1
|
Tahmasbi M, Capela M, Santos T, Mateus J, Ventura T, do Carmo Lopes M. Particular issues to be considered in small field dosimetry for TrueBeam STx commissioning. Appl Radiat Isot 2023; 202:111066. [PMID: 37865066 DOI: 10.1016/j.apradiso.2023.111066] [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: 11/09/2022] [Revised: 08/28/2023] [Accepted: 10/05/2023] [Indexed: 10/23/2023]
Abstract
This study aims to report the relevant issues concerning small fields in the commissioning of a TrueBeam STx for photon energies of 6MV, 10MV, 6FFF, and 10FFF. Percent depth doses, profiles, and field output factors were measured according to the beam model configuration of the treatment planning system. Multiple detectors were used based on the IAEA TRS-483 protocol as well as EBT3 radiochromic film. Analytical Anisotropic and Acuros XB algorithms, were configured and validated through basic dosimetry comparisons and end-to-end clinical tests.
Collapse
Affiliation(s)
- Marziyeh Tahmasbi
- Radiologic Technology Department, School of Allied Medical Sciences, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal.
| | - Miguel Capela
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Tania Santos
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Josefina Mateus
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Tiago Ventura
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Maria do Carmo Lopes
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| |
Collapse
|
2
|
Neupane T, Shang C, Kassel M, Muhammad W, Leventouri T, Williams TR. Viability of the virtual cone technique using a fixed small multi-leaf collimator field for stereotactic radiosurgery of trigeminal neuralgia. J Appl Clin Med Phys 2023; 24:e14148. [PMID: 37722766 PMCID: PMC10691631 DOI: 10.1002/acm2.14148] [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: 11/09/2022] [Revised: 08/04/2023] [Accepted: 08/20/2023] [Indexed: 09/20/2023] Open
Abstract
Dosimetric uncertainties in very small (≤1.5 × 1.5 cm2 ) photon fields are remarkably higher, which undermines the validity of the virtual cone (VC) technique with a diminutive and variable MLC fields. We evaluate the accuracy and reproducibility of the VC method with a very small, fixed MLC field setting, called a fixed virtual cone (fVC), for small target radiosurgery such as trigeminal neuralgia (TGN). The fVC is characterized by 0.5 cm x 0.5 cm high-definition (HD) MLC field of 10MV FFF beam defined at 100 cm SAD, while backup jaws are positioned at 1.5 cm x 1.5 cm. A spherical dose distribution equivalent to 5 mm (diameter) physical cone was generated using 10-14 non-coplanar, partial arcs. Dosimetric accuracy was validated using SRS diode (PTW 60018), SRS MapCHECK (SNC) measurements. As a quality assurance measure, 10 treatment plans (SRS) for TGN, consisting of various arc ranges at different collimator angles were analyzed using 6 MV FFF and 10 MV FFF beams, including a field-by-field study (n = 130 fields). Dose outputs were compared between the Eclipse TPS and measurements (SRS MapCHECK). Moreover, dosimetric changes in the field defining fVC, prompted by a minute (± 0.5-1.0 mm) leaf shift, was examined among TPS, diode measurements, and Monte Carlo (MC) simulations. The beam model for fVC was validated (≤3% difference) using SRS MapCHECK based absolute dose measurements. The equivalent diameters of the 50% isodose distribution were found comparable to that of a 5 mm cone. Additionally, the comparison of field output factors, dose per MU between the TPS and SRS diode measurements using the fVC field, including ± 1 mm leaf shift, yielded average discrepancies within 5.5% and 3.5% for 6 MV FFF and 10 MV FFF beams, respectively. Overall, the fVC method is a credible alternative to the physical cone (5 mm) that can be applied in routine radiosurgical treatment of TGN.
