266 results match your criteria fff photon

Dosimetric evaluation of different planning techniques based on flattening filter-free beams for central and peripheral lung stereotactic body radiotherapy.

Biomed Phys Eng Express 2021 Oct 12. Epub 2021 Oct 12.

Department of Radiotherapy, Government Medical College Patiala, Sangrur Road, Patiala, Punjab, 147001, INDIA.

This study aimed to dosimetrically compare and evaluate the flattening filter-free (FFF) photon beam-based three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) for lungstereotactic body radiotherapy (SBRT). RANDO phantom computed tomography (CT) images were used for treatment planning. Gross tumor volumes (GTVs) were delineated in the central and peripheral lung locations. Read More

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October 2021

Small field measurement and monte carlo model validation of a novel image-guided radiotherapy system.

Med Phys 2021 Oct 10. Epub 2021 Oct 10.

Department of Radiation Oncology, School of Medicine, Stanford University, Stanford, CA, 94304, United States of America.

Purpose: The RefleXion X1 is a novel radiotherapy system that is designed for image-guided radiotherapy and, eventually, biology-guided radiotherapy (BgRT). BgRT is a treatment paradigm that tracks tumor motion using real-time positron emission signals. This study reports the small field measurement results and the validation of a Monte Carlo (MC) model of the first clinical RefleXion unit. Read More

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October 2021

Properties of IBA Razor Nano Chamber in small-field radiation therapy using 6 MV FF, 6 MV FFF, and 10 MV FFF photon beams.

Acta Oncol 2021 Nov 1;60(11):1419-1424. Epub 2021 Oct 1.

Unit of Radiotherapy, Department of Oncology, Tampere University Hospital, Tampere, Finland.

Background: Small megavoltage photon fields are increasingly used in modern radiotherapy techniques such as stereotactic radiotherapy. Therefore, it is important to study the reliability of dosimetry in the small-field conditions. The IBA Razor Nano Chamber (Nano chamber) ionization chamber is particularly intended for small-field measurements. Read More

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November 2021

Feasibility of operating a millimeter-scale graphite calorimeter for absolute dosimetry of small-field photon beams in the clinic.

Med Phys 2021 Sep 22. Epub 2021 Sep 22.

Medical Physics Unit, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada.

Purpose: To characterize and build a cylindrically layered graphite calorimeter the size of a thimble ionization chamber for absolute dosimetry of small fields. This detector has been designed in a familiar probe format to facilitate integration into the clinical workflow. The feasibility of operating this absorbed dose calorimeter in quasi-adiabatic mode is assessed for high-energy accelerator-based photon beams. Read More

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September 2021

Out-of-field mean photon energy and dose from 6 MV and 6 MV FFF beams measured with TLD-300 and TLD-100 dosimeters.

Med Phys 2021 Sep 15. Epub 2021 Sep 15.

Instituto de Física, Universidad Nacional Autónoma de México, Ciudad de México, Mexico.

Purpose: To measure the out-of-field mean photon energy and dose imparted by the secondary radiation field generated by 6 MV and 6 MV FFF beams using TLD-300 and TLD-100 dosimeters and to use the technique to quantify the contributions from the different sources that generate out-of-field radiation.

Methods: The mean photon energy and the dose were measured using the TLD-300 glow curve properties and the TLD-100 response, respectively. The TLD-300 glow curve shape was energy-calibrated with gamma rays from Tc, F, Cs, and Co sources, and its energy dependence was quantified by a parameter obtained from the curve deconvolution. Read More

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September 2021

Verification of Surface Dose for Flattening Filter and Flattening Filter Free Beams in Beam-Matched Medical Linear Accelerators.

Asian Pac J Cancer Prev 2021 Aug 1;22(8):2577-2585. Epub 2021 Aug 1.

Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, India.

Background: The purpose of this study was to evaluate the surface dose (SD) of 6 and 10 MV flattening filter beam (FF) and flattening filter free (FFF) beam for different square field sizes in three Beam-matched medical linear accelerators using a parallel-plate ionization chamber.

Materials And Methods: The experiment was carried out in a phantom composed of 40×40 cm2 solid Water slabs of varying thickness. Further sheets of solid water phantom were added to take readings in the build-up region for both SSD and SAD technique. Read More

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Comparison between flattening filter-free (FFF) and flattened photon beam VMAT plans for the whole brain radiotherapy (WBRT) with hippocampus sparing.

