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Dunn L, Godwin G, Hellyer J, Xu X. A method for time‐independent film dosimetry: Can we obtain accurate patient‐specific QA results at any time postirradiation? J Appl Clin Med Phys 2022; 23:e13534. [PMID: 35049118 PMCID: PMC8906213 DOI: 10.1002/acm2.13534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 12/15/2021] [Accepted: 12/30/2021] [Indexed: 11/09/2022] Open
Affiliation(s)
- Leon Dunn
- St Vincent's GenesisCare Centre for radiation oncology St Vincent's Hospital Basement Level Building C, 41 Victoria Parade, Fitzroy VIC 3065 Melbourne Victoria 3065 Australia
| | - Guy Godwin
- Redland Icon Cancer Care Bayside Business Park, 16/24 Weippin St, Cleveland QLD Brisbane Queensland 4163 Australia
| | - James Hellyer
- Macquarie University GenesisCare Centre for radiation oncology Hospital Building Suite 1, Level B2, 3 Technology Pl, Macquarie University NSW Sydney New South Wales 2109 Australia
| | - Xiaolei Xu
- St Vincent's GenesisCare Centre for radiation oncology St Vincent's Hospital Basement Level Building C, 41 Victoria Parade, Fitzroy VIC 3065 Melbourne Victoria 3065 Australia
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2
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Niroomand‐Rad A, Chiu‐Tsao S, Grams MP, Lewis DF, Soares CG, Van Battum LJ, Das IJ, Trichter S, Kissick MW, Massillon‐JL G, Alvarez PE, Chan MF. Report of AAPM Task Group 235 Radiochromic Film Dosimetry: An Update to TG‐55. Med Phys 2020; 47:5986-6025. [DOI: 10.1002/mp.14497] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 09/15/2020] [Accepted: 09/17/2020] [Indexed: 12/12/2022] Open
Affiliation(s)
| | | | | | | | | | | | - Indra J. Das
- Radiation Oncology Northwestern University Memorial Hospital Chicago IL USA
| | - Samuel Trichter
- New York‐Presbyterian HospitalWeill Cornell Medical Center New York NY USA
| | | | - Guerda Massillon‐JL
- Instituto de Fisica Universidad Nacional Autonoma de Mexico Mexico City Mexico
| | - Paola E. Alvarez
- Imaging and Radiation Oncology Core MD Anderson Cancer Center Houston TX USA
| | - Maria F. Chan
- Memorial Sloan Kettering Cancer Center Basking Ridge NJ USA
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3
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Ahmed S, Zhang G, Moros EG, Feygelman V. Comprehensive evaluation of the high-resolution diode array for SRS dosimetry. J Appl Clin Med Phys 2019; 20:13-23. [PMID: 31478343 PMCID: PMC6806480 DOI: 10.1002/acm2.12696] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/20/2019] [Accepted: 07/24/2019] [Indexed: 11/08/2022] Open
Abstract
A high-resolution diode array has been comprehensively evaluated. It consists of 1013 point diode detectors arranged on the two 7.7 × 7.7 cm2 printed circuit boards (PCBs). The PCBs are aligned face to face in such a way that the active volumes of all diodes are in the same plane. All individual correction factors required for accurate dosimetry have been validated for conventional and flattening filter free (FFF) 6MV beams. That included diode response equalization, linearity, repetition rate dependence, field size dependence, angular dependence at the central axis and off-axis in the transverse, sagittal, and multiple arbitrary planes. In the end-to-end tests the array and radiochromic film dose distributions for SRS-type multiple-target plans were compared. In the equalization test (180° rotation), the average percent dose error between the normal and rotated positions for all diodes was 0.01% ± 0.1% (range -0.3 to 0.4%) and -0.01% ± 0.2% (range -0.9 to 0.9%) for 6 MV and 6MV FFF beams, respectively. For the axial angular response, corrected dose stayed within 2% from the ion chamber for all gantry angles, until the beam direction approached the detector plane. In azimuthal direction, the device agreed with the scintillator within 1% for both energies. For multiple combinations of couch and gantry angles, the average percent errors were -0.00% ± 0.6% (range: -2.1% to 1.6%) and -0.1% ± 0.5% (range -1.6% to 2.1%) for the 6MV and 6MV FFF beams, respectively. The measured output factors were largely within 2% of the scintillator, except for the 5 mm 6MV beam showing a 3.2% deviation. The 2%/1 mm gamma analysis of composite SRS measurements produced the 97.2 ± 1.3% (range 95.8-98.5%) average passing rate against film. Submillimeter (≤0.5 mm) dose profile alignment with film was demonstrated in all cases.
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Affiliation(s)
- Saeed Ahmed
- Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA.,Department of Physics, University of South Florida, Tampa, FL, USA
| | - Geoffrey Zhang
- Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA
| | - Eduardo G Moros
- Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA
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4
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Pellicioli P, Bartzsch S, Donzelli M, Krisch M, Bräuer-Krisch E. High resolution radiochromic film dosimetry: Comparison of a microdensitometer and an optical microscope. Phys Med 2019; 65:106-113. [PMID: 31450120 DOI: 10.1016/j.ejmp.2019.08.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 08/13/2019] [Accepted: 08/14/2019] [Indexed: 11/16/2022] Open
Abstract
PURPOSE Microbeam radiation therapy is a developing technique that promises superior tumour control and better normal tissue tolerance using spatially fractionated X-ray beams only tens of micrometres wide. Radiochromic film dosimetry at micrometric scale was performed using a microdensitometer, but this instrument presents limitations in accuracy and precision, therefore the use of a microscope is suggested as alternative. The detailed procedures developed to use the two devices are reported allowing a comparison. METHODS Films were irradiated with single microbeams and with arrays of 50 µm wide microbeams spaced by a 400 µm pitch, using a polychromatic beam with mean energy of 100 keV. The film dose measurements were performed using two independent instruments: a microdensitometer (MDM) and an optical microscope (OM). RESULTS The mean values of the absolute dose measured with the two instruments differ by less than 5% but the OM provides reproducibility with a standard deviation of 1.2% compared to up to 7% for the MDM. The resolution of the OM was determined to be ~ 1 to 2 µm in both planar directions able to resolve pencil beams irradiation, while the MDM reaches at the best 20 µm resolution along scanning direction. The uncertainties related to the data acquisition are 2.5-3% for the OM and 9-15% for the MDM. CONCLUSION The comparison between the two devices validates that the OM provides equivalent results to the MDM with better precision, reproducibility and resolution. In addition, the possibility to study dose distributions in two-dimensions over wider areas definitely sanctions the OM as substitute of the MDM.