Collapse
Affiliation(s)
- Taindra Neupane
- Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Charles Shang
- RSOSouth Florida Proton Therapy InstituteDelray BeachFloridaUSA
| | - Maxwell Kassel
- Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Wazir Muhammad
- Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Theodora Leventouri
- Center for Biological and Materials Physics (CBAMP)Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Timothy R. Williams
- Medical DirectorSouth Florida Proton Therapy InstituteDelray BeachFloridaUSA
| |
Collapse
|
3
|
Renil Mon P, Meena-Devi V, Bhasi S. Monte Carlo modelling and validation of the elekta synergy medical linear accelerator equipped with radiosurgical cones. Heliyon 2023; 9:e15328. [PMID: 37123913 PMCID: PMC10130217 DOI: 10.1016/j.heliyon.2023.e15328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 04/02/2023] [Accepted: 04/03/2023] [Indexed: 05/02/2023] Open
Abstract
Monte Carlo simulations of medical linear accelerator heads help in visualizing the energy spectrum and angular spread of photons and electrons, energy deposition, and scattering from each of the head components. Hence, the purpose of this study was to validate the Monte Carlo model of the Elekta synergy medical linear accelerator equipped with stereotactic radio surgical connical collimators. For this, the Elekta synergy medical linear accelerator was modelled using the EGSnrc Monte Carlo code. The model results were validated using the measured data. The primary electron beam parameters, beam size, and energy were tuned to match the measured data; a dose profile with a field size of 40 × 40 cm2 and percentage depth dose with a field size of 10 × 10 cm2 were matched during tuning. The validation of the modelled data with the measurement results was performed using gamma analysis, point dose, and field size comparisons. For small radiation fields, relative output factors were also compared. The gamma analysis revealed good agreement between the Monte Carlo modeling results and the measured data. A gamma pass rate of more than 95% was obtained for field sizes of 40 × 40 cm2 to 2 × 2 cm2 with gamma criteria of 1% and 1 mm for the dose difference (DD) and distance to agreement (DTA), respectively; this gamma pass rate was more than 98% for the corresponding values of 2% and 2 mm for the DD and DTA, respectively. A gamma pass rate of more than 99% was obtained for a percentage depth dose with 1 mm and 1% criteria. The field size was also in good agreement with the measurement results, and the maximum deviation observed was 1.1%. The stereotactic cone field also passed this analysis with a gamma pass rate of more than 98% for dose profiles and 99% for the percentage depth dose. The small field output factor exhibited a deviation of 4.3%, 3.4%, and 1.9% for field sizes of 5 mm, 7.5 mm, and 10 mm, respectively. Thus, the Monte Carlo model of the Elekta Linear accelerator was successfully validated. The validation of radio surgical cones passed the analysis in terms of the dose profiles and percentage depth dose. The small field relative output factors exhibited deviations of up to 4.3%, and to resolve this, detector-specific and field-specific correction factors must be derived.
Collapse
Affiliation(s)
- P.S. Renil Mon
- Department of Physics, Noorul Islam Centre for Higher Education, Kumarakoil, Kanyakumari District, Tamilnadu, India
- Corresponding author.
| | - V.N. Meena-Devi
- Department of Physics, Noorul Islam Centre for Higher Education, Kumarakoil, Kanyakumari District, Tamilnadu, India
| | - Saju Bhasi
- Department of Radiation Physics, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
| |
Collapse
|
4
|
Varian eclipse stereotactic 5 mm cone data commissioning. Phys Eng Sci Med 2022; 45:1013-1020. [PMID: 35997923 DOI: 10.1007/s13246-022-01168-6] [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: 04/12/2022] [Accepted: 07/26/2022] [Indexed: 10/15/2022]
Abstract
Conical collimators are effective and readily available accessories for the field shaping of small stereotactic fields, however the measurements required to accurately characterise the smallest radiation fields are difficult, prone to large errors, and there is little published commissioning data to compare measurements against. The aim of this investigation was to commission the cone dose calculation algorithm of a Varian Eclipse treatment planning system for a Varian 5 mm cone attached to a Varian TrueBeam linear accelerator beam-matched to the Varian Golden Beam Data (GBD). Tissue maximum ratios (TMRs) and off-axis ratios (OARs) were measured using PTW 60019 microDiamond and PTW 60018 SRS Diode detectors for a flattening filter free 6MV beam. The output factor (OF) was measured with the microDiamond and EBT-XD film. Results were compared to the GBD for this cone and an OF measured by the Australian Clinical Dosimetry Service during an independent audit. Film dosimetry was used to evaluate Eclipse dose calculations in a solid water phantom and end-to-end accuracy with an anthropomorphic head phantom. Output correction factors were derived from IAEA TRS-483. Gamma analysis was used to compare measured TMRs and OARs, and to compare Eclipse dose planes with film dosimetry results. Comparisons between measured and GBD TMRs passed gamma analysis within the specified criteria, while differences between distances to agreement for OARs measured with different detectors was attributed to different volume averaging characteristics. The OFs measured with the microDiamond and film agreed within measurement uncertainty. It was decided to configure Eclipse with the microDiamond measured OF and the SRS Diode measured TMR and OAR data. This was validated with various comparisons carried out to confirm both measurement accuracy and Eclipse configuration.
