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Silvus A, Mazur TR, Goddu SM, Memming E, Zoberi JE, Markovina S, Altman MB. Dosimetric evaluation of a novel modular cell irradiation platform for multi-modality in vitro studies including high dose rate brachytherapy. Brachytherapy 2024; 23:549-558. [PMID: 38964977 DOI: 10.1016/j.brachy.2024.04.005] [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: 01/19/2024] [Revised: 04/06/2024] [Accepted: 04/30/2024] [Indexed: 07/06/2024]
Abstract
PURPOSE High dose-rate (HDR) brachytherapy is integral for the treatment of numerous cancers. Preclinical studies involving HDR brachytherapy are limited. We aimed to describe a novel platform allowing multi-modality studies with clinical HDR brachytherapy and external beam irradiators, establish baseline dosimetry standard of a preclinical orthovoltage irradiator, to determine accurate dosimetric methods. METHODS A dosimetric assessment of a commercial preclinical irradiator was performed establishing the baseline dosimetry goals for clinical irradiators. A 3D printed platform was then constructed with 14 brachytherapy channels at 1cm spacing to accommodate a standard tissue culture plate at a source-to-cell distance (SCD) of 1 cm or 0.4 cm. 4-Gy CT-based treatment plans were created in clinical treatment planning software and delivered to 96-well tissue culture plates using an Ir192 source or a clinical linear accelerator. Standard calculation models for HDR brachytherapy and external beam were compared to corresponding deterministic model-based dose calculation algorithms (MBDCAs). Agreement between predicted and measured dose was assessed with 2D-gamma passing rates to determine the best planning methodology. RESULTS Mean (±standard deviation) and median dose measured across the plate for the preclinical irradiator was 423.7 ± 8.5 cGy and 430.0 cGy. Mean percentage differences between standard and MBDCA dose calculations were 9.4% (HDR, 1 cm SCD), 0.43% (HDR, 0.4 cm SCD), and 2.4% (EBRT). Predicted and measured dose agreement was highest for MBDCAs for all modalities. CONCLUSION A 3D-printed tissue culture platform can be used for multi-modality irradiation studies with great accuracy. This tool will facilitate preclinical studies to reveal biologic differences between clinically relevant radiation modalities.
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Affiliation(s)
- Aaron Silvus
- Department of Radiation Oncology, Washington University School of Medicine in St. Louis, St. Louis, MO.
| | - Thomas R Mazur
- Department of Radiation Oncology, Washington University School of Medicine in St. Louis, St. Louis, MO
| | - S Murty Goddu
- Department of Radiation Oncology, Washington University School of Medicine in St. Louis, St. Louis, MO
| | - Ethan Memming
- Department of Radiation Oncology, Washington University School of Medicine in St. Louis, St. Louis, MO
| | - Jacqueline E Zoberi
- Department of Radiation Oncology, Washington University School of Medicine in St. Louis, St. Louis, MO
| | - Stephanie Markovina
- Department of Radiation Oncology, Washington University School of Medicine in St. Louis, St. Louis, MO
| | - Michael B Altman
- Department of Radiation Oncology, Washington University School of Medicine in St. Louis, St. Louis, MO
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Sioen S, D'Hondt L, Van Houte F, Demuynck R, Bacher K, De Wagter C, Vral A, Vanderstraeten B, Krysko DV, Baeyens A. Peripheral blood lymphocytes differ in DNA damage response after exposure to X-rays with different physical properties. Int J Radiat Biol 2024; 100:236-247. [PMID: 37819795 DOI: 10.1080/09553002.2023.2261525] [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: 02/06/2023] [Accepted: 09/08/2023] [Indexed: 10/13/2023]
Abstract
Introduction: In radiology, low X-ray energies (<140 keV) are used to obtain an optimal image while in radiotherapy, higher X-ray energies (MeV) are used to eradicate tumor tissue. In radiation research, both these X-ray energies being used to extrapolate in vitro research to clinical practice. However, the energy deposition of X-rays depends on their energy spectrum, which might lead to changes in biological response. Therefore, this study compared the DNA damage response (DDR) in peripheral blood lymphocytes (PBLs) exposed to X-rays with varying beam quality, mean photon energy (MPE) and dose rate.Methods: The DDR was evaluated in peripheral blood lymphocytes (PBLs) by the ɣ-H2AX foci assay, the cytokinesis-block micronucleus assay and an SYTOX-based cell death assay, combined with specific cell death inhibitors. Cell cultures were irradiated with a 220 kV X-ray research cabinet (SARRP, X-Strahl) or a 6 MV X-ray linear accelerator (Elekta Synergy). Three main physical parameters were investigated: beam quality (V), MPE (eV) and dose rate (Gy/min). Additional copper (Cu) filtration caused variation in the MPE (78 keV, 94 keV, 118 keV) at SARRP; dose rates were varied by adjusting tube current for 220 kV X-rays (0.33-3 Gy/min) or water-phantom depth in the 6 MV set-up (3-6 Gy/min).Results: The induction of chromosomal damage and initial (30 min) DNA double-stranded breaks (DSBs) were significantly higher for 220 kV X-rays compared to 6 MV X-rays, while cell death induction was similar. Specific cell death inhibitors for apoptosis, necroptosis and ferroptosis were not capable of blocking cell death after irradiation using low or high-energy X-rays. Additional Cu filtration increased the MPE, which significantly decreased the amount of chromosomal damage and DSBs. Within the tested ranges no specific effects of dose rate variation were observed.Conclusion: The DDR in PBLs is influenced by the beam quality and MPE. This study reinforces the need for consideration and inclusion of all physical parameters in radiation-related studies.
