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Borsavage JM, Cherpak AJ, Robar JL. Investigation of a novel 2.5 MV sintered diamond target beam for intracranial linac-based stereotactic treatments. Biomed Phys Eng Express 2024; 10:055035. [PMID: 39151448 DOI: 10.1088/2057-1976/ad7031] [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: 04/15/2024] [Accepted: 08/16/2024] [Indexed: 08/19/2024]
Abstract
Purpose. This work investigates the small-field dosimetric characteristics of a 2.5 MV sintered diamond target beam and its feasibility for use in linac-based intracranial stereotactic treatments. Due to the increased proportion of low energy photons in the low-Z beam, it was hypothesized that this novel beam would provide sharper dose fall-off compared to the 6 MV beam owing to the reduced energy, and therefore range, of secondary electrons.Methods. Stereotactic treatments of ocular melanoma and trigeminal neuralgia were simulated for 2.5 MV low-Z and 6 MV beams using Monte Carlo to calculate dose in a voxelized anatomical phantom. Two collimation methods were investigated, including a 5 × 3 mm2HDMLC field and a 4 mm cone to demonstrate isolated and combined effects of geometric and radiological contributions to the penumbral width.Results. The measured 2.5 MV low-Z dosimetric profiles demonstrated reduced penumbra by 0.5 mm in both the inline and crossline directions across all depths for both collimation methods, compared to 6 MV. In both treatment cases, the 2.5 MV low-Z beam collimated with the 4 mm cone produced the sharpest dose fall off in profiles captured through isocenter. This improved fall-off resulted in a 59% decrease to the maximum brainstem dose in the trigeminal neuralgia case for the 2.5 MV low-Z MLC collimated beam compared to 6 MV. Reductions to the maximum and mean doses to ipsilateral and contralateral OARs in the ocular melanoma case were observed for the 2.5 MV low-Z beam compared to 6 MV with both collimation methods.Conclusions. While the low dose rate of this novel beam prohibits immediate clinical translation, the results of this study support the further development of this prototype beam to decrease toxicity in intracranial SRS treatments.
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Affiliation(s)
- Jennifer M Borsavage
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Amanda J Cherpak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Medical Physics, Nova Scotia Health Authority, Halifax, Nova Scotia, Canada
| | - James L Robar
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Medical Physics, Nova Scotia Health Authority, Halifax, Nova Scotia, Canada
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Parsons D, Joo M, Iqbal Z, Godley A, Kim N, Spangler A, Albuquerque K, Sawant A, Zhao B, Gu X, Rahimi A. Stability and reproducibility comparisons between deep inspiration breath-hold techniques for left-sided breast cancer patients: A prospective study. J Appl Clin Med Phys 2023; 24:e13906. [PMID: 36691339 PMCID: PMC10161105 DOI: 10.1002/acm2.13906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 12/06/2022] [Accepted: 12/23/2022] [Indexed: 01/25/2023] Open
Abstract
PURPOSE Deep inspiration breath-hold (DIBH) is crucial in reducing the lung and cardiac dose for treatment of left-sided breast cancer. We compared the stability and reproducibility of two DIBH techniques: Active Breathing Coordinator (ABC) and VisionRT (VRT). MATERIALS AND METHODS We examined intra- and inter-fraction positional variation of the left lung. Eight left-sided breast cancer patients were monitored with electronic portal imaging during breath-hold (BH) at every fraction. For each patient, half of the fractions were treated using ABC and the other half with VRT, with an equal amount starting with either ABC or VRT. The lung in each portal image was delineated, and the variation of its area was evaluated. Intrafraction stability was evaluated as the mean coefficient of variation (CV) of the lung area for the supraclavicular (SCV) and left lateral (LLat) field over the course of treatment. Reproducibility was the CV for the first image of each fraction. Daily session time and total imaging monitor units (MU) used in patient positioning were recorded. RESULTS The mean intrafraction stability across all patients for the LLat field was 1.3 ± 0.7% and 1.5 ± 0.9% for VRT and ABC, respectively. Similarly, this was 1.5 ± 0.7% and 1.6 ± 0.8% for VRT and ABC, respectively, for the SCV field. The mean interfraction reproducibility for the LLat field was 11.0 ± 3.4% and 14.9 ± 6.0% for VRT and ABC, respectively. Similarly, this was 13.0 ± 2.5% and 14.8 ± 9% for VRT and ABC, respectively, for the SCV. No difference was observed in the number of verification images required for either technique. CONCLUSIONS The stability and reproducibility were found to be comparable between ABC and VRT. ABC can have larger interfractional variation with less feedback to the treating therapist compared to VRT as shown in the increase in geometric misses at the matchline.
