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Baltz GC, Kirsner SM. Characterization of a novel pulse normalization technology for beam scanning of small fields without a reference chamber. J Appl Clin Med Phys 2024; 25:e14379. [PMID: 38700940 PMCID: PMC11163498 DOI: 10.1002/acm2.14379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/19/2024] [Accepted: 04/15/2024] [Indexed: 05/05/2024] Open
Abstract
PURPOSE A novel pulse normalization technology enabling the acquisition of low noise beam data without the use of a physical reference chamber has recently been commercially released. The purpose of this study was to characterize the use of this technology for beam scanning of small fields required in the commissioning of a stereotactic radiotherapy program. METHODS Three detectors (Edge diode, microDiamond, PinPoint) were used to acquire beam data under three conditions: with a reference chamber, with pulse normalization and no reference chamber (PN), and without pulse normalization and no reference chamber (nPN). Percent depth dose (PDD) scans were acquired for 0.5, 1.0, 2.0, and 3.0 cm2 field sizes and profiles were acquired at 1.4, 10, and 30 cm depths using continuous scanning. The coefficient of variation (CoV) was calculated for all beam data to compare signal-to-noise and gamma comparisons (1%, 1 mm) were calculated of the PN and nPN scans compared to the reference data. RESULTS Average 95th percentile CoV values were similar for all detectors across conditions, with PN data being comparable to reference data and minor increases observed for nPN data. Mean gamma pass rates for PN PDD scans exceeded 98% for all detectors. Profile gamma pass rates were 100% for all detectors at 1.4 and 10 cm depth. At 30 cm depth, profiles acquired with the PinPoint and microDiamond detectors had lower mean gamma pass rates than the Edge, at 95% and 95.7%, respectively. CONCLUSIONS A novel pulse normalization technology was demonstrated to be effective for acquiring beam profiles and PDDs for small fields without the use of a physical reference chamber. Limitations in how the method is implemented led to some errors in data acquired using lower sensitivity detectors. When used with a diode, pulse normalization produced equivalent scans to those acquired with a reference chamber.
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Chi DD, Toan TN, Hill R. A multi-detector comparison to determine convergence of measured relative output factors for small field dosimetry. Phys Eng Sci Med 2024; 47:371-379. [PMID: 37943444 DOI: 10.1007/s13246-023-01351-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 10/24/2023] [Indexed: 11/10/2023]
Abstract
The TRS-483 Code of Practice (CoP) provides generic relative output correction factors, [Formula: see text], for a range of detectors and beam energies as used in small field dosimetry. In this work, the convergence of the relative output factors (ROFs) for 6 MV X-ray beams with and without flattening filters was investigated under different combinations of beam collimation and published detector correction factors. The SFD, PFD and CC04 (IBA) were used to measure ROFs of a TrueBeam STx linear accelerator with small fields collimated by the high-definition MLC, which has 2.5 and 5.0 mm projected leaves. Two configurations were used for the collimators: (1) fixed jaws at 10 × 10 cm2 and (2) with a 2 mm offset from the MLC edge, in line with the recommended geometry from IROC-H as part of their auditing program and published dataset. The [Formula: see text] factors for the three detectors were taken from the TRS483 CoP and other published works. The average differences of ROFs measured by detectors under MLC fields with fixed jaws and with 2 mm jaws offset for the 6 MV-WFF beam are 1.4% and 1.9%, respectively. Similarly, they are 2.3% and 2.4% for the 6MV-FFF beam. The relative differences between the detector-average ROFs and the corresponding IROC-H dataset are 2.0% and 3.1% for the 6 MV-WFF beam, while they are 2.4% and 3.2% for the 6MV-FFF beam at the smallest available field size of 2 × 2 cm2. For smaller field sizes, the average ROFs of the three detectors and corresponding results from Akino and Dufreneix showed the largest difference to be 6.6% and 6.2% under the 6 MV-WFF beam, while they are 3.4% and 3.6% under the 6 MV-WFF beam at the smallest field size of 0.5 × 0.5 cm2. Some well-published specific output correction factors for different small field detector types give better convergence in the calculation of the relative output factor in comparison with the generic data provided by the TRS-483 CoP. Relative output factor measurements should be performed as close as possible to the clinical settings including a combination of collimation systems, beam types and using at least three different types of small field detector for more accurate computation of the treatment planning system. The IROC-H dataset is not available for field size smaller than 2 × 2 cm2 for double checks and so that user should carefully check with other publications with the same setting.