Asia Pac J Clin Oncol 2021 Jul 31. Epub 2021 Jul 31.

Department of Radiation oncology, The First Hospital of China Medical University, Shenyang, China.

Purpose: To evaluate and investigate the feasibility of flattening filter-free (FFF) beam for the whole-brain radiotherapy (WBRT) with hippocampus sparing.

Methods: Eighteen patients with volumetric-modulated arc therapy (VMAT) plans in FFF and conventional beam modes were included in this study. The prescribed dose was 30 Gy in 10 fractions. Read More

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Out-of-field dose in stereotactic radiotherapy for paediatric patients.

Phys Imaging Radiat Oncol 2021 Jul 4;19:1-5. Epub 2021 Jun 4.

RMIT University, School of Science, Melbourne, Australia.

Background And Purpose: Stereotactic radiotherapy combines image guidance and high precision delivery with small fields to deliver high doses per fraction in short treatment courses. In preparation for extension of these treatment techniques to paediatric patients we characterised and compared doses out-of-field in a paediatric anthropomorphic phantom for small flattened and flattening filter free (FFF) photon beams.

Method And Materials: Dose measurements were taken in several organs and structures outside the primary field in an anthropomorphic phantom of a 5 year old child (CIRS) using thermoluminescence dosimetry (LiF:Mg,Cu,P). Read More

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Calculated relative biological effectiveness (RBE) for initial DNA double-strand breaks (DSB) from flattening filter and flattening filter-free 6 MV X-ray fields.

BJR Open 2021 5;3(1):20200072. Epub 2021 Jul 5.

Department of Radiation Oncology, Niigata Neurosurgical Hospital, Niigata, 3057 Yamada, Nishi-ku, Niigata, Japan.

Objectives: We evaluated the radiobiological effectiveness based on the yields of DNA double-strand breaks (DSBs) of field induction with flattening filter (FF) and FF-free (FFF) photon beams.

Methods: We used the particle and heavy ion transport system (PHITS) and a water equivalent phantom (30 × 30 × 30 cm) to calculate the physical qualities of the dose-mean lineal energy (y) with 6 MV FF and FFF. The relative biological effectiveness based on the yields of DNA-DSBs (RBE) was calculated for standard radiation such as 220 kVp X-rays by using the estimating yields of SSBs and DSBs. Read More

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Commissioning and quality assurance of Halcyon 2.0 linear accelerator.

Rep Pract Oncol Radiother 2021 9;26(3):433-444. Epub 2021 Jun 9.

Department of Radiation Oncology, Jawaharlal Nehru Cancer Hospital & Research Centre, Bhopal, India.

Background: Varian Medical Systems has introduced a new medical linear accelerator called Halcyon 2.0, which is based on the ring delivery system (RDS). It is a true IGRT machine having 6MV FFF photon energy. Read More

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Comparison of 2 dynamic conformal arc plans based on high-dose rate flattening filter free beams for peripheral lung cancer.

Zhong Nan Da Xue Xue Bao Yi Xue Ban 2021 Jun;46(6):615-619

Department of Radiation Therapy, Cancer Hospital of Shantou University Medical College, Shantou Guangdong 515000, China.

Objectives: To compare 2 dynamic conformal arc plans based on the high dose rate flattening filter free (FFF) beams, and to evaluate the dosimetric differences.

Methods: A total of 20 patients with early peripheral non-small cell lung cancer were selected, and 2 dynamic conformal arc plans were designed in the Eclipse 10.0 treatment planning system (TPS). Read More

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Dose response of a radiophotoluminescent glass dosimeter for TomoTherapy, CyberKnife, and flattening-filter-free linear accelerator output measurements in dosimetry audit.

Phys Med 2021 Aug 29;88:91-97. Epub 2021 Jun 29.

QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Japan.

Purpose: We experimentally determined the radiophotoluminescent glass dosimeter (RPLD) dose responses for TomoTherapy, CyberKnife, and flattening-filter-free (FFF) linear accelerator (linac) outputs for dosimetry audits in Japan.

Methods: A custom-made solid phantom with a narrow central-axis spacing of three RPLD elements was used for output measurement to minimise the dose-gradient effect of the non-flattening filter beams. For RPLD dose estimation, we used the ISO 22127 formalism. Read More

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Evaluation of a new foetal shielding device for pregnant brain tumour patients.