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Affiliation(s)
- Simon Sioen
- Radiobiology group, Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Louise D'Hondt
- Radiobiology group, Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Fien Van Houte
- Radiobiology group, Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Robin Demuynck
- Cell Death Investigation and Therapy Laboratory, Department of Human Structure and Repair, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Klaus Bacher
- Medical Physics Group, Department of Human Structure and Repair, Gent, Belgium
| | - Carlos De Wagter
- Medical Physics Group, Department of Human Structure and Repair, Gent, Belgium
- Department of Radiotherapy-Oncology, Ghent University Hospital, Gent, Belgium
| | - Anne Vral
- Radiobiology group, Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Barbara Vanderstraeten
- Medical Physics Group, Department of Human Structure and Repair, Gent, Belgium
- Department of Radiotherapy-Oncology, Ghent University Hospital, Gent, Belgium
| | - Dmitri V Krysko
- Cell Death Investigation and Therapy Laboratory, Department of Human Structure and Repair, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Ans Baeyens
- Radiobiology group, Department of Human Structure and Repair, Ghent University, Ghent, Belgium
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
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Gunasekara D, Wilkins R, Tessier F, Beaton-Green L. Monte Carlo modelling of experimental setup used for biodosimetry intercomparison. RADIATION PROTECTION DOSIMETRY 2023; 199:1551-1556. [PMID: 37721067 PMCID: PMC10788615 DOI: 10.1093/rpd/ncad166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 04/21/2023] [Accepted: 05/08/2023] [Indexed: 09/19/2023]
Abstract
When using biodosimetry techniques to assess absorbed dose from an ionising radiation exposure, a calibration curve is required. At Health Canada (HC), these curves are generated for a variety of radiation qualities and assays to translate biological damage into absorbed dose. They are produced by irradiating biological samples in custom-designed water-equivalent phantoms inside a cabinet X-ray machine. In the HC lab, two different phantoms can be used for irradiation that differs in material composition and internal geometry. To ensure consistency, the impact of using the phantoms interchangeably was investigated. This was done through lab measurements and the development of a Monte Carlo (MC) model. Differences up to 6.7% were found between the two experimental setups, indicating the need for careful consideration if using these setups interchangeably in the laboratory. Once validated, the MC model can be used to investigate different aspects of the experimental setup without the need for laboratory measurements.
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Affiliation(s)
- Dinindu Gunasekara
- Environmental and Radiation Health Sciences Directorate, Health Canada 775 Brookfield Rd, Ottawa K1A 1C1, Canada
| | - Ruth Wilkins
- Environmental and Radiation Health Sciences Directorate, Health Canada 775 Brookfield Rd, Ottawa K1A 1C1, Canada
| | - Frédéric Tessier
- Ionizing Radiation Standards, National Research Council Canada 1200 Montréal Rd, Ottawa K1A 0R6, Canada
| | - Lindsay Beaton-Green
- Environmental and Radiation Health Sciences Directorate, Health Canada 775 Brookfield Rd, Ottawa K1A 1C1, Canada
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Tanabe Y, Iseri T, Onizuka R, Ishida T, Eto H, Nakaichi M. Improving animal-specific radiotherapy quality assurance for kilovoltage X-ray radiotherapy using a 3D printed dog skull water phantom. Open Vet J 2023; 13:427-432. [PMID: 37251269 PMCID: PMC10219815 DOI: 10.5455/ovj.2023.v13.i4.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 03/10/2023] [Indexed: 05/31/2023] Open
Abstract
Background Accurate dose assessment during animal radiotherapy is beneficial for veterinary medicine and medical education. Aim To visualize the radiation treatment distribution of orthovoltage X-ray equipment in clinical practice using Monte Carlo simulations and create a dog skull water phantom for animal-specific radiotherapy. Methods EGSnrc-based BEAMnrc and DOSXYZnrc codes were used to simulate orthovoltage dose distributions. At 10, 20, 30, 40, 50, and 80 mm in a water phantom, the depth dose was measured with waterproof Farmer dosimetry chambers, and the diagonal off-axis ratio was measured with Gafchromic EBT3 film to simulate orthovoltage dose distributions. Energy differences between orthovoltage and linear accelerated radiotherapy were assessed with a heterogeneous bone and tissue virtual phantom. The animal-specific phantom for radiotherapy quality assurance (QA) was created from CT scans of a dog and printed with a three-dimensional printer using polyamide 12 nylon, with insertion points for dosimetry chambers and Gafchromic EBT3 film. Results Monte Carlo simulated and measured dose distributions differed by no more than 2.0% along the central axis up to a depth of 80 mm. The anode heel effect occurred in shallow areas. The orthovoltage radiotherapy percentage depth dose in bone was >40%. Build-up was >40%, with build-down after bone exit, whereas linear accelerator radiotherapy absorption changed little in the bone. A highly water-impermeable, animal-specific dog skull water phantom could be created to evaluate dose distribution. Conclusion Animal-specific water phantoms and Monte Carlo simulated pre-treatment radiotherapy are useful QA for orthovoltage radiotherapy and yield a visually familiar phantom that will be useful for veterinary medical education.
