Benchmark of the PenRed Monte Carlo framework for HDR brachytherapy

[EN] Purpose: The purpose of this study is to validate the PenRed Monte Carlo framework for clinical applications in brachytherapy. PenRed is a C++ version of Penelope Monte Carlo code with additional tallies and utilities. Methods and materials: Six benchmarking scenarios are explored to validate the use of PenRed and its improved bachytherapy-oriented capabilities for HDR brachytherapy. A new tally allowing the evaluation of collisional kerma for any material using the track length kerma estimator and the possibility to obtain the seed positions, weights and directions processing directly the DICOM file are now implemented in the PenRed distribution. The four non-clinical test cases developed by the Joint AAPM-ESTRO-ABG-ABS WG-DCAB were evaluated by comparing local and global absorbed dose differences with respect to established reference datasets. A prostate and a palliative lung cases, were also studied. For them, absorbed dose ratios, global absorbed dose differences, and cumulative dose-volume histograms were obtained and discussed. Results: The air-kerma strength and the dose rate constant corresponding to the two sources agree with the reference datatests within 0.3% (Sk) and 0.1% (¿). With respect to the first three WG-DCAB test cases, more than 99.8% of the voxels present local (global) differences within ±1%(±0.1%) of the reference datasets. For test Case 4 reference dataset, more than 94.9%(97.5%) of voxels show an agreement within ±1%(±0.1%), better than similar benchmarking calculations in the literature. The track length kerma estimator scorer implemented increases the numerical efficiency of brachytherapy calculations two orders of magnitude, while the specific brachytherapy source allows the user to avoid the use of error-prone intermediate steps to translate the DICOM information into the simulation. In both clinical cases, only minor absorbed dose differences arise in the low-dose isodoses. 99.8% and 100% of the voxels have a global absorbed dose difference ratio within ±0.2% for the prostate and lung cases, respectively. The role played by the different segmentation and composition material in the bone structures was discussed, obtaining negligible absorbed dose differences. Dose-volume histograms were in agreement with the reference data. Conclusions: PenRed incorporates new tallies and utilities and has been validated for its use for detailed and precise high-dose-rate brachytherapy simulations.This work is partially supported by the Ministerio de Ciencia e Innovación of Spain (MCIN) grants PID2020- 113126RB-I00 and PID2021-125096NB-I00 funded by MCIN/AEI/10.13039/501100011033. V. G. acknowledges partial support from AEI-MICINN under grant PID2020-1 13334GB-I00/AEI/10.13039/501100011033 and by Generalitat Valenciana through the project PROMETEO/2019/087. The work has also been supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) grant RGPIN-2019-05038. Francisco Berumen acknowledges support by the Fonds de Recherche du Québec ¿ Nature et Technologies (FRQNT). J.V. and F.B. would like to acknowledge funding by MCIN/ AEI/10.13039 and the Generalitat Valenciana (GVA) grant PROMETEO/2021/064. Our colleague Prof. Vicent Giménez Gómez passed away on November 16, 2022, during the proofs of this study. We dedicate it to his memory. The Universitat de València lost a dedicated and accomplished physicist.Oliver-Gil, S.; Giménez-Alventosa, V.; Berumen, F.; Giménez, V.; Beaulieu, L.; Ballester, F.; Vijande, J. (2023). Benchmark of the PenRed Monte Carlo framework for HDR brachytherapy. Zeitschrift für Medizinische Physik. 33(4):511-528. https://doi.org/10.1016/j.zemedi.2022.11.00251152833

