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Fisk M, Rowshanfarzad P, Pfefferlé D, Fernandez de Viana M, Cabrera J, Ebert MA. Development and optimisation of grid inserts for a preclinical radiotherapy system and corresponding Monte Carlo beam simulations. Phys Med Biol 2024; 69:055010. [PMID: 38262060 DOI: 10.1088/1361-6560/ad21a1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 01/23/2024] [Indexed: 01/25/2024]
Abstract
Objective. To develop a physical grid collimator compatible with the X-RAD preclinical radiotherapy system and create a corresponding Monte Carlo (MC) model.Approach. This work presents a methodology for the fabrication of a grid collimator designed for utilisation on the X-RAD preclinical radiotherapy system. Additionally, a MC simulation of the grid is developed, which is compatible with the X-RAD treatment planning system. The grid was manufactured by casting a low melting point alloy, cerrobend, into a silicone mould. The silicone was moulded around a 3D-printed replica of the grid, enabling the production of diverging holes with precise radii and spacing. A MC simulation was conducted on an equivalent 3D grid model and validated using 11 layers of GAFChromic EBT-3 film interspersed in a 3D-printed water-equivalent phantom. A 3D dose distribution was constructed from the film layers, enabling a direct comparison with the MC Simulation.Main results. The film and the MC dose distribution demonstrated a gamma passing rate of 99% for a 1%, 0.5 mm criteria with a 10% threshold applied. The peak-to-valley dose ratio and output factor at the surface were determined to be 20.4 and 0.79, respectively.Significance. The pairing of the grid collimator with a MC simulation can significantly enhance the practicality of grid therapy on the X-RAD. This combination enables further exploration of the biological implications of grid therapy, supported by a knowledge of the complex dose distributions. Moreover, this methodology can be adapted for use in other systems and scenarios.
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Affiliation(s)
- Marcus Fisk
- School of Physics, Mathematics, and Computing, University of Western Australia, Crawley WA, Australia
- Riverina Cancer Care Centre, Wagga Wagga NSW, Australia
| | - Pejman Rowshanfarzad
- School of Physics, Mathematics, and Computing, University of Western Australia, Crawley WA, Australia
- Centre for Advanced Technologies in Cancer Research (CATCR), Perth, Australia
| | - David Pfefferlé
- School of Physics, Mathematics, and Computing, University of Western Australia, Crawley WA, Australia
| | | | | | - Martin A Ebert
- School of Physics, Mathematics, and Computing, University of Western Australia, Crawley WA, Australia
- Centre for Advanced Technologies in Cancer Research (CATCR), Perth, Australia
- Department of Radiation Oncology, Sir Charles Gairdner Hospital, Hospital Ave, Nedlands WA, Australia
- 5D Clinics, Claremont, Western Australia, Australia
- School of Medicine and Public Health, University of Wisconsin, Madison WI, United States of America
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Clements N, Bazalova-Carter M, Esplen N. Monte Carlo optimization of a GRID collimator for preclinical megavoltage ultra-high dose rate spatially-fractionated radiation therapy. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac8c1a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 08/23/2022] [Indexed: 11/12/2022]
Abstract
Abstract
Objective. A 2-dimensional pre-clinical SFRT (GRID) collimator was designed for use on the ultra-high dose rate (UHDR) 10 MV ARIEL beamline at TRIUMF. TOPAS Monte Carlo simulations were used to determine optimal collimator geometry with respect to various dosimetric quantities. Approach. The GRID-averaged peak-to-valley dose ratio (PVDR) and mean dose rate of the peaks were investigated with the intent of maximizing both values in a given design. The effects of collimator thickness, focus position, septal width, and hole width on these metrics were found by testing a range of values for each parameter on a cylindrical GRID collimator. For each tested collimator geometry, photon beams with energies of 10, 5, and 1 MV were transported through the collimator and dose rates were calculated at various depths in a water phantom located 1.0 cm from the collimator exit. Main results. In our optimization, hole width proved to be the only collimator parameter which increased both PVDR and peak dose rates. From the optimization results, it was determined that our optimized design would be one which achieves the maximum dose rate for a PVDR
≥
5
at 10 MV. Ultimately, this was achieved using a collimator with a thickness of 75 mm, 0.8 mm septal and hole widths, and a focus position matched to the beam divergence. This optimized collimator maintained the PVDR of 5 in the phantom between water depths of 0–10 cm at 10 MV and had a mean peak dose rate of
3.06
±
0.02
Gy
s
−
1
at 0–1 cm depth. Significance. We have investigated the impact of various GRID-collimator design parameters on the dose rate and spatial fractionation of 10, 5, and 1 MV photon beams. The optimized collimator design for the 10 MV ultra-high dose rate photon beam could become a useful tool for radiobiology studies synergizing the effects of ultra-high dose rate (FLASH) delivery and spatial fractionation.
