90: Comparison of Scintillation Detectors based on BGO and LSO for Prompt Gamma Imaging in Particle Therapy

S44 tumours. Surprisingly, tumour cells can actually survive these adverse conditions and play a crucial role in the development of acquired treatment resistance and are a major driving force for malignant progression by promoting loco-regional invasion of cancer cells and metastatic spread to distant sites. Substantial effort is now being made to image the tumour micro-environment and identify this cell population, thus allowing us to not only predict outcome to therapy, but also select appropriate methods to eliminate these cells. The fact that the tumour vascular supply is grossly different from the normal host vasculature makes it a unique target, thus effort is also being made to image and identify approaches for specifically targeting the vasculature. Current techniques for non-invasively imaging tumour micro-environmental parameters have focused on the use of positron emission tomography (PET), magnetic resonance imaging/spectroscopy (MRI/MRS), or computer tomography (CT). For imaging vasculature the methods of choice appear to be primarily MR based. With regard to targeting tumour vasculature then numerous agents have been developed that either inhibit the angiogenesis process or disrupt the already established tumour vessels and many of these treatments have undergone clinical evaluation. The major target from a micro-environmental perspective is hypoxia and numerous attempts have been made to simply reduce the level, sensitize them to radiation, or just kill this population. More recent suggestions have focused on modifying the radiation treatment to overcome the resistance. While all these approaches will work extremely well against primary tumours, their effects on metastatic disease would be more limited and other approaches, such as inhibition of hypoxia induced signalling mechanisms, are being considered. In this presentation we will review the current status of research on imaging and targeting the tumour micro-environment and vasculature. 90 Comparison of Scintillation Detectors based on BGO and LSO for Prompt Gamma Imaging in Particle Therapy F. Hueso-González1, D. Bemmerer2, M. Berthel1, A.K. Biegun3, J. v. Borany2, P. Dendooven3, A. Dreyer1, W. Enghardt1,2, F. Fiedler2, C. Golnik1, K. Heidel2, T. Kormoll1, J. Petzoldt1, K. Römer2, K. Schmidt2, R. Schwengner2, A. Wagner2, L. Wagner2, G. Pausch1 1 Technische Universität Dresden, OncoRay, Händelallee 28 / PF 41, 01307 Dresden, Germany 2 Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany 3 University of Groningen, Kernfysisch Versneller Instituut (KVI), Zernikelaan 25, 9747, The Netherlands Purpose: Particle range verification is a major challenge for the quality assurance of particle therapy. One approach promising range access and dose quantification in real-time is the measurement of the prompt gamma rays resulting from interactions of the therapy beam with nuclei of the tissue. A Compton camera based on multiple position sensitive gamma ray detectors, together with an imaging algorithm, is expected to reconstruct the prompt gamma ray emission density profile, which is strongly correlated with the dose distribution and particle range. Materials and Methods: At Helmholtz-Zentrum DresdenRossendorf (HZDR) and OncoRay, various Compton-imaging detector setups were tested. Semiconductor CdZnTe cross strip detectors were used for the scatter plane and PET block detectors with Lu2Si05 (LSO) and Bi4Ge3O12 (BGO) scintillators as absorbers, respectively. The data acquisition was based on VME electronics and handled by software developed on the ROOT platform. The tests were performed at the linear electron accelerator ELBE at HZDR, at the Tandem accelerator at HZDR and at the cyclotron AGOR at Groningen. The gamma rays measured at the different scenarios have

ICTR-PHE – 2014 similarities in energy range and timing structure with the prompt gamma rays expected in a clinical cyclotron beam. Results: Based on the different measurement campaigns, BGO and LSO scintillators are compared in terms of absorption efficiency, internal activity, price, energy, time and spatial resolution (see figure 1).

Figure 1 – Flood map of the BGO detector for different prompt gamma energy ranges (0.5-1 MeV, 1-2 MeV, 2-8 MeV), measured at AGOR proton beam with graphite as target. The crystal identification resolution improves significantly for high gamma ray energies (PGI scenario, 2-8 MeV) compared to low energies (PET scenario, <1 MeV). Conclusions: The performance of BGO and LSO scintillators as absorber detectors is assessed for different energy ranges and the suitability of BGO as an alternative to LSO for a Compton camera aiming at prompt gamma imaging (PGI) is discussed. Keywords: detectors and imaging, absorber, Compton camera, scintillator comparison Acknowledgement: Supported by German Federal Ministry of Education and Research (BMBF-03Z1NN12), ENVISION and ENTERVISION (funded by the European Commission under FP7 Grant Agreement N. 241851 and N. 264552 respectively).

91 Harnessing laser-plasma accelerated ion beams for applications using Gabor lenses C. Hughes1, N.P. Dover1, Z. Najmudin1, J.K. Pozimski1, J.S. Green2, P.A. Posocco1,3,4 1 Imperial College London, UK 2 Rutherford Appleton Laboratory 3 The Cockcroft Institute 4 Gunnar Nilssons Cancerstifelse Intense beams of ions are generated when a high intensity laser pulse irradiates a solid target. There has been great recent interest in laser-plasma sources for medical applications such as radiotherapy due to the potential to create affordable, compact treatment devices. Laser-plasma ion sources create divergent beams, which may limit their practicality for many applications. Being able to capture and