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Affiliation(s)
- Yoshinori Tanabe
- Faculty of Medicine, Graduate School of Health Sciences, Okayama University, Okayama, Japan
| | - Toshie Iseri
- Faculty of Agriculture, Animal Medical Emergency Center, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Ryouta Onizuka
- Department of Radiology, Kokura Memorial Hospital, Kitakyusyu, Japan
| | - Takayuki Ishida
- Division of Health Sciences, Graduate School of Medicine, Osaka, Japan
| | - Hidetoshi Eto
- Department of Radiology, Yamaguchi University Hospital, Ube, Japan
| | - Munekazu Nakaichi
- Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
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Choi DH, Ahn SH, Park K, Choi SH, Kim JS. Development of Total Lymphoid Irradiation (TLI)-Dedicated Shielding and Image-Guided System and Dose Evaluation Using 3D-Printed Rat Phantom. Front Vet Sci 2022; 9:832272. [PMID: 35664845 PMCID: PMC9159376 DOI: 10.3389/fvets.2022.832272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 04/04/2022] [Indexed: 11/13/2022] Open
Abstract
Purpose The purpose of this study is to propose a technique for delivering accurate doses in an image-guided system by developing an experimental setup optimized for total lymphoid irradiation (TLI) in rat lung transplantation. Materials and Methods In this study, a position-controlled shielding system was developed, and the dose was quantitatively evaluated using a 3D rat phantom and Gafchromic EBT3 film. In addition, we made our own image-guided system that allows the position of the rat and the shielding system to be confirmed during TLI. Results As a result of using the position-controlled shielding system, it was found that the doses to the head and lungs were reduced by 93.1 and 87.4%, respectively, of the prescribed doses. In addition, it was shown that the position of the shielding system can be easily confirmed by using the image guidance system. Conclusion A shielding apparatus that can control dose delivery according to the size of the rat can optimize the dose for TLI in rat lung transplantation.
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Affiliation(s)
- Dong Hyeok Choi
- Department of Medicine, Yonsei University College of Medicine, Seoul, South Korea
| | - So Hyun Ahn
- Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea
- *Correspondence: So Hyun Ahn
| | - Kwangwoo Park
- Department of Radiation Oncology, Yongin Severance Hospital, Yonsei University College of Medicine, Yongin, South Korea
- Kwangwoo Park
| | - Sang Hyun Choi
- Research Team of Radiological Physics and Engineering, Korea Institute of Radiological and Medical Sciences, Seoul, South Korea
| | - Jin Sung Kim
- Department of Medicine, Yonsei University College of Medicine, Seoul, South Korea
- Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea
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Mahuvava C, Esplen NM, Poirier Y, Kry SF, Bazalova-Carter M. Dose calculations for pre-clinical radiobiology experiments conducted with single-field cabinet irradiators. Med Phys 2022; 49:1911-1923. [PMID: 35066889 DOI: 10.1002/mp.15487] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 11/10/2021] [Accepted: 12/21/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To provide percentage depth-dose (PDD) data along the central axis for dosimetry calculations in small-animal radiation biology experiments performed in cabinet irradiators. The PDDs are provided as a function of source-to-surface distance (SSD), field size and animal size. METHODS The X-ray tube designs for four biological cabinet irradiators, the RS2000, RT250, MultiRad350 and XRAD320, were simulated using the BEAMnrc Monte Carlo code to generate 160, 200, 250 and 320 kVp photon beams, respectively. The 320 kVp beam was simulated with two filtrations: a soft F1 aluminium filter and a hard F2 thoraeus filter made of aluminium, tin and copper. Beams were collimated into circular fields with diameters of 0.5 - 10 cm at SSDs of 10 - 60 cm. Monte Carlo dose calculations in 1 - 5-cm diameter homogeneous (soft tissue) small-animal phantoms as well as in heterogeneous phantoms with 3-mm diameter cylindrical lung and bone inserts (rib and cortical bone) were performed using DOSXYZnrc. The calculated depth doses in three test-cases were estimated by applying SSD, field size and animal size correction factors to a reference case (40 cm SSD, 1 cm field and 5 cm animal size) and these results were compared with the specifically simulated (i.e., expected) doses to assess the accuracy of this method. Dosimetry for two test-case scenarios of 160 and 250 kVp beams (representative of end-user beam qualities) was also performed, whereby the simulated PDDs at two different depths were compared with the results based on the interpolation from reference data. RESULTS The depth doses for three test-cases calculated at 200, 320 kVp F1 and 320 kVp F2, with half value layers (HVL) ranging from ∼0.6 mm to 3.6 mm Cu, agreed well with the expected doses, yielding dose differences of 1.2, 0.1 and 1.0%, respectively. The two end-user test-cases for 160 and 250 kVp beams with respective HVLs of ∼0.8 and 1.8 mm Cu yielded dose differences of 1.4 and 3.2% between the simulated and the interpolated PDDs. The dose increase at the bone-tissue proximal interface ranged from 1.2 to 2.5 times the dose in soft tissue for rib and 1.3 to 3.7 times for cortical bone. The dose drop-off at 1-cm depth beyond the bone ranged from 1.3 - 6.0% for rib and 3.2 - 11.7% for cortical bone. No drastic dose perturbations occurred in the presence of lung, with lung-tissue interface dose of >99% of soft tissue dose and <3% dose increase at 1-cm depth beyond lung. CONCLUSIONS The developed dose estimation method can be used to translate the measured dose at a point to dose at any depth in small-animal phantoms, making it feasible for pre-clinical calculation of dose distributions in animals irradiated with cabinet-style irradiators. The dosimetric impact of bone must be accurately quantified as dramatic dose perturbations at and beyond the bone interfaces can occur due to the relative importance of the photoelectric effect at kilovoltage energies. These results will help improve dosimetric accuracy in pre-clinical experiments. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Courage Mahuvava
