@article{Kelleter2020a, abstract = {The commissioning and operation of a particle therapy centre requires an extensive set of detectors for measuring various parameters of the treatment beam. Among the key devices are detectors for beam range quality assurance. In this work, a novel range telescope based on a plastic scintillator and read out by a large-scale CMOS sensor is presented. The detector is made of a stack of 49 plastic scintillator sheets with a thickness of 2-3 mm and an active area of 100 100 mm2, resulting in a total physical stack thickness of 124.2 mm. This compact design avoids optical artefacts that are common in other scintillation detectors. The range of a proton beam is reconstructed using a novel Bragg curve model that incorporates scintillator quenching effects. Measurements to characterise the performance of the detector were carried out at the Heidelberger Ionenstrahl-Therapiezentrum (HIT, Heidelberg, GER) and the Clatterbridge Cancer Centre (CCC, Bebington, UK). The maximum difference between the measured range and the reference range was found to be 0.41 mm at a proton beam range of 310 mm and was dominated by detector alignment uncertainties. With the new detector prototype, the water-equivalent thickness of PMMA degrader blocks has been reconstructed within 0.1 mm. An evaluation of the radiation hardness proves that the range reconstruction algorithm is robust following the deposition of 6,300 Gy peak dose into the detector. Furthermore, small variations in the beam spot size and transverse beam position are shown to have a negligible effect on the range reconstruction accuracy. The potential for range measurements of ion beams is also investigated.}, author = {Laurent Kelleter and Raffaella Radogna and Lennart Volz and Derek Attree and Anastasia Basharina-Freshville and Joao Seco and Ruben Saakyan and Simon Jolly}, doi = {10.1088/1361-6560/ab9415}, issn = {13616560}, issue = {16}, journal = {Physics in Medicine and Biology}, title = {A scintillator-based range telescope for particle therapy}, volume = {65}, year = {2020} } @article{Shaikh2024, abstract = {

Objective. The superior dose conformity provided by proton therapy relative to conventional x-ray radiotherapy necessitates more rigorous quality assurance (QA) procedures to ensure optimal patient safety. Practically however, time-constraints prevent comprehensive measurements to be made of the proton range in water: a key parameter in ensuring accurate treatment delivery. Approach. A novel scintillator-based device for fast, accurate water-equivalent proton range QA measurements for ocular proton therapy is presented. Experiments were conducted using a compact detector prototype, the quality assurance range calorimeter (QuARC), at the Clatterbridge cancer centre (CCC) in Wirral, UK for the measurement of pristine and spread-out Bragg peaks (SOBPs). The QuARC uses a series of 14 optically-isolated 100 × 100 × 2.85 mm polystyrene scintillator sheets, read out by a series of photodiodes. The detector system is housed in a custom 3D-printed enclosure mounted directly to the nozzle and a numerical model was used to fit measured depth-light curves and correct for scintillator light quenching. Main results. Measurements of the pristine 60 MeV proton Bragg curve found the QuARC able to measure proton ranges accurate to 0.2 mm and reduced QA measurement times from several minutes down to a few seconds. A new framework of the quenching model was deployed to successfully fit depth-light curves of SOBPs with similar range accuracy. Significance. The speed, range accuracy and simplicity of the QuARC make the device a promising candidate for ocular proton range QA. Further work to investigate the performance of SOBP fitting at higher energies/greater depths is warranted.