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Affiliation(s)
- P Pellicioli
- The European Synchrotron Radiation Facility, ID17 Biomedical Beamline, Grenoble, France; Inserm UA7 STROBE, Grenoble Alpes University, Grenoble, France; Swansea University Medical School, Singleton Park, Swansea SA2 8PP, United Kingdom.
| | - S Bartzsch
- Helmholtz-Centre Munich, Institute of Innovative Radiation Therapy, Munich, Germany; Klinikum rechts der Isar, Department for Radiation Oncology, Technical University of Munich, Germany
| | - M Donzelli
- The European Synchrotron Radiation Facility, ID17 Biomedical Beamline, Grenoble, France; ICR - The Institute of Cancer Research, London, United Kingdom
| | - M Krisch
- The European Synchrotron Radiation Facility, ID17 Biomedical Beamline, Grenoble, France
| | - E Bräuer-Krisch
- The European Synchrotron Radiation Facility, ID17 Biomedical Beamline, Grenoble, France
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5
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Li Y, Chen L, Zhu J, Liu X. The combination of the error correction methods of GAFCHROMIC EBT3 film. PLoS One 2017; 12:e0181958. [PMID: 28750023 PMCID: PMC5531657 DOI: 10.1371/journal.pone.0181958] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Accepted: 07/10/2017] [Indexed: 11/18/2022] Open
Abstract
Purpose The aim of this study was to combine a set of methods for use of radiochromic film dosimetry, including calibration, correction for lateral effects and a proposed triple-channel analysis. These methods can be applied to GAFCHROMIC EBT3 film dosimetry for radiation field analysis and verification of IMRT plans. Methods A single-film exposure was used to achieve dose calibration, and the accuracy was verified based on comparisons with the square-field calibration method. Before performing the dose analysis, the lateral effects on pixel values were corrected. The position dependence of the lateral effect was fitted by a parabolic function, and the curvature factors of different dose levels were obtained using a quadratic formula. After lateral effect correction, a triple-channel analysis was used to reduce disturbances and convert scanned images from films into dose maps. The dose profiles of open fields were measured using EBT3 films and compared with the data obtained using an ionization chamber. Eighteen IMRT plans with different field sizes were measured and verified with EBT3 films, applying our methods, and compared to TPS dose maps, to check correct implementation of film dosimetry proposed here. Results The uncertainty of lateral effects can be reduced to ±1 cGy. Compared with the results of Micke A et al., the residual disturbances of the proposed triple-channel method at 48, 176 and 415 cGy are 5.3%, 20.9% and 31.4% smaller, respectively. Compared with the ionization chamber results, the difference in the off-axis ratio and percentage depth dose are within 1% and 2%, respectively. For the application of IMRT verification, there were no difference between two triple-channel methods. Compared with only corrected by triple-channel method, the IMRT results of the combined method (include lateral effect correction and our present triple-channel method) show a 2% improvement for large IMRT fields with the criteria 3%/3 mm.
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Affiliation(s)
- Yinghui Li
- School of Physics, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China
| | - Lixin Chen
- State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, People’s Republic of China
| | - Jinhan Zhu
- State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, People’s Republic of China
| | - Xiaowei Liu
- School of Physics, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China
- * E-mail:
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Calvo Ortega JF, Moragues S, Pozo M, José SS, Puertas E, Fernández J, Casals J. A dosimetric evaluation of the Eclipse AAA algorithm and Millennium 120 MLC for cranial intensity-modulated radiosurgery. Med Dosim 2013; 39:129-33. [PMID: 24342166 DOI: 10.1016/j.meddos.2013.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 10/18/2013] [Accepted: 11/11/2013] [Indexed: 11/30/2022]
Abstract
The aim of this study is to assess the accuracy of a convolution-based algorithm (anisotropic analytical algorithm [AAA]) implemented in the Eclipse planning system for intensity-modulated radiosurgery (IMRS) planning of small cranial targets by using a 5-mm leaf-width multileaf collimator (MLC). Overall, 24 patient-based IMRS plans for cranial lesions of variable size (0.3 to 15.1cc) were planned (Eclipse, AAA, version 10.0.28) using fixed field-based IMRS produced by a Varian linear accelerator equipped with a 120 MLC (5-mm width on central leaves). Plan accuracy was evaluated according to phantom-based measurements performed with radiochromic film (EBT2, ISP, Wayne, NJ). Film 2D dose distributions were performed with the FilmQA Pro software (version 2011, Ashland, OH) by using the triple-channel dosimetry method. Comparison between computed and measured 2D dose distributions was performed using the gamma method (3%/1mm). Performance of the MLC was checked by inspection of the DynaLog files created by the linear accelerator during the delivery of each dynamic field. The absolute difference between the calculated and measured isocenter doses for all the IMRS plans was 2.5% ± 2.1%. The gamma evaluation method resulted in high average passing rates of 98.9% ± 1.4% (red channel) and 98.9% ± 1.5% (blue and green channels). DynaLog file analysis revealed a maximum root mean square error of 0.46mm. According to our results, we conclude that the Eclipse/AAA algorithm provides accurate cranial IMRS dose distributions that may be accurately delivered by a Varian linac equipped with a Millennium 120 MLC.
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Affiliation(s)
| | - Sandra Moragues
- Departamento de Oncología Radioterápica, Hospital Quirón, Barcelona, Spain
| | - Miquel Pozo
- Departamento de Oncología Radioterápica, Hospital Quirón, Barcelona, Spain
| | - Sol San José
- Departamento de Oncología Radioterápica, Hospital Quirón, Barcelona, Spain
| | - Enrique Puertas
- Departamento de Oncología Radioterápica, Hospital Quirón, Barcelona, Spain
| | - Jaime Fernández
- Departamento de Oncología Radioterápica, Hospital Quirón, Barcelona, Spain
| | - Joan Casals
- Departamento de Oncología Radioterápica, Hospital Quirón, Barcelona, Spain
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7
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Ong CL, Cuijpers JP, Senan S, Slotman BJ, Verbakel WFAR. Impact of the calculation resolution of AAA for small fields and RapidArc treatment plans. Med Phys 2011; 38:4471-9. [PMID: 21928616 DOI: 10.1118/1.3605468] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To investigate the impact of the calculation resolution of the anisotropic analytical algorithms (AAA) for a variety of small fields in homogeneous and heterogeneous media and for RapidArc plans. METHODS Dose distributions calculated using AAA version 8.6.15 (AAA8) and 10.0.25 (AAA10) were compared to measurements performed with GafChromic EBT film, using phantoms made of polystyrene or a combination of polystyrene and cork. The accuracy of the algorithms calculated using grid resolutions of 2.5 and 1.0 mm was investigated for different field sizes, and for a limited selection of RapidArc plans (head and neck, small meningioma, and lung). Additional plans were optimized to create excessive multileaf collimator modulation and measured on a homogenous phantom. Gamma evaluation criterion of 3% dose difference and 2- or 1-mm distance to agreement (DTA) were applied to evaluate the accuracy of the algorithms. RESULTS For fields < or = 3 x 3 cm2, both versions of AAA predicted lower peak doses and broader penumbra widths than the measurements. However, AAA10 and a finer calculation grid improved the agreement. For RapidArc plans with many small multileaf collimator (MLC) segments and relatively high number of monitor units (MU), AAA8 failed to identify small dose peaks within the target. Both versions performed better in polystyrene than in cork. In homogeneous cork layers, AAA8 underestimated the average target dose for a clinical lung plan. This was improved with AAA10 calculated using a 1 mm grid. CONCLUSIONS AAA10 improves the accuracy of dose calculations, and calculation grid of 1.0 mm is superior to using 2.5 mm, although calculation times increased by factor of 5. A suitable upper MU constraint should be assigned during optimization to avoid plans with high modulation. For plans with a relative high number of monitor units, calculations using 1 mm grid resolution are recommended. For planning target volume (PTV) which contains relatively large area of low density tissue, users should be aware of possible dose underestimation in the low density region and recalculation with AAA10 grid 1.0 mm is recommended.
