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Khan AU, Das IJ, Yadav P. Computational and experimental small field dosimetry using a commercial plastic scintillator detector for the 0.35 T MR-linac. Phys Med 2024; 123:103403. [PMID: 38870643 DOI: 10.1016/j.ejmp.2024.103403] [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: 12/18/2023] [Revised: 05/08/2024] [Accepted: 06/05/2024] [Indexed: 06/15/2024] Open
Abstract
PURPOSE Although plastic scintillator detectors (PSDs) are considered ideal dosimeters for small field dosimetry in conventional linear accelerators (linacs), the impact of the magnetic field strength on the response of the PSD must be investigated. METHODS A linac Monte Carlo (MC) head model for a low-field MR-linac was validated for small field dosimetry and utilized to calculate field output factors (OFs). The MC-calculated OFs were compared with the treatment planning system (TPS)-calculated OFs and measured OFs using a Blue Physics (BP) Model 10 commercial PSD and a synthetic diamond detector. The field-specific correction factors, [Formula: see text] , were calculated for the PSD in the presence of a 0.35 T and magnetic field. The impact of the source focal spot size and initial electron energy on the MC-calculated OFs was investigated. RESULTS Good agreement to within 2 % was found between the MC-calculated OFs and BP PSD OFs except for the 0.415 × 0.415 cm2 field size. The BP PSD [Formula: see text] correction factors were calculated to be within 1 % of unity. For field sizes ≥1.66 × 1.66 cm2, the MC-calculated OFs were relatively insensitive to the focal spot size and initial electron energy to within 2.5 %. However, for smaller field sizes, the MC-calculated OFs were found to differ up to 9.50 % and 7.00 % when the focal spot size and initial electron energy was varied, respectively. CONCLUSIONS The BP PSD was deemed suitable for small field dosimetry in MR-linacs without requiring any [Formula: see text] correction factors.
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Affiliation(s)
- Ahtesham Ullah Khan
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
| | - Indra J Das
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Poonam Yadav
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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Katano A, Minamitani M, Ohira S, Yamashita H. Recent Advances and Challenges in Stereotactic Body Radiotherapy. Technol Cancer Res Treat 2024; 23:15330338241229363. [PMID: 38321892 PMCID: PMC10851756 DOI: 10.1177/15330338241229363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2024] Open
Affiliation(s)
- Atsuto Katano
- Department of Radiology, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan
| | - Masanari Minamitani
- Department of Comprehensive Radiation Oncology, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Shingo Ohira
- Department of Comprehensive Radiation Oncology, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Hideomi Yamashita
- Department of Radiology, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan
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Ketabi A, Karbasi S, Faghihi R, Mosleh-Shirazi MA. A phantom-based experimental and Monte Carlo study of the suitability of in-vivo diodes and TLD for entrance in-vivo dosimetry in small-to-medium sized 6 MV photon fields. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2022.110411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Klimanov VA, Kirpichev YS, Serikbekova ZK, Belousov AV, Krusanov GA, Walwyn‐Salas G, Morozov VN, Kolyvanova MA. Monte-Carlo calculation of output correction factors for ionization chambers, solid-state detectors, and EBT3 film in small fields of high-energy photons. J Appl Clin Med Phys 2022; 24:e13753. [PMID: 35998153 PMCID: PMC9860002 DOI: 10.1002/acm2.13753] [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: 01/08/2022] [Revised: 07/13/2022] [Accepted: 07/25/2022] [Indexed: 01/26/2023] Open
Abstract
High-energy accelerators are often used in oncological practice, but the information on the small-field dosimetry for the photon beams with nominal energy above 10 MV is limited. The goal of the present work was to determine the values of the output correction factor ( k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ ) for solid-state detectors (Diode E, PTW 60017; microDiamond, PTW 60019), EBT3 film, and ionization chambers (Semiflex, PTW 31010; Semiflex 3D, PTW 31021; PinPoint, PTW 31015; PinPoint 3D, PTW 31016) in the small fields formed by 10, 15, 18, and 20 MV photon beams. The output correction factors were calculated by Monte-Carlo method using EGSnrc toolkit for six field sizes (from 0.5 × 0.5 cm 2 $0.5 \times 0.5\ {\rm{cm}}^2$ to 10 × 10 cm 2 $10 \times 10\ {\rm{cm}}^2$ ) for isocentric and constant source-to-surface distance (SSD) techniques. The decrease in the field size led to an increase in k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ for ionization chambers, while for solid-state detectors and radiochromic film, k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ were less than unity at the smallest field size. A larger sensitive volume of ionization chamber corresponded to a stronger deviation of output correction factor from unity: 1.847 (125 mm3 PTW 31010) versus up to 1.183 (16 mm3 PTW 31016) at the smallest field of 10 MV beam. The calculated output correction factors were used to correct the output factors for PTW 60017, PTW 60019, and EBT3. The deviation of the corrected output factor from the results of Monte-Carlo simulation did not exceed 3% in the fields from 1.0 × 1.0 cm 2 $1.0 \times 1.0\ {\rm{cm}}^2$ to 4.0 × 4.0 cm 2 $4.0 \times 4.0\ {\rm{cm}}^2$ for 10 and 18 MV beams. Thus, Diode E, microDiamond, and EBT3 film can be recommended for small-field dosimetry of high-energy photons.
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Affiliation(s)
- Vladimir A. Klimanov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia,National Research Nuclear University MEPhIMoscowRussia
| | | | | | - Alexandr V. Belousov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia
| | - Grigorii A. Krusanov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia
| | | | - Vladimir N. Morozov
- Emanuel Institute of Biochemical PhysicsRussian Academy of SciencesMoscowRussia
| | - Maria A. Kolyvanova
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia,Emanuel Institute of Biochemical PhysicsRussian Academy of SciencesMoscowRussia
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Dose area product primary standards established by graphite calorimetry at the LNE-LNHB for small radiation fields in radiotherapy. Phys Med 2022; 98:18-27. [PMID: 35489128 DOI: 10.1016/j.ejmp.2022.03.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 03/10/2022] [Accepted: 03/19/2022] [Indexed: 11/22/2022] Open
Abstract
PURPOSE To present primary standards establishment in terms of Dose Area Product (DAP) for small field sizes. METHODS A large section graphite calorimeter and two plane-parallel ionization chambers were designed and built in-house. These chambers were calibrated in a 6MV FFF beam at the maximum dose rate of 1400 UM/min for fields defined by specifically designed circular collimators of 5, 7.5, 10, 13 and 15 mm diameter and jaws of 5, 7, 10, 13 and 15 mm side length on a Varian TrueBeam linac. RESULTS The two chambers show the same behaviour regardless of field shape and size. From 5 to 15 mm, calibration coefficients slightly increase with the field size with a magnitude of 1.8% and 1.1% respectively for the two chambers, and are independent of the field shape. This tendency was confirmed by Monte Carlo calculations. The average associated uncertainty of the calibration coefficients is around 0.6% at k=1. CONCLUSIONS For the first time, primary standards in terms of DAP were established by graphite calorimetry for an extended range of small field sizes. These promising results open the door for an alternative approach in small fields dosimetry.