Radiat Oncol 2021 Jun 13;16(1):109. Epub 2021 Jun 13.

Department of Radiation Oncology, Seoul National University Bundang Hospital, 82 Gumi-ro 173 Beon-gil, Bundang-gu, Seongnam-si, 13620, Gyeonggi-do, Korea.

Background: The present study aimed to propose a new foetal shielding device for pregnant cancer patients to reduce the foetal dose associated with treatment techniques using multiple gantry angles, such as intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT).

Methods: Three shielding structures were designed to minimise the scattered and leaked radiation from various gantry angles and radiation scattering within the patient. The base-plate part that can be placed on the treatment couch was designed to reduce the scattered and leaked radiation generated at gantry angles located near 180°. Read More

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Survey on utilization of flattening filter-free photon beams in Japan.

J Radiat Res 2021 Jul;62(4):726-734

Department of Information Technology and Medical engineering, Human Health Science, Graduate School of Medicine, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.

To understand the current state of flattening filter-free (FFF) beam implementation in C-arm linear accelerators (LINAC) in Japan, the quality assurance (QA)/quality control (QC) 2018-2019 Committee of the Japan Society of Medical Physics (JSMP) conducted a 37-question survey, designed to investigate facility information and specifications regarding FFF beam adoption and usage. The survey comprised six sections: facility information, devices, clinical usage, standard calibration protocols, modeling for treatment planning (TPS) systems and commissioning and QA/QC. A web-based questionnaire was developed. Read More

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Delta Discover transmission detector: A comprehensive characterization for in-vivo VMAT monitoring.

Phys Med 2021 May 1;85:15-23. Epub 2021 May 1.

Medical Physics Department, A.S.L. TO4, 10015 Ivrea, TO, Italy. Electronic address:

Objective: To investigate the dosimetric behaviour, influence on photon beam fluence and error detection capability of Delta Discover transmission detector.

Methods: The transmission detector (TRD) was characterized on a TrueBeam linear accelerator with 6 MV beams. Linearity, reproducibility and dose rate dependence were investigated. Read More

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Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors.

Biomed Phys Eng Express 2021 May 11;7(4). Epub 2021 May 11.

Department of Physics, Dr Bhimrao Ambedkar University, Agra, Uttar Pradesh, 282004, India.

The present study aimed to dosimetrically evaluate the small-fields of a 6 MV flattening filter-free (FFF) photon beam using different detectors.The 6 MV FFF photon beam was used for measurement of output factor, depth dose, and beam profile of small-fields of sizes 0.6 cm × 0. Read More

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Radiotherapy dose calculations in high-Z materials: comprehensive comparison between experiment, Monte Carlo, and conventional planning algorithms.

Biomed Phys Eng Express 2021 Apr 22;7(3). Epub 2021 Apr 22.

School of Physics, University of Sydney, Sydney NSW, Australia.

. To compare the accuracies of the AAA and AcurosXB dose calculation algorithms and to predict the change in the down-stream and lateral dose deposition of high energy photons in the presence of material with densities higher that commonly found in the body.. Read More

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[Biological dose estimation for photons of different qualities in radiation therapy].

Magy Onkol 2021 Mar 27;65(1):30-37. Epub 2020 Nov 27.

Klinikai Sugárbiológiai és Onkocytogenetikai Osztály, Országos Onkológiai Intézet, Budapest, Hungary.

Flattening filter free mode (FFF) has been introduced in radiotherapy during the past decades, however, not much has been reported on its radiobiological effect. The purpose of our study was to compare the radiobiological effects of flattening filter and flattening filter free photon beams on chromosomal aberrations in peripheral blood lymphocytes. In our study the blood of the same healthy donor was irradiated with linear accelerator using both conventional flattening filter (FF) and FFF photon beams at dose rate of 3. Read More

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Monte Carlo simulation of conical collimators for stereotactic radiosurgery with a 6 MV flattening-filter-free photon beam.

Med Phys 2021 Jun 4;48(6):3160-3171. Epub 2021 May 4.

West German Proton Therapy Centre Essen (WPE), Hufelandstr. 55, Essen, 45147, Germany.