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Affiliation(s)
- Chin Loon Ong
- Department of Radiation Oncology, Vu University Medical Center, 1081HV Amsterdam, The Netherlands
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8
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Sharma SD, Kumar S, Dagaonkar SS, Bisht G, Dayanand S, Devi R, Deshpande SS, Chaudhary S, Bhatt BC, Kannan S. Dosimetric comparison of linear accelerator-based stereotactic radiosurgery systems. J Med Phys 2011; 32:18-23. [PMID: 21217914 PMCID: PMC3003883 DOI: 10.4103/0971-6203.31145] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Accepted: 12/04/2006] [Indexed: 11/04/2022] Open
Abstract
Stereotactic radiosurgery (SRS) is a special radiotherapy technique used to irradiate intracranial lesions by 3-D arrangements of narrow photon beams eliminating the needs of invasive surgery. Three different tertiary collimators, namely BrainLab and Radionics circular cones and BrainLab micro multileaf collimator (mMLC), are used for linear accelerator-based SRS systems (X-Knife). Output factor (S(t)), tissue maximum ratio (TMR) and off axis ratio (OAR) of these three SRS systems were measured using CC01 (Scanditronix/ Welhofer) and Pinpoint (PTW) cylindrical and Markus plane parallel ionization chambers as well as TLD and radiochromic film. Measurement results of CC01 and Pinpoint chambers were very close to each other which indicate that further reduction in volume and physical dimensions of cylindrical ionization chamber is not necessary for SRS/SRT dosimetry. Output factors of BrainLab and Radionics SRS cones were very close to each other while output factors of equivalent diameter mMLC field were different from SRS circular cones. TMR of the three SRS systems compared were very close to one another. OAR of Radionics cone and BrainLab mMLC were very close to each other, within 2%. However, OARs of BrainLab cone were found comparable to OARs of Radionics cone and BrainLab mMLC within maximum variation of 4%. In addition, user-measured similar data of other three mMLC X-Knives were compared with the mMLC X-Knife data measured in this work and found comparable. The concept of switching over to mMLC-based SRS/SRT is thus validated from dosimetric characteristics as well.
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Affiliation(s)
- S D Sharma
- Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, CT and CRS Building, Anushaktinagar, Mumbai - 400 094, India
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9
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Practical use of Gafchromic® EBT films in electron beams for in-phantom dose distribution measurements and monitor units verification. Phys Med 2011; 27:81-8. [DOI: 10.1016/j.ejmp.2010.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 01/29/2010] [Accepted: 04/28/2010] [Indexed: 11/21/2022] Open
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10
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Low DA, Moran JM, Dempsey JF, Dong L, Oldham M. Dosimetry tools and techniques for IMRT. Med Phys 2011; 38:1313-38. [DOI: 10.1118/1.3514120] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Richley L, John AC, Coomber H, Fletcher S. Evaluation and optimization of the new EBT2 radiochromic film dosimetry system for patient dose verification in radiotherapy. Phys Med Biol 2010; 55:2601-17. [PMID: 20393235 DOI: 10.1088/0031-9155/55/9/012] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A new radiochromic film, the yellow Gafchromic EBT2, has been marketed as a drop-in replacement for the discontinued blue EBT film. In order to verify the manufacturer's claims prior to clinical use, EBT2 was characterized in transmission, and the less commonly used, reflection modes with an Epson Expression 10000XL A3 flatbed scanner. The red channel was confirmed to provide the greatest sensitivity and was used for all measurements. The post-irradiation darkening of the film was investigated, and the relative response was found to be dose dependent with higher doses stabilizing earlier than lower doses. After 13 h all dose levels had stabilized to within 1% of their value at 24 h. Uniformity of irradiated EBT2 films was within 0.8% and 1.2% (2SD of signal), in reflection and transmission modes, respectively. The light scattering effect, arising from the structure and thickness of EBT2, was found to give rise to an apparent scanner non-uniformity of up to 5.5% in signal. In reflection mode, differences of up to 1.2% were found between the signal obtained from a small film fragment (5 x 5 cm(2)) and the signal obtained from the same fragment bordered by extra film. Further work is needed to determine the origin of this effect, as there will be implications for reflection dosimetry of intensity modulated fields; reflection mode cannot yet be regarded as a viable alternative to transmission mode. Our results suggest that EBT2 film is a valid alternative, rather than a direct replacement for EBT film.
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Affiliation(s)
- L Richley
- Bristol Haematology and Oncology Centre, Bristol BS28ED, UK.
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12
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Holly R, Keller BM, Pignol JP, Lemaire C, Peemoeller H. Initial investigation on the use of MR spectroscopy and micro-MRI of GAFCHROMIC EBT radiotherapy film. Med Phys 2009; 36:5341-6. [PMID: 19994542 DOI: 10.1118/1.3242216] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This article presents an initial investigation of the efficacy of using 1H MRS and micro-MRI as analysis techniques for irradiated GAFCHROMIC EBT radiotherapy films. METHODS GAFCHROMIC EBT radiotherapy film was irradiated with 6 MV x rays to known doses ranging from 5 to 1000 cGy. 24 h following irradiation 1H MRS measurements were performed to access the degree of post-irradiation polymer cross-linking. 2D 1H micro-MRI experiments were also performed for film irradiations of 0 and 300 cGy. RESULTS Linear response of the 1H MRS linewidth to dose in the range from 0 to 400 cGy (R2 = 0.98) was observed. Such linearity is not seen when analyzed under conventional light analysis. The sensitivity of the film, as measured by the slope of the curve between 0 and 400 cGy, is 0.0042 +/- 0.0003 kHz/cGy, demonstrating the sensitivity of the 1H MRS technique used to analyze the film. The film saturates at a dose of approximately 900 cGy. Broadline 1H MRS provides a quantitative measure of the degree of polymerization of the film. CONCLUSIONS A quantitative measurement of the degree of polymerization of GAFCHROMIC EBT film has been presented using 1H MRS. The saturation of the film at approximately 900 cGy is corroborated by that observed with light analysis. Further MR spectroscopic experiments are needed to investigate the response of the film to dose, allowing for a better understanding of the relationship between polymer cross-linking in the active layer.
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Affiliation(s)
- Rick Holly
- Department of Medical Physics, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5, Canada.
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13
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Buchauer K, Hillbrand E, de Vries A. GAFCHROMIC®
EBT photospectral dose response dependence on temperature and implications for flat bed scanning. Med Phys 2009; 36:5044-51. [DOI: 10.1118/1.3231825] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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14
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Evaluation of the magnitude of EBT Gafchromic film polarization effects. ACTA ACUST UNITED AC 2009; 32:21-5. [PMID: 19400549 DOI: 10.1007/bf03178624] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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15
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Rah J, Shin D, Jang J, Kim M, Yoon S, Suh T. Application of a glass rod detector for the output factor measurement in the CyberKnife. Appl Radiat Isot 2008; 66:1980-5. [DOI: 10.1016/j.apradiso.2008.06.041] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 06/05/2008] [Accepted: 06/29/2008] [Indexed: 11/15/2022]
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16
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Chiu-Tsao ST, Medich D, Munro J. The use of new GAFCHROMIC EBT film for 125I seed dosimetry in Solid Water phantom. Med Phys 2008; 35:3787-99. [PMID: 18777938 DOI: 10.1118/1.2955746] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Radiochromic film dosimetry has been extensively used for intravascular brachytherapy applications for near field within 1 cm from the sources. With the recent introduction of new model of radiochromic films, GAFCHROMIC EBT, with higher sensitivity than earlier models, it is promising to extend the distances out to 5 cm for low dose rate (LDR) source dosimetry. In this study, the use of new model GAFCHROMIC EBT film for 125I seed dosimetry in Solid Water was evaluated for radial distances from 0.06 cm out to 5 cm. A multiple film technique was employed for four 125I seeds (Implant Sciences model 3500) with NIST traceable air kerma strengths. Each experimental film was positioned in contact with a 125I seed in a Solid Water phantom. The products of the air kerma strength and exposure time ranged from 8 to 3158 U-h, with the initial air kerma strength of 6 U in a series of 25 experiments. A set of 25 calibration films each was sequentially exposed to one 125I seed at about 0.58 cm distance for doses from 0.1 to 33 Gy. A CCD camera based microdensitometer, with interchangeable green (520 nm) and red (665 nm) light boxes, was used to scan all the films with 0.2 mm pixel resolution. The dose to each 125I calibration film center was calculated using the air kerma strength of the seed (incorporating decay), exposure time, distance from seed center to film center, and TG43U1S1 recommended dosimetric parameters. Based on the established calibration curve, dose conversion from net optical density was achieved for each light source. The dose rate constant was determined as 0.991 cGy U(-1)h(-1) (+/-6.9%) and 1.014 cGy U(-1)h(-1) (+/-6.8%) from films scanned using green and red light sources, respectively. The difference between these two values was within the uncertainty of the measurement. Radial dose function and 2D anisotropy function were also determined. The results obtained using the two light sources corroborated each other. We found good agreement with the TG43U1S1 recommended values of radial dose function and 2D anisotropy function, to within the uncertainty of the measurement. We also verified the dosimetric parameters in the near field calculated by Rivard using Monte Carlo method. The radial dose function values in Solid Water were lower than those in water recommended by TG43U1S1, by about 2%, 3%, 7%, and 14% at 2, 3, 4, and 5 cm, respectively, partially due to the difference in the phantom material composition. Radiochromic film dosimetry using GAFCHROMIC EBT model is feasible in determining 2D dose distributions around low dose rate 125I seed. It is a viable alternative to TLD dosimetry for 125I seed dose characterization.