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 5C2, Canada
| | - Nolan Matthew Esplen
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 5C2, Canada
| | - Yannick Poirier
- Department of Medical Physics, McGill University, Montreal, Quebec, H4A 3J1, Canada
| | - Stephen F Kry
- Department of Radiation Physics, University of Texas MD Anderson, Cancer Centre, Houston, TX, 77030, USA
| | - Magdalena Bazalova-Carter
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 5C2, Canada
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Heidarloo N, Aghamiri SMR, Saghamanesh S, Azma Z, Alaei P. Generation of material-specific energy deposition kernels for kilovoltage x-ray dose calculations. Med Phys 2021; 48:5423-5439. [PMID: 34173989 DOI: 10.1002/mp.15061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 06/11/2021] [Accepted: 06/14/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE Dose calculation of kilovoltage x rays used in Image-Guided Radiotherapy has been investigated in recent years using various methods. Among these methods are model-based ones that suffer from inaccuracies in high-density materials and at interfaces when used in the kilovoltage energy range. The main reason for this is the use of water energy deposition kernels and simplifications employed such as density scaling in heterogeneous media. The purpose of this study was to produce and characterize material-specific energy deposition kernels, which could be used for dose calculations in this energy range. These kernels will also have utility in dose calculations in superficial radiation therapy and orthovoltage beams utilized in small animal irradiators. METHODS Water energy deposition kernels with various resolutions; and high-resolution, material-specific energy deposition kernels were generated in the energy range of 10-150 kVp, using the EGSnrc Monte Carlo toolkit. The generated energy deposition kernels were further characterized by calculating the effective depth of penetration, the effective radial distance, and the effective lateral distance. A simple benchmarking of the kernels against Monte Caro calculations has also been performed. RESULTS There was good agreement with previously reported water kernels, as well as between kernels with different resolution. The evaluation of effective depth of penetration, and radial and laterals distances, defines the relationship between energy, material density, and the shape of the material-specific kernels. The shape of these kernels becomes more forwardly scattered as the energy and material density are increased. The comparison of the dose calculated using the kernels with Monte Carlo provides acceptable results. CONCLUSIONS Water and material-specific energy deposition kernels in the kilovoltage energy range have been generated, characterized, and compared to previous work. These kernels will have utility in dose calculations in this energy range once algorithms capable of employing them are fully developed.
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Affiliation(s)
- Nematollah Heidarloo
- Department of Medical Radiation Engineering, Shahid Beheshti University, Tehran, Iran
| | | | - Somayeh Saghamanesh
- Center for X-ray Analytics, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Zohreh Azma
- Department of Medical Radiation Engineering, Shahid Beheshti University, Tehran, Iran.,Erfan Radiation Oncology Center, Erfan-Niyayesh Hospital, Iran University of Medical Science, Tehran, Iran
| | - Parham Alaei
- Department of Radiation Oncology, University of Minnesota, Minneapolis, MN, USA
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Scott BR, Lin Y, Saxton B, Chen W, Potter CA, Belinsky SA. Modeling Cell Survival Fraction and Other Dose-Response Relationships for Immunodeficient C.B-17 SCID Mice Exposed to 320-kV X Rays. Dose Response 2021; 19:15593258211019887. [PMID: 34104124 PMCID: PMC8170291 DOI: 10.1177/15593258211019887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 04/27/2021] [Accepted: 04/30/2021] [Indexed: 11/16/2022] Open
Abstract
US homeland security concerns related to potential misuse of γ-ray-emitting radiation sources employed in radiobiological research (eg, shielded cesium-137 irradiators) led to recommendations by the National Research Council to conduct studies into possibly replacing γ-ray irradiators used in research involving small rodent and other models with X-ray instruments. A limiting factor is suitability of the X-ray photon energy spectra. The objective of our research was to demonstrate the suitability of the radiation energy spectrum of 320-kV X rays after filtration (HVL = 4 mm Cu) for in-vivo cytotoxicity studies in immunodeficient C.B-17 SCID mice. By using a previously-published Hazard Function (HF) model to characterize dose-response relationships for in vivo bone marrow and spleen cell survival fractions and also to characterize the acute lethality risk (hematopoietic syndrome mode) we demonstrate that the filtered 320-kV X-ray beam appears suitable for such studies. A key finding for C.B-17 SCID mice when compared to results previously obtained for immunocompetent C.B-17 mice is that the immunodeficient mice appear to be more radioresistant, implicating a possible role of the immune system capacity in radiosensitivity of mammals.