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Affiliation(s)
- David Parsons
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Mindy Joo
- Department of Radiation Oncology, Inova Fairfax Hospital, Falls Church, Virginia, USA
| | - Zohaib Iqbal
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Andrew Godley
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Nathan Kim
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Ann Spangler
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kevin Albuquerque
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Amit Sawant
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Bo Zhao
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Xuejun Gu
- Department of Radiation Oncology, Stanford University, Palo Alto, California, USA
| | - Asal Rahimi
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Khaledi N, Hayes C, Belshaw L, Grattan M, Khan R, Gräfe JL. Treatment planning with a 2.5 MV photon beam for radiation therapy. J Appl Clin Med Phys 2022; 23:e13811. [PMID: 36300870 PMCID: PMC9797178 DOI: 10.1002/acm2.13811] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 09/23/2022] [Indexed: 01/01/2023] Open
Abstract
PURPOSE The shallow depth of maximum dose and higher dose fall-off gradient of a 2.5 MV beam along the central axis that is available for imaging on linear accelerators is investigated for treatment of shallow tumors and sparing the organs at risk (OARs) beyond it. In addition, the 2.5 MV beam has an energy bridging the gap between kilo-voltage (kV) and mega-voltage (MV) beams for applications of dose enhancement with high atomic number (Z) nanoparticles. METHODS We have commissioned and utilized a MATLAB-based, open-source treatment planning software (TPS), matRad, for intensity-modulated radiation therapy (IMRT) dose calculations. Treatment plans for prostate, liver, and head and neck (H&N), nasal cavity, two orbit cases, and glioblastoma multiforme (GBM) were performed and compared to a conventional 6 MV beam. Additional Monte Carlo calculations were also used for benchmarking the central axis dose. RESULTS Both beams had similar planning target volume (PTV) dose coverage for all cases. However, the 2.5 MV beam deposited 6%-19% less integral doses to the nasal cavity, orbit, and GBM cases than 6 MV photons. The mean dose to the heart in the liver plan was 10.5% lower for 2.5 MV beam. The difference between the doses to OARs of H&N for two beams was under 3%. Brain mean dose, brainstem, and optic chiasm max doses were, respectively, 7.5%-14.9%, 2.2%-8.1%, and 2.5%-19.0% lower for the 2.5 MV beam in the nasal cavity, orbit, and GBM plans. CONCLUSIONS This study demonstrates that the 2.5 MV beam can produce clinically relevant treatment plans, motivating future efforts for design of single-energy LINACs. Such a machine will be capable of producing beams at this energy beneficial for low- and middle-income countries, and investigations on dose enhancement from high-Z nanoparticles.
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Affiliation(s)
- Navid Khaledi
- Department of PhysicsFaculty of ScienceToronto Metropolitan UniversityTorontoOntarioCanada
| | - Chris Hayes
- Radiotherapy PhysicsNorthern Ireland Cancer CentreBelfast Health and Social Care TrustBelfastUK
| | - Louise Belshaw
- Radiotherapy PhysicsNorthern Ireland Cancer CentreBelfast Health and Social Care TrustBelfastUK
| | - Mark Grattan
- Radiotherapy PhysicsNorthern Ireland Cancer CentreBelfast Health and Social Care TrustBelfastUK
| | - Rao Khan
- Department of PhysicsFaculty of ScienceToronto Metropolitan UniversityTorontoOntarioCanada,Department of Physics and Astronomy and Department of Radiation OncologyHoward UniversityWashingtonDistrict of ColumbiaUSA
| | - James L. Gräfe
- Department of PhysicsFaculty of ScienceToronto Metropolitan UniversityTorontoOntarioCanada
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van Eeden D, Mutsakanyi S, du Plessis F. Photon beam dose enhancement in AuNP AC tumour through energy moderation of a 6 MeV electron beam: A Monte Carlo study. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2021.109925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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O'Connell J, Bazalova‐Carter M. Investigation of image quality of MV and kV CBCT with low‐Z beams and high DQE detector. Med Phys 2022; 49:2334-2341. [DOI: 10.1002/mp.15503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 01/06/2022] [Accepted: 01/20/2022] [Indexed: 11/12/2022] Open
Affiliation(s)
- Jericho O'Connell
- Department of Physics and Astronomy University of Victoria Victoria BC V8W 2Y2 Canada