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17
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Rink A, Lewis DF, Varma S, Vitkin IA, Jaffray DA. Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium. Med Phys 2008; 35:4545-55. [PMID: 18975701 PMCID: PMC2736758 DOI: 10.1118/1.2975483] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 06/18/2008] [Accepted: 08/02/2008] [Indexed: 11/07/2022] Open
Abstract
The effects of temperature on real time changes in optical density (DeltaOD) of GAFCHROMIC EBT film were investigated. The spectral peak of maximum change in absorbance (lambdamax) was shown to downshift linearly when the temperature of the film was increased from 22 to 38 degrees C. The DeltaOD values were also shown to decrease linearly with temperature, and this decrease could not be attributed to the shift in lambdamax. A compensation scheme using lambdamax and a temperature-dependent correction factor was investigated, but provided limited improvement. Part of the reason may be the fluctuations in hydration of the active component, which were found to affect both position of absorbance peaks and the sensitivity of the film. To test the effect of hydration, laminated and unlaminated films were desiccated. This shifted both the major and minor absorbance peaks in the opposite direction to the change observed with temperature. The desiccated film also exhibited reduced sensitivity to ionizing radiation. Rehydration of the desiccated films did not reverse the effects, but rather gave rise to another form of the polymer with absorbance maxima upshifted further 20 nm. Hence, the spectral characteristics and sensitivity of the film can be dependent on its history, potentially complicating both real-time and conventional radiation dosimetry.
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Affiliation(s)
- Alexandra Rink
- Princess Margaret Hospital/Ontario Cancer Institute, Department of Medical Biophysics and Radiation Oncology, University of Toronto, Toronto, Ontario M5G 2M9, Canada.
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18
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GABOR M, LITOBORSKI M. Dose measurement verification in solid state phantom in place of field connection for non-standard radiotherapy conditions. Rep Pract Oncol Radiother 2008. [DOI: 10.1016/s1507-1367(10)60094-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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19
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Ohuchi H. High sensitivity radiochromic film dosimetry using an optical common-mode rejection and a reflective-mode flatbed color scanner. Med Phys 2008; 34:4207-12. [PMID: 18072484 DOI: 10.1118/1.2795828] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A novel method that can greatly improve the dosimetric sensitivity limit of a radiochromic film (RCF) through use of a set of color components, e.g., red and green, outputs from a RGB color scanner has been developed. RCFs are known to have microscopic and macroscopic nonuniformities, which come from the thickness variations in the film's active radiochromic layer and coating. These variations in the response make the optical signal-to-noise ratio lower, resulting in lower film sensitivity. To mitigate the effects of RCF nonuniform response, an optical common-mode rejection (CMR) was developed. The CMR compensates nonuniform response by creating a ratio of the two signals where the factors common to both numerator and denominator cancel out. The CMR scheme was applied to the mathematical operation of creating a ratio using two components, red and green outputs from a scanner. The two light component lights are neighboring wavebands about 100 nm apart and suffer a common fate, with the exception of wavelength-dependent events, having passed together along common attenuation paths. Two types of dose-response curves as a function of delivered dose ranging from 3.7 mGy to 8.1 Gy for 100 kV x-ray beams were obtained with the optical CMR scheme and the conventional analysis method using red component, respectively. In the range of 3.7 mGy to 81 mGy, the optical densities obtained with the optical CMR showed a good consistency among eight measured samples and an improved consistency with a linear fit within 1 standard deviation of each measured optical densities, while those with the conventional analysis exhibited a large discrepancy among eight samples and did not show a consistency with a linear fit.
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Affiliation(s)
- Hiroko Ohuchi
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8578, Japan.
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20
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Das IJ, Ding GX, Ahnesjö A. Small fields: Nonequilibrium radiation dosimetry. Med Phys 2007; 35:206-15. [DOI: 10.1118/1.2815356] [Citation(s) in RCA: 484] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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21
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Wilcox E, Daskalov G, Nedialkova L. Comparison of the Epson Expression 1680 flatbed and the Vidar VXR-16 Dosimetry PRO™ film scanners for use in IMRT dosimetry using Gafchromic and radiographic film. Med Phys 2006; 34:41-8. [PMID: 17278488 DOI: 10.1118/1.2402584] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Intensity-modulated radiotherapy (IMRT) treatment plan verification is often done using Kodak EDR2 film and a Vidar Dosimetry PRO film digitizer. However, since many hospitals are moving towards a filmless environment, access to a film processor may not be available. Therefore, we have investigated a newly available Gafchromic EBT film for IMRT dosimetry. Planar IMRT dose distributions are delivered to both EBT and EDR2 film and scanned with the Vidar VXR-16 as well as an Epson Expression 1680 flatbed scanner. The measured dose distributions are then compared to those calculated with a Pinnacle treatment planning system. The IMRT treatments consisted of 7-9 6 MV beams for treatment of prostate, head and neck, and a few other sites. The films were analyzed using FilmQATM (3cognition LLC) software. Comparisons between measured and calculated dose distributions are reported as dose difference (DD) (pixels within +/-5%), distance to agreement (DTA) (3 mm), as well as gamma values (y) (dose= +/-3%, dist. =2 mm). Using EDR2 with the Vidar scanner is an established technique and agreement between calculated and measured dose distributions was better than 90% in all indices (DD, DTA, and gamma). However, agreement with calculations deteriorated reaching the lower 80% for EBT film scans with the Vidar scanner in logarithmic mode. The EBT Vidar scans obtained in linear mode showed an improved agreement to the upper 80% range, but artifacts were still observed across the scan. These artifacts were very distinct in all EBT scans and can be attributed to the way the film is transported through the scanner. In the Epson scanner both films are rigidly immobilized and the light source scans over the film. It was found that the Epson scanner performed equally well with both types of film giving agreement to better than 90% in all indices.
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Affiliation(s)
- Ellen Wilcox
- Radiation Oncology, Saint Francis Hospital and Medical Center, 114 Woodland Street, Hartford, Connecticut 06105, USA.