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Affiliation(s)
- Bobby R Scott
- Lovelace Biomedical Research Institute, Albuquerque, NM, USA
| | - Yong Lin
- Lovelace Biomedical Research Institute, Albuquerque, NM, USA
| | - Bryanna Saxton
- Lovelace Biomedical Research Institute, Albuquerque, NM, USA
| | - Wenshu Chen
- Lovelace Biomedical Research Institute, Albuquerque, NM, USA
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Wang Y, Huang J, Wu Q, Zhang J, Ma Z, Ma S, Zhang S. Downregulation of breast cancer resistance protein by long-term fractionated radiotherapy sensitizes lung adenocarcinoma to SN-38. Invest New Drugs 2021; 39:458-468. [PMID: 33475937 DOI: 10.1007/s10637-020-01003-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 09/11/2020] [Indexed: 12/24/2022]
Abstract
Chemotherapy is usually the subsequent treatment for non-small cell lung cancer patients with acquired radioresistance after long-term fractionated radiotherapy. However, few studies have focused on the selection of chemotherapeutic drugs to treat lung adenocarcinoma patients with radioresistance. Our study compared the sensitivity changes of lung adenocarcinoma cells to conventional chemotherapeutic drugs under radioresistant circumstances by using three lung adenocarcinoma cell models, which were irradiated with fractionated X-rays at a total dose of 60 Gy. The results showed that the toxicities of paclitaxel, docetaxel and SN-38 were increased in radioresistant cells. The IC50 values of docetaxel and SN-38 decreased 0 ~ 3 times and 3 ~ 36 times in radioresistant cells, respectively. Notably, the A549 radioresistant cells were approximately 36 times more sensitive to SN-38 than the parental cells. Further results revealed that the downregulation of the efflux transporter BCRP by long-term fractionated irradiation was an important factor contributing to the increased cytotoxicity of SN-38. In addition, the reported miRNAs and transcriptional factors that regulate BCRP did not participate in the downregulation. In conclusion, these results presented important data on the sensitivity changes of lung adenocarcinoma cells to chemotherapeutic drugs after acquiring radioresistance and suggested that irinotecan (the prodrug of SN-38) might be a promising drug candidate for lung adenocarcinoma patients with acquired radioresistance.
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Affiliation(s)
- Yuqing Wang
- Translational Medicine Research Center, Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, 310006, China
| | - Jie Huang
- Translational Medicine Research Center, Hangzhou First People's Hospital, Nanjing Medical University, Nanjing, 211166, China
| | - Qiong Wu
- The fourth College of Clinical Medicine, Zhejiang Chinese Medical University, Hangzhou, 310053, China
| | - Jingjing Zhang
- Translational Medicine Research Center, Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, 310006, China
| | - Zhiyuan Ma
- Translational Medicine Research Center, Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, 310006, China
| | - Shenglin Ma
- Translational Medicine Research Center, Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, 310006, China.
| | - Shirong Zhang
- Translational Medicine Research Center, Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, 310006, China.
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Gott KM, Potter CA, Doyle-Eisele M, Lin Y, Wilder J, Scott BR. A Comparison of Cs-137 γ Rays and 320-kV X-Rays in a Mouse Bone Marrow Transplantation Model. Dose Response 2020; 18:1559325820916572. [PMID: 32284702 PMCID: PMC7139189 DOI: 10.1177/1559325820916572] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 02/11/2020] [Accepted: 02/18/2020] [Indexed: 01/14/2023] Open
Abstract
US homeland security concerns regarding the potential misuse of some radiation
sources used in radiobiological research, for example, cesium-137
(137Cs), have resulted in recommendations by the National
Research Council to conduct studies into replacing these sources with suitable
X-ray instruments. The objective of this research is to compare the
effectiveness of an X-RAD 320 irradiator (PXINC 2010) with a 137Cs
irradiator (Gammacell-1000 Unit) using an established bone marrow chimeric
model. Using measured radiation doses for each instrument, we characterized the
dose–response relationships for bone marrow and splenocyte ablation, using a
cytotoxicity-hazard model. Our results show that the X-RAD 320 photon energy
spectrum was suitable for ablating bone marrow at the 3 exposure levels used,
similar to that of 137Cs photons. However, the 320-kV X-rays were not
as effective as the much higher energy γ rays at depleting mouse splenocytes.
Furthermore, the 3 X-ray levels used were less effective than the higher energy
γ rays in allowing the successful engraftment of donor bone marrow, potentially
as a result of the incomplete depletion of the spleen cells. More defined
studies are warranted for determining whether bone marrow transplantation in
mice can be successfully achieved using 320-kV X-rays. A higher X-ray dose then
used is likely needed for transplantation success.
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Affiliation(s)
| | | | | | - Yong Lin
- Lovelace Respiratory Research Institute, Albuquerque, NM, USA
| | - Julie Wilder
- Sandia National Laboratories, Albuquerque, NM, USA
| | - Bobby R Scott
- Lovelace Respiratory Research Institute, Albuquerque, NM, USA
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Saikkonen A, Niemelä J, Sipilä P, Keyriläinen J. Commissioning of the MultiRad 350 cell and small animal x-ray irradiation system. Phys Med 2019; 59:107-111. [PMID: 30928058 DOI: 10.1016/j.ejmp.2019.03.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 01/22/2019] [Accepted: 03/05/2019] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The main objective of this study was to commission a commercial x-ray irradiation system to be used for cell and small animal studies. MATERIALS AND METHODS Evaluated characteristics of an x-ray irradiator included dose linearity and dose repeatability with respect to time, x-ray beam profiles, light field to irradiation field agreement and absolute radiation dose. Radiochromic films, ionization chambers and radiophotoluminescence dosimeters were used for dosimetry and the maximum settings of the irradiator were applied. RESULTS The dose was linear with time using several voltage settings and the dose repeatability with time was within 5% beyond 15 s of irradiation time. The x-ray beam profiles were acceptable, flatness being less than 4%. The light field to irradiation field agreement appeared to have a maximum difference of 0.5 cm; the irradiation field being closer to the irradiator's door than the light field. CONCLUSIONS The MultiRad 350 x-ray irradiation system can be used in a safe and controlled manner for irradiating cells and small animals. However, the user should be careful to verify the filter position prior the irradiation.