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O'Connell J, Bazalova-Carter M. fastCAT: Fast cone beam CT (CBCT) simulation. Med Phys 2021; 48:4448-4458. [PMID: 34053094 DOI: 10.1002/mp.15007] [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: 10/09/2020] [Revised: 05/19/2021] [Accepted: 05/21/2021] [Indexed: 01/08/2023] Open
Abstract
PURPOSE To develop fastCAT, a fast cone-beam computed tomography (CBCT) simulator. fastCAT uses pre-calculated Monte Carlo (MC) CBCT phantom-specific scatter and detector response functions to reduce simulation time for megavoltage (MV) and kilovoltage (kV) CBCT imaging. METHODS Pre-calculated x-ray beam energy spectra, detector optical spread functions and energy deposition, and phantom scatter kernels are combined with GPU raytracing to produce CBCT volumes. MV x-ray beam spectra are simulated with EGSnrc for 2.5- and 6 MeV electron beams incident on a variety of target materials and kV x-ray beam spectra are calculated analytically for an x-ray tube with a tungsten anode. Detectors were modeled in Geant4 extended by Topas and included optical transport in the scintillators. Two MV detectors were modeled-a standard Varian AS1200 GOS detector and a novel CWO high detective quantum efficiency detector. A kV CsI detector was also modeled. Energy-dependent scatter kernels were created in Topas for two 16 cm diameter phantoms: A Catphan 515 contrast phantom and an anthropomorphic head phantom. The Catphan phantom contained inserts of 1-5 mm in diameter of six different tissue types: brain, deflated lung, compact and cortical bone, adipose, and B-100. RESULTS fastCAT simulations retain high fidelity to measurements and MC simulations: MTF curves were within 3.5% and 1.2% of measured values for the CWO and GOS detectors, respectively. HU values and CNR in a fastCAT Catphan 515 simulation were seen to be within 95% confidence intervals of an equivalent MC simulation for all of the tissues with root mean squared errors less than 16 HU and 1.6 in HU values and CNR comparisons, respectively. The anthropomorphic head phantom CWO detector CBCT image resulted in much higher tissue contrast and lower noise compared to the GOS detector CBCT image. A fastCAT simulation of the Catphan 515 module with an image size of 1024 × 1024 × 10 voxels took 61 s on a GPU while the equivalent Topas MC was estimated to take more than 0.3 CPU years. CONCLUSIONS We present an open source fast CBCT simulation with high fidelity to MC simulations. The fastCAT python package can be found at https://github.com/jerichooconnell/fastCAT.git.
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Affiliation(s)
- Jericho O'Connell
- Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2, Canada
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Borsavage JM, Cherpak A, Robar JL. Investigation of planar image quality for a novel 2.5 MV diamond target beam from a radiotherapy linear accelerator. PHYSICS & IMAGING IN RADIATION ONCOLOGY 2021; 16:103-108. [PMID: 33458352 PMCID: PMC7807593 DOI: 10.1016/j.phro.2020.10.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 10/09/2020] [Accepted: 10/14/2020] [Indexed: 12/05/2022]
Abstract
Background and purpose A commercial 2.5 MV beam has been clinically available for beam’s-eye-view imaging in radiotherapy, offering improved contrast-to-noise ratio (CNR) compared to therapeutic beams, due to the softer spectrum. Previous research suggested that imaging performance could be improved using a low-Z diamond target to reduce the self-absorption of diagnostic energy photons. The aim of this study was to 1) investigate the feasibility of two 2.5 MV diamond target beamline configurations and 2) characterize the dosimetry and planar image quality of these novel low-Z beams. Materials and methods The commercial 2.5 MV beam was modified by replacing the copper target with sintered diamond. Two beamlines were investigated: a carousel-mounted diamond target beamline and a ‘conventional’ beamline, with the diamond target in the target arm. Planar image quality was assessed in terms of spatial resolution and CNR. Results Due to image artifacts, image quality could not be assessed for the carousel-mounted low-Z target beam. The ‘conventional’ 2.5 MV low-Z beam quality was softer by 2.7% compared to the commercial imaging beam, resulting in improved CNR by factors of up to 1.3 and 1.7 in thin and thick phantoms, respectively. In regard to spatial resolution, the ‘conventional’ 2.5 MV low-Z beam slightly outperformed the commercial imaging beam. Conclusion With a simple modification to the 2.5 MV commercial beamline, we produced an improved energy spectrum for imaging. This 2.5 MV diamond target beam proved to be an advantageous alternative to the commercial target configuration, offering both superior resolution and CNR.
