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Koksal Akbas C, Vurro F, Fiorino C, Cozzarini C, Cavaliere F, Milani P, Broggi S, Del Vecchio A, Di Muzio N, Tacchetti C, Enrico Spinelli A. Preclinical photon minibeam radiotherapy using a custom collimator: Dosimetry characterization and preliminary in-vivo results on a glioma model. Phys Med 2024; 124:103420. [PMID: 38970950 DOI: 10.1016/j.ejmp.2024.103420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 05/28/2024] [Accepted: 06/28/2024] [Indexed: 07/08/2024] Open
Abstract
PURPOSE The purpose of this study is to investigate the dosimetric characteristics of a collimator for minibeam radiotherapy (MBRT) with film dosimetry and Monte Carlo (MC) simulations. The outcome of MBRT with respect to conventional RT using a glioma preclinical model was also evaluated. METHODS A multi-slit collimator was designed to be used with commercial small animal irradiator. The collimator was built by aligning 0.6 mm wide and 5 mm thick parallel lead leaves at 0.4 mm intervals. Dosimetry characteristics were evaluated by Gafchromic (CG) films and TOPAS Monte Carlo (MC) code. An in vivo experiment was performed using a glioma preclinical model by injecting two million GL261cells subcutaneously and treating with 25 Gy, single fraction, with MBRT and conventional RT. Survival curves and acute radiation damage were measured to compare both treatments. RESULTS A satisfactory agreement between experimental results and MC simulations were obtained, the measured FWHM and distance between the peaks were respectively 0.431 and 1.098 mm. In vivo results show that MBRT can provide local tumor control for three weeks after RT treatment and a similar survival fraction of open beam radiotherapy. No severe acute effects were seen for the MBRT group. CONCLUSIONS We developed a minibeam collimator and presented its dosimetric features. Satisfactory agreement between MC and GC films was found with differences consistent with uncertainties due to fabrication and set-up errors. The survival curves of MBRT and open field RT are similar while atoxicity is dramatically lower with MBRT, preliminarily confirming the expected effect.
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Affiliation(s)
- Canan Koksal Akbas
- Experimental Imaging Center, IRCCS San Raffaele Scientific Institute, Milan, Italy; Medical Physics Department, Istanbul University Oncology Institute, Istanbul, Turkey
| | - Federica Vurro
- Experimental Imaging Center, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Claudio Fiorino
- Medical Physics Department, IRCCS San Raffaele Scientific Institute, Milan, Italy.
| | - Cesare Cozzarini
- Radiotherapy Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | | | - Paolo Milani
- Department of Physics, University of Milan, Milan, Italy
| | - Sara Broggi
- Medical Physics Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | | | - Nadia Di Muzio
- Radiotherapy Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Carlo Tacchetti
- Experimental Imaging Center, IRCCS San Raffaele Scientific Institute, Milan, Italy
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Bazyar S, O’Brien ET, Benefield T, Roberts VR, Kumar RJ, Gupta GP, Zhou O, Lee YZ. Immune-Mediated Effects of Microplanar Radiotherapy with a Small Animal Irradiator. Cancers (Basel) 2021; 14:155. [PMID: 35008319 PMCID: PMC8750301 DOI: 10.3390/cancers14010155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 12/15/2021] [Accepted: 12/23/2021] [Indexed: 12/30/2022] Open
Abstract
Spatially fractionated radiotherapy has been shown to have effects on the immune system that differ from conventional radiotherapy (CRT). We compared several aspects of the immune response to CRT relative to a model of spatially fractionated radiotherapy (RT), termed microplanar radiotherapy (MRT). MRT delivers hundreds of grays of radiation in submillimeter beams (peak), separated by non-radiated volumes (valley). We have developed a preclinical method to apply MRT by a commercial small animal irradiator. Using a B16-F10 murine melanoma model, we first evaluated the in vitro and in vivo effect of MRT, which demonstrated significant treatment superiority relative to CRT. Interestingly, we observed insignificant treatment responses when MRT was applied to Rag-/- and CD8-depleted mice. An immuno-histological analysis showed that MRT recruited cytotoxic lymphocytes (CD8), while suppressing the number of regulatory T cells (Tregs). Using RT-qPCR, we observed that, compared to CRT, MRT, up to the dose that we applied, significantly increased and did not saturate CXCL9 expression, a cytokine that plays a crucial role in the attraction of activated T cells. Finally, MRT combined with anti-CTLA-4 ablated the tumor in half of the cases, and induced prolonged systemic antitumor immunity.