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Duchaine J, Wahl M, Markel D, Bouchard H. A probabilistic approach for determining Monte Carlo beam source parameters: II. Impact of beam modeling uncertainties on dosimetric functions and treatment plans. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac4efb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/26/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Objective. The Monte Carlo method is recognized as a valid approach for the evaluation of dosimetric functions for clinical use. This procedure requires the accurate modeling of the considered linear accelerator. In Part I, we propose a new method to extract the probability density function of the beam model physical parameters. The aim of this work is to evaluate the impact of beam modeling uncertainties on Monte Carlo evaluated dosimetric functions and treatment plans in the context of small fields. Approach. Simulations of output factors, output correction factors, dose profiles, percent-depth doses and treatment plans are performed using the CyberKnife M6 model developed in Part I. The optimized pair of electron beam energy and spot size, and eight additional pairs of beam parameters representing a 95% confidence region are used to propagate the uncertainties associated to the source parameters to the dosimetric functions. Main results. For output factors, the impact of beam modeling uncertainties increases with the reduction of the field size and confidence interval half widths reach 1.8% for the 5 mm collimator. The impact on output correction factors cancels in part, leading to a maximum confidence interval half width of 0.44%. The impact is less significant for percent-depth doses in comparison to dose profiles. For these types of measurement, in absolute terms and in comparison to the reference dose, confidence interval half widths less than or equal to 1.4% are observed. For simulated treatment plans, the impact is more significant for the treatment delivered with a smaller field size with confidence interval half widths reaching 2.5% and 1.4% for the 5 and 20 mm collimators, respectively. Significance. Results confirm that AAPM TG-157's tolerances cannot apply to the field sizes studied. This study provides an insight on the reachable dose calculation accuracy in a clinical setup.
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Hachemi T, Chaoui ZEA, Khoudri S. PENELOPE simulations and experiment for 6 MV clinac iX accelerator for standard and small static fields. Appl Radiat Isot 2021; 174:109749. [PMID: 33940355 DOI: 10.1016/j.apradiso.2021.109749] [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: 03/30/2020] [Revised: 03/25/2021] [Accepted: 04/23/2021] [Indexed: 11/18/2022]
Abstract
The goal of this work was to produce accurate data for use as a 'gold standard' and a valid tool for measurements in reference dosimetry for standard/small static field sizes from 0.5 × 0.5 to 10 × 10 cm2. It is based on the accuracy of the phase space files (PSFs) as a key quantity. Because the IAEA general public database provides few PSFs for the Varian iX, we simulated the head through Monte Carlo (MC) simulations and calculated validated PSFs for 12 square field sizes including seven for small static fields. The resulting dosimetric calculations allowed us to reach a good level of agreement in comparison to our relative and absolute dose measurements performed on a Varian iX in water phantom. Measured and MC calculated output factors were investigated for different detectors. Based on the TRS 483 formalism and MC (PENELOPE/penEasy), we calculated output correction factors for the unshielded Diode-E (T60017) and the PinPoint-3D (T31016) micro-chamber according to manufacturers' blueprints. Our MC results were in agreement with the recommended data; they compete with recent measurements and MC simulations and in particular the TRS 483 MC data obtained from similar simulations. Moreover, our MC results provide supplemental data in comparison to TRS 483 data in particular for the PinPoint-3D (T31016). We suggest our MC output correction factors as new datasets for future TRS compilations. The work was substantial, used different robust MC strategies depending on the scoring regions, and led in most cases to uncertainties of less than 1%.
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Affiliation(s)
- Taha Hachemi
- Physics Department, Faculty of Sciences, Laboratory of Optoelectronic and Devices, University Ferhat Abbas Sétif 1, Algeria.
| | - Zine-El-Abidine Chaoui
- Physics Department, Faculty of Sciences, Laboratory of Optoelectronic and Devices, University Ferhat Abbas Sétif 1, Algeria
| | - Saad Khoudri
- Physics Department, Faculty of Sciences, Laboratory of Optoelectronic and Devices, University Ferhat Abbas Sétif 1, Algeria; Centre de Lutte Contre le Cancer de Sétif, Algeria
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Bouchard H. Reference dosimetry of modulated and dynamic photon beams. Phys Med Biol 2021; 65:24TR05. [PMID: 33438582 DOI: 10.1088/1361-6560/abc3fb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In the late 1980s, a new technique was proposed that would revolutionize radiotherapy. Now referred to as intensity-modulated radiotherapy, it is at the core of state-of-the-art photon beam delivery techniques, such as helical tomotherapy and volumetric modulated arc therapy. Despite over two decades of clinical application, there are still no established guidelines on the calibration of dynamic modulated photon beams. In 2008, the IAEA-AAPM work group on nonstandard photon beam dosimetry published a formalism to support the development of a new generation of protocols applicable to nonstandard beam reference dosimetry (Alfonso et al 2008 Med. Phys. 35 5179-86). The recent IAEA Code of Practice TRS-483 was published as a result of this initiative and addresses exclusively small static beams. But the plan-class specific reference calibration route proposed by Alfonso et al (2008 Med. Phys. 35 5179-86) is a change of paradigm that is yet to be implemented in radiotherapy clinics. The main goals of this paper are to provide a literature review on the dosimetry of nonstandard photon beams, including dynamic deliveries, and to discuss anticipated benefits and challenges in a future implementation of the IAEA-AAPM formalism on dynamic photon beams.
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Affiliation(s)
- Hugo Bouchard
- Département de physique, Université de Montréal, Complexe des sciences, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, Québec H2V 0B3, Canada. Centre de recherche du Centre hospitalier de l'Université de Montréal, 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada. Département de radio-oncologie, Centre hospitalier de l'Université de Montréal (CHUM), 1051 Rue Sanguinet, Montréal, Québec H2X 3E4, Canada
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Kumar S, Nahum AE, Chetty IJ. Monte-Carlo-computed dose, kerma and fluence distributions in heterogeneous slab geometries irradiated by small megavoltage photon fields. ACTA ACUST UNITED AC 2020; 65:175012. [DOI: 10.1088/1361-6560/ab98d1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Fogliata A, Esposito E, Paganini L, Reggiori G, Tomatis S, Scorsetti M, Cozzi L. The impact of scanning data measurements on the Acuros dose calculation algorithm configuration. Radiat Oncol 2020; 15:169. [PMID: 32650815 PMCID: PMC7350585 DOI: 10.1186/s13014-020-01610-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 07/02/2020] [Indexed: 11/24/2022] Open
Abstract
Background Many dose calculation algorithms for radiotherapy planning need to be configured for each clinical beam using pre-defined measurements. An optimization process adjusts the physical parameters able to estimate the energy released in the medium in any geometrical condition. This work investigates the impact of measured input data quality on the configuration of the type “c” Acuros-XB dose calculation algorithm in the Eclipse (Varian Medical Systems) treatment planning system. Methods Different datasets were acquired with the BeamScan water phantom (PTW) to configure 6 MV beams, for both flattened (6X) and flattening filter free mode (6FFF) for a Varian TrueBeam: (i) a correct dataset measured using a Semiflex-3D ion chamber, (ii) a set in missing lateral scatter conditions (MLS), (iii) a set with incorrect effective point of measurement (EPoM), (iv) sets acquired with PinPoint-3D chamber, DiodeP, microDiamond detectors. The Acuros-XB dose calculation algorithm (version 15.6) was configured using the reference dataset, the sets measured with the different detectors, with intentional errors, and using the representative beam data (RBD) made available by the vendor. The physical parameters obtained from each optimization process (spectrum, mean radial energy, electron contamination), were analyzed and compared. Calculated data were finally compared against the input and reference measurements. Results Concerning the physical parameters, the configurations presenting the largest differences were the MLS conditions (mean radial energy) and the incorrect EPoM (electron contamination). The calculation doses relative to the input data present low accuracy, with mean differences > 2% in some conditions. The PinPoint-3D ion chamber presented lower accuracy for the 6FFF beam. Regarding the RBD, calculations compared well with the input data used for the configuration, but not with the reference data. Conclusion The MLS conditions and the incorrect setting of the EPoM lead to erroneous configurations and should be avoided. The choice of an appropriate detector is important. Whenever the representative beam data is used, a careful check under more clinical geometrical conditions is advised.