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Affiliation(s)
- Jennifer M Borsavage
- Dalhousie University, Department of Physics and Atmospheric Science, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada
| | - Amanda Cherpak
- Dalhousie University, Department of Physics and Atmospheric Science, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Dalhousie University, Department of Radiation Oncology, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Nova Scotia Health Authority, Department of Medical Physics, Halifax, Canada
| | - James L Robar
- Dalhousie University, Department of Physics and Atmospheric Science, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Dalhousie University, Department of Radiation Oncology, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Nova Scotia Health Authority, Department of Medical Physics, Halifax, Canada
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Ma C, Parsons D, Chen M, Jiang S, Hou Q, Gu X, Lu W. Electron modulated arc therapy (EMAT) using photon MLC for postmastectomy chest wall treatment I: Monte Carlo-based dosimetric characterizations. Phys Med 2019; 67:1-8. [PMID: 31606657 PMCID: PMC6925626 DOI: 10.1016/j.ejmp.2019.10.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 10/02/2019] [Accepted: 10/03/2019] [Indexed: 12/14/2022] Open
Abstract
PURPOSE To study the dosimetric properties of electron arc beams delivered by photon-beam multi-leaf collimators (pMLC) in electron modulated arc therapy (EMAT) for postmastectomy chest wall treatments. METHODS Using the Monte Carlo method, we simulated a 2100EX Varian linear accelerator and verified the beam models in a water tank. Dosimetric characterizations were performed on cylindrical water phantoms of elliptical bases with various field sizes, arc ranges and source-to-surface distances (SSDs) for 6, 9 and 12 MeV beam energy. RESULTS The arc beam has a higher bremsstrahlung dose than the static beam at the isocenter due to crossfire, but choosing a field size greater than 5 cm effectively reduces the bremsstrahlung dose. The depths of the 90% maximum dose located at 1.7, 2.8 and 4.1 cm for 6, 9 and 12 MeV, respectively, are similar to those of the static beams and independent of the field size and arc range. CONCLUSION Based on the study, we recommend using the 5 cm field width for electron arc beams considering both bremsstrahlung dose at the isocenter and the arc profile penumbra. To ensure sufficient PTV edge coverage, we recommend a field length extension of at least 4 cm from PTV's edge for all beam energies and an arc extension of around 7°, 5°, and 5° for beam energies 6, 9, and 12 MeV, respectively. These dosimetric characterizations are the basis of pMLC-delivered EMAT treatment planning for postmastectomy chest wall patients.
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Affiliation(s)
- Chaoqiong Ma
- Key Lab for Radiation Physics and Technology of Education Ministry of China, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, Sichuan 610064, China; Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - David Parsons
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - Mingli Chen
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - Steve Jiang
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - Qing Hou
- Key Lab for Radiation Physics and Technology of Education Ministry of China, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, Sichuan 610064, China
| | - Xuejun Gu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - Weiguo Lu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA.
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Baek J, Kim H, Kim B, Oh Y, Jang H. Assessment of portal image resolution improvement using an external aluminum target and polystyrene electron filter. Radiat Oncol 2019; 14:70. [PMID: 31023340 PMCID: PMC6485051 DOI: 10.1186/s13014-019-1274-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 04/09/2019] [Indexed: 11/10/2022] Open
Abstract
Background In this study, an external 8 mm thick aluminum target was installed on the upper accessory tray mount of a medical linear accelerator head. The purpose of this study was to determine the effects of the external aluminum target beam (Al-target beam) on the portal image quality by analyzing the spatial and contrast resolutions. In addition, the image resolutions with the Al-target beams were compared with those of conventional 6 megavoltage (MV) images. Methods The optimized Al-target beam was calculated using Monte Carlo simulations. To validate the simulations, the percentage depth dose and lateral profiles were measured and compared with the modeled dose distributions. A PTW resolution phantom was used for imaging to assess the image resolution. The spatial resolution was quantified by determining the modulation transfer function. The contrast resolution was determined by a fine contrast difference between the 27 measurement areas. The spatial and contrast resolutions were compared with the those of conventional portal images. Results The measured and calculated percentage depth dose of the Al-target beam were consistent within 1.6%. The correspondence of measured and modelled profiles was evaluated by gamma analysis (3%, 3 mm) and all gamma values inside the field were less than one. The critical spatial frequencies (f50) of the images obtained with the Al-target beam and conventional imaging beam were 0.745 lp/mm and 0.451 lp/mm, respectively. The limiting spatial frequencies (f10) for the Al-target beam image and the conventional portal image were 2.39 lp/mm and 1.82 lp/mm, respectively. The Al-target beam resolved the smaller and lower contrast objects better than that of the MV photon beam. Conclusion The Al-target beams generated by the simple target installation method provided better spatial and contrast resolutions than those of the conventional 6 MV imaging beam.