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Affiliation(s)
- Soha Bazyar
- Department of Radiation Oncology, University of Maryland, Maryland, MD 21201, USA;
| | - Edward Timothy O’Brien
- Department of Physics and Astronomy, The University of North Carolina, Chapel Hill, NC 27514, USA;
| | - Thad Benefield
- Department of Radiology, The University of North Carolina, Chapel Hill, NC 27514, USA;
| | | | - Rashmi J. Kumar
- Medical Scientist Training Program, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA;
| | - Gaorav P. Gupta
- Department of Radiation Oncology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA;
| | - Otto Zhou
- Department of Applied Physics Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA;
| | - Yueh Z. Lee
- Department of Radiology, The University of North Carolina, Chapel Hill, NC 27514, USA;
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA
- Biomedical Research Imaging Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA
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Cecchi DD, Therriault-Proulx F, Lambert-Girard S, Hart A, Macdonald A, Pfleger M, Lenckowski M, Bazalova-Carter M. Characterization of an x-ray tube-based ultrahigh dose-rate system for in vitro irradiations. Med Phys 2021; 48:7399-7409. [PMID: 34528283 DOI: 10.1002/mp.15234] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 07/21/2021] [Accepted: 08/30/2021] [Indexed: 01/06/2023] Open
Abstract
PURPOSE To present an x-ray tube system capable of in vitro ultrahigh dose-rate (UHDR) irradiation of small < 0.3 mm samples and to characterize it by means of a plastic scintillation detector (PSD). METHODS AND MATERIALS A conventional x-ray tube was modified for the delivery of short UHDR irradiations. A beam shutter system with a sample holder was designed and installed in a close proximity of an x-ray tube window to enable <1 s irradiations at UHDR. The dosimetry was performed with a small 0.5-mm long 0.5-mm in diameter PSD irradiated with 80, 100, and 120 kVp beams and beam currents of 1-37.5 mA. The PSD signal was recorded at frame rates of 20 and 50 fps for shutter exposure between 100 and 1125 ms. Irradiation reproducibility was studied with the PSD. The x-ray tube irradiation setup was modeled with Monte Carlo (MC) and dose on a surface of a phantom was also measured with films. The effect of dose delivery uncertainty to 300-μm spheroids due to positioning and spheroid size was evaluated. RESULTS MC simulations showed good agreement with PSD measurements acquired at both frame rates of 20 and 50 fps in terms of beam temporal profile. PSD-measured dose exhibited excellent linearity as a function of instantaneous dose rate from 3.1 to 118.0 Gy/s as well as shutter exposure time from 100 and 1125 ms for all investigated beam energies. PSD absorbed dose for the 80, 100, and 120 kVp beams agreed with MC simulations to within 5%. The total delivered doses ranged from 0.4 Gy for a 1-mA, 80 kVp beam, and 100 ms shutter exposure to 166.9 Gy for a 37.5-mA, 80 kVp beam, and a 1125 ms exposure. PSD irradiation reproducibility was < 0.5%. Simulated and measured dose fall off agreed and it was steep along the axis of the shutter slit (1%/0.1 mm) and with depth (2%/0.1 mm at 1-mm depth). Spheroid positioning uncertainty of 300 μm resulted in dose difference of < 3% for x and y shifts but up to 7% uncertainty for a z-shift parallel to the beam axis. A 16% difference in spheroid size resulted in <5% dose difference in spheroid absorbed dose. CONCLUSIONS We have presented a cost-effective x-ray tube-based system with a beam shutter designed for in vitro UHDR delivery and reaching dose rates of up to 118.0 Gy/s. The described shutter system can be easily implemented at other institutions, which might enable new researchers to investigate the radiobiology of UHDR irradiations in vitro.