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Affiliation(s)
- A Fogliata
- Radiotherapy and Radiosurgery Dept, Humanitas Clinical and Research Center - IRCCS, Via Manzoni 56, Milan-Rozzano, Italy.
| | - E Esposito
- Radiotherapy and Radiosurgery Dept, Humanitas Clinical and Research Center - IRCCS, Via Manzoni 56, Milan-Rozzano, Italy
| | - L Paganini
- Radiotherapy and Radiosurgery Dept, Humanitas Clinical and Research Center - IRCCS, Via Manzoni 56, Milan-Rozzano, Italy
| | - G Reggiori
- Radiotherapy and Radiosurgery Dept, Humanitas Clinical and Research Center - IRCCS, Via Manzoni 56, Milan-Rozzano, Italy
| | - S Tomatis
- Radiotherapy and Radiosurgery Dept, Humanitas Clinical and Research Center - IRCCS, Via Manzoni 56, Milan-Rozzano, Italy
| | - M Scorsetti
- Radiotherapy and Radiosurgery Dept, Humanitas Clinical and Research Center - IRCCS, Via Manzoni 56, Milan-Rozzano, Italy.,Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, Milan-Pieve Emanuele, Italy
| | - L Cozzi
- Radiotherapy and Radiosurgery Dept, Humanitas Clinical and Research Center - IRCCS, Via Manzoni 56, Milan-Rozzano, Italy.,Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, Milan-Pieve Emanuele, Italy
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Rose MS, Tirpak L, Van Casteren K, Zack J, Simon T, Schoenfeld A, Simon W. Multi‐institution validation of a new high spatial resolution diode array for SRS and SBRT plan pretreatment quality assurance. Med Phys 2020; 47:3153-3164. [DOI: 10.1002/mp.14153] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 02/20/2020] [Accepted: 03/12/2020] [Indexed: 12/31/2022] Open
Affiliation(s)
- Mark S. Rose
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | - Lena Tirpak
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | | | - Jeff Zack
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | - Tom Simon
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | | | - William Simon
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
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Ghazal M, Westermark M, Kaveckyte V, Carlsson‐Tedgren Å, Benmakhlouf H. 6‐MV small field output factors: intra‐/intermachine comparison and implementation of TRS‐483 using various detectors and several linear accelerators. Med Phys 2019; 46:5350-5359. [DOI: 10.1002/mp.13830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 09/05/2019] [Accepted: 09/05/2019] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mohammed Ghazal
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
| | - Mathias Westermark
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
| | - Vaiva Kaveckyte
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
- Radiation Physics Department of Medical and Health Sciences Linköping University SE‐581 85Linköping Sweden
| | - Åsa Carlsson‐Tedgren
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
- Radiation Physics Department of Medical and Health Sciences Linköping University SE‐581 85Linköping Sweden
| | - Hamza Benmakhlouf
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
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Borzov E, Nevelsky A, Bar-Deroma R, Orion I. Reconstruction of the electron source intensity distribution of a clinical linear accelerator using in-air measurements and a genetic algorithm. Phys Imaging Radiat Oncol 2019; 12:67-73. [PMID: 33458298 PMCID: PMC7807614 DOI: 10.1016/j.phro.2019.11.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/24/2019] [Accepted: 11/25/2019] [Indexed: 12/04/2022] Open
Abstract
Background and purpose The electron source intensity distribution of a clinical linear accelerator has a great influence on the calculation of output factors for small radiation fields where source occlusion by the collimating devices takes place. The purpose of this study was to present a new method for the electron source reconstruction problem. Materials and methods The measurements were performed in-air using diode and 6 MV 1 × 1 cm2 photon field in flattening filter-free mode. In Monte Carlo simulation, an electron target area was divided into a number of square subsources. Then, the in-air doses in 2D silicon chip array were calculated individually from each subsource. A genetic algorithm search was applied in order to determine the optimal weight factors for all subsources that provide the best agreement between simulated and measured doses. Results It was found that the reconstructed electron source intensity from a clinical linear accelerator has the two-dimensional elliptical double Gaussian distribution. The source intensity distribution consisted of two intensity components along the in-plane (x) and cross-plane (y) directions characterized by full width half-maximum (FWHM): FWHMx1 = 0.27 cm, FWHMx2 = 0.08 cm, FWHMy1 = 0.24 cm, FWHMy2 = 0.06 cm, where broader components are 81% and 53% of the total intensity along × and y axis respectively. Conclusions The obtained results demonstrated an elliptical double Gaussian intensity distribution of the incident electron source. We anticipate that the proposed method has universal applications independent of the type of linear accelerator, modality or energy.
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Affiliation(s)
- Egor Borzov
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa 32000, Israel
- Corresponding author at: HaAliya HaShniya St 8, Haifa, 3109601, Israel.
| | - Alexander Nevelsky
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa 32000, Israel
| | - Raquel Bar-Deroma
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa 32000, Israel
| | - Itzhak Orion
- Department of Nuclear Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
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Sendani NG, Karimian A, Mahdavi SR, Jabbari I, Alaei P. Effect of beam configuration with inaccurate or incomplete small field output factors on the accuracy of treatment planning dose calculation. Med Phys 2019; 46:5273-5283. [DOI: 10.1002/mp.13796] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 08/16/2019] [Accepted: 08/16/2019] [Indexed: 11/11/2022] Open
Affiliation(s)
- Neda Gholizadeh Sendani
- Faculty of Advanced Sciences and Technologies University of Isfahan Isfahan 81746‐73441Iran
- Department of Radiation Oncology University of Minnesota Minneapolis MN 55455USA
| | - Alireza Karimian
- Department of Biomedical Engineering Faculty of Engineering University of Isfahan Isfahan 81746‐73441Iran
| | - S. Rabie Mahdavi
- Radiation Biology Research Center and Department of Medical Physics Iran University of Medical Sciences Tehran 14496Iran
| | - Iraj Jabbari
- Faculty of Advanced Sciences and Technologies University of Isfahan Isfahan 81746‐73441Iran
| | - Parham Alaei
- Department of Radiation Oncology University of Minnesota Minneapolis MN 55455USA
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The effect of SSD, Field size, Energy and Detector type for Relative Output Factor measurement in small photon beams as compared with Monte Carlo simulation. POLISH JOURNAL OF MEDICAL PHYSICS AND ENGINEERING 2019. [DOI: 10.2478/pjmpe-2019-0014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Introduction: Small fields photon dosimetry is associated with many problems. Using the right detector for measurement plays a fundamental role. This study investigated the measurement of relative output for small photon fields with different detectors. It was investigated for three-photon beam energies at SSDs of 90, 95, 100 and 110 cm. As a benchmark, the Monte Carlo simulation was done to calculate the relative output of these small photon beams for the dose in water.