}, author = {Saad Shaikh and Sonia Escribano-Rodriguez and Raffaella Radogna and Laurent Kelleter and Connor Godden and Matthew Warren and Derek Attree and Ruben Saakyan and Linda Mortimer and Peter Corlett and Alison Warry and Andrew Gosling and Colin Baker and Andrew Poynter and Andrzej Kacperek and Simon Jolly}, doi = {10.1088/1361-6560/ad42fd}, issn = {0031-9155}, issue = {11}, journal = {Physics in Medicine \& Biology}, pages = {115015}, title = {Spread-out Bragg peak measurements using a compact quality assurance range calorimeter at the Clatterbridge cancer centre}, volume = {69}, year = {2024} } @article{Kelleter2020b, abstract = {Purpose: Recently, there has been increasing interest in the development of scintillator-based detectors for the measurement of depth–dose curves of therapeutic proton beams (Beaulieu and Beddar [2016], Phys Med Biol., 61:R305–R343). These detectors allow the measurement of single beam parameters such as the proton range or the reconstruction of the full three-dimensional dose distribution. Thus, scintillation detectors could play an important role in beam quality assurance, online beam monitoring, and proton imaging. However, the light output of the scintillator as a function of dose deposition is subject to quenching effects due to the high-specific energy loss of incident protons, particularly in the Bragg peak. The aim of this work is to develop a model that describes the percent depth-light curve in a quenching scintillator and allow the extraction of information about the beam range and the strength of the quenching. Methods: A mathematical expression of a depth-light curve, derived from a combination of Birks’ law (Birks [1951], Proc Phys Soc A., 64:874) and Bortfeld’s Bragg curve (Bortfeld [1997], Med Phys., 24:2024–2033) that is termed a “quenched Bragg” curve, is presented. The model is validated against simulation and measurement. Results: A fit of the quenched Bragg model to simulated depth-light curves in a polystyrene-based scintillator shows good agreement between the two, with a maximum deviation of 2.5% at the Bragg peak. The differences are larger behind the Bragg peak and in the dose build-up region. In the same simulation, the difference between the reconstructed range and the reference proton range is found to be always smaller than 0.16 mm. The comparison with measured data shows that the fitted beam range agrees with the reference range within their respective uncertainties. Conclusions: The quenched Bragg model is, therefore, an accurate tool for the range measurement from quenched depth–dose curves. Moreover, it allows the reconstruction of the beam energy spread, the particle fluence, and the magnitude of the quenching effect from a measured depth-light curve.}, author = {Laurent Kelleter and Simon Jolly}, doi = {10.1002/mp.14099}, issn = {24734209}, issue = {5}, journal = {Medical Physics}, title = {A mathematical expression for depth-light curves of therapeutic proton beams in a quenching scintillator}, volume = {47}, year = {2020} } @article{Volz2020, abstract = {Recently, it has been proposed that a mixed helium/carbon beam could be used for online monitoring in carbon ion beam therapy. Fully stripped, the two ion species exhibit approximately the same mass/charge ratio and hence could potentially be accelerated simultaneously in a synchrotron to the same energy per nucleon. At the same energy per nucleon, helium ions have about three times the range of carbon ions, which could allow for simultaneous use of the carbon ion beam for treatment and the helium ion beam for imaging. In this work, measurements and simulations of PMMA phantoms as well as anthropomorphic phantoms irradiated sequentially with a helium ion and a carbon ion beam at equal energy per nucleon are presented. The range of the primary helium ion beam and the fragment tail of the carbon ion beam exiting the phantoms were detected using a novel range telescope made of thin plastic scintillator sheets read out by a flat-panel CMOS sensor. A 10:1 carbon to helium mixing ratio is used, generating a helium signal well above the carbon fragment background while adding little to the dose delivered to the patient. The range modulation of a narrow air gap of 1 mm thickness in the PMMA phantom that affects less than a quarter of the particles in a pencil beam were detected, demonstrating the achievable relative sensitivity of the presented method. Using two anthropomorphic pelvis phantoms it is shown that small rotations of the phantom as well as simulated bowel gas movements cause detectable changes in the helium/carbon beam exiting the phantom. The future prospects and limitations of the helium/carbon mixing as well as its technical feasibility are discussed.}, author = {L. Volz and L. Kelleter and S. Brons and L. Burigo and C. Graeff and N. I. Niebuhr and R. Radogna and S. Scheloske and C. Schoemers and S. Jolly and J. Seco}, doi = {10.1088/1361-6560/ab6e52}, issn = {13616560}, issue = {5}, journal = {Physics in Medicine and Biology}, title = {Experimental exploration of a mixed helium/carbon beam for online treatment monitoring in carbon ion beam therapy}, volume = {65}, year = {2020} }