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Affiliation(s)
- Daniel D Cecchi
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada
| | | | | | - Alexander Hart
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada
| | - Andrew Macdonald
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada
| | - Mike Pfleger
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada
| | - Mark Lenckowski
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada
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Treibel F, Nguyen M, Ahmed M, Dombrowsky A, Wilkens JJ, Combs SE, Schmid TE, Bartzsch S. Establishment of Microbeam Radiation Therapy at a Small-Animal Irradiator. Int J Radiat Oncol Biol Phys 2021; 109:626-636. [PMID: 33038461 DOI: 10.1016/j.ijrobp.2020.09.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 07/03/2020] [Accepted: 09/21/2020] [Indexed: 11/27/2022]
Abstract
PURPOSE Microbeam radiation therapy is a preclinical concept in radiation oncology. It spares normal tissue more effectively than conventional radiation therapy at equal tumor control. The radiation field consists of peak regions with doses of several hundred gray, whereas doses between the peaks (valleys) are below the tissue tolerance level. Widths and distances of the beams are in the submillimeter range for microbeam radiation therapy. A similar alternative concept with beam widths and distances in the millimeter range is presented by minibeam radiation therapy. Although both methods were developed at large synchrotron facilities, compact alternative sources have been proposed recently. METHODS AND MATERIALS A small-animal irradiator was fitted with a special 3-layered collimator that is used for preclinical research and produces microbeams of flexible width of up to 100 μm. Film dosimetry provided measurements of the dose distributions and was compared with Monte Carlo dose predictions. Moreover, the micronucleus assay in Chinese hamster CHO-K1 cells was used as a biological dosimeter. The focal spot size and beam emission angle of the x-ray tube were modified to optimize peak dose rate, peak-to-valley dose ratio (PVDR), beam shape, and field homogeneity. An equivalent collimator with slit widths of up to 500 μm produced minibeams and allowed for comparison of microbeam and minibeam field characteristics. RESULTS The setup achieved peak entrance dose rates of 8 Gy/min and PVDRs >30 for microbeams. Agreement between Monte Carlo simulations and film dosimetry is generally better for larger beam widths; qualitative measurements validated Monte Carlo predicted results. A smaller focal spot enhances PVDRs and reduces beam penumbras but substantially reduces the dose rate. A reduction of the beam emission angle improves the PVDR, beam penumbras, and dose rate without impairing field homogeneity. Minibeams showed similar field characteristics compared with microbeams at the same ratio of beam width and distance but had better agreement with simulations. CONCLUSION The developed setup is already in use for in vitro experiments and soon for in vivo irradiations. Deviations between Monte Carlo simulations and film dosimetry are attributed to scattering at the collimator surface and manufacturing inaccuracies and are a matter of ongoing research.
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Affiliation(s)
- Franziska Treibel
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany; Physics Department, Technical University of Munich, Garching, Germany
| | - Mai Nguyen
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany
| | - Mabroor Ahmed
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany; Physics Department, Technical University of Munich, Garching, Germany
| | - Annique Dombrowsky
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany
| | - Jan J Wilkens
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Physics Department, Technical University of Munich, Garching, Germany
| | - Stephanie E Combs
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany
| | - Thomas E Schmid
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany
| | - Stefan Bartzsch
- School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Technical University of Munich, Munich, Germany; Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany.