Materials and Methods: 6, 10 and 15 MV beams were delivered from a Synergy LINAC equipped with an Agility 160 multileaf collimator (MLC). A CC01 ion chamber, EFD-3G diode, PTW60019 microdiamond, EBT2 radiochromic film, and EDR2 radiographic film were used to measure the relative output of the linac. Measurements were taken in water for the CC01 ion chamber, EFD-3G diode, and the PTW60019. Films were measured in water equivalent RW3 phantom slabs. Measurements were made for 1 × 1, 2 × 2, 3 × 3, 4 × 4, 5 × 5 and a reference field of 10 × 10 cm2. Field sizes were defined at 100cm SSD. Relative output factors were also compared with Monte Carlo (MC) simulation of the LINAC and a water phantom model. The influence of voxel size was also investigated for relative output measurement. Results and Discussion: The relative output factor (ROF) increased with energy for all fields large enough to have lateral electronic equilibrium (LEE). This relation broke down as the field sizes decreased due to the onset of lateral electronic disequilibrium (LED). The high-density detector, PTW60019 gave the highest ROF for the different energies, with the less dense CC01 giving the lowest ROFs.
Conclusion: These are results compared to MC simulation, higher density detectors give higher ROF values. Relative to water, the ROF measured with the air-chamber remained virtually unchanged. The ROFs, as measured in this study showed little variation due to increased SSDs. The effect of voxel size for the Monte Carlo calculations in water does not lead to significant ROF variation over the small fields studied.
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Monasor Denia P, Castellet García MDC, Manjón García C, Quirós Higueras JD, de Marco Blancas N, Bonaque Alandí J, Juan Senabre XJ, Santos Serra A, López-Tarjuelo J. Comparison of detector performance in small 6 MV and 6 MV FFF beams using a Versa HD accelerator. PLoS One 2019; 14:e0213253. [PMID: 30856183 PMCID: PMC6411166 DOI: 10.1371/journal.pone.0213253] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 02/18/2019] [Indexed: 11/18/2022] Open
Abstract
1. BACKGROUND & PURPOSE Investigate the applicability of a series of detectors in small field dosimetry and the possible differences between their responses to FF and FFF beams. This work extends upon the series of detectors used by other authors to also include metal-oxide-semiconductor field-effect transistors (MOSFETs) detectors and radiochromic film. We also included a later correction of output factors (OFs) recommended by the recently published IAEA´s code of practice TRS 483 on dosimetry of small static fields used in external beam radiotherapy. 2. MATERIALS & METHODS The OFs, profiles, and PDDs of 6 MV and 6 MV FFF beams were measured with 11 different detectors using field sizes between 0.6 × 0.6 cm2 and 10 × 10 cm2. 3. RESULTS The OFs of the FFF beams were lower than those of the FF beams for field sizes larger than 3 × 3 cm2 but higher for field sizes smaller than 3 × 3 cm2. After applying the IAEA´s TRS 483 corrections, the final OFs were compatible with our initial results when considering uncertainties involved. Small-volume detectors are preferable for measuring the penumbra of these small fields where this attribute is higher in the crossline direction than in the inline direction. The R100 of equivalent-quality FFF beams was higher compared to the corresponding flattened beams. 4. CONCLUSIONS We observed no difference for the dose responses between 6 MV and 6 MV FFF beams for any of the detectors. OF results, profiles and PDDs were clearly consistent with the previously published literature regarding the Versa HD linac. Correcting our first OFs, taken as ratio of detector charges, with the IAEA´s TRS 483 corrections to obtain the final OFs, did not make the former significantly different.
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Affiliation(s)
- Paula Monasor Denia
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | | | - Carla Manjón García
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Juan David Quirós Higueras
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Noelia de Marco Blancas
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Jorge Bonaque Alandí
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Xavier Jordi Juan Senabre
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Agustín Santos Serra
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Juan López-Tarjuelo
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
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Alhujaili SF, Biasi G, Alzorkany F, Grogan G, Al Kafi MA, Lane J, Hug B, Aldosari AH, Alshaikh S, Farzad PR, Ebert MA, Moftah B, Rosenfeld AB, Petasecca M. Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector. J Appl Clin Med Phys 2018; 20:76-88. [PMID: 30565856 PMCID: PMC6333148 DOI: 10.1002/acm2.12496] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 10/01/2018] [Accepted: 10/05/2018] [Indexed: 11/06/2022] Open
Abstract
Purpose The aim of this work was to evaluate the use of an angularly independent silicon detector (edgeless diodes) developed for dosimetry in megavoltage radiotherapy for Cyberknife in a phantom and for patient quality assurance (QA). Method The characterization of the edgeless diodes has been performed on Cyberknife with fixed and IRIS collimators. The edgeless diode probes were tested in terms of basic QA parameters such as measurements of tissue‐phantom ratio (TPR), output factor and off‐axis ratio. The measurements were performed in both water and water‐equivalent phantoms. In addition, three patient‐specific plans have been delivered to a lung phantom with and without motion and dose measurements have been performed to verify the ability of the diodes to work as patient‐specific QA devices. The data obtained by the edgeless diodes have been compared to PTW 60016, SN edge, PinPoint ionization chamber, Gafchromic EBT3 film, and treatment planning system (TPS). Results The TPR measurement performed by the edgeless diodes show agreement within 2.2% with data obtained with PTW 60016 diode for all the field sizes. Output factor agrees within 2.6% with that measured by SN EDGE diodes corrected for their field size dependence. The beam profiles’ measurements of edgeless diodes match SN EDGE diodes with a measured full width half maximum (FWHM) within 2.3% and penumbra widths within 0.148 mm. Patient‐specific QA measurements demonstrate an agreement within 4.72% in comparison with TPS. Conclusion The edgeless diodes have been proved to be an excellent candidate for machine and patient QA for Cyberknife reproducing commercial dosimetry device measurements without need of angular dependence corrections. However, further investigation is required to evaluate the effect of their dose rate dependence on complex brain cancer dose verification.