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Affiliation(s)
- Aleksi Saikkonen
- Department of Physics and Astronomy, Turku University, Vesilinnantie 5, FIN-20521 Turku, Finland; Department of Medical Physics & Department of Oncology and Radiotherapy, Turku University Hospital, Hämeentie 11, FIN-20521 Turku, Finland.
| | - Jarkko Niemelä
- Department of Physics and Astronomy, Turku University, Vesilinnantie 5, FIN-20521 Turku, Finland; Department of Medical Physics & Department of Oncology and Radiotherapy, Turku University Hospital, Hämeentie 11, FIN-20521 Turku, Finland
| | - Petri Sipilä
- Radiation and Nuclear Safety Authority (STUK), Laippatie 4, FIN-00880 Helsinki, Finland
| | - Jani Keyriläinen
- Department of Physics and Astronomy, Turku University, Vesilinnantie 5, FIN-20521 Turku, Finland; Department of Medical Physics & Department of Oncology and Radiotherapy, Turku University Hospital, Hämeentie 11, FIN-20521 Turku, Finland
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Chen Q, Molloy J, Izumi T, Sterpin E. Impact of backscatter material thickness on the depth dose of orthovoltage irradiators for radiobiology research. Phys Med Biol 2019; 64:055001. [PMID: 30673636 DOI: 10.1088/1361-6560/ab0120] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The orthovoltage x-ray energy frequently used in radiation research is prone to dosimetry errors due to insufficient backscatter conditions. In many radiobiology studies, especially for cell irradiations, precise dose calculation algorithms such as Convolution-Superposition or Monte Carlo are impractical and as such, less accurate hand calculation methods are used for dose estimation. These dose estimation methods typically assume full backscatter conditions. The purpose of this study is to demonstrate the magnitude of the dose error that results from insufficient backscatter, and to provide lookup tables to account this issue. The beam spectra of several widely used commercial systems (XRAD-225, XRAD-320, SARRP) were used in Monte Carlo (MC) simulations on a series of phantom setups to investigate the impact of varying backscatter conditions on dosimetry. The depth dose curves for different field sizes, water phantom thicknesses and beam qualities were generated. In addition, depth dependent backscatter factors for different field sizes and different beam qualities were calculated. It is demonstrated that as much as a 50% dose difference exists for different backscatter conditions at the beam qualities studied. The choice of cell dish size as well as other changes in the experiment setup can have more than 10% impact on the dose. The impact of backscatter is reduced with a decrease in field size. Further, the thickness needed to provide full backscatter can be approximated as being equal to the field size. It is imperative to ensure full backscatter conditions during system and dosimeter calibration, or to use the look-up table provided in this study.
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Affiliation(s)
- Quan Chen
- Department of Radiation Medicine, The University of Kentucky, Lexington, KY 40536, United States of America. Author to whom any correspondence should be addressed. Radiation Medicine, University of Kentucky, Markey Cancer Center, Rm CC063, 800 Rose St., Lexington, KY 40536-0293, United States of America
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Poirier Y, Johnstone CD, Kirkby C. The potential impact of ultrathin filter design on dosimetry and relative biological effectiveness in modern image-guided small animal irradiators. Br J Radiol 2018; 92:20180537. [PMID: 30281330 DOI: 10.1259/bjr.20180537] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE: Modern image-guided small animal irradiators like the Xstrahl Small Animal Radiation Research Platform (SARRP) are designed with ultrathin 0.15 mm Cu filters, which compared with more heavily filtrated traditional cabinet-style biological irradiators, produce X-ray spectra weighted toward lower energies, impacting the dosimetric properties and the relative biological effectiveness (RBE). This study quantifies the effect of ultrathin filter design on relative depth dose profiles, absolute dose output, and RBE using Monte Carlo techniques. METHODS: The percent depth-dose and absolute dose output are calculated using kVDoseCalc and EGSnrc, respectively, while a tally based on the induction of double-strand breaks as a function of electron spectra invoked in PENELOPE is used to estimate the RBE. RESULTS: The RBE increases by >2.4% in the ultrathin filter design compared to a traditional irradiator. Furthermore, minute variations in filter thickness have notable effects on the dosimetric properties of the X-ray beam, increasing the percent depth dose (at 2 cm in water) by + 0.4%/0.01 mm Cu and decreasing absolute dose (at 2 cm depth in water) by -1.8%/0.01 mm Cu for the SARRP. CONCLUSIONS: These results show that modern image-guided irradiators are quite sensitive to small manufacturing variations in filter thickness, and show a small change in RBE compared to traditional X-ray irradiators. ADVANCES IN KNOWLEDGE: We quantify the consequences of ultrathin filter design in modern image-guided biological irradiators on relative and absolute dose, and RBE. Our results show these to be small, but not insignificant, suggesting laboratories transitioning between irradiators should carefully design their radiobiological experiments.