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Clinical microbeam radiation therapy with a compact source: specifications of the line-focus X-ray tube. PHYSICS & IMAGING IN RADIATION ONCOLOGY 2021; 14:74-81. [PMID: 33458318 PMCID: PMC7807643 DOI: 10.1016/j.phro.2020.05.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 05/20/2020] [Accepted: 05/29/2020] [Indexed: 02/02/2023]
Abstract
Line-focus X-ray tubes are suitable for clinical microbeam radiation therapy (MRT). A modular high-voltage supply safely enables high electron beam powers. An electron accelerator was designed to generate an eccentric focal spot. We simulated a peak-to-valley dose ratio above 20 for single-field MRT. Microbeam arc therapy spares healthy brain tissue compared to single-field MRT.
Background and purpose Microbeam radiotherapy (MRT) is a preclinical concept in radiation oncology with arrays of alternating micrometer-wide high-dose peaks and low-dose valleys. Experiments demonstrated a superior normal tissue sparing at similar tumor control rates with MRT compared to conventional radiotherapy. Possible clinical applications are currently limited to large third-generation synchrotrons. Here, we investigated the line-focus X-ray tube as an alternative microbeam source. Materials and methods We developed a concept for a high-voltage supply and an electron source. In Monte Carlo simulations, we assessed the influence of X-ray spectrum, focal spot size, electron incidence angle, and photon emission angle on the microbeam dose distribution. We further assessed the dose distribution of microbeam arc therapy and suggested to interpret this complex dose distribution by equivalent uniform dose. Results An adapted modular multi-level converter can supply high-voltage powers in the megawatt range for a few seconds. The electron source with a thermionic cathode and a quadrupole can generate an eccentric, high-power electron beam of several 100 keV energy. Highest dose rates and peak-to-valley dose ratios (PVDRs) were achieved for an electron beam impinging perpendicular onto the target surface and a focal spot smaller than the microbeam cross-section. The line-focus X-ray tube simulations demonstrated PVDRs above 20. Conclusion The line-focus X-ray tube is a suitable compact source for clinical MRT. We demonstrated its technical feasibility based on state-of-the-art high-voltage and electron-beam technology. Microbeam arc therapy is an effective concept to increase the target-to-entrance dose ratio of orthovoltage microbeams.
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Chicilo F, Hanson AL, Geisler FH, Belev G, Edgar A, Ramaswami KO, Chapman D, Kasap SO. Dose profiles and x-ray energy optimization for microbeam radiation therapy by high-dose, high resolution dosimetry using Sm-doped fluoroaluminate glass plates and Monte Carlo transport simulation. Phys Med Biol 2020; 65:075010. [PMID: 32242527 DOI: 10.1088/1361-6560/ab7361] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Microbeam radiation therapy (MRT) utilizes highly collimated synchrotron generated x-rays to create narrow planes of high dose radiation for the treatment of tumors. Individual microbeams have a typical width of 30-50 µm and are separated by a distance of 200-500 µm. The dose delivered at the center of the beam is lethal to cells in the microbeam path, on the order of hundreds of Grays (Gy). The tissue between each microbeam is spared and helps aid in the repair of adjacent damaged tissue. Radiation interactions within the peak of the microbeam, such as the photoelectric effect and incoherent (atomic Compton) scattering, cause some dose to be delivered to the valley areas adjacent to the microbeams. As the incident x-ray energy is modified, radiation interactions within a material change and affect the probability of interactions, as well as the directionality and energy of ionizing particles (electrons) that deposit energy in the valley regions surrounding the microbeam peaks. It is crucial that the valley dose between microbeams be minimal to maintain the effectiveness of MRT. Using a monochromatic x-ray source with x-ray energies ranging from 30 to 150 keV, a detailed investigation into the effect of incident x-ray energy on the dose profiles of microbeams was performed using samarium doped fluoroaluminate (FA) glass as the medium. All dosimetric measurements were carried out using a purpose-built fluorescence confocal microscope dosimetric technique that used Sm-doped FA glass plates as the irradiated