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Affiliation(s)
- Sultan Fahad Alhujaili
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.,Radiology and Medical Imaging Department, College of Applied Medical Sciences, Aljouf University, Aljouf, Saudi Arabia
| | - Giordano Biasi
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Faisal Alzorkany
- Biomedical Physics Department, Research Center, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Garry Grogan
- Department of Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, Australia
| | - Muhammed A Al Kafi
- Biomedical Physics Department, Research Center, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Jonathan Lane
- Department of Medical Physics and Clinical Engineering, Oxford University Hospitals NHS Foundation Trust (Churchill Hospital), Oxford, UK
| | - Benjamin Hug
- Department of Radiation Oncology, Sir Charles Gairdner Hospital, Perth, WA, Australia.,School of Physics and Astrophysics, University of Western Australia, Perth, WA, Australia
| | | | | | - Pejman Rowshan Farzad
- School of Physics and Astrophysics, University of Western Australia, Perth, WA, Australia
| | - Martin A Ebert
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.,Department of Radiation Oncology, Sir Charles Gairdner Hospital, Perth, WA, Australia.,School of Physics and Astrophysics, University of Western Australia, Perth, WA, Australia
| | - Belal Moftah
- Biomedical Physics Department, Research Center, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Anatoly B Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Marco Petasecca
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
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Gholampourkashi S, Cygler JE, Belec J, Vujicic M, Heath E. Monte Carlo and analytic modeling of an Elekta Infinity linac with Agility MLC: Investigating the significance of accurate model parameters for small radiation fields. J Appl Clin Med Phys 2018; 20:55-67. [PMID: 30408308 PMCID: PMC6333188 DOI: 10.1002/acm2.12485] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 09/21/2018] [Accepted: 09/27/2018] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To explain the deviation observed between measured and Monaco calculated dose profiles for a small field (i.e., alternating open-closed MLC pattern). A Monte Carlo (MC) model of an Elekta Infinity linac with Agility MLC was created and validated against measurements. In addition, an analytic model which predicts the fluence at the isocenter plane was used to study the impact of multiple beam parameters on the accuracy of dose calculations for small fields. METHODS A detailed MC model of a 6 MV Elekta Infinity linac with Agility MLC was created in EGSnrc/BEAMnrc and validated against measurements. An analytic model using primary and secondary virtual photon sources was created and benchmarked against the MC simulations and the impact of multiple beam parameters on the accuracy of the model for a small field was investigated. Both models were used to explain discrepancies observed between measured/EGSnrc simulated and Monaco calculated dose profiles for alternating open-closed MLC leaves. RESULTS MC-simulated dose profiles (PDDs, cross- and in-line profiles, etc.) were found to be in very good agreements with measurements. The best fit for the leaf bank rotation was found to be 9 mrad to model the defocusing of Agility MLC. Moreover, a very good agreement was observed between results from the analytic model and MC simulations for a small field. Modifying the radial size of the incident electron beam in the BEAMnrc model improved the agreement between Monaco and EGSnrc calculated dose profiles by approximately 16% and 30% in the position of maxima and minima, respectively. CONCLUSION Accurate modeling of the full-width-half-maximum (FWHM) of the primary photon source as well as the MLC leaf design (leaf bank rotation, etc.) is essential for accurate calculations of dose delivered by small radiation fields when using virtual source or MC models of the beam.
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Affiliation(s)
| | - Joanna E. Cygler
- Department of PhysicsCarleton UniversityOttawaONCanada
- Department of Medical PhysicsThe Ottawa Hospital Cancer CentreOttawaONCanada
| | - Jason Belec
- Department of Medical PhysicsThe Ottawa Hospital Cancer CentreOttawaONCanada
| | - Miro Vujicic
- Department of Medical PhysicsThe Ottawa Hospital Cancer CentreOttawaONCanada
| | - Emily Heath
- Carleton Laboratory for Radiotherapy PhysicsCarleton UniversityOttawaONCanada
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Fenwick JD, Georgiou G, Rowbottom CG, Underwood TSA, Kumar S. Reply to comment on ‘origins of the changing detector response in small megavoltage photon radiation fields’. Phys Med Biol 2018; 63:198002. [DOI: 10.1088/1361-6560/aae0e4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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20
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Kawahara D, Ozawa S, Nakashima T, Aita M, Tsuda S, Ochi Y, Okumura T, Masuda H, Ohno Y, Murakami Y, Nagata Y. Evaluation of beam modeling for small fields using a flattening filter-free beam. Radiol Phys Technol 2017; 10:33-40. [DOI: 10.1007/s12194-016-0365-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 06/10/2016] [Accepted: 06/13/2016] [Indexed: 10/21/2022]
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21
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Andreo P, Benmakhlouf H. Role of the density, density effect and mean excitation energy in solid-state detectors for small photon fields. Phys Med Biol 2017; 62:1518-1532. [DOI: 10.1088/1361-6560/aa562e] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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22
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Swinnen ACC, Öllers MC, Roijen E, Nijsten SM, Verhaegen F. Influence of the jaw tracking technique on the dose calculation accuracy of small field VMAT plans. J Appl Clin Med Phys 2017; 18:186-195. [PMID: 28291941 PMCID: PMC5689875 DOI: 10.1002/acm2.12029] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 11/07/2016] [Accepted: 11/21/2016] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The aim of this study was to evaluate experimentally the accuracy of the dose calculation algorithm AcurosXB in small field highly modulated Volumetric Modulated Arc Therapy (VMAT). METHOD The 1000SRS detector array inserted in the rotational Octavius 4D phantom (PTW) was used for 3D dose verification of VMAT treatments characterized by small to very small targets. Clinical treatment plans (n = 28) were recalculated on the phantom CT data set in the Eclipse TPS. All measurements were done on a Varian TrueBeamSTx, which can provide the jaw tracking technique (JTT). The effect of disabling the JTT, thereby fixing the jaws at static field size of 3 × 3 cm2 and applying the MLC to shape the smallest apertures, was investigated for static fields between 0.5 × 0.5-3 × 3 cm2 and for seven VMAT patients with small brain metastases. The dose calculation accuracy has been evaluated by comparing the measured and calculated dose outputs and dose distributions. The dosimetric agreement has been presented by a local gamma evaluation criterion of 2%/2 mm. RESULTS Regarding the clinical plans, the mean ± SD of the volumetric gamma evaluation scores considering the dose levels for evaluation of 10%, 50%, 80% and 95% are (96.0 ± 6.9)%, (95.2 ± 6.8)%, (86.7 ± 14.8)% and (56.3 ± 42.3)% respectively. For the smallest field VMAT treatments, discrepancies between calculated and measured doses up to 16% are obtained. The difference between the 1000SRS central chamber measurements compared to the calculated dose outputs for static fields 3 × 3, 2 × 2, 1 × 1 and 0.5 × 0.5 cm2 collimated with MLC whereby jaws are fixed at 3 × 3 cm2 and for static fields shaped with the collimator jaws only (MLC retracted), is on average respectively, 0.2%, 0.8%, 6.8%, 5.7% (6 MV) and 0.1%, 1.3%, 11.7%, 21.6% (10 MV). For the seven brain mets patients was found that the smaller the target volumes, the higher the improvement in agreement between measured and calculated doses after disabling the JTT. CONCLUSION Fixing the jaws at 3 × 3 cm2 and using the MLC with high positional accuracy to shape the smallest apertures in contrast to the JTT is currently found to be the most accurate treatment technique.