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Moghaddasi L, Reid P, Bezak E, Marcu LG. Radiobiological and Treatment-Related Aspects of Spatially Fractionated Radiotherapy. Int J Mol Sci 2022; 23:3366. [PMID: 35328787 PMCID: PMC8954016 DOI: 10.3390/ijms23063366] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 03/13/2022] [Accepted: 03/17/2022] [Indexed: 11/17/2022] Open
Abstract
The continuously evolving field of radiotherapy aims to devise and implement techniques that allow for greater tumour control and better sparing of critical organs. Investigations into the complexity of tumour radiobiology confirmed the high heterogeneity of tumours as being responsible for the often poor treatment outcome. Hypoxic subvolumes, a subpopulation of cancer stem cells, as well as the inherent or acquired radioresistance define tumour aggressiveness and metastatic potential, which remain a therapeutic challenge. Non-conventional irradiation techniques, such as spatially fractionated radiotherapy, have been developed to tackle some of these challenges and to offer a high therapeutic index when treating radioresistant tumours. The goal of this article was to highlight the current knowledge on the molecular and radiobiological mechanisms behind spatially fractionated radiotherapy and to present the up-to-date preclinical and clinical evidence towards the therapeutic potential of this technique involving both photon and proton beams.
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Affiliation(s)
- Leyla Moghaddasi
- Department of Medical Physics, Austin Health, Ballarat, VIC 3350, Australia;
- School of Physical Sciences, University of Adelaide, Adelaide, SA 5001, Australia;
| | - Paul Reid
- Radiation Health, Environment Protection Authority, Adelaide, SA 5000, Australia;
| | - Eva Bezak
- School of Physical Sciences, University of Adelaide, Adelaide, SA 5001, Australia;
- Cancer Research Institute, University of South Australia, Adelaide, SA 5001, Australia
| | - Loredana G. Marcu
- Cancer Research Institute, University of South Australia, Adelaide, SA 5001, Australia
- Faculty of Informatics and Science, University of Oradea, 1 Universitatii Str., 410087 Oradea, Romania
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Zhang H, Wu X, Zhang X, Chang SX, Megooni A, Donnelly ED, Ahmed MM, Griffin RJ, Welsh JS, Simone CB, Mayr NA. Photon GRID Radiation Therapy: A Physics and Dosimetry White Paper from the Radiosurgery Society (RSS) GRID/LATTICE, Microbeam and FLASH Radiotherapy Working Group. Radiat Res 2021; 194:665-677. [PMID: 33348375 DOI: 10.1667/rade-20-00047.1] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 09/18/2020] [Indexed: 11/03/2022]
Abstract
The limits of radiation tolerance, which often deter the use of large doses, have been a major challenge to the treatment of bulky primary and metastatic cancers. A novel technique using spatial modulation of megavoltage therapy beams, commonly referred to as spatially fractionated radiation therapy (SFRT) (e.g., GRID radiation therapy), which purposefully maintains a high degree of dose heterogeneity across the treated tumor volume, has shown promise in clinical studies as a method to improve treatment response of advanced, bulky tumors. Compared to conventional uniform-dose radiotherapy, the complexities of megavoltage GRID therapy include its highly heterogeneous dose distribution, very high prescription doses, and the overall lack of experience among physicists and clinicians. Since only a few centers have used GRID radiation therapy in the clinic, wide and effective use of this technique has been hindered. To date, the mechanisms underlying the observed high tumor response and low toxicity are still not well understood. To advance SFRT technology and planning, the Physics Working Group of the Radiosurgery Society (RSS) GRID/Lattice, Microbeam and Flash Radiotherapy Working Groups, was established after an RSS-NCI Workshop. One of the goals of the Physics Working Group was to develop consensus recommendations to standardize dose prescription, treatment planning approach, response modeling and dose reporting in GRID therapy. The objective of this report is to present the results of the Physics Working Group's consensus that includes recommendations on GRID therapy as an SFRT technology, field dosimetric properties, techniques for generating GRID fields, the GRID therapy planning methods, documentation metrics and clinical practice recommendations. Such understanding is essential for clinical patient care, effective comparisons of outcome results, and for the design of rigorous clinical trials in the area of SFRT. The results of well-conducted GRID radiation therapy studies have the potential to advance the clinical management of bulky and advanced tumors by providing improved treatment response, and to further develop our current radiobiology models and parameters of radiation therapy design.