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Affiliation(s)
- Do Duc Chi
- 108 Military Central Hospital, Hanoi, Vietnam.
- Vietnam Atomic Energy Institute, Hanoi, Vietnam.
| | | | - Robin Hill
- Department of Radiation Oncology, Chris O'Brien Lifehouse, Missenden Rd, Camperdown, Sydney, NSW, 2050, Australia
- Arto Hardy Family Biomedical Innovation Hub, Chris O'Brien Lifehouse, Missenden Rd, Camperdown, Sydney, NSW, 2050, Australia
- Institute of Medical Physics, School of Physics, The University of Sydney, Sydney, NSW, 2006, Australia
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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.
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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
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Kawata K, Hirashima H, Tsuruta Y, Sasaki M, Matsushita N, Fujimoto T, Nakamura M, Nakata M. Applicability evaluation of the TRS-483 protocol for the determination of small-field output factors using different multi-leaf collimator and field-shaping types. Phys Med 2023; 113:102664. [PMID: 37573811 DOI: 10.1016/j.ejmp.2023.102664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 08/06/2023] [Accepted: 08/07/2023] [Indexed: 08/15/2023] Open
Abstract
PURPOSE To evaluate the applicability of TRS-483 output correction factors (CFs) for small-field output factors (OFs) using different multi-leaf collimators (MLC) and field-shaping types. METHODS All measurements were performed on TrueBeam, TrueBeam STx, and Halcyon using 6 MV flattening filter-free energy. Four detectors, including CC01, CC04, microDiamond, and EDGE, were used. Nominal field sizes ranging from 1 × 1 to 4 × 4, and 10 × 10 cm2 were used to measure small-field OFs at source-to-axis distance of 100 cm with a 0° gantry angle in a 3D water phantom. Further, the field-shaping types were defined using jaw collimator or MLC (five different configurations). A field size of 10 × 10 cm2 was used as the reference for calculation of OFs obtained as ratio of detector readings (OFdet). The percentage difference and coefficient of variation of OFdet and OFdet corrected by applying CF were compared for each field size and configuration. RESULTS For OFdet corrected by applying CF, the ranges of percentage difference and coefficient of variation in all configurations for ≥ 2 × 2 cm2 fields were reduced from 1.2-2.2 to 0.8-1.3 percentage points (%pt) and from 0.5-1.0 to 0.4-0.7%, respectively. For 1 × 1 cm2 field, the ranges of percentage difference and coefficient of variation were reduced from 3.3-5.7 to 1.2-2.2 %pt and from 2.2-3.7 to 0.8-1.1%, respectively. CONCLUSIONS The CFs described in TRS-483 dosimetry protocol have broad applicability in reducing OF variations between detectors under different MLC and field-shaping types.
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Affiliation(s)
- Kohei Kawata
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Hideaki Hirashima
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan.