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22
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Sankar A, Ayyangar KM, Nehru RM, Kurup PGG, Murali V, Enke CA, Velmurugan J. Comparison of Kodak EDR2 and Gafchromic EBT film for intensity-modulated radiation therapy dose distribution verification. Med Dosim 2006; 31:273-82. [PMID: 17134667 DOI: 10.1016/j.meddos.2006.06.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Accepted: 06/02/2006] [Indexed: 10/23/2022]
Abstract
The quantitative dose validation of intensity-modulated radiation therapy (IMRT) plans require 2-dimensional (2D) high-resolution dosimetry systems with uniform response over its sensitive region. The present work deals with clinical use of commercially available self-developing Radio Chromic Film, Gafchromic EBT film, for IMRT dose verification. Dose response curves were generated for the films using a VXR-16 film scanner. The results obtained with EBT films were compared with the results of Kodak extended dose range 2 (EDR2) films. The EBT film had a linear response between the dose range of 0 to 600 cGy. The dose-related characteristics of the EBT film, such as post irradiation color growth with time, film uniformity, and effect of scanning orientation, were studied. There was up to 8.6% increase in the color density between 2 to 40 hours after irradiation. There was a considerable variation, up to 8.5%, in the film uniformity over its sensitive region. The quantitative differences between calculated and measured dose distributions were analyzed using DTA and Gamma index with the tolerance of 3% dose difference and 3-mm distance agreement. The EDR2 films showed consistent results with the calculated dose distributions, whereas the results obtained using EBT were inconsistent. The variation in the film uniformity limits the use of EBT film for conventional large-field IMRT verification. For IMRT of smaller field sizes (4.5 x 4.5 cm), the results obtained with EBT were comparable with results of EDR2 films.
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Affiliation(s)
- A Sankar
- Department of Radiation Oncology, Apollo Specialty Hospital, Chennai, India.
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23
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Yu PKN, Butson M, Cheung T. Does mechanical pressure on radiochromic film affect optical absorption and dosimetry? AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2006; 29:285-7. [PMID: 17058593 DOI: 10.1007/bf03178580] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
EBT Gafchromic film, a new high sensitivity radiochromic film has been tested to evaluate if external pressure on the film can affect absorption spectra analysis and thus radiation dosimetry. This question arises from the fact that Gafchromic film is often cut into smaller pieces or to certain shapes for dosimetric analysis using scissors which can apply significant pressure to the sides of the film and small film pieces are placed within a solid phantom at depth which can produce significant pressure on the film if appropriate weight distribution procedures are not performed. As expected, results have shown that films cut by scissors can produce a large increase in OD near the film edge up to 5-10 mm away due to physical damage to the EBT film layers. Films placed within a solid phantom receiving up to 39.5 kg/cm2 pressure showed negligible differences in measured absorption spectra compared with control films subject to no external pressure. This equates to negligible external pressure effects for as much as 44 cm of 30 cm x 30 cm solid water placed on a 1 cm2 area film piece. As such, we recommend based on results herein, that film analysis should be performed with a boundary around every film edge, which can be defined visually based in the film. Also film dosimetry in a phantom can be performed with weights up to 39.5 kg/cm2 (or 44 cm of 30 cm x 30 cm solid water or equivalent) placed on the film without effecting the absorption spectra and thus dosimetry of radiation beams.
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Affiliation(s)
- P K N Yu
- City University of Hong Kong, Department of Physics and Materials Science, Kowloon Tong, Hong Kong
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24
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Le Y, Ali I, Dempsey JF, Williamson JF. Prospects for quantitative two-dimensional radiochromic film dosimetry for low dose-rate brachytherapy sources. Med Phys 2006; 33:4622-34. [PMID: 17278815 DOI: 10.1118/1.2390546] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Radiochromic film (RCF) has been shown to be a precise and accurate two-dimensional dosimeter for acute exposure radiation fields. However, "temporal history" mismatch between calibration and brachytherapy films due to RCF dose-rate effects could introduce potentially large uncertainties in low dose-rate (LDR) brachytherapy absolute dose measurement. This article presents a quantitative evaluation of the precision and accuracy of a laser scanner-based RCF-dosimetry system and the effect of the temporal history mismatch in LDR absolute dose measurement. MD-55-2 RCF was used to measure absolute dose for a low dose-rate 137Cs brachytherapy source using both single- and double-exposure techniques. Dose-measurement accuracy was evaluated by comparing RCF to Monte Carlo photon-transport simulation. The temporal history mismatch effect was investigated by examining dependence of RCF accuracy on irradiation-to-densitometry time interval. The predictions of the empirical cumulative dose superposition model (CDSM) were compared with measurements. For the double-exposure technique, the agreement between measurement and Monte Carlo simulation was better than 4% in the 3-60 Gy dose range with measurement precisions (coverage factor k = 1) of <2% and <6% for the doses greater or less than 3 Gy, respectively. The overall uncertainty (k = 1) of dose rate/air-kerma strength measurements achievable by this dosimetry system for a spatial resolution of 0.1 mm is less than 4% for doses greater than 5 Gy. The measured temporal history mismatch systematic error is about 1.8% for a 48 h postexposure time when using the double exposure technique and agrees with CDSM's prediction qualitatively. This work demonstrates that the model MD-55-2 RCF detector has the potential to support quantitative dose measurements about LDR brachytherapy sources with precision and accuracy better than that of previously described dosimeters. The impacts of this work on the future use of new type of RCF were also discussed.
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Affiliation(s)
- Yi Le
- Department of Radiation Oncology, Virginia Commonwealth University, 401 College Street, PO Box 980058, Richmond, Virginia 23298, USA.
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25
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Lynch BD, Kozelka J, Ranade MK, Li JG, Simon WE, Dempsey JF. Important considerations for radiochromic film dosimetry with flatbed CCD scanners and EBT GAFCHROMIC® film. Med Phys 2006; 33:4551-6. [PMID: 17278806 DOI: 10.1118/1.2370505] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In this study, we present three significant artifacts that have the potential to negatively impact the accuracy and precision of film dosimetry measurements made using GAFCHROMIC EBT radiochromic film when read out with CCD flatbed scanners. Films were scanned using three commonly employed instruments: a Macbeth TD932 spot densitometer, an Epson Expression 1680 CCD array scanner, and a Microtek ScanMaker i900 CCD array scanner. For the two scanners we assessed the variation in optical density (OD) of GAFCHROMIC EBT film with scanning bed position, angular rotation of the film with respect to the scan line direction, and temperature inside the scanner due to repeated scanning. Scanning uniform radiochromic films demonstrated a distinct bowing effect in profiles in the direction of the CCD array with a nonuniformity of up to 17%. Profiles along a direction orthogonal to the CCD array demonstrated a 7% variation. A strong angular dependence was found in measurements made with the flatbed scanners; the effect could not be reproduced with the spot densitometer. An IMRT quality assurance film was scanned twice rotating the film 90' between the scans. For films scanned on the Epson scanner, up to 12% variation was observed in unirradiated EBT films rotated between 0 degrees and 90 degrees, which decreased to approximately 8% for EBT films irradiated to 300 cGy. Variations of up to 80% were observed for films scanned with the Microtek scanner. The scanners were found to significantly increase the film temperature with repeated scanning. Film temperature between 18 and 33 degrees C caused OD changes of approximately 7%. Considering these effects, we recommend adherence to a strict scanning protocol that includes: maintaining the orientation of films scanned on flatbed scanners, limiting scanning to the central portion of the scanner bed, and limiting the number of consecutive scans to minimize changes in OD caused by film heating.