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Affiliation(s)
- Ans C C Swinnen
- Radiotherapy Department, Maastro Clinic, 6229 ET, Maastricht, The Netherlands
| | - Michel C Öllers
- Radiotherapy Department, Maastro Clinic, 6229 ET, Maastricht, The Netherlands
| | - Erik Roijen
- Radiotherapy Department, Maastro Clinic, 6229 ET, Maastricht, The Netherlands
| | | | - Frank Verhaegen
- Radiotherapy Department, Maastro Clinic, 6229 ET, Maastricht, The Netherlands
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Small field output factors evaluation with a microDiamond detector over 30 Italian centers. Phys Med 2016; 32:1644-1650. [DOI: 10.1016/j.ejmp.2016.10.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 11/18/2022] Open
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Qin Y, Zhong H, Wen N, Snyder K, Huang Y, Chetty IJ. Deriving detector-specific correction factors for rectangular small fields using a scintillator detector. J Appl Clin Med Phys 2016; 17:379-391. [PMID: 27929510 PMCID: PMC5690516 DOI: 10.1120/jacmp.v17i6.6433] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/30/2016] [Accepted: 08/29/2016] [Indexed: 11/23/2022] Open
Abstract
The goal of this study was to investigate small field output factors (OFs) for flattening filter‐free (FFF) beams on a dedicated stereotactic linear accelerator‐based system. From this data, the collimator exchange effect was quantified, and detector‐specific correction factors were generated. Output factors for 16 jaw‐collimated small fields (from 0.5 to 2 cm) were measured using five different detectors including an ion chamber (CC01), a stereotactic field diode (SFD), a diode detector (Edge), Gafchromic film (EBT3), and a plastic scintillator detector (PSD, W1). Chamber, diodes, and PSD measurements were performed in a Wellhofer water tank, while films were irradiated in solid water at 100 cm source‐to‐surface distance and 10 cm depth. The collimator exchange effect was quantified for rectangular fields. Monte Carlo (MC) simulations of the measured configurations were also performed using the EGSnrc/DOSXYZnrc code. Output factors measured by the PSD and verified against film and MC calculations were chosen as the benchmark measurements. Compared with plastic scintillator detector (PSD), the small volume ion chamber (CC01) underestimated output factors by an average of ‐1.0%±4.9%(max.=‐11.7% for 0.5×0.5cm2 square field). The stereotactic diode (SFD) overestimated output factors by 2.5%±0.4%(max.=3.3% for 0.5×1cm2 rectangular field). The other diode detector (Edge) also overestimated the OFs by an average of 4.2%±0.9%(max.=6.0% for 1×1cm2 square field). Gafchromic film (EBT3) measurements and MC calculations agreed with the scintillator detector measurements within 0.6%±1.8% and 1.2%±1.5%, respectively. Across all the X and Y jaw combinations, the average collimator exchange effect was computed: 1.4%±1.1% (CC01), 5.8%±5.4% (SFD), 5.1%±4.8% (Edge diode), 3.5%±5.0% (Monte Carlo), 3.8%±4.7% (film), and 5.5%±5.1% (PSD). Small field detectors should be used with caution with a clear understanding of their behaviors, especially for FFF beams and small, elongated fields. The scintillator detector exhibited good agreement against Gafchromic film measurements and MC simulations over the range of field sizes studied. The collimator exchange effect was found to be important at these small field sizes. Detector‐specific correction factors were computed using the scintillator measurements as the benchmark. PACS number(s): 87.56.Fc
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Fogliata A, Lobefalo F, Reggiori G, Stravato A, Tomatis S, Scorsetti M, Cozzi L. Evaluation of the dose calculation accuracy for small fields defined by jaw or MLC for AAA and Acuros XB algorithms. Med Phys 2016; 43:5685. [DOI: 10.1118/1.4963219] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Papaconstadopoulos P, Levesque IR, Maglieri R, Seuntjens J. Direct reconstruction of the source intensity distribution of a clinical linear accelerator using a maximum likelihood expectation maximization algorithm. Phys Med Biol 2016; 61:1078-94. [PMID: 26758232 DOI: 10.1088/0031-9155/61/3/1078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Direct determination of the source intensity distribution of clinical linear accelerators is still a challenging problem for small field beam modeling. Current techniques most often involve special equipment and are difficult to implement in the clinic. In this work we present a maximum-likelihood expectation-maximization (MLEM) approach to the source reconstruction problem utilizing small fields and a simple experimental set-up. The MLEM algorithm iteratively ray-traces photons from the source plane to the exit plane and extracts corrections based on photon fluence profile measurements. The photon fluence profiles were determined by dose profile film measurements in air using a high density thin foil as build-up material and an appropriate point spread function (PSF). The effect of other beam parameters and scatter sources was minimized by using the smallest field size ([Formula: see text] cm(2)). The source occlusion effect was reproduced by estimating the position of the collimating jaws during this process. The method was first benchmarked against simulations for a range of typical accelerator source sizes. The sources were reconstructed with an accuracy better than 0.12 mm in the full width at half maximum (FWHM) to the respective electron sources incident on the target. The estimated jaw positions agreed within 0.2 mm with the expected values. The reconstruction technique was also tested against measurements on a Varian Novalis Tx linear accelerator and compared to a previously commissioned Monte Carlo model. The reconstructed FWHM of the source agreed within 0.03 mm and 0.11 mm to the commissioned electron source in the crossplane and inplane orientations respectively. The impact of the jaw positioning, experimental and PSF uncertainties on the reconstructed source distribution was evaluated with the former presenting the dominant effect.
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Affiliation(s)
- P Papaconstadopoulos
- McGill University, Medical Physics Unit and the Research Institute of the McGill University Health Centre, Montreal, QC H3A 0G4, Canada
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Godson HF, Ravikumar M, Ganesh K, Sathiyan S, Ponmalar YR. Small field output factors: Comparison of measurements with various detectors and effects of detector orientation with primary jaw setting. RADIAT MEAS 2016. [DOI: 10.1016/j.radmeas.2015.12.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Pappas EP, Moutsatsos A, Pantelis E, Zoros E, Georgiou E, Torrens M, Karaiskos P. On the development of a comprehensive MC simulation model for the Gamma Knife Perfexion radiosurgery unit. Phys Med Biol 2016; 61:1182-203. [PMID: 26788618 DOI: 10.1088/0031-9155/61/3/1182] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This work presents a comprehensive Monte Carlo (MC) simulation model for the Gamma Knife Perfexion (PFX) radiosurgery unit. Model-based dosimetry calculations were benchmarked in terms of relative dose profiles (RDPs) and output factors (OFs), against corresponding EBT2 measurements. To reduce the rather prolonged computational time associated with the comprehensive PFX model MC simulations, two approximations were explored and evaluated on the grounds of dosimetric accuracy. The first consists in directional biasing of the (60)Co photon emission while the second refers to the implementation of simplified source geometric models. The effect of the dose scoring volume dimensions in OF calculations accuracy was also explored. RDP calculations for the comprehensive PFX model were found to be in agreement with corresponding EBT2 measurements. Output factors of 0.819 ± 0.004 and 0.8941 ± 0.0013 were calculated for the 4 mm and 8 mm collimator, respectively, which agree, within uncertainties, with corresponding EBT2 measurements and published experimental data. Volume averaging was found to affect OF results by more than 0.3% for scoring volume radii greater than 0.5 mm and 1.4 mm for the 4 mm and 8 mm collimators, respectively. Directional biasing of photon emission resulted in a time efficiency gain factor of up to 210 with respect to the isotropic photon emission. Although no considerable effect on relative dose profiles was detected, directional biasing led to OF overestimations which were more pronounced for the 4 mm collimator and increased with decreasing emission cone half-angle, reaching up to 6% for a 5° angle. Implementation of simplified source models revealed that omitting the sources' stainless steel capsule significantly affects both OF results and relative dose profiles, while the aluminum-based bushing did not exhibit considerable dosimetric effect. In conclusion, the results of this work suggest that any PFX simulation model should be benchmarked in terms of both RDP and OF results.