Collapse
|
5
|
Investigation of field output factors using IAEA-AAPM TRS-483 code of practice recommendations and Monte Carlo simulation for 6 MV photon beams. JOURNAL OF RADIOTHERAPY IN PRACTICE 2021. [DOI: 10.1017/s1460396921000662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Abstract
Introduction:
This study aims to experimentally determine field output factors using the methodologies suggested by the IAEA-AAPM TRS-483 for small field dosimetry and compare with the calculation from Monte Carlo (MC) simulation.
Methods:
The IBA-CC01, Sun Nuclear EDGE and IBA-SFD detectors were employed to determine the uncorrected and the corrected field output factors for 6 MV photon beams. Measurements were performed at 100 cm source to axis distance, 10 cm depth in water, and the field sizes ranged from 1 × 1 to 10 × 10 cm2. The use of field output correction factors proposed by the TRS-483 was utilised to determine field output factors. The measured field output factors were compared to that calculated using the egs_chamber user code.
Results:
The decrease in the percentage standard deviation of the measured three detectors was observed after applying the field output correction factors. Measured field output factors using CC01 and EDGE detectors agreed with MC values within 3% for field sizes down to 1 × 1 cm2, except the SFD detector.
Conclusions:
The corrected field output factors agree with the calculation from MC, except the SFD detector. CC01 and EDGE are suitable for determining field output factors, while the SFD may need more implementation of the intermediate field method.
Collapse
|
6
|
Kang DJ, Shin YJ, Jeong S, Jung JY, Lee H, Lee B. Development of clinical application program for radiotherapy induced cancer risk calculation using Monte Carlo engine in volumetric-modulated arc therapy. Radiat Oncol 2021; 16:108. [PMID: 34118968 PMCID: PMC8199704 DOI: 10.1186/s13014-020-01722-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 12/06/2020] [Indexed: 11/10/2022] Open
Abstract
Background The purpose of this study is to develop a clinical application program that automatically calculates the effect for secondary cancer risk (SCR) of individual patient. The program was designed based on accurate dose calculations using patient computed tomography (CT) data and Monte Carlo engine. Automated patient-specific evaluation program was configured to calculate SCR. Methods The application program is designed to re-calculate the beam sequence of treatment plan using the Monte Carlo engine and patient CT data, so it is possible to accurately calculate and evaluate scatter and leakage radiation, difficult to calculate in TPS. The Monte Carlo dose calculation system was performed through stoichiometric calibration using patient CT data. The automatic SCR evaluation program in application program created with a MATLAB was set to analyze the results to calculate SCR. The SCR for organ of patient was calculated based on Biological Effects of Ionizing Radiation (BEIR) VII models. The program is designed to sequentially calculate organ equivalent dose (OED), excess absolute risk (EAR), excess relative risk (ERR), and the lifetime attributable risk (LAR) in consideration of 3D dose distribution analysis. In order to confirm the usefulness of the developed clinical application program, the result values from clinical application program were compared with the manual calculation method used in the previous study. Results The OED values calculated in program were calculated to be at most approximately 13.3% higher than results in TPS. The SCR result calculated by the developed clinical application program showed a maximum difference of 1.24% compared to the result of the conventional manual calculation method. And it was confirmed that EAR, ERR and LAR values can be easily calculated by changing the biological parameters. Conclusions We have developed a patient-specific SCR evaluation program that can be used conveniently in the clinic. The program consists of a Monte Carlo dose calculation system for accurate calculation of scatter and leakage radiation and a patient-specific automatic SCR evaluation program using 3D dose distribution. The clinical application program that improved the disadvantages of the existing process can be used as an index for evaluating a patient treatment plan.