| | - Yusuke Tsuruta
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan; Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Makoto Sasaki
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Norimasa Matsushita
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Takahiro Fujimoto
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Mitsuhiro Nakamura
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan; Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Manabu Nakata
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
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Wu NG. Extending the Eclipse TM AcurosXB output factor table for small field radiosurgery. J Appl Clin Med Phys 2022; 24:e13877. [PMID: 36585844 PMCID: PMC9859982 DOI: 10.1002/acm2.13877] [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: 01/23/2022] [Revised: 11/05/2022] [Accepted: 12/01/2022] [Indexed: 01/01/2023] Open
Abstract
PURPOSE To investigate the necessity of extending the output factor table (OF Table) of the Varian EclipseTM Treatment Planning System for small field stereotactic radiosurgery (SRS) and stereotactic body radiosurgery (SBRT) treatments. METHODS A new AcurosXB 15.6 beam model was created in the Eclipse Beam Configuration, which is identical to the one that has been used in the clinic with a default 3 × 3 cm to 40 × 40 cm OF Table, except the OF Table in the new model was extended to cover the range from 1 × 1 cm to 40 × 40 cm. 80 small square and rectangular output factors were measured on a Varian TrueBeam utilizing a Standard Imaging Exradin W2-1×1 scintillator detector, inside a PTW BeamScan water tank with 95 cm SSD at 5 cm depth. Cerenkov contamination was corrected using a rectangular field method (2 cm × 15 cm field). Nine Radiosurgery plans with primary jaw setting ranging from 0.7 cm to 2.0 cm were evaluated by both beam models. The monitor unit (MU) differences between the two beam models were calculated for identical 3-dimensional (3D) absolute dose distributions. Output factors, measured versus Eclipse calculated, were compared down to 0.5 × 0.5 cm primary jaw setting. RESULTS For the 6FFF beam, the difference between the two beam models was ∼ 6% for 1 × 1 cm jaw settings and 4% at 1.5 × 1.5 cm, with the extended OF Table requiring higher MUs for the same dose prescription and same 3-dimensional isodose distribution. For the 6MV beam, the corresponding difference is ∼7.5% for 1 × 1 cm, 5% for 1.5 × 1.5 cm, and 3% for 2 × 2 cm jaw settings, with the extended OF Table requiring higher MUs. For jaw settings smaller than 1 × 1 cm, measured dose can be considerably smaller than Eclipse predicted dose, even with the OF Table extension. This is reflected by the fact that the output factor for 0.5 × 0.5 cm, calculated via Eclipse external beam, was more than 30% greater than that measured for both 6FFF and 6MV beams. CONCLUSIONS Eclipse does a satisfactory job for primary jaw sizes down to 2 cm. For jaw settings smaller than 1.5 cm, the OF Table in Eclipse should be extended to improve the dose calculation accuracy.
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Affiliation(s)
- Ning Genevieve Wu
- Department of Radiation MedicineOregon Health and Science UniversityPortlandOregonUSA
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Lechner W, Alfonso R, Arib M, Huq MS, Ismail A, Kinhikar R, Lárraga-Gutiérrez JM, Mani KR, Maphumulo N, Sauer OA, Shoeir S, Suriyapee S, Christaki K. A multi-institutional evaluation of small field output factor determination following the recommendations of IAEA/AAPM TRS-483. Med Phys 2022; 49:5537-5550. [PMID: 35717637 PMCID: PMC9541513 DOI: 10.1002/mp.15797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 03/31/2022] [Accepted: 05/25/2022] [Indexed: 11/15/2022] Open
Abstract
Purpose The aim of this work was to test the implementation of small field dosimetry following TRS‐483 and to develop quality assurance procedures for the experimental determination of small field output factors (SFOFs). Materials and methods Twelve different centers provided SFOFs determined with various detectors. Various linac models using the beam qualities 6 MV and 10 MV with flattening filter and without flattening filter were utilized to generate square fields down to a nominal field size of 0.5 cm × 0.5 cm. The detectors were positioned at 10 cm depth in water. Depending on the local situation, the source‐to‐surface distance was either set to 90 cm or 100 cm. The SFOFs were normalized to the output of the 10 cm × 10 cm field. The spread of SFOFs measured with different detectors was investigated for each individual linac beam quality and field size. Additionally, linac‐type specific SFOF curves were determined for each beam quality and the SFOFs determined using individual detectors were compared to these curves. Example uncertainty budgets were established for a solid state detector and a micro ionization chamber. Results The spread of SFOFs for each linac and field was below 5% for all field sizes. With the exception of one linac‐type, the SFOFs of all investigated detectors agreed within 10% with the respective linac‐type SFOF curve, indicating a potential inter‐detector and inter‐linac variability. Conclusion Quality assurance on the SFOF measurements can be done by investigation of the spread of SFOFs measured with multiple detectors and by comparison to linac‐type specific SFOFs. A follow‐up of a measurement session should be conducted if the spread of SFOFs is larger than 5%, 3%, and 2% for field sizes of 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 2 cm × 2 cm, respectively. Additionally, deviations of measured SFOFs to the linac‐type‐curves of more than 7%, 3%, and 2% for field sizes 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 1 cm × 1 cm, respectively, should be followed up.