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Affiliation(s)
- Hualin Zhang
- Department of Radiation Oncology, Northwestern Memorial Hospital, Chicago, Illinois 60611
| | - Xiaodong Wu
- Excecutive Medical Physics Associates and Biophysics Research Institute of America, Miami, Florida 33179
| | - Xin Zhang
- Department of Radiation Oncology, Boston Medical Center, Boston, Massachusetts 02118
| | - Sha X Chang
- Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27516
| | - Ali Megooni
- Department of Radiation Therapy, Comprehensive Cancer Center of Nevada, Las Vegas, Nevada 86169
| | - Eric D Donnelly
- Department of Radiation Oncology, Northwestern Memorial Hospital, Chicago, Illinois 60611
| | - Mansoor M Ahmed
- Division of Cancer Treatment and Diagnosis, Rockville, Maryland 20892
| | - Robert J Griffin
- University of Arkansas for Medical Sciences, Department of Radiation Oncology, Little Rock, Arkansas
| | - James S Welsh
- Loyola University Chicago, Edward Hines Jr. VA Hospital, Stritch School of Medicine, Department of Radiation Oncology, Maywood, Illinois 60153
| | - Charles B Simone
- New York Proton Center, Department of Radiation Oncology, New York, New York 10035
| | - Nina A Mayr
- Department of Radiation Oncology, University of Washington Medical Center, Seattle, Washington 98195
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González W, Prezado Y. Spatial fractionation of the dose in heavy ions therapy: An optimization study. Med Phys 2018; 45:2620-2627. [PMID: 29633284 DOI: 10.1002/mp.12902] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 03/07/2018] [Accepted: 03/21/2018] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The alliance of charged particle therapy and the spatial fractionation of the dose, as in minibeam or Grid therapy, is an innovative strategy to improve the therapeutic index in the treatment of radioresistant tumors. The aim of this work was to assess the optimum irradiation configuration in heavy ion spatially fractionated radiotherapy (SFRT) in terms of ion species, beam width, center-to-center distances, and linear energy transfer (LET), information that could be used to guide the design of the future biological experiments. The nuclear fragmentation leading to peak and valley regions composed of different secondary particles, creates the need for a more complete dosimetric description that the classical one in SFRT. METHODS Monte Carlo simulations (GATE 6.2) were performed to evaluate the dose distributions for different ions, beam widths, and spacings. We have also assessed the 3D-maps of dose-averaged LET and proposed a new parameter, the peak-to-valley-LET ratio, to offer a more thorough physical evaluation of the technique. RESULTS Our results show that beam widths larger than 400 μm are needed in order to keep a ratio between the dose in the entrance and the dose in the target of the same order as in conventional irradiations. A large ctc distance (3500 μm) would favor tissue sparing since it provides higher PVDR, it leads to a reduced contribution of the heavier nuclear fragments and a LET value in the valleys a factor 2 lower than the LET in the ctc leading to homogeneous distributions in the target. CONCLUSIONS Heavy ions MBRT provide advantageous dose distributions. Thanks to the reduced lateral scattering, the use of submillimetric beams still allows to keep a ratio between the dose in the entrance and the dose in the target of the same order as in conventional irradiations. Large ctc distances (3500 μm) should be preferred since they lead to valley doses composed of lighter nuclear fragments resulting in a much reduced dose-averaged LET values in normal tissue, favoring its preservation. Among the different ions species evaluated, Ne stands out as the one leading to the best balance between high PVDR and PVLR in normal tissues and high LET values (close to 100 keV/μm) and a favorable oxygen enhancement ratio in the target region.
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Affiliation(s)
- W González
- IMNC-UMR 8165, CNRS, Paris 7 and Paris 11 Universities, 15 rue Georges Clemenceau, 91406, Orsay Cedex, France
| | - Y Prezado
- IMNC-UMR 8165, CNRS, Paris 7 and Paris 11 Universities, 15 rue Georges Clemenceau, 91406, Orsay Cedex, France
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