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Affiliation(s)
- Bart D Lynch
- Department of Nuclear Engineering, University of Florida, Gainesville, Florida 32611-8300, USA
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26
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Devic S, Wang YZ, Tomic N, Podgorsak EB. Sensitivity of linear CCD array based film scanners used for film dosimetry. Med Phys 2006; 33:3993-6. [PMID: 17153378 DOI: 10.1118/1.2357836] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Film dosimetry is commonly performed by using linear CCD array transmission optical densitometers. However, these devices suffer from a variation in response along the detector array. If not properly corrected for, this nonuniformity may lead to significant overestimations of the measured dose as one approaches regions close to the edges of the scanning region. In this note, we present measurements of the spatial response of an AGFA Arcus II document scanner used for radiochromic film dosimetry. Results and methods presented in this work can be generalized to other CCD based transmission scanners used for film dosimetry employing either radiochromic or radiographic films.
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Affiliation(s)
- Slobodan Devic
- Medical Physics Department, McGill University Health Centre, Montreal, Quebec, Canada.
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27
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Butson MJ, Cheung T, Yu PKN. Scanning orientation effects on Gafchromic EBT film dosimetry. ACTA ACUST UNITED AC 2006; 29:281-4. [PMID: 17058592 DOI: 10.1007/bf03178579] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Gafchromic EBT film, a new high sensitivity radiochromic film has been tested for variations in optical properties due to scanning orientation. Gafchromic EBT film has been shown to produce a scanning orientation effect whereby variations in measured relative optical density are found due to the films orientation relative to the scanner direction. This relative optical density change was found to be relatively consistent for different films exposed to varying dose levels ranging from 0 Gy to 3 Gy. A maximum variation of 0.0157 +/- 0.0035 in optical density (OD) was found. This relates to an approximate 15% variation in net OD for a 50 cGy irradiated film and 4% variation for a 3 Gy irradiated film. No noticeable effects or variations were seen with changing scanning resolution or with the film placed "up or down" during scanning. Other Gafchromic film types were tested and compared to EBT for unirradiated film to assess the magnitude of this orientation effect on the scanner used and results showed that EBT produced a significantly higher effect that MD-55-2, HS, XR type T and XR type R film by up to 3 times. As such, providing the same orientation of EBT film when scanning for dosimetric analysis becomes an essential part of EBT film dosimetry.
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Affiliation(s)
- M J Butson
- City University of Hong Kong, Department of Physics and Materials Science, Kowloon Tong, Hong Kong.
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28
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Todorovic M, Fischer M, Cremers F, Thom E, Schmidt R. Evaluation of GafChromic EBT prototype B for external beam dose verification. Med Phys 2006; 33:1321-8. [PMID: 16752567 DOI: 10.1118/1.2188077] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The capability of the new GafChromic EBT prototype B for external beam dose verification is investigated in this paper. First the general characteristics of this film (dose response, postirradiation coloration, influence of calibration field size) were derived using a flat-bed scanner. In the dose range from 0.1 to 8 Gy, the sensitivity of the EBT prototype B film is ten times higher than the response of the GafChromic HS, which so far was the GafChromic film with the highest sensitivity. Compared with the Kodak EDR2 film, the response of the EBT is higher by a factor of 3 in the dose range from 0.1 to 8 Gy. The GafChromic EBT almost does not show a temporal growth of the optical density and there is no influence of the chosen calibration field size on the dose response curve obtained from this data. A MatLab program was written to evaluate the two-dimensional dose distributions from treatment planning systems and GafChromic EBT film measurements. Verification of external beam therapy (SRT, IMRT) using the above-mentioned approach resulted in very small differences between the planned and the applied dose. The GafChromic EBT prototype B together with the flat-bed scanner and MatLab is a successful approach for making the advantages of the GafChromic films applicable for verification of external beam therapy.
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Affiliation(s)
- M Todorovic
- Department of Radiotherapy and Radio-Oncology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
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29
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d'Errico F. Dosimetric issues in radiation protection of radiotherapy patients. RADIATION PROTECTION DOSIMETRY 2006; 118:205-12. [PMID: 16581918 DOI: 10.1093/rpd/ncl034] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
As life expectancy increases, thanks to improving general medical practices, cancer treatments for the ageing population become evermore necessary. Radiation therapy is increasingly a treatment of choice, promoted by continuing improvements in dose delivery technologies. Some techniques, collectively referred to as intensity-modulated radiation therapy, are encountering widespread acceptance and implementation, promoted by reports of superior tumour control and reduced toxicity. However, these new techniques pose new challenges in terms of radiation protection of patients, as they cause a more extensive low-dose exposure of normal tissues compared with conventional radiation therapy. The related dosimetric challenges and the methods available to tackle them are reviewed in this paper, which also emphasises the need for standard radiation protection dosimetry procedures so that information may be consistently gathered for a comparative evaluation of the different treatment modalities.
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Affiliation(s)
- Francesco d'Errico
- Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, Università di Pisa, Italy.
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30
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Rink A, Vitkin IA, Jaffray DA. Characterization and real-time optical measurements of the ionizing radiation dose response for a new radiochromic medium. Med Phys 2005; 32:2510-6. [PMID: 16193781 DOI: 10.1118/1.1951447] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A new radiochromic film, GafChromic EBT, was investigated for use in a real-time radiation dosimetry system. It was found to be approximately eight times more sensitive to ionizing radiation dose, exhibited less postexposure development and achieved stable readout faster than one of its predecessors, GafChromic MD-55. A clear distinction in change in optical density between exposure and postexposure was observed, but the measurements obtained during exposure were not linear with time or dose. This could not be explained by a shift in wavelength of maximum change in absorbance, as it was stable at approximately 636 nm during the entire exposure range (up to 9.52 Gy). Increasing the spectral window of interest over which calculations were performed did little to correct the nonlinearity. The radiochromic film exhibited small dose rate dependence in real-time measurements, with an increase in standard deviation of change in optical density measurements from 0.9% to 1.8% over a sixfold variation in dose rate. Overall, GafChromic EBT has increased sensitivity and decreased postexposure darkening, and this bodes well for its potential role as a radiation dosimeter, including real-time applications.
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Affiliation(s)
- Alexandra Rink
- Princess Margaret Hospital/Ontario Cancer Institute, Department of Medical Biophysics aind Radiation Oncology, University of Toronto, Toronto, Ontario Canada
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31
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Devic S, Seuntjens J, Sham E, Podgorsak EB, Schmidtlein CR, Kirov AS, Soares CG. Precise radiochromic film dosimetry using a flat-bed document scanner. Med Phys 2005; 32:2245-2253. [PMID: 16121579 DOI: 10.1118/1.1929253] [Citation(s) in RCA: 441] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Revised: 04/19/2005] [Accepted: 04/20/2005] [Indexed: 11/07/2022] Open
Abstract
In this study, a measurement protocol is presented that improves the precision of dose measurements using a flat-bed document scanner in conjunction with two new GafChromic film models, HS and Prototype A EBT exposed to 6 MV photon beams. We established two sources of uncertainties in dose measurements, governed by measurement and calibration curve fit parameters contributions. We have quantitatively assessed the influence of different steps in the protocol on the overall dose measurement uncertainty. Applying the protocol described in this paper on the Agfa Arcus II flat-bed document scanner, the overall one-sigma dose measurement uncertainty for an uniform field amounts to 2% or less for doses above around 0.4 Gy in the case of the EBT (Prototype A), and for doses above 5 Gy in the case of the HS model GafChromic film using a region of interest 2 X 2 mm2 in size.
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Affiliation(s)
- Slobodan Devic
- Medical Physics Department, McGill University Health Centre, Montréal, Québec H3G IA4, Canada.