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Affiliation(s)
- Wolfgang Lechner
- Department of Radiation Oncology, Division of Medical Physics, Medical University Vienna, Vienna, 1090, Austria
| | - Rodolfo Alfonso
- Department of Nuclear Engineering, Higher Institute of Technology and Applied Sciences, University of Havana, Havana, 10400, Cuba
| | - Mehenna Arib
- King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania, USA
| | - Anas Ismail
- Protection and Safety Department, Atomic Energy Commission of Syria, Damascus, PO Box 6091, Syria
| | - Rajesh Kinhikar
- Department of Medical Physics, Tata Memorial Centre, Mumbai, India 400012 & Homi Bhabha National Institute, Mumbai, 400094, India
| | - José M Lárraga-Gutiérrez
- Laboratorio de Física-Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, La Fama, Tlalpan 14269, CDMX, México
| | - Karthick Raj Mani
- Department of Radiation Oncology, United Hospital Ltd., Dhaka, 1212, Bangladesh
| | - Nkosingiphile Maphumulo
- Radiation Dosimetry Section, National Metrology Institute of South Africa, Pretoria, South Africa
| | - Otto A Sauer
- Department of Radiation Oncology, University of Würzburg, 97080, Würzburg, Germany
| | | | - Sivalee Suriyapee
- Division of Radiation Oncology, Department of Radiology, Chulalongkorn University, Bangkok, Thailand
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Xu Q, Huynh K, Nie W, Rose MS, Chawla AK, Choe KS, Kanani S, Kubicek GJ, Fan J. Implementing and evaluating a high-resolution diode array for patient-specific quality assurance of robotic brain stereotactic radiosurgery/radiotherapy. J Appl Clin Med Phys 2022; 23:e13569. [PMID: 35278033 PMCID: PMC9121027 DOI: 10.1002/acm2.13569] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 01/22/2022] [Accepted: 01/24/2022] [Indexed: 12/31/2022] Open
Abstract
The purpose of the study was to introduce and evaluate a high-resolution diode array for patient-specific quality assurance (PSQA) of CyberKnife brain stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). Thirty-three intracranial plans were retrospectively delivered on the SRS MapCHECK using fixed cone, Iris, and multileaf collimator (MLC). The plans were selected to cover a range of sites from large tumor bed, single/multiple small brain metastases (METs) to trigeminal neuralgia. Fiducial tracking using the four fiducials embedded around the detector plane was used as image guidance. Results were analyzed before and after registration based on absolute dose gamma criterion of 1 mm distance-to-agreement and 0.5%-3% dose-difference. Overall, the gamma passing rates (1 mm and 3% criterion) before registration for all the patients were above 90% for all three treatment modalities (96.8 ± 3.5%, the lowest passing rate of 90.4%), and were improved after registration (99.3 ± 1.5%). When tighter criteria (1 mm and 2%) were applied, the gamma passing rates after registration for all the cases dropped to 97.3 ± 3.2%. For trigeminal neuralgia cases, we applied 1 mm and 0.5% criterion and the passing rates dropped from 100 ± 0.0% to 98.5 ± 2.0%. The mean delivery time was 33.4 ± 11.7 min, 24.0 ± 4.9 min, and 17.1 ± 2.6 min for the fixed cone, Iris, and MLC, respectively. With superior gamma passing rates and reasonable quality assurance (QA) time, we believe the SRS MapCHECK could be a good option for routine PSQA for CyberKnife SRS/SRT.
