the patient. The efficacy of the radiation treatment, however, re- quires knowledge of the absorbed dose in the organ of interest to better than ±5% as there is a higher risk of local recurrence or complications with incorrect exposure. Furthermore, since it is inevitable that healthy organs and tissue will also be exposed during treatment, overexposure increases the risk of secondary cancers. International regulations [1, 2] have been introduced to adapt to the fast introduction of new radiotherapy technologies and demand an improve- ment of in vivo dosimetry. Ideally, a real-time in vivo dosimeter would measure absorbed doses during radiotherapy. Optical stimulated luminescent (OSL) dosimeters, using the high sensi- tive material Al2O3:C, have been successfully used for measuring whole body doses that result from exposure to high energetic photon and beta radiation. OSL dosimeters have also been introduced in medical dosim- etry of low and high LET beams [3, 4]. Al2O3:C detectors can also be used as real time dosemeters, because the emitted stimulated light can be guided via light fibers to a remotely placed photomultiplier tube. Furthermore, during exposure to ionizing radiation Al2O3:C emits radi- oluminescent light (RL), of which the intensity is proportional to the dose rate [5]. In this study, we investigated the dosimetric response of an optical fibre coupled Al203:C RL/OSL dosemeter prototype. In our prototype, a PMMA fibre is coupled to an Al2O3:C detector composed of microparticles of Al2O3:C with diameters ranging from 5 mm to 35 mm dissolved in a photo- curable polymer. The RL/OSL dosimeter prototype is a portable and robust instrument that has been developed for the routine assessment of patient exposure to ionizing radiation during radiotherapy treatments. The design principles of hardware and software are described elsewhere [6]. In this study, we present the results obtained using radioluminescence (RL) from Al2O3:C irradiated with a 6 MV linear accelerator (Compact, Elekta, Crawly) and preliminary results obtained using optically stimulated luminescence (OSL). The dose rate dependence was assessed by varying the photon flux (MU/ min) of the linac, effectively changing the pulse rate and keeping the dose per pulse fixed. It was found that the RL measured dose response demonstrated low dose-rate dependency, to within 1%. The dose response was found to be linear in a dose range from 0.1 up to a dose of 6 Gy, with reproducibility below 0.5%. The dosimeter is benchmarked by evaluating the ability to measure depth- dose distributions and lateral dose profiles accurately. RL derived dose profiles have been compared with dose profiles measured with a standard ion chamber (PTW). Depth-dose distributions in water were acquired for a 6 MV photon beam using a 10 10 cm2 field, set at 350 MU/min, corre- sponding with 3.5 Gy/min at 10 cm depth. All data have been normalized to the depth-dose maximum. The RL measured dose agreed with the ionization chamber measured dose to within 1% (1 SD) for depths from 0.5 to 20 cm. Lateral dose profile was set at 350 MU/min (3.5 Gy/min at depth 10 cm), using a 10x10 cm2 field size. Differences between measured RL and ion chamber are within 1.5% for de direct beam and 5% in the penumbra region. These results show that the RL/OSL detector system makes it suitable for measurements of depth and lateral dose distributions in clinical photon beams. Furthermore, basic characteristics of OSL in irradiated fibers with Al2O3:C for dosimetry in therapeutic 6 MV photon beam were investigated. References [1] International Commission on Radiological Protection, 2000. Prevention of accidental exposures to patients undergoing radiation therapy. ICRP Publication 86. Ann. ICRP 30, 1e70. [2] IAEA Human Health Reports 8, 2013. Development of Procedures for In Vivo Dosimetry in Radiotherapy. IAEA Publication. [3] Viamonte, A., Rosa, L. A., Buckley, L. A., Cherpak, A., & Cygler, J. E. (2008). Radiotherapy dosimetry using a commercial OSL system.Medical Physics 