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Affiliation(s)
- Jonggeun Baek
- Department of Radiation Oncology, Dongguk University Gyeongju Hospital, Gyeongju, South Korea
| | - Hyungdong Kim
- Department of Radiation Oncology, Daegu Fatima Hospital, Daegu, South Korea
| | - Byungyong Kim
- Department of Radiation Oncology, Semyung Christianity Hospital, Pohang, South Korea
| | - Youngkee Oh
- Department of Radiation Oncology, Keimyung University College of Medicine, Daegu, South Korea.
| | - Hyunsoo Jang
- Department of Radiation Oncology, Dongguk University School of Medicine, Gyeongju, South Korea. .,Department of Medical Sciences, Radiation Oncology, Graduate School of Ajou University, Suwon, South Korea.
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Kim H, Kim B, Baek J, Oh Y, Yun S, Jang H. Investigation of the use of external aluminium targets for portal imaging in a medical accelerator using Geant4 Monte Carlo simulation. Br J Radiol 2018; 91:20170376. [PMID: 29338304 DOI: 10.1259/bjr.20170376] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE To install a low-Z target on the wedge tray mount of a medical linear accelerator to create a new image beam and to confirm image contrast enhancement. METHODS Experimental low-energy photon beams were produced with the linac running in the 6 MeV electron mode and with a low-Z target installed on the wedge tray mount [denoted 6 MeV (low-Z target)]. Geant4 Monte Carlo simulation was performed to analyse the energy spectrum and image contrast of a 6 MeV (low-Z target) beam. This study modelled the 6 MeV (low-Z target) beam and the 6 MV (megavoltage) radiotherapy photon beam and verified model validity by measurement. In addition, a contrast phantom was modelled to quantitatively compare the image contrasts of the 6 MeV (low-Z target) beam and the 6 MV radiotherapy photon beam. A low-Z target was fabricated to generate low-energy photons (25-150 keV) from incident electrons, and a portal image of the Alderson RANDO phantom was acquired using a clinical linear accelerator for qualitative analysis. RESULTS The measured and calculated percentage depth dose of the 6 MV photon and 6 MeV (Al) beams were consistent within 1.5 and 1.6%, respectively, and calculated lateral profiles of the 6 MV photon beam and the 6 MeV (Al) beam were consistent with the measured results within 1.5 and 1.9%, respectively. Although low-energy photons (25-150 keV) of the 6 MV photon beam were only 0.3%, the Be, C, and Al low-Z targets, but not the Ti target, generated 34.4 to 38.5% low-energy photons. In 5 to 20 cm water phantoms, contrast of the 6 MeV (Al) beam was approximately 1.16 times greater than that of the 6 MV beam. The contrasts of 6 MeV (Al) and 6 MV photon beams in the 20 cm water phantom were ~34% lower than those in the 5 cm water phantom. 6 MeV (Al)/CR (computed radiography) images of the human body phantom were more vivid and detailed than 6 MV/EPID (electronic portal imaging device) and 6 MeV (Al)/EPID images. CONCLUSION The experimental beam with a low-Z target, which was simply installed on the wedge tray mount of the radiotherapy linear accelerator, generated significantly more low-energy photons than the 6 MV radiotherapy photon beam, and provided better quality portal images. Advances in knowledge: This study shows that, unlike the existing low-Z beam studies, a low-Z target can be installed outside the head of a linear accelerator to improve portal image quality.