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Affiliation(s)
- Qianyi Xu
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Kiet Huynh
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Wei Nie
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | | | - Ashish K. Chawla
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Kevin S. Choe
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Samir Kanani
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
| | - Gregory J. Kubicek
- Department of Radiation OncologyMD Anderson Cancer Center at CooperCamdenNew JerseyUSA
| | - Jiajin Fan
- Department of Advanced Radiation Oncology and Proton TherapyInova Schar Cancer InstituteFairfaxVirginiaUSA
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Lárraga-Gutiérrez JM, García-Garduño OA, Herrera-González JA, Galván de la Cruz OO. Evaluation of Acuros® XB accuracy for static small fields dose calculations based on the IAEA/AAPM TRS-483 recommendation. Phys Med 2021; 89:140-146. [PMID: 34365118 DOI: 10.1016/j.ejmp.2021.06.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Revised: 06/14/2021] [Accepted: 06/27/2021] [Indexed: 12/01/2022] Open
Abstract
PURPOSE Evaluate Acuros® XB dose calculation accuracy following TRS-483 recommendations in small static fields for flattened and un-flattened 6 MV X-ray beams. METHODS Field output factors were measured following TRS-483 recommendations using four radiation detectors. Two sets of field output factors were measured. One set was used to configure the beam model into Acuros® XB down to a jaw-defined field size of 1.0 cm × 1.0 cm. The second set was used to evaluate the differences between calculated and measured field output factors for MLC-fields down to a field size of 0.5 cm × 0.5 cm. RESULTS Acuros® XB showed an accuracy within 1.5% down to an MLC-field of 1.0 cm × 1.0 cm, for a focal spot size of 1.0 and 0.0 mm in the cross and in-plane directions. For an MLC-field of 0.5 cm × 0.5 cm, an agreement was found within 3% between calculated and measured field output factors. These results were addressed by optimizing the focal spot size to minimize the differences between calculated and measured dose profiles. CONCLUSIONS By optimizing the focal spot size, Acuros® XB showed an acceptable agreement within 3% down to an MLC-field of 0.5 cm × 0.5 cm. The results of this work suggest that if static and modulated delivery of very small targets is planned, then a field output factor table down to a field size of 1.0 cm is required in the beam configuration model.
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Affiliation(s)
- José M Lárraga-Gutiérrez
- Lab. de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, La Fama, Tlalpan 14269, CMDX, Mexico.
| | - Olivia A García-Garduño
- Lab. de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, La Fama, Tlalpan 14269, CMDX, Mexico
| | - José A Herrera-González
- Unidad de Radioneurocirugía, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, La Fama, Tlalpan 14269, CMDX, Mexico; Depto. de Biofísica, Instituto Nacional de Cancerología, San Fernando 22, Belisario Domínguez Secc 16, Tlalpan 14080, CDMX, Mexico
| | - Olga O Galván de la Cruz
- Unidad de Radioneurocirugía, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, La Fama, Tlalpan 14269, CMDX, Mexico
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Das IJ, Francescon P, Moran JM, Ahnesjö A, Aspradakis MM, Cheng CW, Ding GX, Fenwick JD, Saiful Huq M, Oldham M, Reft CS, Sauer OA. Report of AAPM Task Group 155: Megavoltage photon beam dosimetry in small fields and non-equilibrium conditions. Med Phys 2021; 48:e886-e921. [PMID: 34101836 DOI: 10.1002/mp.15030] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 05/06/2021] [Accepted: 06/02/2021] [Indexed: 12/14/2022] Open
Abstract
