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Walter AE, DeWerd LA. Feasibility of implementing a megavoltage ionization chamber calibration service at the secondary standards level. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2022.110699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Shaw M, Lye J, Alves A, Keehan S, Lehmann J, Hanlon M, Kenny J, Baines J, Porumb C, Geso M, Brown R. Characterisation of a synthetic diamond detector for end-to-end dosimetry in stereotactic body radiotherapy and radiosurgery. Phys Imaging Radiat Oncol 2021; 20:40-45. [PMID: 34722939 PMCID: PMC8536779 DOI: 10.1016/j.phro.2021.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 10/09/2021] [Accepted: 10/10/2021] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE Synthetic diamond detectors offer real time measurement of dose in radiotherapy applications which require high spatial resolution. Additional considerations and corrections are required for measurements where the diamond detector is orientated at various angles to the incident beam. This study investigated diamond detectors for end-to-end testing of Stereotactic Body Radiotherapy (SBRT) and Stereotactic Radiosurgery (SRS) in the context of dosimetry audits. MATERIAL AND METHODS Seven individual diamond detectors were investigated and compared with respect to warm up stability, dose-rate dependence, linearity, detector shadowing, energy response, cross-calibration, angular dependence and positional sensitivity in SBRT and SRS. RESULTS Large variation in the cross calibration factors was found between the seven individual detectors. For each detector, the energy dependence in the cross calibration factor was on average <0.6% across the beam qualities investigated (Co-60 Gamma Knife, and MV beams with TPR20,10 0.684-0.733). The angular corrections for individual fields were up to 5%, and varied with field size. However, the average angular dependence for all fields in a typical SRS treatment delivery was <1%. The overall measurement uncertainty was 3.6% and 3.1% (2σ) for an SRS and SBRT treatment plan respectively. CONCLUSION Synthetic diamond detectors were found to be reliable and robust for end-to-end dosimetry in SBRT and SRS applications. Orientation of the detector relative to the beam axis is an important consideration, as significant corrections are required for angular dependence.
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Affiliation(s)
- Maddison Shaw
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
- School of Health and Biomedical Science, RMIT University, Melbourne, VIC, Australia
| | - Jessica Lye
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
- Olivia Newtown John Cancer Wellness & Research Centre, Heidelberg, VIC, Australia
| | - Andrew Alves
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
| | - Stephanie Keehan
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
| | - Joerg Lehmann
- Department of Radiation Oncology, Calvary Mater Newcastle, Newcastle, Australia
- School of Science, RMIT University, Melbourne, Australia
- School of Mathematical and Physical Sciences, University of Newcastle, Australia
- Institute of Medical Physics, University of Sydney, Australia
| | - Maximilian Hanlon
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
| | - John Kenny
- Medical Physics Specialists, Health Stem Solutions, Melbourne, VIC, Australia
| | - John Baines
- Radiation Oncology, Townsville Cancer Centre, Townsville, QLD, Australia
| | - Claudiu Porumb
- Alfred Health Radiation Oncology, Melbourne VIC, Australia
| | - Moshi Geso
- School of Health and Biomedical Science, RMIT University, Melbourne, VIC, Australia
| | - Rhonda Brown
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
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Buchegger N, Grogan G, Hug B, Oliver C, Ebert M. CyberKnife reference dosimetry: An assessment of the impact of evolving recommendations on correction factors and measured dose. Med Phys 2020; 47:3573-3585. [DOI: 10.1002/mp.14190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/29/2020] [Accepted: 03/30/2020] [Indexed: 11/06/2022] Open
Affiliation(s)
- Nicole Buchegger
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
| | - Garry Grogan
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
| | - Ben Hug
- 5D Clinics Claremont WA 6010 Australia
| | - Chris Oliver
- Australian Radiation Protection and Nuclear Safety Agency Yallambie Vic. 3085 Australia
| | - Martin Ebert
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
- 5D Clinics Claremont WA 6010 Australia
- Department of Physics University of Western Australia Crawley WA 6009 Australia
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Renaud J, Palmans H, Sarfehnia A, Seuntjens J. Absorbed dose calorimetry. ACTA ACUST UNITED AC 2020; 65:05TR02. [DOI: 10.1088/1361-6560/ab4f29] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Renaud J, Sarfehnia A, Bancheri J, Seuntjens J. Absolute dosimetry of a 1.5 T MR-guided accelerator-based high-energy photon beam in water and solid phantoms using Aerrow. Med Phys 2019; 47:1291-1304. [PMID: 31834640 DOI: 10.1002/mp.13968] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/03/2019] [Accepted: 12/05/2019] [Indexed: 11/09/2022] Open
Abstract