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Affiliation(s)
- Hyungdong Kim
- 1 Department of Radiation Oncology, Daegu Fatima Hospital , Daegu , South Korea
| | - Byungyong Kim
- 2 Department of Radiation Oncology, Semyung Christianity Hospital , Pohang , South Korea
| | - Jonggeun Baek
- 3 Department of Radiation Oncology, Dongguk University Gyeongju Hospital , Gyeongju , South Korea
| | - Youngkee Oh
- 4 Department of Radiation Oncology, Keimyung University College of Medicine , Daegu , South Korea
| | - Sangmo Yun
- 1 Department of Radiation Oncology, Daegu Fatima Hospital , Daegu , South Korea
| | - Hyunsoo Jang
- 3 Department of Radiation Oncology, Dongguk University Gyeongju Hospital , Gyeongju , South Korea
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Liu B, Zygmanski P, Sajo E. Portal MV imaging with thin-film high-energy current X-ray detectors: A Monte Carlo study. Med Phys 2017; 44:6128-6137. [DOI: 10.1002/mp.12613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 09/03/2017] [Accepted: 09/23/2017] [Indexed: 11/09/2022] Open
Affiliation(s)
- Bo Liu
- Department of Physics and Applied Physics; Medical Physics Program; University of Massachusetts Lowell; Lowell MA USA
| | - Piotr Zygmanski
- Harvard Medical School; Dana Farber Cancer Institute; Brigham and Women's Hospital; Boston MA USA
| | - Erno Sajo
- Department of Physics and Applied Physics; Medical Physics Program; University of Massachusetts Lowell; Lowell MA USA
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Berbeco RI, Detappe A, Tsiamas P, Parsons D, Yewondwossen M, Robar J. Low Z target switching to increase tumor endothelial cell dose enhancement during gold nanoparticle-aided radiation therapy. Med Phys 2016; 43:436. [PMID: 26745936 DOI: 10.1118/1.4938410] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
PURPOSE Previous studies have introduced gold nanoparticles as vascular-disrupting agents during radiation therapy. Crucial to this concept is the low energy photon content of the therapy radiation beam. The authors introduce a new mode of delivery including a linear accelerator target that can toggle between low Z and high Z targets during beam delivery. In this study, the authors examine the potential increase in tumor blood vessel endothelial cell radiation dose enhancement with the low Z target. METHODS The authors use Monte Carlo methods to simulate delivery of three different clinical photon beams: (1) a 6 MV standard (Cu/W) beam, (2) a 6 MV flattening filter free (Cu/W), and (3) a 6 MV (carbon) beam. The photon energy spectra for each scenario are generated for depths in tissue-equivalent material: 2, 10, and 20 cm. The endothelial dose enhancement for each target and depth is calculated using a previously published analytic method. RESULTS It is found that the carbon target increases the proportion of low energy (<150 keV) photons at 10 cm depth to 28% from 8% for the 6 MV standard (Cu/W) beam. This nearly quadrupling of the low energy photon content incident on a gold nanoparticle results in 7.7 times the endothelial dose enhancement as a 6 MV standard (Cu/W) beam at this depth. Increased surface dose from the low Z target can be mitigated by well-spaced beam arrangements. CONCLUSIONS By using the fast-switching target, one can modulate the photon beam during delivery, producing a customized photon energy spectrum for each specific situation.
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Affiliation(s)
- Ross I Berbeco
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115
| | - Alexandre Detappe
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115
| | - Panogiotis Tsiamas
- Department of Radiation Oncology, St. Jude Children's Hospital, Memphis, Tennessee 38105
| | - David Parsons
- Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7, Canada
| | - Mammo Yewondwossen
- Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7, Canada
| | - James Robar
- Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7, Canada
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Energy Modulated Photon Radiotherapy: A Monte Carlo Feasibility Study. BIOMED RESEARCH INTERNATIONAL 2016; 2016:7319843. [PMID: 26977413 PMCID: PMC4763028 DOI: 10.1155/2016/7319843] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 12/24/2015] [Accepted: 01/03/2016] [Indexed: 11/17/2022]
Abstract
A novel treatment modality termed energy modulated photon radiotherapy (EMXRT) was investigated. The first step of EMXRT was to determine beam energy for each gantry angle/anatomy configuration from a pool of photon energy beams (2 to 10 MV) with a newly developed energy selector. An inverse planning system using gradient search algorithm was then employed to optimize photon beam intensity of various beam energies based on presimulated Monte Carlo pencil beam dose distributions in patient anatomy. Finally, 3D dose distributions in six patients of different tumor sites were simulated with Monte Carlo method and compared between EMXRT plans and clinical IMRT plans. Compared to current IMRT technique, the proposed EMXRT method could offer a better paradigm for the radiotherapy of lung cancers and pediatric brain tumors in terms of normal tissue sparing and integral dose. For prostate, head and neck, spine, and thyroid lesions, the EMXRT plans were generally comparable to the IMRT plans. Our feasibility study indicated that lower energy (<6 MV) photon beams could be considered in modern radiotherapy treatment planning to achieve a more personalized care for individual patient with dosimetric gains.