Collapse
Affiliation(s)
- Dong-Jin Kang
- Department of Radiation Oncology, Inje University Sanggye Paik Hospital, 1342, Dongil-ro, Nowon-gu, Seoul, Korea
| | - Young-Joo Shin
- Department of Radiation Oncology, Inje University Sanggye Paik Hospital, 1342, Dongil-ro, Nowon-gu, Seoul, Korea.
| | - Seonghoon Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Korea
| | - Jae-Yong Jung
- Department of Radiation Oncology, Inje University Sanggye Paik Hospital, 1342, Dongil-ro, Nowon-gu, Seoul, Korea
| | | | - Boram Lee
- Department of Radiation Oncology, Samsung Medical Center, School of Medicine, Sungkyunkwan University, 81, Irwon-Ro, Gangnam-Gu, Seoul, 06351, Korea.
| |
Collapse
|
7
|
Hermida-López M, Sánchez-Artuñedo D, Rodríguez M, Brualla L. Monte Carlo simulation of conical collimators for stereotactic radiosurgery with a 6 MV flattening-filter-free photon beam. Med Phys 2021; 48:3160-3171. [PMID: 33715167 DOI: 10.1002/mp.14837] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 02/19/2021] [Accepted: 03/08/2021] [Indexed: 11/07/2022] Open
Abstract
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. In other cases, the cone output factors reported do not take into account the effect of the small cone diameter on the detector response. Finally, few data exist on the dosimetry of cones with flattening-filter-free (FFF) beams from modern linac models. This work aims at obtaining a dosimetric characterization of the conical collimators manufactured by Brainlab AG (Munich, Germany) in a 6 MV FFF beam from a TrueBeam STx linac (Varian Medical Systems). METHODS Percentage depth dose curves, lateral dose profiles and cone output factors were obtained using Monte Carlo simulations for the cones with diameters of 4, 5, 6, 7.5, 8, 10, 12.5, 15, 17.5, 20, 25, and 30 mm. The simulation of the linac head was carried out with the PRIMO Monte Carlo software, and the simulations of the cones and the water phantom were run with the general-purpose Monte Carlo code PENELOPE. The Monte Carlo model was validated by comparing the simulation results with measurements performed for the cones of 4, 5, and 7.5 mm of diameter using a stereotactic field diode, a microDiamond detector and EBT3 radiochromic film. In addition, for those cones, simulations and measurements were done for comparison purposes, by reproducing the experimental setups from the available publications. RESULTS The experimental data acquired for the cones of 4, 5, and 7.5 mm validated the developed Monte Carlo model. The simulations accurately reproduced the experimental depths of maximum dose and the dose ratio at 20- and 10-cm depth (PDD20/10 ). A good agreement was obtained between simulated and experimental lateral dose profiles: The differences in the full-width at half-maximum were smaller than 0.2 mm, and the differences in the penumbra 80%-20% were smaller than 0.25 mm. The difference between the simulated and the average of the experimental output factors for the cones of 4, 5, and 7.5 mm of diameter was 0.0%, 0.0%, and 3.0%, respectively, well within the statistical uncertainty of the simulations (4.4% with coverage factor k = 2). It was also found that the simulated cone output factors agreed within 2% with the average of output factors reported in the literature for a variety of setup conditions, detectors, beam qualities, and cone manufacturers. CONCLUSION A Monte Carlo model of cones for stereotactic radiosurgery has been developed and validated. The cone dosimetry dataset obtained in this work, consisting of percentage depth doses, lateral dose profiles and output factors, is useful to benchmark data acquired for the commissioning of cone-based radiosurgery treatment planning systems.