Small-field dosimetry used in advance treatment technologies poses challenges due to loss of lateral charged particle equilibrium (LCPE), occlusion of the primary photon source, and the limited choice of suitable radiation detectors. These challenges greatly influence dosimetric accuracy. Many high-profile radiation incidents have demonstrated a poor understanding of appropriate methodology for small-field dosimetry. These incidents are a cause for concern because the use of small fields in various specialized radiation treatment techniques continues to grow rapidly. Reference and relative dosimetry in small and composite fields are the subject of the International Atomic Energy Agency (IAEA) dosimetry code of practice that has been published as TRS-483 and an AAPM summary publication (IAEA TRS 483; Dosimetry of small static fields used in external beam radiotherapy: An IAEA/AAPM International Code of Practice for reference and relative dose determination, Technical Report Series No. 483; Palmans et al., Med Phys 45(11):e1123, 2018). The charge of AAPM task group 155 (TG-155) is to summarize current knowledge on small-field dosimetry and to provide recommendations of best practices for relative dose determination in small megavoltage photon beams. An overview of the issue of LCPE and the changes in photon beam perturbations with decreasing field size is provided. Recommendations are included on appropriate detector systems and measurement methodologies. Existing published data on dosimetric parameters in small photon fields (e.g., percentage depth dose, tissue phantom ratio/tissue maximum ratio, off-axis ratios, and field output factors) together with the necessary perturbation corrections for various detectors are reviewed. A discussion on errors and an uncertainty analysis in measurements is provided. The design of beam models in treatment planning systems to simulate small fields necessitates special attention on the influence of the primary beam source and collimating devices in the computation of energy fluence and dose. The general requirements for fluence and dose calculation engines suitable for modeling dose in small fields are reviewed. Implementations in commercial treatment planning systems vary widely, and the aims of this report are to provide insight for the medical physicist and guidance to developers of beams models for radiotherapy treatment planning systems.
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Affiliation(s)
- Indra J Das
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Paolo Francescon
- Department of Radiation Oncology, Ospedale Di Vicenza, Vicenza, Italy
| | - Jean M Moran
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Anders Ahnesjö
- Medical Radiation Sciences, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Maria M Aspradakis
- Institute of Radiation Oncology, Cantonal Hospital of Graubünden, Chur, Switzerland
| | - Chee-Wai Cheng
- Department of Radiation Oncology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - George X Ding
- Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - John D Fenwick
- Molecular and Clinical Cancer Medicine, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh, School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Mark Oldham
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
| | - Chester S Reft
- Department of Radiation Oncology, University of Chicago, Chicago, IL, USA
| | - Otto A Sauer
- Department of Radiation Oncology, Klinik fur Strahlentherapie, University of Würzburg, Würzburg, Germany
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Dwivedi S, Kansal S, Dangwal VK, Bharati A, Shukla J. Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors. Biomed Phys Eng Express 2021; 7. [PMID: 33930875 DOI: 10.1088/2057-1976/abfd80] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 04/30/2021] [Indexed: 11/12/2022]
Abstract
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 × 0.6 cm to 6.0 cm × 6.0 cm. The five detectors used were SNC125c, PinPoint, EDGE, EBT3, and TLD-100. All measurements were performed as per the International Atomic Energy Agency TRS 483 protocol. Output factors measured using different detectors as direct reading ratios showed significant variation for the smallest fields, whereas after correcting them according to TRS 483, all sets of output factors were nearly compatible with each other when measurement uncertainty was also considered. The beam profile measured using SNC125c showed the largest penumbra for all field sizes, whereas the smallest was recorded with EDGE. Compared with that of EBT3, the surface dose was found to be much higher for all the other detectors. PinPoint, EBT3, TLD-100, and EDGE were found to be the detector of choice for small-field output factor measurements; however, PinPoint needs special attention when used for the smallest field size (0.6 cm × 0.6 cm). EDGE and EBT3 are optimal for measuring beam profiles. EBT3, PinPoint, and EDGE can be selected for depth dose measurements, and EBT3 is suitable for surface dose estimation.