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Affiliation(s)
- Yannick Poirier
- 1 Department of Radiation Oncology, Division of Translational Radiation Sciences, University of Maryland School of Medicine , Baltimore, MD , USA.,2 Department of Radiation Oncology, Division of Medical Physics, University of Maryland School of Medicine , Baltimore, MD , USA
| | - Christopher Daniel Johnstone
- 1 Department of Radiation Oncology, Division of Translational Radiation Sciences, University of Maryland School of Medicine , Baltimore, MD , USA.,3 Department of Physics and Astronomy, University of Victoria , Victoria, BC , Canada
| | - Charles Kirkby
- 4 Department of Medical Physics, Jack Ady Cancer Center , Lethbridge, AB , Canada.,5 Department of Physics and Astronomy, University of Calgary , Calgary, AB , Canada.,6 Department of Oncology, University of Calgary , Calgary, AB , Canada
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Kim TJ, Jung KO, Fahimian B, Pratx G. Flexible optically stimulated luminescence band for 1D in vivo radiation dosimetry. Phys Med Biol 2018; 63:165006. [PMID: 29999496 DOI: 10.1088/1361-6560/aad319] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In vivo dosimetry helps ensure the accuracy of radiation treatments. However, standard techniques are only capable of point sampling, making it difficult to accurately measure dose variation along curved surfaces in a continuous manner. The purpose of this work is to introduce a flexible dosimeter band and validate its performance using pre-clinical and clinical x-ray sources. Dosimeter bands were fabricated by uniformly mixing BaFBr:Eu storage phosphor powders into a silicone based elastomer. An optical readout device with dual-wavelength excitation was designed and built to correct for non-uniform phosphor density and extract accurate dose information. Results demonstrated significant correction of the non-uniform readout signal and excellent dose linearity up to 8 Gy irradiation using a pre-clinical 320 kV x-ray system. Beam profile measurements were demonstrated over a long distance of ~30 cm by placing multiple dosimeters in a single line and stitching the results. The performance of the dosimeters was also tested using a clinical linear accelerator (6 MV) and compared to radiochromic film. Once bias corrected, the bands displayed a linear dose response over the 1.02-9.36 Gy range (R 2 > 0.99). The proposed system can be further improved by reducing the size of the readout beam and by more uniformly mixing the phosphor powder with the elastomer. We expect this technique to find application for large-field treatments such as total-skin irradiation and total-body irradiation.
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Affiliation(s)
- Tae Jin Kim
- Department of Radiation Oncology, Stanford University, Stanford, CA 94305, United States of America
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Claridge Mackonis E, Hammond L, Esteves AIS, Suchowerska N. Radiation dosimetry in cell biology: comparison of calculated and measured absorbed dose for a range of culture vessels and clinical beam qualities. Int J Radiat Biol 2018; 94:150-156. [PMID: 29254418 DOI: 10.1080/09553002.2018.1419304] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE Cell culture studies are frequently used to evaluate the effects of cancer treatments such as radiotherapy, hormone therapy, chemotherapy, nanoparticle enhancement, and to determine any synergies between the treatments. To achieve valid results, the absorbed dose of each therapy needs to be well known and controlled. In this study, we aim to determine the uncertainty associated with radiation exposure in different experimental conditions. MATERIALS AND METHODS We have performed an in-depth evaluation of the absorbed dose and dose distribution that would be delivered to a cell sample when cultivated in a number of the more popular designs of culture vessels. We focus on exposure to two beam types: a kilovoltage x-ray beam and a megavoltage photon beam, both of which are routinely used to treat cancer patients in the clinical environment. CONCLUSIONS Our results identify large variations of up to 16% in the absorbed dose across multi-well culture plates, which if ignored in radiobiological experiments, have the potential to lead to erroneous conclusions.
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Affiliation(s)
| | - Lauren Hammond
- a Department of Radiation Oncology , Chris O'Brien Lifehouse , Camperdown , Australia
| | - Ana I S Esteves
- a Department of Radiation Oncology , Chris O'Brien Lifehouse , Camperdown , Australia.,b School of Physics , The University of Sydney , Camperdown , Australia
| | - Natalka Suchowerska
- a Department of Radiation Oncology , Chris O'Brien Lifehouse , Camperdown , Australia.,b School of Physics , The University of Sydney , Camperdown , Australia
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Poirier Y, Kuznetsova S, Villarreal-Barajas JE. Characterization of nanoDot optically stimulated luminescence detectors and high-sensitivity MCP-N thermoluminescent detectors in the 40-300 kVp energy range. Med Phys 2017; 45:402-413. [DOI: 10.1002/mp.12691] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 10/10/2017] [Accepted: 10/27/2017] [Indexed: 01/04/2023] Open
Affiliation(s)
- Yannick Poirier
- Department of Radiation Oncology; University of Maryland School of Medicine; Baltimore MD 21201 USA
| | - Svetlana Kuznetsova
- Department of Physics and Astronomy; University of Calgary; Calgary AB T2N 1N4 Canada
- Department of Oncology; University of Calgary; Calgary AB T2N 1N4 Canada
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Early assessment of dosimetric and biological differences of total marrow irradiation versus total body irradiation in rodents. Radiother Oncol 2017; 124:468-474. [PMID: 28778346 DOI: 10.1016/j.radonc.2017.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 07/15/2017] [Accepted: 07/15/2017] [Indexed: 11/22/2022]
Abstract
PURPOSE To develop a murine total marrow irradiation (TMI) model in comparison with the total body irradiation (TBI) model. MATERIALS AND METHODS Myeloablative TMI and TBI were administered in mice using a custom jig, and the dosimetric differences between TBI and TMI were evaluated. The early effects of TBI/TMI on bone marrow (BM) and organs were evaluated using histology, FDG-PET, and cytokine production. TMI and TBI with and without cyclophosphamide (Cy) were evaluated for donor cell engraftment and tissue damage early after allogeneic hematopoietic cell transplantation (HCT). Stromal derived factor-1 (SDF-1) expression was evaluated. RESULTS TMI resulted in similar dose exposure to bone and 50% reduction in dose to bystander organs. BM histology was similar between the groups. In the non-HCT model, TMI mice had significantly less acute intestinal and lung injury compared to TBI. In the HCT model, recipients of TMI had significantly less acute intestinal injury and spleen GVHD, but increased early donor cell engraftment and BM:organ SDF-1 ratio compared to TBI recipients. CONCLUSIONS The expected BM damage was similar in both models, but the damage to other normal tissues was reduced by TMI. However, BM engraftment was improved in the TMI group compared to TBI, which may be due to enhanced production of SDF-1 in BM relative to other organs after TMI.