PURPOSE In this work, the fabrication, operation, and evaluation of a probe-format graphite calorimeter - herein referred to as Aerrow - as an absolute clinical dosimeter of high-energy photon beams while in the presence of a B = 1.5 T magnetic field is described. Comparable to a cylindrical ionization chamber (IC) in terms of utility and usability, Aerrow has been developed for the purpose of accurately measuring absorbed dose to water in the clinic with a minimum disruption to the existing clinical workflow. To our knowledge, this is the first reported application of graphite calorimetry to magnetic resonance imaging (MRI)-guided radiotherapy. METHODS Based on a previously numerically optimized and experimentally validated design, an Aerrow prototype capable of isothermal operation was constructed in-house. Graphite-to-water dose conversions as well as magnetic field perturbation factors were calculated using Monte Carlo, while heat transfer and mass impurity corrections and uncertainties were assessed analytically. Reference dose measurements were performed in the absence and presence of a B = 1.5 T magnetic field using Aerrow in the 7 MV FFF photon beam of an Elekta MRI-linac and were directly compared to the results obtained using two calibrated reference-class IC types. The feasibility of performing solid phantom-based dosimetry with Aerrow and the possible influence of clearance gaps is also investigated by performing reference-type dosimetry measurements for multiple rotational positions of the detector and comparing the results to those obtained in water. RESULTS In the absence of the B-field, as well as in the parallel orientation while in the presence of the B-field, the absorbed dose to water measured using Aerrow was found to agree within combined uncertainties with those derived from TG-51 using calibrated reference-class ICs. Statistically significant differences on the order of (2-4)%, however, were observed when measuring absorbed dose to water using the ICs in the perpendicular orientation in the presence of the B-field. Aerrow had a peak-to-peak response of about 0.5% when rotated within the solid phantom regardless of whether the B-field was present or not. CONCLUSIONS This work describes the successful use of Aerrow as a straightforward means of measuring absolute dose to water for large high-energy photon fields in the presence of a 1.5 T B-field to a greater accuracy than currently achievable with ICs. The detector-phantom air gap does not appear to significantly influence the response of Aerrow in absolute terms, nor does it contribute to its rotational dependence. This work suggests that the accurate use of solid phantoms for absolute point dose measurement is possible with Aerrow.
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Affiliation(s)
- James Renaud
- Metrology Research Centre, National Research Council Canada, Ottawa, ON, K1T 0R6, Canada.,Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada
| | - Arman Sarfehnia
- Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada.,Department of Radiation Oncology, University of Toronto, Toronto, ON, M5S 3E2, Canada
| | - Julien Bancheri
- Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada
| | - Jan Seuntjens
- Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada
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Kinoshita N, Oguchi H, Adachi T, Shioura H, Kimura H. Uncertainty in positioning ion chamber at reference depth for various water phantoms. Rep Pract Oncol Radiother 2018; 23:199-206. [PMID: 29760594 PMCID: PMC5948320 DOI: 10.1016/j.rpor.2018.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 12/28/2017] [Accepted: 03/09/2018] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Uncertainty in the calibration of high-energy radiation sources is dependent on user and equipment type. AIM We evaluated the uncertainty in the positioning of a cylindrical chamber at a reference depth for reference dosimetry of high-energy photon beams and the resulting uncertainty in the chamber readings for 6- and 10-MV photon beams. The aim was to investigate major contributions to the positioning uncertainty to reduce the uncertainty in calibration for external photon beam radiotherapy. MATERIALS AND METHODS The following phantoms were used: DoseView 1D, WP1D, 1D SCANNER, and QWP-07 as one-dimensional (1D) phantoms for a vertical-beam geometry; GRI-7632 as a phantom for a fixed waterproofing sleeve; and PTW type 41023 and QWP-04 as 1D phantoms for a horizontal-beam geometry. The uncertainties were analyzed as per the Guide to the Expression of Uncertainty in Measurement. RESULTS The positioning and resultant uncertainties in chamber readings ranged from 0.22 to 0.35 mm and 0.12-0.25%, respectively, among the phantoms (using a coverage factor k = 1 in both cases). The major contributions to positioning uncertainty are: definition of the origin for phantoms among users for the 1D phantoms for a vertical-beam geometry, water level adjustment among users for the phantom for a fixed waterproofing sleeve, phantom window deformation, and non-water material of the window for the 1D phantoms for a horizontal-beam geometry. CONCLUSION The positioning and resultant uncertainties in chamber readings exhibited minor differences among the seven phantoms. The major components of these uncertainties differed among the phantom types investigated.