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Affiliation(s)
- Shekhar Dwivedi
- Department of Medical Physics, Tata Memorial Centre, Homi Bhabha Cancer Hospital and Research Centre, Mullanpur, Mohali, Punjab, 140901, India.,Department of Physics, Maharaja Ranjit Singh Punjab Technical University, Bathinda, Punjab, 151001, India
| | - Sandeep Kansal
- Department of Physics, Maharaja Ranjit Singh Punjab Technical University, Bathinda, Punjab, 151001, India
| | - Vinod Kumar Dangwal
- Department of Radiotherapy, Government Medical College, Patiala, Punjab, 147001, India
| | - Avinav Bharati
- Department of Radiation Oncology, Dr Ram Manohar Lohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, 226010, India
| | - Jooli Shukla
- Department of Physics, Dr Bhimrao Ambedkar University, Agra, Uttar Pradesh, 282004, India
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Hernández-Becerril MA, Lárraga-Gutiérrez JM, Saldivar B, Hernández-Servín JA. Monte Carlo verification of output correction factors for a TrueBeam STx®. Appl Radiat Isot 2021; 173:109701. [PMID: 33813187 DOI: 10.1016/j.apradiso.2021.109701] [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: 10/04/2019] [Revised: 03/18/2021] [Accepted: 03/19/2021] [Indexed: 11/15/2022]
Abstract
The recent publication of the new code of practice IAEA/AAPM TRS-483 introduces output correction factors to correct detector response changes in relative dosimetry of small photon beams. In TRS-483, average correction factors are reported for several detectors in high-energy photon beams at 6 and 10 MV with and without flattening filter. These correction factors were determined by Monte Carlo simulation or experimental measurements using several linacs of different brands and vendors. The goal of this work was to validate the output correction factors reported in TRS-483 for 6 MV photon beams of a TrueBeam STx® linac. The validation was performed using Monte Carlo simulations of four radiation detectors employed in the dosimetry of small photon beams and whose output correction factors were determined using a different radiation source than TrueBeam STx®. The results show that Monte Carlo calculated output correction factors, and those reported in the code of practice TRS-483 fully agree within ∼1%. The use of generic correction factors for a TrueBeam STx® and the detectors studied in this work is suitable for small field dosimetry static beams within the uncertainties of Monte Carlo calculations and output correction factors reported in TRS-483.
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Affiliation(s)
- Mario A Hernández-Becerril
- Facultad de Ingeniería,Universidad Autónoma del Estado de México, Cerro de Coatepec s/n, Ciudad Universitaria, Toluca 50100, Estado de México, Mexico
| | - José M Lárraga-Gutiérrez
- Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, Tlalpan 14269, CDMX, Mexico.
| | - Belem Saldivar
- Facultad de Ingeniería,Universidad Autónoma del Estado de México, Cerro de Coatepec s/n, Ciudad Universitaria, Toluca 50100, Estado de México, Mexico; Cátedras CONACYT, Av. Insurgentes sur 1582, Col. Crédito Constructor, Alcaldía Benito Juárez, CDMX 03940, Mexico
| | - J A Hernández-Servín
- Facultad de Ingeniería,Universidad Autónoma del Estado de México, Cerro de Coatepec s/n, Ciudad Universitaria, Toluca 50100, Estado de México, Mexico
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Lorenz FH, Paris MI. Identification of a potential source of error for 6FFF beams delivered on an Agility TM multileaf collimator. J Appl Clin Med Phys 2021; 22:92-98. [PMID: 33675145 PMCID: PMC8035561 DOI: 10.1002/acm2.13212] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 01/02/2021] [Accepted: 01/02/2021] [Indexed: 11/07/2022] Open
Abstract
Purpose The performance of the AgilityTM multileaf collimator was investigated with a focus on dynamic, small fields for flattening filter free (FFF) beams. Methods In this study we have developed a simple tool to test the robustness of the control mechanisms during dynamic beam delivery for Elekta’s VersaHD linear accelerator with Integrity 4.0.4 control software. We have programed the planning system to calculate dose for delivery of sweeping gaps. These sweeping gaps have a constant speed, constant size, and are delivered at a constant dose rate. Therefore they specifically identify delivery problems in dynamic mode. Results The Elekta AgilityTM control mechanism fails to maintain accurate delivery for small, dynamic sweeping gaps. For small gap sizes, the AgilityTM control mechanism delivers a field that is more than four times the size of the planned field width without generating an interlock. This has dosimetric implications: The discrepancy between calculated and measured doses increases with decreasing gap size and exceeds 10% and 60% at isocenter for a 3.5 mm and 1 mm gap size, respectively. Conclusion A deficiency of the AgilityTM control system was identified in this study. This deficiency is a potential source of error for volumetric modulated arc therapy fields and could therefore contribute to relatively high failure rates in quality assurance measurements, especially for FFF beams.