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Zhang Y, Feng Y, Ahmad M, Ming X, Zhou L, Deng J. Intermediate Megavoltage Photon Beams for Improved Lung Cancer Treatments. PLoS One 2015; 10:e0145117. [PMID: 26672752 PMCID: PMC4682946 DOI: 10.1371/journal.pone.0145117] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 11/28/2015] [Indexed: 02/05/2023] Open
Abstract
The goal of this study is to evaluate the effects of intermediate megavoltage (3-MV) photon beams on SBRT lung cancer treatments. To start with, a 3-MV virtual beam was commissioned on a commercial treatment planning system based on Monte Carlo simulations. Three optimized plans (6-MV, 3-MV and dual energy of 3- and 6-MV) were generated for 31 lung cancer patients with identical beam configuration and optimization constraints for each patient. Dosimetric metrics were evaluated and compared among the three plans. Overall, planned dose conformity was comparable among three plans for all 31 patients. For 21 thin patients with average short effective path length (< 10 cm), the 3-MV plans showed better target coverage and homogeneity with dose spillage index R50% = 4.68±0.83 and homogeneity index = 1.26±0.06, as compared to 4.95±1.01 and 1.31±0.08 in the 6-MV plans (p < 0.001). Correspondingly, the average/maximum reductions of lung volumes receiving 20 Gy (V20Gy), 5 Gy (V5Gy), and mean lung dose (MLD) were 7%/20%, 9%/30% and 5%/10%, respectively in the 3-MV plans (p < 0.05). The doses to 5% volumes of the cord, esophagus, trachea and heart were reduced by 9.0%, 10.6%, 11.4% and 7.4%, respectively (p < 0.05). For 10 thick patients, dual energy plans can bring dosimetric benefits with comparable target coverage, integral dose and reduced dose to the critical structures, as compared to the 6-MV plans. In conclusion, our study indicated that 3-MV photon beams have potential dosimetric benefits in treating lung tumors in terms of improved tumor coverage and reduced doses to the adjacent critical structures, in comparison to 6-MV photon beams. Intermediate megavoltage photon beams (< 6-MV) may be considered and added into current treatment approaches to reduce the adjacent normal tissue doses while maintaining sufficient tumor dose coverage in lung cancer radiotherapy.
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Affiliation(s)
- Ying Zhang
- Department of Biomedical Engineering, Tianjin University, Tianjin, China
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Yuanming Feng
- Department of Biomedical Engineering, Tianjin University, Tianjin, China
| | - Munir Ahmad
- Department of Radiation Oncology, William W. Backus Hospital, Norwich, Connecticut, United States of America
| | - Xin Ming
- Department of Biomedical Engineering, Tianjin University, Tianjin, China
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Li Zhou
- Center for Radiation Physics and Technology, West China Hospital Cancer Center, Sichuan University, Chengdu, China
| | - Jun Deng
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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Parsons D, Robar JL. An investigation of kV CBCT image quality and dose reduction for volume-of-interest imaging using dynamic collimation. Med Phys 2015; 42:5258-69. [DOI: 10.1118/1.4928474] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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Parsons D, Robar JL, Sawkey D. A Monte Carlo investigation of low-Z target image quality generated in a linear accelerator using Varian's VirtuaLinac. Med Phys 2014; 41:021719. [PMID: 24506610 DOI: 10.1118/1.4861818] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The focus of this work was the demonstration and validation of VirtuaLinac with clinical photon beams and to investigate the implementation of low-Z targets in a TrueBeam linear accelerator (Linac) using Monte Carlo modeling. METHODS VirtuaLinac, a cloud based web application utilizing Geant4 Monte Carlo code, was used to model the Linac treatment head components. Particles were propagated through the lower portion of the treatment head using BEAMnrc. Dose distributions and spectral distributions were calculated using DOSXYZnrc and BEAMdp, respectively. For validation, 6 MV flattened and flattening filter free (FFF) photon beams were generated and compared to measurement for square fields, 10 and 40 cm wide and at dmax for diagonal profiles. Two low-Z targets were investigated: a 2.35 MeV carbon target and the proposed 2.50 MeV