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32
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Scheib SG, Gianolini S, Lomax NJ, Mack A. High precision radiosurgery and technical standards. ACTA NEUROCHIRURGICA. SUPPLEMENT 2005; 91:9-23. [PMID: 15707022 DOI: 10.1007/978-3-7091-0583-2_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
BACKGROUND A high degree of precision and accuracy in radiosurgery is a fundamental requirement for therapeutic success. Small radiation fields and steep dose gradients are clinically applied thus necessitating a dedicated quality assurance program in order to guarantee dosimetric and geometric accuracy. MATERIAL AND METHODS A detailed analysis of the course of treatment independent of the irradiation technique used results in the so-called chain of uncertainties in radiosurgery (immobilisation, imaging, treatment planning system, definition of regions of interest, mechanical accuracy, dose planning, dose verification). Each link in this chain is analysed for accuracy and the established quality assurance procedures are discussed. A "System Test" was used to check the whole chain of uncertainties simultaneously. RESULTS The tests described are compatible with published reports on quality assurance in radiosurgery. In terms of accuracy the weakest link in the chain of uncertainties is stereotactic MR imaging. Geometric overall accuracy measured in the "System Test" is less than 0.7 mm. CONCLUSION The established quality assurance routines have clinically been validated. MR imaging dominates geometric overall accuracy in radiosurgery, which can be limited to less than 1 mm by an adequate quality assurance protocol.
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MESH Headings
- Adenoma/diagnosis
- Adenoma/surgery
- Angiography, Digital Subtraction/instrumentation
- Angiography, Digital Subtraction/standards
- Artifacts
- Brain Neoplasms/diagnosis
- Brain Neoplasms/surgery
- Equipment Design
- Follow-Up Studies
- Humans
- Image Processing, Computer-Assisted/instrumentation
- Image Processing, Computer-Assisted/standards
- Imaging, Three-Dimensional/instrumentation
- Imaging, Three-Dimensional/standards
- Magnetic Resonance Imaging/instrumentation
- Magnetic Resonance Imaging/standards
- Neurilemmoma/diagnosis
- Neurilemmoma/surgery
- Neuronavigation/instrumentation
- Neuronavigation/standards
- Phantoms, Imaging
- Pituitary Neoplasms/diagnosis
- Pituitary Neoplasms/surgery
- Quality Assurance, Health Care/standards
- Radiosurgery/instrumentation
- Radiosurgery/standards
- Sensitivity and Specificity
- Stereotaxic Techniques/instrumentation
- Tomography, X-Ray Computed/instrumentation
- Tomography, X-Ray Computed/standards
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Affiliation(s)
- S G Scheib
- Department of Medical Radiation Physics, Klinik Im Park, Zurich, Switzerland.
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33
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Rink A, Vitkin IA, Jaffray DA. Suitability of radiochromic medium for real-time optical measurements of ionizing radiation dose. Med Phys 2005; 32:1140-55. [PMID: 15895598 DOI: 10.1118/1.1877832] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A system, consisting of a novel optical fiber-based readout configuration and model-based method, has been developed to test suitability of a certain radiochromic medium for real-time measurements of ionizing radiation dose. Using this system with the radiochromic film allowed dose measurements to be performed during, and immediately after, exposure. The rates of change in OD before, during, and after exposure differ, and the change in OD during exposure was found to be proportional to applied dose in the tested range of 0-4 Gy. Estimating applied dose within an average error of less than 5% did not require a waiting time of 24-48 h as generally recommended with this radiochromic film. The errors can be further reduced by performing a calibration for each individual dosimeter setup instead of relying on batch calibration. Measurements of change in OD were found to be independent of dose-rate in the 95-570 cGy/min range for applied dose of 1 Gy or less. Some error was introduced due to dose-rate variation for doses of 2 Gy and above. The major limiting factor in utilizing this radiation sensitive medium for real-time in vivo dosimetry is the strong dependence on temperature in the clinically relevant range of 20-38 degrees C.
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Affiliation(s)
- Alexandra Rink
- Princess Margaret Hospital/Ontario Cancer Institute, Department of Medical Biophysics and Radiation Oncology, University of Toronto, Toronto, Ontario M5G 2M9, Canada.
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34
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Mack A, Mack G, Scheib S, Czempiel H, Kreiner HJ, Lomax NJ, Gianolini S, Rieker M, Weltz D, Wolff R, Muacevic A, Wowra B, Böttcher HD, Seifert V. Quality Assurance in Stereotactic Radiosurgery/Radiotherapy according to DIN 6875-1. Stereotact Funct Neurosurg 2005; 82:235-43. [PMID: 15637445 DOI: 10.1159/000083175] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The new DIN ('Deutsche Industrie-Norm') 6875-1, which is currently being finalised, deals with quality assurance (QA) criteria and tests methods for linear accelerator and Gamma Knife stereotactic radiosurgery/radiotherapy including treatment planning, stereotactic frame and stereotactic imaging and a system test to check the whole chain of uncertainties. Our existing QA program, based on dedicated phantoms and test procedures, has been refined to fulfill the demands of this new DIN. The radiological and mechanical isocentre corresponded within 0.2 mm and the measured 50% isodose lines were in agreement with the calculated ones within less than 0.5 mm. The measured absorbed dose was within 3%. The resultant output factors measured for the 14-, 8- and 4-mm collimator helmet were 0.9870 +/- 0.0086, 0.9578 +/- 0.0057 and 0.8741 +/- 0.0202, respectively. For 170 consecutive tests, the mean geometrical accuracy was 0.48 +/- 0.23 mm. Besides QA phantoms and analysis software developed in-house, the use of commercially available tools facilitated the QA according to the DIN 6875-1 with which our results complied.
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Affiliation(s)
- A Mack
- Gamma Knife Centre Frankfurt, GKF GmbH, DE-60258 Frankfurt, Germany.
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Dini SA, Koona RA, Ashburn JR, Meigooni AS. Dosimetric evaluation of GAFCHROMIC XR type T and XR type R films. J Appl Clin Med Phys 2005; 6:114-34. [PMID: 15770202 PMCID: PMC5723503 DOI: 10.1120/jacmp.v6i1.2051] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The high spatial resolution of radiochromic film makes it ideal for dosimetric measurements and dose distributions in regions of high dose gradient. Intensity‐modulated radiation therapy, intravascular brachytherapy, and eye‐plaque radiation therapy demand precise spatial dosimetric calculations. Such precision is not possible with conventional dosimeters, such as thermoluminescent dosimeters and ionization chambers. Recently, new GAFCHROMIC® XR type T and type R films have been developed for radiation dosimetry, specifically in interventional radiology procedures. Dosimetric characteristics (i.e., linearity, post‐exposure density growth, energy dependence, dose‐rate dependence, and UV light sensitivity) of these new films were investigated. To evaluate the clinical applications of these films, their characteristics were compared with other commercially available film models. GAFCHROMIC® XR type T and type R films were found to be more sensitive to low‐energy doses as compared with GAFCHROMIC® MD‐55 films. PACS numbers: 87.66‐a, 87.53‐j
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Affiliation(s)
- Sharifeh A. Dini
- Department of Radiation MedicineUniversity of Kentucky Medical Center800 Rose StreetLexingtonKentucky40536U.S.A.
| | - Rafiq A. Koona
- Department of Radiation MedicineUniversity of Kentucky Medical Center800 Rose StreetLexingtonKentucky40536U.S.A.
| | - John R. Ashburn
- Department of Radiation MedicineUniversity of Kentucky Medical Center800 Rose StreetLexingtonKentucky40536U.S.A.
| | - Ali S. Meigooni
- Department of Radiation MedicineUniversity of Kentucky Medical Center800 Rose StreetLexingtonKentucky40536U.S.A.
