Monte Carlo simulations play a crucial role for in-vivo treatment monitoring based on PET and prompt gamma imaging in proton and carbon-ion therapies. The accuracy of the nuclear fragmentation models ...implemented in these codes might affect the quality of the treatment verification. In this paper, we investigate the nuclear models implemented in GATE Geant4 and FLUKA by comparing the angular and energy distributions of secondary particles exiting a homogeneous target of PMMA. Comparison results were restricted to fragmentation of 16O and 12C. Despite the very simple target and set-up, substantial discrepancies were observed between the two codes. For instance, the number of high energy (>1 MeV) prompt gammas exiting the target was about twice as large with GATE Geant4 than with FLUKA both for proton and carbon ion beams. Such differences were not observed for the predicted annihilation photon production yields, for which ratios of 1.09 and 1.20 were obtained between GATE and FLUKA for the proton beam and the carbon ion beam, respectively. For neutrons and protons, discrepancies from 14% (exiting protons-carbon ion beam) to 57% (exiting neutrons-proton beam) have been identified in production yields as well as in the energy spectra for neutrons.
A Compton camera is being developed for the purpose of ion-range monitoring during hadrontherapy via the detection of prompt-gamma rays. The system consists of a scintillating fiber beam tagging ...hodoscope, a stack of double sided silicon strip detectors (90 Â 90 Â 2 mm 3 , 2 Â 64 strips) as scatter detectors, as well as bismuth germanate (BGO) scintillation detectors (38 Â 35 Â 30 mm 3 , 100 blocks) as absorbers. The individual components will be described, together with the status of their characterization.
Monte Carlo simulations based on the Geant4 toolkit (version 9.1) were performed to study the emission of secondary prompt-gamma rays produced by nuclear reactions during carbon ion-beam therapy. ...These simulations were performed along with an experimental program and instrumentation developments which aim at designing a prompt-gamma ray device for real-time control of hadrontherapy. The objective of the present study is twofold: firstly, to present the features of the prompt-gamma radiation in the case of carbon ion irradiation; secondly, to simulate the experimental setup and to compare measured and simulated counting rates corresponding to four different experiments. For each experiment, we found that simulations overestimate prompt-gamma ray detection yields by a factor of 12. Uncertainties in fragmentation cross sections and binary cascade model cannot explain such discrepancies. The so-called "photon evaporation" model is therefore questionable and its modification is currently in progress.
Light and heavy ions particle therapy, mainly by means of protons and carbon ions, represents an advantageous treatment modality for deep-seated and/or radioresistant tumours. An in-beam quality ...assurance principle is based on the detection of secondary particles induced by nuclear fragmentations between projectile and target nuclei. Three different strategies are currently under investigation: prompt γ rays imaging, proton interaction vertex imaging and in-beam positron emission tomography. Geant4 simulations have been performed first in order to assess the accuracy of some hadronic models to reproduce experimental data. Two different kinds of data have been considered: β+-emitting isotopes and prompt γ-ray production rates. On the one hand simulations reproduce experimental β+ emitting isotopes production rates to an accuracy of 24%. Moreover simulated β+ emitting nuclei production rate as a function of depth reproduce well the peak-to-plateau ratio of experimental data. On the other hand by tuning the tolerance factor of the photon evaporation model available in Geant4, we reduce significantly prompt γ-ray production rates until a very good agreement is reached with experimental data. Then we have estimated the total amount of induced annihilation photons and prompt γ rays for a simple treatment plan of ∼1 physical Gy in a homogenous equivalent soft tissue tumour (6 cm depth, 4 cm radius and 2 cm wide). The average annihilation photons emitted during a 45 s irradiation in a 4 π solid angle are ∼2 × 106 annihilation photon pairs and 108 single prompt γ whose energy ranges from a few keV to 10 MeV.
We present the first results obtained with a detector, called Large Area Pixelized Detector (LAPD), dedicated to the study the ballistic control of the beam delivered to the patient by in-beam and ...real time detection of secondary particles, emitted during its irradiation in the context of hadrontherapy. These particles are 511keV γ from the annihilation of a positron issued from the β+ emitters induced in the patient tissues along the beam path. The LAPD basic concepts are similar to a conventional PET camera. The 511keV γ are detected and the reconstructed lines of response allow to measure the β+ activity distribution. Nevertheless, when trying to use γ from positron annihilation for the ballistic control in hadrontherapy, the large prompt γ background should be taken into account and properly rejected. First reconstruction results, obtained with a phantom filled with a high intensity FDG source at the cancer research centre of Clermont-Ferrand are shown. We also report results of measurements performed at the Heidelberg Ion-Beam Therapy Centre with one third of the detector, using proton and carbon ion beams.
Prompt secondary radiations such as gamma rays and protons can be used for ion-range monitoring during ion therapy either on an energy-slice basis or on a pencil-beam basis. We present a review of ...the ongoing activities in terms of detector developments, imaging, experimental and theoretical physics issues concerning the correlation between the physical dose and hadronic processes.
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