commercial imaging target for the TrueBeam platform. A 2.35 MeV carbon target was also simulated in a 2100EX Clinac using BEAMnrc. Contrast simulations were made by scoring the dose in the phosphor layer of an IDU20 aSi detector after propagating through a 4 or 20 cm thick phantom composed of water and ICRP bone. RESULTS Measured and modeled depth dose curves for 6 MV flattened and FFF beams agree within 1% for 98.3% of points at depths greater than 0.85 cm. Ninety three percent or greater of points analyzed for the diagonal profiles had a gamma value less than one for the criteria of 1.5 mm and 1.5%. The two low-Z target photon spectra produced in TrueBeam are harder than that from the carbon target in the Clinac. Percent dose at depth 10 cm is greater by 3.6% and 8.9%; the fraction of photons in the diagnostic energy range (25-150 keV) is lower by 10% and 28%; and contrasts are lower by factors of 1.1 and 1.4 (4 cm thick phantom) and 1.03 and 1.4 (20 cm thick phantom), for the TrueBeam 2.35 MV/carbon and commercial imaging beams, respectively. CONCLUSIONS VirtuaLinac is a promising new tool for Monte Carlo modeling of novel target designs. A significant spectral difference is observed between the low-Z target beam on the Clinac platform and the proposed imaging beam line on TrueBeam, with the former providing greater diagnostic energy content.
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Affiliation(s)
- David Parsons
- Department of Physics and Atmospheric Science, Dalhousie University, 5820 University Avenue, Halifax, Nova Scotia B3H 1V7, Canada
| | - James L Robar
- Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, 5820 University Avenue, Halifax, Nova Scotia B3H 1V7, Canada
| | - Daren Sawkey
- Varian Medical Systems, Inc., 3120 Hansen Way, Palo Alto, California 94304
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Tsiamas P, Mishra P, Cifter F, Berbeco RI, Marcus K, Sajo E, Zygmanski P. Low-Z linac targets for low-MV gold nanoparticle radiation therapy. Med Phys 2014; 41:021701. [DOI: 10.1118/1.4859335] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Leary D, Robar JL. CBCT with specification of imaging dose and CNR by anatomical volume of interest. Med Phys 2013; 41:011909. [DOI: 10.1118/1.4855835] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Wang J, Robar J, Guan H. Noise suppression in reconstruction of low-Z target megavoltage cone-beam CT images. Med Phys 2012; 39:5111-7. [PMID: 22894436 DOI: 10.1118/1.4737116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To improve the image contrast-to-noise (CNR) ratio for low-Z target megavoltage cone-beam CT (MV CBCT) using a statistical projection noise suppression algorithm based on the penalized weighted least-squares (PWLS) criterion. METHODS Projection images of a contrast phantom, a CatPhan(®) 600 phantom and a head phantom were acquired by a Varian 2100EX LINAC with a low-Z (Al) target and low energy x-ray beam (2.5 MeV) at a low-dose level and at a high-dose level. The projections were then processed by minimizing the PWLS objective function. The weighted least square (WLS) term models the noise of measured projection and the penalty term enforces the smoothing constraints of the projection image. The variance of projection data was chosen as the weight for the PWLS objective function and it determined the contribution of each measurement. An anisotropic quadratic form penalty that incorporates the gradient information of projection image was used to preserve edges during noise reduction. Low-Z target MV CBCT images were reconstructed by the FDK algorithm after each projection was processed by the PWLS smoothing. RESULTS Noise in low-Z target MV CBCT images were greatly suppressed after the PWLS projection smoothing, without noticeable sacrifice of the spatial resolution. Depending on the choice of smoothing parameter, the CNR of selected regions of interest in the PWLS processed low-dose low-Z target MV CBCT image can be higher than the corresponding high-dose image. CONCLUSION The CNR of low-Z target MV CBCT images was substantially improved by using PWLS projection smoothing. The PWLS projection smoothing algorithm allows the reconstruction of high contrast low-Z target MV CBCT image with a total dose of as low as 2.3 cGy.
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Affiliation(s)
- Jing Wang
- Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas 75235, USA.
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