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Aoyama H, Azuma Y, Goto S, Tahara S, Uno H, Inamura K, Kadohisa S, Nakagiri Y, Kanazawa S, Sumimoto T, Azuma M. [Accuracy of measurement of radiochromic film density for high-energy X-rays]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2004; 60:1533-42. [PMID: 15568005 DOI: 10.6009/jjrt.kj00003326577] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Radiochromic film (RC-film) is of great interest as a film-type dosimeter for radiation oncology applications. We present a two-dimensional image-based evaluation of the measurement accuracy of a commercial RC-film product (Gafchromic MD-55-2 film, ISP TECHNOLOGIES, Inc.) by using a commercial Laser Densitometer (Model 1710, Computerized Medical Systems, Inc.) as an optical density imaging system. The coefficient of variation of the density (pixel-value) in one sample was approximately 3% to 11% at 3 Gy or less, and 3% or less at 4 to 60 Gy. Although the coefficient of variation between three samples at the same dose was about 14% at 1 Gy, it decreased as the dose increased, reaching several percent. In 1 to 6 Gy samples, geometric imaging artifacts [interference (moire) patterns] were observed, and it was found that scan-sampling pitch influenced the accuracy of measurement of the density of the sample. To improve the accuracy of density measurement, sufficient knowledge about characteristic features of the density measuring system is essential.
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Affiliation(s)
- Hideki Aoyama
- Central Division of Radiology, Okayama University Hospital
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Chiu-Tsao ST, Duckworth T, Zhang C, Patel NS, Hsiung CY, Wang L, Shih JA, Harrison LB. Dose response characteristics of new models of GAFCHROMIC films: Dependence on densitometer light source and radiation energy. Med Phys 2004; 31:2501-8. [PMID: 15487731 DOI: 10.1118/1.1767103] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
This paper presents a systematic study of the dose response characteristics of two new models and one commonly used model of GAFCHROMIC film: HS, XR-T, and MD55-2, respectively. We irradiated these film models with three different radiation sources: I-125, Ir-192, and 6 MV photon beam (6 MVX). We scanned the films with three different densitometers: a He-Ne laser with a wavelength of 633 nm, a spot densitometer with a wavelength of 671 nm, and a CCD camera densitometer with interchangeable LED boxes with wavelengths of 665 nm (red), 520 nm (green), and 465 nm (blue). We compared the film sensitivities in terms of net optical density (NOD) per unit dose in Gy. The sensitivity of each film model depends on radiation energy and the densitometer light source. Using He-Ne laser based densitometer as a reference standard, we found the sensitivities (NOD/Gy) for the red lights of wavelengths, 671 nm and 665 nm, are higher by factors of about 2.5 and 2, respectively. The sensitivities for green (520 nm) and blue (465 nm) lights are lower than that for He-Ne laser (633 nm) by factors of about 2 and 4, respectively. The energy dependence of the sensitivity varies with the film model, but is similar for all densitometer light sources. Comparing I-125 to Ir-192 and 6MVX, we note that (a) model XR-T is about eight times more sensitive, and (b) models HS and MD55-2 are about 40% less sensitive. Relative to MD55-2, XR-T is 12 times more sensitive for I-125 but comparable for Ir-192 and 6MVX, whereas HS is 2 to 3 times more sensitive in all cases. This set of results can serve as useful information for making decisions in selecting the film model and compatible densitometer to achieve the best accuracy of dosimetry in the appropriate dose range.
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Affiliation(s)
- Sou-Tung Chiu-Tsao
- Beth Israel Medical Center and St. Luke's-Roosevelt Hospital Center, New York, New York 10003, USA.
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Fusi F, Mercatelli L, Marconi G, Cuttone G, Romano G. Optical characterization of a radiochromic film by total reflectance and transmittance measurements. Med Phys 2004; 31:2147-54. [PMID: 15305469 DOI: 10.1118/1.1764701] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The GafChromic film (GCF) MD-55-2, a radiochromic material, was examined for its optical properties through total reflectance and transmittance measurements in visible spectrum (400-700 nm). By using a multilayer model of the film and Kubelka-Munk's (KM) theory, absorption and scattering coefficients of the film sensitive layer (K and S, respectively) were obtained from measurements of irradiated and nonirradiated slides. This has allowed calculation of the absorbance A(KM) of the sensitive layer of the GCF. The model easily splits scattering from absorption. Unlike absorption, scattering is essentially insensitive to irradiation dose and decreases slowly as the wavelength increases. The scattering effect is predominant over absorption in the 400-500 nm range, while beyond 600 nm absorption prevails. The A(KM) absorbance of the sensitive layer was calculated using the K coefficient and compared with the optical densities (OD) measured considering only ballistic photons (as in a standard spectrophotometer) as well as the optical densities measured collecting all the transmitted photons (as in many densitometers). The values of A(KM) found were always lower than OD measured by the other methods and they had the best linearity on the whole visible range. These data support the hypothesis that the sensitive layer reacts to irradiation more linearly than that shown by measurements using standard commercial devices. However, in the 600-680 nm range, correction is not very important because absorption is predominant over scattering. When GCF is used for imaging, scattering produces a loss of spatial information. Consequently, it is necessary to collect only ballistic photons and to correct absorbance by K and S coefficients.
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Affiliation(s)
- Franco Fusi
- Laser Center for Medical Application-CEO, Department of Clinical Physiopathology, University of Florence, and Sezione A INFM, Viale G. Pieraccini 6, 50139 Florence, Italy.
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Cozzi L, Fogliata A, Nicolini G. Pre-treatment verification of intensity modulated photon beams with films and electronic portal imaging – Two years of clinical experience. Z Med Phys 2004; 14:239-50. [PMID: 15656106 DOI: 10.1078/0939-3889-00226] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Aim of this report was to summarise clinical experience in the field of pre-treatment dosimetric verification of intensity-modulated photon beams (IRMT). From May 2001 to July 2003, 50 patients were irradiated according to IMRT techniques with 6 MV photon beams produced by a Varian Clinac equipped with a 80 leaves multileaf collimator. Dose plans were computed using commercial treatment planning systems, Nucletron Helax-TMS for static cases and Varian Eclipse-Helios for dynamic cases. Pre-treatment dosimetric verification was carried out on a field-per-field basis measuring 2D absolute dose distributions in solid water at 10 cm depth using films or an electronic portal imaging device (EPID). Verification measurements were compared with expected dose maps, and differences were evaluated by means of both a point-to-point analysis and the Gamma Index. Irradiated target volumes (30 head and neck, 8 breast, 12 other patients) ranged from 111 to 2121 cm3 with a mean of 652 +/- 378 cm3. Twenty-nine dose plans were delivered with dynamic technique and 44 with static technique. On average, 5.9 +/- 1.3 fields were applied per plan, with 12.1 +/- 1.6 segments per field in the static mode. Averaging over the whole number of fields we obtained a mean difference (on a pixel-by-pixel basis and per 100 MU delivered) of -0.22 +/- 0.64 cGy between calculation and measurement, with a standard deviation of 1.93 +/- 0.65 cGy. The mean value for the Gamma Index evaluation was 0.47 +/- 0.10, with a mean standard deviation of 0.35 +/- 0.17. The fraction of pixels lying inside the field and showing a gamma index larger than 1 was 5.7% for the triplet Eclipse-film-dynamic delivery and 9.9% for the triplet Helax-TMS-EPID-static delivery. The employed IMRT treatments proved that this technique is feasible and dosimetrically accurate. Treatment verification stability and dosimetric analysis of treated plans are highly satisfactory and allow the safe introduction of this modality in the spectrum of techniques offered to a large class of patients.
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Affiliation(s)
- Luca Cozzi
- Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, Switzerland.
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