Collapse
Affiliation(s)
- Marcelino Hermida-López
- Servei de Física i Protecció Radiològica, Hospital Universitari Vall d'Hebron, Vall d'Hebron Barcelona Hospital Campus, Passeig Vall d'Hebron 119-129, Barcelona, 08035, Spain
| | - David Sánchez-Artuñedo
- Servei de Física i Protecció Radiològica, Hospital Universitari Vall d'Hebron, Vall d'Hebron Barcelona Hospital Campus, Passeig Vall d'Hebron 119-129, Barcelona, 08035, Spain
| | - Miguel Rodríguez
- Centro Médico Paitilla, Calle 53 y ave. Balboa, Panama City, Panama.,Instituto de Investigaciones Científicas y de Alta Tecnología, INDICASAT-AIP, City of Knowledge, Building 219, Panama City, Panama
| | - Lorenzo Brualla
- West German Proton Therapy Centre Essen (WPE), Hufelandstr. 55, Essen, 45147, Germany.,West German Cancer Centre (WTZ), Hufelandstr. 55, Essen, 45147, Germany.,Faculty of Medicine, University of Duisburg-Essen, Hufelandstr. 55, Essen, 45147, Germany
| |
Collapse
|
8
|
Yani S, Budiansah I, Rhani MF, Haryanto F. Monte carlo model and output factors of elekta infinity™ 6 and 10 MV photon beam. Rep Pract Oncol Radiother 2020; 25:470-478. [PMID: 32494222 DOI: 10.1016/j.rpor.2020.03.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 02/02/2020] [Accepted: 03/20/2020] [Indexed: 10/24/2022] Open
Abstract
Aim This study aimed to commission the Elekta Infinity™ working in 6 and 10 MV photon beam installed in Concord International Hospital, Singapore, and compare the OFs between MC simulation and measurement using PTW semiflex and microDiamond detector for small field sizes. Material and Methods There are two main steps in this study: modelling of Linac 6 and 10 MV photon beam and analysis of the output factors for field size 2 × 2-10 × 10 cm2. The EGSnrc/BEAMnrc-DOSXYZnrc code was used to model and characterize the Linac and to calculate the dose distributions in a water phantom. The dose distribution and OFs were compared to the measurement data in the same condition. Results The commissioning process was only conducted for a 10 × 10 cm2 field size. The PDD obtained from MC simulation showed a good agreement with the measurement. The local dose difference of PDDs was less than 2% for 6 and 10 MV. The initial electron energy was 5.2 and 9.4 MeV for 6 and 10 MV photon beam, respectively. This Linac model can be used for dose calculation in other situations and different field sizes because this Linac has been commissioned and validated using Monte Carlo simulation. The 10 MV Linac produces higher electron contamination than that of 6 MV. Conclusions The Linac model in this study was acceptable. The most important result in this work comes from OFs resulted from MC calculation. This value was more significant than the OFs from measurement using semiflex and microDiamond for all beam energy and field sizes because of the CPE phenomenon.