Purpose: Conical collimators, or cones, are tertiary collimators that attach to a radiotherapy linac and are suited for the stereotactic radiosurgery treatment of small brain lesions. The small diameter of the most used cones makes difficult the acquisition of the dosimetry data needed for the commissioning of treatment planning systems. Although many publications report dosimetric data of conical collimators for stereotactic radiosurgery, most of the works use different setups, which complicates comparisons. Read More

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Comparison of the RayStation photon Monte Carlo dose calculation algorithm against measured data under homogeneous and heterogeneous irradiation geometries.

Phys Med 2021 Feb 15;82:87-99. Epub 2021 Feb 15.

Department of Radiotherapy Physics, Northern Centre for Cancer Care, Freeman Hospital, Freeman Road, Newcastle upon Tyne NE7 7DN, UK.

Purpose: This work compares Monte Carlo dose calculations performed using the RayStation treatment planning system against data measured on a Varian Truebeam linear accelerator with 6 MV and 10 MV FFF photon beams.

Methods: The dosimetric performance of the RayStation Monte Carlo calculations was evaluated in a variety of irradiation geometries employing homogeneous and heterogeneous phantoms. Profile and depth dose comparisons against measurement were carried out in relative mode using the gamma index as a quantitative measure of similarity within the central high dose regions. Read More

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February 2021

Comparison of Air-Gaps Effect in a Small Cavity on Dose Calculation for 6 MV Linac.

J Biomed Phys Eng 2021 Feb 1;11(1):17-28. Epub 2021 Feb 1.

PhD, Department of Physics, Faculty of Mathematics and Natural Sciences, University of Indonesia, Depok, West Java, 16424, Indonesia.

Background: Many authors stated that cavities or air-gaps were the main challenge of dose calculation for head and neck with flattening filter medical linear accelerator (Linac) irradiation.

Objective: The study aimed to evaluate the effect of air-gap dose calculation on flattening-filter-free (FFF) small field irradiation.

Material And Methods: In this comparative study, we did the experimental and Monte Carlo (MC) simulation to evaluate the presence of heterogeneities in radiotherapy. Read More

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February 2021

EPID-based 3D dosimetry for pre-treatment FFF VMAT stereotactic body radiotherapy plan verification using dosimetry Check.

Phys Med 2021 Jan 20;81:227-236. Epub 2021 Jan 20.

Medical Physics Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy; School of Engineering, Cardiff University, Cardiff, UK.

Purpose: The software Dosimetry Check (DC) reconstructs the 3D dose distribution on CT images data set by using EPID measured signal. This study aimed to evaluate DC for stereotactic body radiotherapy (SBRT) with unflattened photon beams (FFF) for dosimetric independent plan verification in pre-treatment modality.

Methods: DC v. Read More

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January 2021

Reference dose determination in 60Co and high-energy radiotherapy photon beams by using Farmer-type cylindrical ionization chambers - an experimental investigation.

John Swanpalmer

Biomed Phys Eng Express 2020 05 6;6(4):045003. Epub 2020 May 6.

Sahlgrenska University Hospital, Department of Medical Physics and Biomedical Engineering, Gothenburg, Sweden. Department of Radiation Physics, Sahlgrenska Academy, University of Gothenburg, Sweden.

Ionization chamber dosimetry is predominantly used for determination of the absorbed dose to water in Co and high-energy radiotherapy photon beams. The most widespread ionization chambers employed for absolute or reference dose determinations in reference conditions are the Farmer-type cylindrical ionization chambers. The Farmer-type ionization chambers have a variety of constructions and materials and their responses vary in the radiation beam. Read More

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Experimental determination of thermal neutron fluence around Elekta Versa HD linear accelerator for various photon energies.

Biomed Phys Eng Express 2020 09 8;6(5):055018. Epub 2020 Sep 8.

Department of Physics, Noorul Islam Centre for Higher Education, Kumaracoil- 629 180, Kanyakumari District, Tamil Nadu, India. Department of Medical Physics and Radiation Safety, MVR Cancer Centre & Research Institute, Calicut, India.

A complex neutron spectrum generated along with a useful photon beam imposes an additional radiation protection risk around medical linear accelerators (linac). The thermal neutron component of this complex neutron spectrum formed during different photon modes of operation of Elekta Versa HD linac has been quantified using Indium foil activation technique. The thermal neutron fluence (Φ ) at isocenter for 15 MV, 10 MV and 10 MV FFF beams was found to be 2. Read More

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September 2020

Characterization of Gas Electron Multiplier-based detector for external beam radiation therapy dosimetry.