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Affiliation(s)
- E P Pappas
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
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Kumar S, Fenwick JD, Underwood TSA, Deshpande DD, Scott AJD, Nahum AE. Breakdown of Bragg–Gray behaviour for low-density detectors under electronic disequilibrium conditions in small megavoltage photon fields. Phys Med Biol 2015; 60:8187-212. [DOI: 10.1088/0031-9155/60/20/8187] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Spang FJ, Rosenberg I, Hedin E, Royle G. Photon small-field measurements with a CMOS active pixel sensor. Phys Med Biol 2015; 60:4383-98. [PMID: 25985207 DOI: 10.1088/0031-9155/60/11/4383] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In this work the dosimetric performance of CMOS active pixel sensors for the measurement of small photon beams is presented. The detector used consisted of an array of 520 × 520 pixels on a 25 µm pitch. Dosimetric parameters measured with this sensor were compared with data collected with an ionization chamber, a film detector and GEANT4 Monte Carlo simulations. The sensor performance for beam profiles measurements was evaluated for field sizes of 0.5 × 0.5 cm(2). The high spatial resolution achieved with this sensor allowed the accurate measurement of profiles, beam penumbrae and field size under lateral electronic disequilibrium. Field size and penumbrae agreed within 5.4% and 2.2% respectively with film measurements. Agreements with ionization chambers better than 1.0% were obtained when measuring tissue-phantom ratios. Output factor measurements were in good agreement with ionization chamber and Monte Carlo simulation. The data obtained from this imaging sensor can be easily analyzed to extract dosimetric information. The results presented in this work are promising for the development and implementation of CMOS active pixel sensors for dosimetry applications.
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Affiliation(s)
- F Jiménez Spang
- Department of Medical Physics and Bioengineering, University College London, Gower Street, London WC1E 6BT, UK
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Clinical use of diodes and micro-chambers to obtain accurate small field output factor measurements. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2015; 38:357-67. [DOI: 10.1007/s13246-015-0334-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 02/19/2015] [Indexed: 12/22/2022]
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Hug B, Warrener K, Liu P, Ralston A, Suchowerska N, McKenzie D, Ebert MA. On the measurement of dose in-air for small radiation fields: choice of mini-phantom material. Phys Med Biol 2015; 60:2391-402. [DOI: 10.1088/0031-9155/60/6/2391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Kumar S, Deshpande DD, Nahum AE. Monte-Carlo-derived insights into dose–kerma–collision kerma inter-relationships for 50 keV–25 MeV photon beams in water, aluminum and copper. Phys Med Biol 2014; 60:501-19. [DOI: 10.1088/0031-9155/60/2/501] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Warrener K, Hug B, Liu P, Ralston A, Ebert MA, McKenzie DR, Suchowerska N. Small field in-air output factors: the role of miniphantom design and dosimeter type. Med Phys 2014; 41:021723. [PMID: 24506614 DOI: 10.1118/1.4861710] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The commissioning of treatment planning systems and beam modeling requires measured input parameters. The measurement of relative output in-air, Sc is particularly difficult for small fields. The purpose of this study was to investigate the influence of miniphantom design and detector selection on measured Sc values for small fields and to validate the measurements against Monte Carlo simulations. METHODS Measurements were performed using brass caps (with sidewalls) or tops (no sidewalls) of varying heights and widths. The performance of two unshielded diodes (60012 and SFD), EBT2 radiochromic film, and a fiber optic dosimeter (FOD) were compared for fields defined by MLCs (5-100 mm) and SRS cones (4-30 mm) on a Varian Novalis linear accelerator. Monte Carlo simulations were performed to theoretically predict Sc as measured by the FOD. RESULTS For all detectors, Sc agreed to within 1% for fields larger than 10 mm and to within 2.3% for smaller fields. Monte Carlo simulation matched the FOD measurements for all size of cone defined fields to within 0.5%. CONCLUSIONS Miniphantom design is the most important variable for reproducible and accurate measurements of the in-air output ratio, S(c), in small photon fields (less than 30 mm). Sidewalls are not required for fields ≤ 30 mm and tops are therefore preferred over the larger caps. Unlike output measurements in water, S(cp), the selection of detector type for Sc is not critical, provided the active dosimeter volume is small relative to the field size.
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Affiliation(s)
- Kirbie Warrener
- Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, New South Wales 2521, Australia and Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Benjamin Hug
- School of Physics, University of Western Australia, Crawley, Western Australia 6009, Australia and Department of Radiation Oncology, Sir Charles Gairdner Hospital, Perth, Western Australia 6009, Australia
| | - Paul Liu
- School of Physics, University of Sydney, Darlington, New South Wales 2008, Australia
| | - Anna Ralston
- Chris O'Brien Lifehouse, Radiation Oncology, Sydney, New South Wales 2050, Australia
| | - Martin A Ebert
- School of Physics, University of Western Australia, Crawley, Western Australia 6009, Australia and Department of Radiation Oncology, Sir Charles Gairdner Hospital, Perth, Western Australia 6009, Australia
| | - David R McKenzie
- School of Physics, University of Sydney, Darlington, New South Wales 2008, Australia
| | - Natalka Suchowerska
- School of Physics, University of Sydney, Darlington, New South Wales 2008, Australia and Chris O'Brien Lifehouse, Radiation Oncology, Sydney, New South Wales 2050, Australia
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Azangwe G, Grochowska P, Georg D, Izewska J, Hopfgartner J, Lechner W, Andersen CE, Beierholm AR, Helt-Hansen J, Mizuno H, Fukumura A, Yajima K, Gouldstone C, Sharpe P, Meghzifene A, Palmans H. Detector to detector corrections: A comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams. Med Phys 2014; 41:072103. [DOI: 10.1118/1.4883795] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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36
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Benmakhlouf H, Sempau J, Andreo P. Output correction factors for nine small field detectors in 6 MV radiation therapy photon beams: A PENELOPE Monte Carlo study. Med Phys 2014; 41:041711. [DOI: 10.1118/1.4868695] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Kairn T, Crowe SB, Charles PH, Trapp JV. Using narrow beam profiles to quantify focal spot size, for accurate Monte Carlo simulations of SRS/SRT systems. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/1742-6596/489/1/012014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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38
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Charles PH, Cranmer-Sargison G, Thwaites DI, Crowe SB, Kairn T, Knight RT, Kenny J, Langton CM, Trapp JV. A practical and theoretical definition of very small field size for radiotherapy output factor measurements. Med Phys 2014; 41:041707. [DOI: 10.1118/1.4868461] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Lechner W, Palmans H, Sölkner L, Grochowska P, Georg D. Detector comparison for small field output factor measurements in flattening filter free photon beams. Radiother Oncol 2013; 109:356-60. [DOI: 10.1016/j.radonc.2013.10.022] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 10/11/2013] [Accepted: 10/19/2013] [Indexed: 11/28/2022]
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40
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Charles PH, Crowe SB, Kairn T, Knight RT, Hill B, Kenny J, Langton CM, Trapp JV. Monte Carlo-based diode design for correction-less small field dosimetry. Phys Med Biol 2013; 58:4501-12. [DOI: 10.1088/0031-9155/58/13/4501] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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41
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Fenwick JD, Kumar S, Scott AJD, Nahum AE. Using cavity theory to describe the dependence on detector density of dosimeter response in non-equilibrium small fields. Phys Med Biol 2013; 58:2901-23. [DOI: 10.1088/0031-9155/58/9/2901] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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42