Collapse
Affiliation(s)
- Sitti Yani
- Department of Physics, Faculty of Mathematics and Natural Sciences, IPB University (Bogor Agricultural University), Babakan, Bogor, Indonesia.,Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
| | - Indra Budiansah
- Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
| | | | - Freddy Haryanto
- Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
| |
Collapse
|
9
|
Irmen P, Reft C, Fitzherbert C, Solin L, Hand C. Verification of representative data for output factors of SRS cones utilizing IAEA TRS 483 recommendations. ACTA ACUST UNITED AC 2019; 64:215011. [DOI: 10.1088/1361-6560/ab47dd] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
10
|
Lee B, Jeong S, Chung K, Yoon M, Park HC, Han Y, Jung SH. Feasibility of a GATE Monte Carlo platform in a clinical pretreatment QA system for VMAT treatment plans using TrueBeam with an HD120 multileaf collimator. J Appl Clin Med Phys 2019; 20:101-110. [PMID: 31544350 PMCID: PMC6806485 DOI: 10.1002/acm2.12718] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 08/15/2019] [Accepted: 08/23/2019] [Indexed: 12/31/2022] Open
Abstract
Purpose To evaluate the quality of patient‐specific complicated treatment plans, including commercialized treatment planning systems (TPS) and commissioned beam data, we developed a process of quality assurance (QA) using a Monte Carlo (MC) platform. Specifically, we constructed an interface system that automatically converts treatment plan and dose matrix data in digital imaging and communications in medicine to an MC dose‐calculation engine. The clinical feasibility of the system was evaluated. Materials and Methods A dose‐calculation engine based on GATE v8.1 was embedded in our QA system and in a parallel computing system to significantly reduce the computation time. The QA system automatically converts parameters in volumetric‐modulated arc therapy (VMAT) plans to files for dose calculation using GATE. The system then calculates dose maps. Energies of 6 MV, 10 MV, 6 MV flattening filter free (FFF), and 10 MV FFF from a TrueBeam with HD120 were modeled and commissioned. To evaluate the beam models, percentage depth dose (PDD) values, MC calculation profiles, and measured beam data were compared at various depths (Dmax, 5 cm, 10 cm, and 20 cm), field sizes, and energies. To evaluate the feasibility of the QA system for clinical use, doses measured for clinical VMAT plans using films were compared to dose maps calculated using our MC‐based QA system. Results A LINAC QA system was analyzed by PDD and profile according to the secondary collimator and multileaf collimator (MLC). Values for MC calculations and TPS beam data obtained using CC13 ion chamber (IBA Dosimetry, Germany) were consistent within 1.0%. Clinical validation using a gamma index was performed for VMAT treatment plans using a solid water phantom and arbitrary patient data. The gamma evaluation results (with criteria of 3%/3 mm) were 98.1%, 99.1%, 99.2%, and 97.1% for energies of 6 MV, 10 MV, 6 MV FFF, and 10 MV FFF, respectively. Conclusions We constructed an MC‐based QA system for evaluating patient treatment plans and evaluated its feasibility in clinical practice. We observed robust agreement between dose calculations from our QA system and measurements for VMAT plans. Our QA system could be useful in other clinical settings, such as small‐field SRS procedures or analyses of secondary cancer risk, for which dose calculations using TPS are difficult to verify.
Collapse
Affiliation(s)
- Boram Lee
- Department of Radiation Oncology, Samsung Medical Center, Seoul, Korea
| | - Seonghoon Jeong
- Department of Bio-convergence Engineering, Korea University, Seoul, Korea
| | - Kwangzoo Chung
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Myonggeun Yoon
- Department of Bio-convergence Engineering, Korea University, Seoul, Korea
| | - Hee Chul Park
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Youngyih Han
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.,Department of Health Sciences and Technology,, SAIHST, Sungkyunkwan University, Seoul, Korea
| | - Sang Hoon Jung
- Department of Radiation Oncology, Samsung Medical Center, Seoul, Korea
| |
Collapse
|
11
|
Borzov E, Nevelsky A, Bar-Deroma R, Orion I. Dosimetric characterization of Elekta stereotactic cones. J Appl Clin Med Phys 2017; 19:194-203. [PMID: 29266744 PMCID: PMC5768017 DOI: 10.1002/acm2.12242] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 11/18/2017] [Accepted: 11/20/2017] [Indexed: 11/14/2022] Open
Abstract