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Affiliation(s)
- Friedlieb H. Lorenz
- Department of Radiation OncologySouthern District Health BoardDunedinNew Zealand
| | - Matthew I. Paris
- Department of Radiation OncologySouthern District Health BoardDunedinNew Zealand
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Akino Y, Okamura K, Das IJ, Isohashi F, Seo Y, Tamari K, Hirata T, Hayashi K, Inoue S, Ogawa K. Technical Note: Characteristics of a microSilicon X shielded diode detector for photon beam dosimetry. Med Phys 2021; 48:2004-2009. [DOI: 10.1002/mp.14639] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 11/09/2020] [Accepted: 11/24/2020] [Indexed: 11/07/2022] Open
Affiliation(s)
- Yuichi Akino
- Oncology Center Osaka University Hospital 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Keita Okamura
- Department of Medical Technology Osaka University Hospital 2‐15 Yamadaoka, Suita Osaka565‐0871Japan
| | - Indra J. Das
- Department of Radiation Oncology Northwestern Memorial HospitalNorthwestern University Feinberg School of Medicine 251 East Huron Street, Galter Pavilion Chicago ILLC‐17860611USA
| | - Fumiaki Isohashi
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Yuji Seo
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Keisuke Tamari
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Takero Hirata
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Kazuhiko Hayashi
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Shinichi Inoue
- Department of Medical Technology Osaka University Hospital 2‐15 Yamadaoka, Suita Osaka565‐0871Japan
| | - Kazuhiko Ogawa
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
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Dufreneix S, Bellec J, Josset S, Vieillevigne L. Field output factors for small fields: A large multicentre study. Phys Med 2021; 81:191-196. [PMID: 33465756 DOI: 10.1016/j.ejmp.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 12/30/2020] [Accepted: 01/02/2021] [Indexed: 02/06/2023] Open
Abstract
PURPOSE The determination of output factors in small field dosimetry is a crucial point, especially when implementing stereotactic radiotherapy (SRT). Herein, a working group of the French medical physicist society (SFPM) was created to collect small field output factors. The objective was to gather and disseminate information on small field output factors based on different detectors for various clinical SRT equipment and measurement configurations. METHOD Participants were surveyed for information about their SRT equipment, including the type of linear particle accelerator (linac), collimator settings, measurement conditions for the output factors and the detectors used. Participants had to report both the ratio of detector readings and the correction factors applied as described in the IAEA TRS-483 code of practice for nominal field sizes smaller or equal to 3 cm. Mean field output factors and their associated standard deviations were calculated when data from at least 3 linacs were available. RESULTS 23 centres were enrolled in the project. Standard deviations of the mean field output factors were systematically smaller than 1.5% for field sizes larger or equal to 1 cm and reached 5% for the smallest field size (0.5 cm). Deviations with published data were smaller than 2% except for the 0.5 cm circular fixed aperture collimator of the CyberKnife where it reached 3.5%. CONCLUSION These field output factor values obtained via a large multicentre study can be considered as an external cross verification for any radiotherapy centre starting a SRT program and should help minimize systematic errors when determining small field output factors.
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Affiliation(s)
- S Dufreneix
- Institut de Cancérologie de l'Ouest, Angers, Saint-Herblain, France.
| | - J Bellec
- Centre Eugène Marquis, Rennes, France
| | - S Josset
- Institut de Cancérologie de l'Ouest, Angers, Saint-Herblain, France
| | - L Vieillevigne
- Institut Claudius Régaud, Institut Universitaire du Cancer de Toulouse, France; Centre de Recherche et de Cancérologie de Toulouse, UMR1037 INSERM - Université Toulouse 3 - ERL5294 CNRS, Oncopole, Toulouse, France
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