TOF studies for dedicated PET with open geometries

[EN] Recently, two novel PET devices have been developed with open geometries, namely: breast and prostate-dedicated scanners. The breast-dedicated system comprises two detector rings of twelve modules with a field of view of 170 mm x 170 mm x 94 mm. Each module consists of a continuous trapezoidal LYSO crystal and a PSPMT. The system has the capability to vary the opening of the rings up to 60 mm in order to allow the insertion of a needle to perform a biopsy procedure. The prostate system has an open geometry consisting on two parallel plates separated 28 cm. One panel includes 18 detectors organized in a 6 x 3 matrix while the second one comprises 6 detectors organized in a 3 x 2 matrix. All detectors are formed by continuous LYSO crystals of 50 mm x 50 mm x15 mm, and a SiPM array of 12 x 12 individual photo-detectors. The system geometry is asymmetric maximizing the sensitivity of the system at the prostate location, located at about 2/3 in the abdomen-anus distance. The reconstructed images for PET scanners with open geometries present severe artifacts due to this peculiarity. These artifacts can be minimized using Time Of Flight information (TOF). In this work we present a TOF resolution study for open geometries. With this aim, the dedicated breast and prostate systems have been simulated using GATE (8.1 version) with different TOF resolutions in order to determine the image quality improvements that can be achieved with the existing TOF-dedicated electronics currently present in the market. The images have been reconstructed using the LMOS algorithm including TOF modeling in the calculation of the voxel-Line Of Response emission probabilities.This work was supported in part by the Spanish Government Grants TEC2016-79884-C2 and RTC-2016-5186-1 and by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant Agreement No. 695536).Moliner, L.; Ilisie, V.; González Martínez, AJ.; Oliver-Gil, S.; Gonzalez, A.; Giménez-Alventosa, V.; Cañizares, G.... (2019). TOF studies for dedicated PET with open geometries. Journal of Instrumentation. 14:1-8. https://doi.org/10.1088/1748-0221/14/02/C02006S181

Building blocks of a multi-layer PET with time sequence photon interaction discrimination and double Compton camera

[EN] Current PET detectors have a very low sensitivity, of the order of a few percent. One of the reasons is the fact that Compton interactions are rejected. If an event involves multiple Compton scattering and the total deposited energy lays within the photoelectric peak, then an energy-weighted centroid is the given output for the coordinates of the reconstructed interaction point. This introduces distortion in the final reconstructed image. The aim of our work is to prove that Compton events are a very rich source of additional information as one can improve the resolution of the detector and implicitly the final reconstructed image. This could be a real breakthrough for PET detector technology as one should be able to obtain better results with less patient radiation. Using a PET as a double Compton camera, by means of Compton cone matching i.e., Compton cones coming from the same event should be compatible, is applied to discard randoms, patient scattered events and also, to perform a correct matching among events with multiple coincidences. In order to fully benefit experimentally from Compton events using monolithic scintillators a multi-layer configuration is needed and a good time-of-flight resolution.This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 695536). This work was supported in part by the Spanish Government Grants TEC2016-79884-C2 and RTC-2016-5186-1.Ilisie, V.; Giménez-Alventosa, V.; Moliner Martínez, L.; Sánchez, F.; González Martínez, AJ.; Rodríguez-Álvarez, M.; Benlloch Baviera, JM. (2018). Building blocks of a multi-layer PET with time sequence photon interaction discrimination and double Compton camera. Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment. 895:74-83. https://doi.org/10.1016/j.nima.2018.03.076S748389

PenRed: An extensible and parallel Monte-Carlo framework for radiation transport based on PENELOPE

The authors are deeply indebted to F. Salvat for many com-ments and suggestions, for clarifying many subtleties of the sim-ulation algorithms of the transport of particles through matter, specially using PENELOPE, and for his patience and understanding. The work of V. Gimenez-Alventosa was supported by the program "Ayudas para la contratacion de personal investigador en formacion de carhcter predoctoral, programa VALi+d" under grant number ACIF/2018/148 from the Conselleria d'Educacio of the Generalitat Valenciana and the Fondo Social Europeo (FSE) . V. Gimenez ac-knowledges partial support from FEDER/MCIyU-AEI under grant FPA201784543P, by the Severo Ochoa Excellence Program under grant SEV-2014-0398 and by Generalitat Valenciana through the project PROMETEO/2019/087.Giménez-Alventosa, V.; Giménez Gómez, V.; Oliver-Gil, S. (2021). PenRed: An extensible and parallel Monte-Carlo framework for radiation transport based on PENELOPE. Computer Physics Communications. 267:1-12. https://doi.org/10.1016/j.cpc.2021.108065S11226