Med Phys 2021 Apr 26;48(4):1931-1940. Epub 2021 Feb 26.

Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.

Purpose: Electronic portal imaging devices (EPIDs) are commonly installed on modern linear accelerators (LINACs) and are convenient for imaging and, potentially, dosimetry. However, owing to their construction with metal and scintillating layers of high atomic number, they exhibit nonwater-equivalent response and oversensitivity to low-energy photons. Therefore, EPIDs are not ideal for dosimetry purposes. Read More

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An electronic portal image device (EPID)-based multiplatform rapid daily LINAC QA tool.

J Appl Clin Med Phys 2021 Jan 7;22(1):45-58. Epub 2021 Jan 7.

Department of Radiation Oncology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.

Purpose: To develop an efficient and economic daily quality research tool (DQRT) for daily check of multiplatform linear accelerators (LINACs) with flattening filter (FF) and flattening filter-free (FFF) photon beams by using an Electronic Portal Image Device (EPID).

Materials And Methods: After EPID calibration, the monitored parameters were analyzed from a 10 cm × 10 cm open and 60° wedge portal images measured by the EPID with 100 MU exposure. Next, the repeatability of the EPID position accuracy, long-term stability, and linearity between image gray value and exposure were verified. Read More

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January 2021

Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem.

BJR Open 2020 11;2(1):20190048. Epub 2020 Dec 11.

Department of Radiation Oncology and Image-applied Therapy, Kyoto University Hospital, Kyoto 606-8507, Japan.

Objective: To quantify and correct megavoltage (MV) scattered X-rays (MV-scatter) on an image acquired using a linac-mounted kilovoltage (kV) imaging subsystem.

Methods And Materials: A linac-mounted flat-panel detector (FPD) was used to acquire an image containing MV-scatter by activating the FPD only during MV beam irradiation. 6-, 10-, and 15 MV with a flattening-filter (FF; 6X-FF, 10X-FF, 15X-FF), and 6- and 10 MV without an FF (6X-FFF, 10X-FFF) were used. Read More

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December 2020

Simplified sigmoidal curve fitting for a 6 MV FFF photon beam of the Halcyon to determine the field size for beam commissioning and quality assurance.

Radiat Oncol 2020 Dec 7;15(1):273. Epub 2020 Dec 7.

Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, 06591, Republic of Korea.

Background: An O-ring gantry-type linear accelerator (LINAC) with a 6-MV flattening filter-free (FFF) photon beam, Halcyon, includes a reference beam that contains representative information such as the percent depth dose, profile and output factor for commissioning and quality assurance. However, because it does not provide information about the field size, we proposed a method to determine all field sizes according to all depths for radiation therapy using simplified sigmoidal curve fitting (SCF).

Methods: After mathematical definition of the SCF using four coefficients, the defined curves were fitted to both the reference data (RD) and the measured data (MD). Read More

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December 2020

Effect of an integral quality monitor on 4-, 6-, 10-MV, and 6-MV flattening filter-free photon beams.

J Appl Clin Med Phys 2021 Jan 3;22(1):76-91. Epub 2020 Dec 3.

Department of Radiological Technology, Kanazawa University Hospital, Kanazawa, Japan.

Purpose: To investigate the effect of an integral quality monitor (IQM; iRT Systems GmbH, Koblenz, Germany) on 4, 6, 10, and 6-MV flattening filter-free (FFF) photon beams.

Methods: We assessed surface dose, PDD , TPR , PDD curves, inline and crossline profiles, transmission factor, and output factor with and without the IQM. PDD, transmission factor, and output factor were measured for square fields of 3, 5, 10, 15, 20, 25, and 30 cm and profiles were performed for square fields of 3, 5, 10, 20, and 30 cm at 5-, 10-, and 30-cm depth. Read More

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January 2021

GPU-accelerated Monte Carlo simulation of MV-CBCT.

Phys Med Biol 2020 12 2;65(23):235042. Epub 2020 Dec 2.

Medical Physics Program, Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, MA, United States of America. Brigham and Women's Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, United States of America.

Monte Carlo simulation (MCS) is one of the most accurate computation methods for dose calculation and image formation in radiation therapy. However, the high computational complexity and long execution time of MCS limits its broad use. In this paper, we present a novel strategy to accelerate MCS using a graphic processing unit (GPU), and we demonstrate the application in mega-voltage (MV) cone-beam computed tomography (CBCT) simulation. Read More

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December 2020