35. [4] Akselrod, M.S., Lucas, A.C., Polf, J.C., McKeever, S.W.S., 1998. Optically stimulated luminescence of Al2O3. Radiat. Meas. 29, 391-399. [5] Marckmann CJ, Andersen CE, Aznar MC, Botter-Jensen L. Optical fibre dosemeter systems for clinical applications based on radioluminescence and optically stimulated luminescence from Al2O3:C. Radiat Prot Dosim- etry 120(1-4), 28-32. [6] Nascimento, L. F, Vanhavere, F, Boogers, E, Vandecasteele, J, De Deene, Y. 2014. Medical Dosimetry Using a RL/OSL Prototype. Radiation Measur- ements. ION BEAMS OF THERAPEUTICAL ENERGY ON PMMA PHANTOMS MEASUREMENTS IN VIEW OF AN INNOVATIVE DOSE PROFILER REALIZATION FOR ON LINE MONITORING IN HADRONTHERAPY TREATMENTS F. Bellini , F. Collamati , E. De Lucia , R. Faccini , F. Ferroni , P.M. Frallicciardi , M. Marafini , I. Mattei , S. Morganti , V. Patera , L. Piersanti , D. Pinci , A. Russomando , A. Sarti , A. Sciubba , E. Solfaroli Camillocci , C. Voena . Dipartimento di Fisica, Sapienza Universit a di Roma, Roma, Italy; b INFN Sezione di Roma, Roma, Italy; c Laboratori Nazionali di Frascati dell’INFN, Frascati, Italy; Dipartimento di Scienze di Base e Applicate per Ingegneria, Sapienza Universit a di Roma, Roma, Italy; Museo Storico della Fisica e Centro Studi e Ricerche “E. Fermi”, Roma, Italy; Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Roma, Italy; Dipartimento di Matematica e Fisica, Roma Tre Universit a di Roma, Roma, Italy; Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Universit a di Roma, Roma, Italy Hadrontherapy is a technique that uses accelerated charged ions for cancer treatment. The high irradiation precision and conformity achievable dur- ing hadrontherapy treatments allow the tumor control while sparing the surrounding healthy tissues. The improved spatial selectiveness required the development of a new dose monitoring techniques. It has been proved that secondary protons emitted at large angles can be used to monitor Bragg Peak (BP) position and the related dose release. In this contribution we present the measured flux and energy spectra for secondary particles produced by 12C He and O ion beams of therapeutical energy impinging on PMMA phantoms. We found that the rate of produced protons is large enough to provide the track sample needed for a fast online monitor operating during a typical treatment with the required O(mm) spatial resolution. A clear correlation between the proton generation region and BP position has been measured. In this work we also discuss a novel hadrontherapy monitor (DoseProfiler) whose technology is based on the backtracking of secondary charged particles and prompt photons emitted during the irradiation of the patient, allowing for a precise reconstruction of the BP position and a measure- ment of the released dose. The DoseProfiler combines a tracker detector made of scintillating fibers and a calorimeter built with pixelated LYSO crystals, for gamma detection and energy measurements. The six tracker squared layers, built from two orthogonal planes of squared scintillating fibers, will provide the particle direction information, while the LYSO crystals will measure the particle energy. PROTON RADIOGRAPHY IMAGING TOOL TO IMPROVE A PROTON THERAPY TREATMENT N. Ghazanfari , M.-J. Van Goethem, M. Van Beuzekom , T. Klaver , J. Visser , S. Brandenburg , A.K. Biegun . KVI-Center for Advanced Radiation Technology, University of Groningen, The Netherlands; Department of Radiation Oncology, University Medical Center, University of Groningen, The Netherlands; National Institute for Subatomic Physics (Nikhef), Amsterdam, The Netherlands Background: Radiotherapy is one of the most effective and a common method in cancer treatment. Typically in clinics, patients are treated with photons. Treatment with charged particles, mostly protons, due to their highly localized dose deposition, have a significant advantage over the commonly used photons in achieving a sufficient radiation dose to the tumor area to ensure complete tumor destruction, while at the same time minimizing the dose to the surrounding healthy tissue [1].