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Affiliation(s)
- Naoki Kinoshita
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya-shi, Aichi-ken 461-8673, Japan
- Radiological Center, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
| | - Hiroshi Oguchi
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya-shi, Aichi-ken 461-8673, Japan
| | - Toshiki Adachi
- Radiological Center, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
| | - Hiroki Shioura
- Department of Radiology, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
| | - Hirohiko Kimura
- Department of Radiology, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
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Renaud J, Sarfehnia A, Bancheri J, Seuntjens J. Aerrow: A probe-format graphite calorimeter for absolute dosimetry of high-energy photon beams in the clinical environment. Med Phys 2017; 45:414-428. [DOI: 10.1002/mp.12669] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 10/05/2017] [Accepted: 10/27/2017] [Indexed: 11/06/2022] Open
Affiliation(s)
- James Renaud
- Medical Physics Unit; McGill University; Montréal QC Canada
| | - Arman Sarfehnia
- Medical Physics Unit; McGill University; Montréal QC Canada
- Department of Radiation Oncology; University of Toronto; Toronto ON Canada
| | | | - Jan Seuntjens
- Medical Physics Unit; McGill University; Montréal QC Canada
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Kupfer T, Lehmann J, Butler DJ, Ramanathan G, Bailey TE, Franich RD. Commissioning of a PTW 34070 large-area plane-parallel ionization chamber for small field megavoltage photon dosimetry. J Appl Clin Med Phys 2017; 18:206-217. [PMID: 28980432 PMCID: PMC5689907 DOI: 10.1002/acm2.12185] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 07/26/2017] [Accepted: 08/04/2017] [Indexed: 11/10/2022] Open
Abstract
PURPOSE This study investigates a large-area plane-parallel ionization chamber (LAC) for measurements of dose-area product in water (DAPw ) in megavoltage (MV) photon fields. METHODS Uniformity of electrode separation of the LAC (PTW34070 Bragg Peak Chamber, sensitive volume diameter: 8.16 cm) was measured using high-resolution microCT. Signal dependence on angle α of beam incidence for square 6 MV fields of side length s = 20 cm and 1 cm was measured in air. Polarity and recombination effects were characterized in 6, 10, and 18 MV photons fields. To assess the lateral setup tolerance, scanned LAC profiles of a 1 × 1 cm2 field were acquired. A 6 MV calibration coefficient, ND,w,LAC , was determined in a field collimated by a 5 cm diameter stereotactic cone with known DAPw . Additional calibrations in 10 × 10 cm2 fields at 6, 10, and 18 MV were performed. RESULTS Electrode separation is uniform and agrees with specifications. Volume-averaging leads to a signal increase proportional to ~1/cos(α) in small fields. Correction factors for polarity and recombination range between 0.9986 to 0.9996 and 1.0007 to 1.0024, respectively. Off-axis displacement by up to 0.5 cm did not change the measured signal in a 1 × 1 cm2 field. ND,w,LAC was 163.7 mGy cm-2 nC-1 and differs by +3.0% from the coefficient derived in the 10 × 10 cm2 6 MV field. Response in 10 and 18 MV fields increased by 1.0% and 2.7% compared to 6 MV. CONCLUSIONS The LAC requires only small correction factors for DAPw measurements and shows little energy dependence. Lateral setup errors of 0.5 cm are tolerated in 1 × 1 cm2 fields, but beam incidence must be kept as close to normal as possible. Calibration in 10 × 10 fields is not recommended because of the LAC's over-response. The accuracy of relative point-dose measurements in the field's periphery is an important limiting factor for the accuracy of DAPw measurements.
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Affiliation(s)
- Tom Kupfer
- School of ScienceRMIT UniversityMelbourneVic.Australia
- Radiation Oncology CentreAustin HealthHeidelbergVic.Australia
| | - Joerg Lehmann
- School of ScienceRMIT UniversityMelbourneVic.Australia
- Faculty of ScienceThe University of SydneySydneyNSWAustralia
- Department of Radiation OncologyCalvary Mater NewcastleWaratahNSWAustralia
| | - Duncan J. Butler
- Australian Radiation Protection and Nuclear Safety AgencyYallambieVic.Australia
| | - Ganesan Ramanathan
- Australian Radiation Protection and Nuclear Safety AgencyYallambieVic.Australia
| | - Tracy E. Bailey
- Australian Radiation Protection and Nuclear Safety AgencyYallambieVic.Australia
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Lye JE, Harty PD, Butler DJ, Crosbie JC, Livingstone J, Poole CM, Ramanathan G, Wright T, Stevenson AW. Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and ionization chambers. Phys Med Biol 2016; 61:4201-22. [DOI: 10.1088/0031-9155/61/11/4201] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Ganesan R, McEwen MR, Orton CG. Point/Counterpoint. Calibration of radiotherapy ionization chambers using Co-60 is outdated and should be replaced by direct calibration in linear accelerator beams. Med Phys 2015; 42:5003-6. [PMID: 26328950 DOI: 10.1118/1.4922710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Ramanathan Ganesan
- Radiotherapy Section, Medical Radiation Services Branch, Australian Radiation Protection and Nuclear Safety Agency, Yallambie 3085, Victoria, Australia (Tel: 61 3 9433 2273; E-mail: )
| | - Malcolm R McEwen
- Ionizing Radiation Standards, National Research Council, Ottawa, Ontario K1A OR6, Canada (Tel: 613-993-2197 Ext: 226; E-mail: )
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