medium. Dose profiles are measured over a very a wide range of x-ray energies at micrometer resolution and dose distribution in the microbeam are mapped. The measured microbeam profiles at different energies are compared with the MCNP6 radiation transport code, a general transport code which can calculate the energy deposition of electrons as they pass through a given material. The experimentally measured distributions can be used to validate the results for electron energy deposition in fluoroaluminate glass. Code validation is necessary for using transport codes in future treatment planning for MRT and other radiation therapies. It is shown that simulated and measured micro beam-profiles are in good agreement, and micrometer level changes can be observed using this high-resolution dosimetry technique. Full width at 10% of the maximum peak (FW@10%) was used to quantify the microbeam width. Experimental measurements on FA glasses and simulations on the dependence of the FW@10% at various energies are in good agreement. Simulations on energy deposited in water indicate that FW@10% reaches a local minimum around energies 140 keV. In addition, variable slit width experiments were carried out at an incident x-ray energy of 100 keV in order to determine the effect of the narrowing slit width on the delivered peak dose. The microbeam width affects the peak dose, which decreases with the width of the microbeam. Experiments suggest that a typical microbeam width for MRT is likely to be between 20-50 µm based on this work.
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Affiliation(s)
- F Chicilo
- Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, Canada
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Bartzsch S, Corde S, Crosbie JC, Day L, Donzelli M, Krisch M, Lerch M, Pellicioli P, Smyth LML, Tehei M. Technical advances in x-ray microbeam radiation therapy. Phys Med Biol 2020; 65:02TR01. [PMID: 31694009 DOI: 10.1088/1361-6560/ab5507] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In the last 25 years microbeam radiation therapy (MRT) has emerged as a promising alternative to conventional radiation therapy at large, third generation synchrotrons. In MRT, a multi-slit collimator modulates a kilovoltage x-ray beam on a micrometer scale, creating peak dose areas with unconventionally high doses of several hundred Grays separated by low dose valley regions, where the dose remains well below the tissue tolerance level. Pre-clinical evidence demonstrates that such beam geometries lead to substantially reduced damage to normal tissue at equal tumour control rates and hence drastically increase the therapeutic window. Although the mechanisms behind MRT are still to be elucidated, previous studies indicate that immune response, tumour microenvironment, and the microvasculature may play a crucial role. Beyond tumour therapy, MRT has also been suggested as a microsurgical tool in neurological disorders and as a primer for drug delivery. The physical properties of MRT demand innovative medical physics and engineering solutions for safe treatment delivery. This article reviews technical developments in MRT and discusses existing solutions for dosimetric validation, reliable treatment planning and safety. Instrumentation at synchrotron facilities, including beam production, collimators and patient positioning systems, is also discussed. Specific solutions reviewed in this article include: dosimetry techniques that can cope with high spatial resolution, low photon energies and extremely high dose rates of up to 15 000 Gy s-1, dose calculation algorithms-apart from pure Monte Carlo Simulations-to overcome the challenge of small voxel sizes and a wide dynamic dose-range, and the use of dose-enhancing nanoparticles to combat the limited penetrability of a kilovoltage energy spectrum. Finally, concepts for alternative compact microbeam sources are presented, such as inverse Compton scattering set-ups and carbon nanotube x-ray tubes, that may facilitate the transfer of MRT into a hospital-based clinical environment. Intensive research in recent years has resulted in practical solutions to most of the technical challenges in MRT. Treatment planning, dosimetry and patient safety systems at synchrotrons have matured to a point that first veterinary and clinical studies in MRT are within reach. Should these studies confirm the promising results of pre-clinical studies, the authors are confident that MRT will become an effective new radiotherapy option for certain patients.