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Czarnecki D, Zink K. Monte Carlo calculated correction factors for diodes and ion chambers in small photon fields. Phys Med Biol 2013; 58:2431-44. [DOI: 10.1088/0031-9155/58/8/2431] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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43
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Followill DS, Kry SF, Qin L, Lowenstein J, Molineu A, Alvarez P, Aguirre JF, Ibbott GS. The Radiological Physics Center's standard dataset for small field size output factors. J Appl Clin Med Phys 2012; 13:3962. [PMID: 22955664 PMCID: PMC5718235 DOI: 10.1120/jacmp.v13i5.3962] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Revised: 05/16/2012] [Accepted: 05/30/2012] [Indexed: 11/23/2022] Open
Abstract
Delivery of accurate intensity‐modulated radiation therapy (IMRT) or stereotactic radiotherapy depends on a multitude of steps in the treatment delivery process. These steps range from imaging of the patient to dose calculation to machine delivery of the treatment plan. Within the treatment planning system's (TPS) dose calculation algorithm, various unique small field dosimetry parameters are essential, such as multileaf collimator modeling and field size dependence of the output. One of the largest challenges in this process is determining accurate small field size output factors. The Radiological Physics Center (RPC), as part of its mission to ensure that institutions deliver comparable and consistent radiation doses to their patients, conducts on‐site dosimetry review visits to institutions. As a part of the on‐site audit, the RPC measures the small field size output factors as might be used in IMRT treatments, and compares the resulting field size dependent output factors to values calculated by the institution's treatment planning system (TPS). The RPC has gathered multiple small field size output factor datasets for X‐ray energies ranging from 6 to 18 MV from Varian, Siemens and Elekta linear accelerators. These datasets were measured at 10 cm depth and ranged from 10×10 cm2 to 2×2 cm2. The field sizes were defined by the MLC and for the Varian machines the secondary jaws were maintained at a 10×10 cm2. The RPC measurements were made with a micro‐ion chamber whose volume was small enough to gather a full ionization reading even for the 2×2 cm2 field size. The RPC measured output factors are tabulated and are reproducible with standard deviations (SD) ranging from 0.1% to 2.4%, while the institutions' calculated values had a much larger SD range, ranging up to 7.9%. The absolute average percent differences were greater for the 2×2 cm2 than for the other field sizes. The RPC's measured small field output factors provide institutions with a standard dataset against which to compare their TPS calculated values. Any discrepancies noted between the standard dataset and calculated values should be investigated with careful measurements and with attention to the specific beam model. PACS number: 87.53.Bn
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Affiliation(s)
- David S Followill
- Department of Radiation Physics, Radiological Physics Center, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
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Brualla-González L, Gómez F, Vicedo A, González-Castaño DM, Gago-Arias A, Pazos A, Zapata M, Roselló JV, Pardo-Montero J. A two-dimensional liquid-filled ionization chamber array prototype for small-field verification: characterization and first clinical tests. Phys Med Biol 2012; 57:5221-34. [DOI: 10.1088/0031-9155/57/16/5221] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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45
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Cranmer-Sargison G, Weston S, Evans JA, Sidhu NP, Thwaites DI. Monte Carlo modelling of diode detectors for small field MV photon dosimetry: detector model simplification and the sensitivity of correction factors to source parameterization. Phys Med Biol 2012; 57:5141-53. [DOI: 10.1088/0031-9155/57/16/5141] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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46
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Pantelis E, Moutsatsos A, Zourari K, Petrokokkinos L, Sakelliou L, Kilby W, Antypas C, Papagiannis P, Karaiskos P, Georgiou E, Seimenis I. On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the kQclin,Qmsrfclin,fmsr correction factors for microchamber and diode detectors. Med Phys 2012; 39:4875-85. [DOI: 10.1118/1.4736810] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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47
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Scott AJD, Kumar S, Nahum AE, Fenwick JD. Characterizing the influence of detector density on dosimeter response in non-equilibrium small photon fields. Phys Med Biol 2012; 57:4461-76. [DOI: 10.1088/0031-9155/57/14/4461] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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48
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Khelashvili G, Chu J, Diaz A, Turian J. Dosimetric characteristics of the small diameter BrainLab™ cones used for stereotactic radiosurgery. J Appl Clin Med Phys 2012; 13:3610. [PMID: 22231212 PMCID: PMC5716132 DOI: 10.1120/jacmp.v13i1.3610] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 07/16/2011] [Accepted: 07/14/2011] [Indexed: 11/23/2022] Open
Abstract
The purpose was to study the dosimetric characteristics of the small diameter (≤10.0 mm) BrainLAB cones used for stereotactic radiosurgery (SRS) treatments in conjunction with a Varian Trilogy accelerator. Required accuracy and precision in dose delivery during SRS can be achieved only when the geometric and dosimetric characteristics of the small radiation fields is completely understood. Although a number of investigators have published the dosimetric characteristics of SRS cones, to our knowledge, there is no generally accepted value for the relative output factor (ROF) for the 5.0 mm diameter cone. Therefore, we have investigated the dosimetric properties of the small (≤10.0 mm) diameter BrainLAB SRS cones used in conjunction with the iPlan TPS and a Trilogy linear accelerator with a SRS beam mode. Percentage depth dose (PDD), off‐axis ratios (OAR), and ROF were measured using a SRS diode and verified with Monte Carlo (MC) simulations. The dependence of ROF on detector material response was studied. The dependence of PDD, OAR, and ROF on the alignment of the beam CAX with the detector motion line was also investigated using MC simulations. An agreement of 1% and 1 mm was observed between measurements and MC for PDD and OAR. The calculated ROF for the 5.0 mm diameter cone was 0.692±0.008 — in good agreement with the measured value of 0.683±0.007 after the diode response was corrected. Simulations of the misalignment between the beam axis and detector motion axis for angles between 0.5°–1.0° have shown a deviation > 2% in PDD beyond a certain depth. We have also provided a full set of dosimetric data for BrainLAB SRS cones. Monte Carlo calculated ROF values for cones with diameters less than 10.0 mm agrees with measured values to within 1.8%. Care should be exercised when measuring PDD and OAR for small cones. We recommend the use of MC to confirm the measurement under these conditions. PACS numbers: 87.53.Ly, 87.55.‐x, 87.53.Bn, 87.55.K‐
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Affiliation(s)
- Gocha Khelashvili
- Radiation Oncology Center, Northwestern Memorial Hospital, Chicago, Illinois 60611, USA.
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Almberg SS, Frengen J, Kylling A, Lindmo T. Monte Carlo linear accelerator simulation of megavoltage photon beams: Independent determination of initial beam parameters. Med Phys 2011; 39:40-7. [DOI: 10.1118/1.3668315] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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50
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Cranmer-Sargison G, Weston S, Evans JA, Sidhu NP, Thwaites DI. Implementing a newly proposed Monte Carlo based small field dosimetry formalism for a comprehensive set of diode detectors. Med Phys 2011; 38:6592-602. [DOI: 10.1118/1.3658572] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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