First experimental test of a coded-mask gamma camera for proton therapy monitoring
Magdalena Kołodziej, Stephan Brons, Mikołaj Dubiel, George N Farah, Alexander Fenger, Ronja Hetzel, Jonas Kasper, Monika Kercz, Barbara Kołodziej, Linn Mielke, Gabriel Ostrzołek, Magdalena Rafecas, Jorge Roser, Katarzyna Rusiecka, Achim Stahl, Vitalii Urbanevych, Ming-Liang Wong and Aleksandra Wrońska
abstract
Objective. The objective of the presented study was to evaluate the feasibility of a coded-mask (CM) gamma camera for real-time range verification in proton therapy, addressing the need for a precise and efficient method of treatment monitoring. Approach. A CM gamma camera prototype was tested in clinical conditions. The setup incorporated a scintillator-based detection system and a structured tungsten collimator. The experiment consisted of the irradiation of PMMA phantom with proton beams of energies ranging from 70.51 to 108.15 MeV. Experimental data were benchmarked against Monte Carlo simulations. The distal falloff position (DFP) was determined for both experimental data and simulations. Main results. The tested CM camera achieved a statistical precision of DFP determination of 1.7 mm for 108 protons, which is consistent with simulation predictions, despite hardware limitations such as non-functional detector pixels. Simulations indicated that a fully operational setup would further improve the performance of the detector. The system demonstrated rate capability sufficient for clinical proton beam intensities and maintained performance without significant dead time. Significance. This study validates the potential of the CM gamma camera for real-time proton therapy monitoring. The technology promises to enhance treatment accuracy and patient safety, offering a competitive alternative to existing approaches such as single-slit and multi-slit systems.
Comparison of readout systems for high-rate silicon photomultiplier applications
M. L. Wong, M. Kołodziej, K. Briggl, R. Hetzel, G. Korcyl, R. Lalik, A. Malige, A. Magiera, G. Ostrzołek, K. Rusiecka, A. Stahl, V. Urbanevych, M. Wiebusch, A. Wrońska
abstract
Recent years have shown an increased use of silicon photomultipliers (SiPM) in experimentsas they are of reasonable cost, have relatively low power consumption and are easily available in avariety of form factors allowing for a large number of readout channels. At the same time, experimentsare generating data at increasingly high rates requiring the use of more efficient readout systems. Inthis work, the dead time, efficiency, dynamic range, coincidence time resolution and energy resolutionof five different readout systems at various stages of maturity are evaluated to determine the bestsystem for acquiring data from a detector in a high rate experiment. Additional functionalities ofthe systems are also discussed.
Near-field coded-mask technique and its potential for proton therapy monitoring
R. Hetzel, V. Urbanevych, A. Bolke, J. Kasper, M. Kercz, M. Kołodziej, A. Magiera, F. Mueller, S. Müller, M. Rafecas, K. Rusiecka, D. Schug, V. Schulz, A. Stahl, B. Weissler, M.-L. Wong, A. Wrońska
abstract
Objective. Prompt-gamma imaging encompasses several approaches to the online monitoring of the beam range or deposited dose distribution in proton therapy. We test one of the imaging techniques - a coded mask approach - both experimentally and via simulations. Approach. Two imaging setups have been investigated experimentally. Each of them comprised a structured tungsten collimator in the form of a modified uniformly redundant array mask and a LYSO:Ce scintillation detector of fine granularity. The setups differed in detector dimensions and operation mode (1D or 2D imaging). A series of measurements with radioactive sources have been conducted, testing the performance of the setups for near-field gamma imaging. Additionally, Monte Carlo simulations of a larger setup of the same type were conducted, investigating its performance with a realistic gamma source distribution occurring during proton therapy. Main results. The images of point-like sources reconstructed from two small-scale prototypes' data using the maximum-likelihood expectation maximisation algorithm constitute the experimental proof of principle for the near-field coded-mask imaging modality, both in the 1D and the 2D mode. Their precision allowed us to calibrate out certain systematic offsets appearing due to the limited alignment accuracy of setup elements. The simulation of the full-scale setup yielded a mean distal falloff retrieval precision of 0.72 mm in the studies for beam energy range 89.5?107.9 MeV and with 1 × 108 protons (a typical number for distal spots). The implemented algorithm of image reconstruction is relatively fast?a typical procedure needs several seconds. Significance. Coded-mask imaging appears a valid option for proton therapy monitoring. The results of simulations let us conclude that the proposed full-scale setup is competitive with the knife-edge-shaped and the multi-parallel slit cameras investigated by other groups.