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Affiliation(s)
- Stefan Bartzsch
- Department of Radiation Oncology, School of Medicine, Technical University of Munich, Klinikum rechts der Isar, Munich, Germany. Helmholtz Centre Munich, Institute for Radiation Medicine, Munich, Germany
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Esplen N, Therriault-Proulx F, Beaulieu L, Bazalova-Carter M. Preclinical dose verification using a 3D printed mouse phantom for radiobiology experiments. Med Phys 2019; 46:5294-5303. [PMID: 31461781 DOI: 10.1002/mp.13790] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 08/16/2019] [Accepted: 08/16/2019] [Indexed: 01/14/2023] Open
Abstract
PURPOSE Dose verification in preclinical radiotherapy is often challenged by a lack of standardization in the techniques and technologies commonly employed along with the inherent difficulty of dosimetry associated with small-field kilovoltage sources. As a consequence, the accuracy of dosimetry in radiobiological research has been called into question. Fortunately, the development and characterization of realistic small-animal phantoms has emerged as an effective and accessible means of improving dosimetric accuracy and precision in this context. The application of three-dimensional (3D) printing, in particular, has enabled substantial improvements in the conformity of representative phantoms with respect to the small animals they are modeled after. In this study, our goal was to evaluate a fully 3D printed mouse phantom for use in preclinical treatment verification of sophisticated therapies for various anatomical targets of therapeutic interest. METHODS An anatomically realistic mouse phantom was 3D printed based on segmented microCT data of a tumor-bearing mouse. The phantom was modified to accommodate both laser-cut EBT3 radiochromic film within the mouse thorax and a plastic scintillator dosimeter (PSD), which may be placed within the brain, abdomen, or 1-cm flank subcutaneous tumor. Various treatments were delivered on an image-guided small-animal irradiator in order to determine the doses to isocenter using a PSD and validate lateral- and depth-dose distributions using film dosimeters. On-board cone-beam CT imaging was used to localize isocenter to the film plane or PSD active element prior to irradiation. The PSD irradiations comprised a 3 × 3 mm2 brain arc, 5 × 5 mm2 parallel-opposed pair (POP), and 5-beam 10 × 10 mm2 abdominal coplanar arrangement while two-dimensional (2D) film dose distributions were acquired using a 3 × 3 mm2 arc and both 5 × 5 and 10 × 10 mm2 3-beam coplanar plans. A validated Monte Carlo (MC) model of the source was used as to verify the accuracy of the film and PSD dose measurements. computer-aided design (CAD) geometries for the mouse phantom and dosimeters were imported directly into the MC code to allow for highly accurate reproduction of the physical experiment conditions. Experimental and MC-derived film data were co-registered and film dose profiles were compared for points above 90% of the dose maximum. Point dose measurements obtained with the PSD were similarly compared for each of the candidate (brain, abdomen, and tumor) treatment sites. RESULTS For each treatment configuration and anatomical target, the MC-calculated and measured doses met the proposed 5% agreement goal for dose accuracy in radiobiology experiments. The 2D film and MC dose distributions were successfully registered and mean doses for lateral profiles were found to agree to within 2.3% in all cases. Isocentric point-dose measurements taken with the PSD were similarly consistent, with a maximum percentage deviation of 3.2%. CONCLUSIONS Our study confirms the utility of 3D printed phantom design in providing accurate dose estimates for a variety of preclinical treatment paradigms. As a tool for pretreatment dose verification, the phantom may be of particular interest to researchers for its ability to facilitate precise dosimetry while fostering a reduction in cost for radiobiology experiments.
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Affiliation(s)
- Nolan Esplen
- Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - François Therriault-Proulx
- Departement de Radio-Oncologie and Centre de recherche du CHU de Quebec, CHU de Quebec, Quebec, QC, G1R 3S1, Canada
| | - Luc Beaulieu
- Departement de Radio-Oncologie and Centre de recherche du CHU de Quebec, CHU de Quebec, Quebec, QC, G1R 3S1, Canada.,Departement de physique and Centre de recherche sur le Cancer, Université Laval, Quebec, QC, G1V 0A6, Canada
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