Purpose Dosimetry of small fields defined by stereotactic cones remains a challenging task. In this work, we report the results of commissioning measurements for the new Elekta stereotactic conical collimator system attached to the Elekta VersaHD linac and present the comparison between the measured and Monte Carlo (MC) calculated data for the 6 MV FFF beam. In addition, relative output factor (ROF) dependence on the stereotactic cone aperture variation was studied and penumbra comparison for small MLC‐based and cone‐based fields was performed. Methods Cones with nominal diameters of 15 mm, 12.5 mm, 10 mm, 7.5 mm, and 5 mm were employed in our study. Percentage depth dose (PDD), off‐axis ratios (OAR), and ROF were measured using a stereotactic field diode (SFD). BEAMnrc code was used for MC simulations. Results MC calculated and measured PDDs for all cones agreed within 1%/0.5 mm, and OAR profiles agreed within 1%/0.5 mm. ROF obtained from the measurements and MC calculations agreed within 2% for all cone sizes. Small‐field correction factors for the SFD detector Kfield,3 × 3(SFD) were derived using MC calculations as a baseline and were found to be 0.982, 0.992, 0.997, 1.015, and 1.017 for the 5, 7.5, 10, 12.5, and 15‐mm cones respectively. The difference in ROF was about 10%, 6%, 3.5%, 3%, 2.5%, and 2% for ±0.3 mm variations in 5, 7.5, 10, 12.5, and 15‐mm cone aperture respectively. In case of single static field, cone‐based collimation produced a sharper penumbra compared to the MLC‐based. Conclusions Accurate MC simulation can be an effective tool for verification of dosimetric measurements of small fields. Due to the very high sensitivity of output factors on the cone diameter, manufacture‐related variations in cone size may lead to considerable variations in dosimetric characteristics of stereotactic cones.
Collapse
Affiliation(s)
- Egor Borzov
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa, Israel
| | - Alexander Nevelsky
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa, Israel
| | - Raquel Bar-Deroma
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa, Israel
| | - Itzhak Orion
- Department of Nuclear Engineering, Ben-Gurion University of the Negev, Beer Sheva, Israel
| |
Collapse
|
12
|
Han Z, Friesen S, Hacker F, Zygmanski P. Two-argument total scatter factor for small fields simultaneously collimated by MLC and jaws: application to stereotactic radiosurgery and radiotherapy. Phys Med Biol 2017; 63:015002. [PMID: 29106378 DOI: 10.1088/1361-6560/aa9872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Direct use of the total scatter factor (S tot) for independent monitor unit (MU) calculations can be a good alternative approach to the traditional separate treatment of head/collimator scatter (S c) and phantom scatter (S p), especially for stereotactic small fields under the simultaneous collimation of secondary jaws and tertiary multileaf collimators (MLC). We have carried out the measurement of S tot in water for field sizes down to 0.5 × 0.5 cm2 on a Varian TrueBeam STx medical linear accelerator (linac) equipped with high definition MLCs. Both the jaw field size (c) and MLC field size (s) significantly impact the linac output factors, especially when c [Formula: see text] s and s is small (e.g. s < 5 cm). The combined influence of MLC and jaws gives rise to a two-argument dependence of the total scatter factor, S tot(c,s), which is difficult to functionally decouple. The (c,s) dependence can be conceived as a set of s-dependent functions ('branches') defined on domain [s min, s max = c] for a given jaw size of c. We have also developed a heuristic model of S tot to assist the clinical implementation of the measured S tot data for small field dosimetry. The model has two components: (i) empirical fit formula for the s-dependent branches and (ii) interpolation scheme between the branches. The interpolation scheme preserves the characteristic shape of the measured branches and effectively transforms the measured trapezoidal domain in (c,s) plane to a rectangular domain to facilitate easier two-dimensional interpolation to determine S tot for arbitrary (c,s) combinations. Both the empirical fit and interpolation showed good agreement with experimental validation data.
Collapse
Affiliation(s)
- Zhaohui Han
- Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, MA, United States of America. Harvard Medical School, Boston, MA, United States of America. Author to whom any correspondence should be addressed
| | | | | | | |
Collapse
|
13
|
Beilla S, Younes T, Vieillevigne L, Bardies M, Franceries X, Simon L. Monte Carlo dose calculation in presence of low-density media: Application to lung SBRT treated during DIBH. Phys Med 2017; 41:46-52. [DOI: 10.1016/j.ejmp.2017.04.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 02/22/2017] [Accepted: 04/09/2017] [Indexed: 12/25/2022] Open
|