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Fagerstrom JM, Bender ET, Lawless MJ, Culberson WS. Design of a modulated orthovoltage stereotactic radiosurgery system. Med Phys 2017; 44:3776-3787. [PMID: 28498612 DOI: 10.1002/mp.12336] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 05/01/2017] [Accepted: 05/01/2017] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To achieve stereotactic radiosurgery (SRS) dose distributions with sharp gradients using orthovoltage energy fluence modulation with inverse planning optimization techniques. METHODS A pencil beam model was used to calculate dose distributions from an orthovoltage unit at 250 kVp. Kernels for the model were derived using Monte Carlo methods. A Genetic Algorithm search heuristic was used to optimize the spatial distribution of added tungsten filtration to achieve dose distributions with sharp dose gradients. Optimizations were performed for depths of 2.5, 5.0, and 7.5 cm, with cone sizes of 5, 6, 8, and 10 mm. In addition to the beam profiles, 4π isocentric irradiation geometries were modeled to examine dose at 0.07 mm depth, a representative skin depth, for the low energy beams. Profiles from 4π irradiations of a constant target volume, assuming maximally conformal coverage, were compared. Finally, dose deposition in bone compared to tissue in this energy range was examined. RESULTS Based on the results of the optimization, circularly symmetric tungsten filters were designed to modulate the orthovoltage beam across the apertures of SRS cone collimators. For each depth and cone size combination examined, the beam flatness and 80-20% and 90-10% penumbrae were calculated for both standard, open cone-collimated beams as well as for optimized, filtered beams. For all configurations tested, the modulated beam profiles had decreased penumbra widths and flatness statistics at depth. Profiles for the optimized, filtered orthovoltage beams also offered decreases in these metrics compared to measured linear accelerator cone-based SRS profiles. The dose at 0.07 mm depth in the 4π isocentric irradiation geometries was higher for the modulated beams compared to unmodulated beams; however, the modulated dose at 0.07 mm depth remained <0.025% of the central, maximum dose. The 4π profiles irradiating a constant target volume showed improved statistics for the modulated, filtered distribution compared to the standard, open cone-collimated distribution. Simulations of tissue and bone confirmed previously published results that a higher energy beam (≥ 200 keV) would be preferable, but the 250 kVp beam was chosen for this work because it is available for future measurements. CONCLUSIONS A methodology has been described that may be used to optimize the spatial distribution of added filtration material in an orthovoltage SRS beam to result in dose distributions with decreased flatness and penumbra statistics compared to standard open cones. This work provides the mathematical foundation for a novel, orthovoltage energy fluence-modulated SRS system.
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Affiliation(s)
- Jessica M Fagerstrom
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | | | - Michael J Lawless
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | - Wesley S Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53705, USA
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Moore CS, Wood TJ, Cawthorne C, Hilton KL, Maher S, Saunderson JR, Archibald S, Beavis AW. A method to calibrate the RS 2000 x-ray biological irradiator for radiobiological flank irradiation of mice. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/3/037001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Indirect Tumor Cell Death After High-Dose Hypofractionated Irradiation: Implications for Stereotactic Body Radiation Therapy and Stereotactic Radiation Surgery. Int J Radiat Oncol Biol Phys 2015; 93:166-72. [PMID: 26279032 DOI: 10.1016/j.ijrobp.2015.05.016] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 05/06/2015] [Accepted: 05/12/2015] [Indexed: 01/14/2023]
Abstract
PURPOSE The purpose of this study was to reveal the biological mechanisms underlying stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS). METHODS AND MATERIALS FSaII fibrosarcomas grown subcutaneously in the hind limbs of C3H mice were irradiated with 10 to 30 Gy of X rays in a single fraction, and the clonogenic cell survival was determined with in vivo--in vitro excision assay immediately or 2 to 5 days after irradiation. The effects of radiation on the intratumor microenvironment were studied using immunohistochemical methods. RESULTS After cells were irradiated with 15 or 20 Gy, cell survival in FSaII tumors declined for 2 to 3 days and began to recover thereafter in some but not all tumors. After irradiation with 30 Gy, cell survival declined continuously for 5 days. Cell survival in some tumors 5 days after 20 to 30 Gy irradiation was 2 to 3 logs less than that immediately after irradiation. Irradiation with 20 Gy markedly reduced blood perfusion, upregulated HIF-1α, and increased carbonic anhydrase-9 expression, indicating that irradiation increased tumor hypoxia. In addition, expression of VEGF also increased in the tumor tissue after 20 Gy irradiation, probably due to the increase in HIF-1α activity. CONCLUSIONS Irradiation of FSaII tumors with 15 to 30 Gy in a single dose caused dose-dependent secondary cell death, most likely by causing vascular damage accompanied by deterioration of intratumor microenvironment. Such indirect tumor cell death may play a crucial role in the control of human tumors with SBRT and SRS.
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