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Bakshi AK, Shrivastava V, Chattaraj A, Samuel K, Palani Selvam T, Sapra BK, Sinharoy P, Banerjee D, Sugilala G, Manohar S, Kaushik CP. Surface dose rate variations in planar and curved geometries of 106Ru/ 106Rh plaque sources for ocular tumors. Phys Med 2021; 89:200-209. [PMID: 34399207 DOI: 10.1016/j.ejmp.2021.08.001] [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: 03/01/2021] [Revised: 07/31/2021] [Accepted: 08/02/2021] [Indexed: 11/19/2022] Open
Abstract
PURPOSE Investigation of surface dose rate variation with respect to the source configuration of 106Ru/106Rh eye plaque. To explore an alternate way to determine activity of brachytherapy plaques. METHODS The surface dose rates of 106Ru/106Rh plaque developed indigenously were measured by extrapolation chamber. To rule out possibility of any error in the activity distribution and quantity, same source was used in two different configurations namely planar and curved. EBT3 Gafchromic film was used for determination of uniformity in activity. Monte Carlo-based Codes EGSnrc and FLUKA were used to calculate dose rate in tissue, percentage depth dose and for determination of activity. Parameters and correction factors were estimated using simulations. RESULTS The measured reference absorbed dose rates for planar and curved 106Ru/106Rh eye plaques are found to be 589 ± 29 mGy/h and 560 ± 28 mGy/h, respectively. The difference in the reference absorbed dose rate of curved eye plaque is about ~5% as compared to planar configuration. The FLUKA-calculated dose values are almost independent of cavity length of the extrapolation chamber for both eye plaques. The FLUKA-based dose rates per μCi 106Ru/106Rh are about 17.28 ± 0.08 mGy/h and 16.48 ± 0.06 mGy/h, respectively for planar and curved eye plaques which match well with the measurements. The calculated activities for planar and curved eye plaques are 34.08 μCi and 33.98 μCi, respectively. CONCLUSIONS Surface dose rates for a prototype 106Ru/106Rh eye plaque with different configurations were estimated using simulations and measured experimentally. An alternate way to determine activity of beta-gamma brachytherapy plaque has been proposed.
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Affiliation(s)
- A K Bakshi
- Radiological Physics & Advisory Division, India; Homi Bhabha National Institute, Mumbai 400 094, India.
| | | | | | | | - T Palani Selvam
- Radiological Physics & Advisory Division, India; Homi Bhabha National Institute, Mumbai 400 094, India
| | - B K Sapra
- Radiological Physics & Advisory Division, India; Homi Bhabha National Institute, Mumbai 400 094, India
| | - Prithwish Sinharoy
- Nuclear Recycle Group, Bhabha Atomic Research Centre, Mumbai 400 085, India; Homi Bhabha National Institute, Mumbai 400 094, India
| | - Dayamoy Banerjee
- Nuclear Recycle Group, Bhabha Atomic Research Centre, Mumbai 400 085, India; Homi Bhabha National Institute, Mumbai 400 094, India
| | - G Sugilala
- Nuclear Recycle Group, Bhabha Atomic Research Centre, Mumbai 400 085, India; Homi Bhabha National Institute, Mumbai 400 094, India
| | - Smitha Manohar
- Radiological Physics & Advisory Division, India; Nuclear Recycle Group, Bhabha Atomic Research Centre, Mumbai 400 085, India; Homi Bhabha National Institute, Mumbai 400 094, India
| | - C P Kaushik
- Nuclear Recycle Group, Bhabha Atomic Research Centre, Mumbai 400 085, India; Homi Bhabha National Institute, Mumbai 400 094, India
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Zaragoza FJ, Eichmann M, Flühs D, Timmermann B, Brualla L. Monte Carlo Computation of Dose-Volume Histograms in Structures at Risk of an Eye Irradiated with Heterogeneous Ruthenium-106 Plaques. Ocul Oncol Pathol 2020; 6:353-359. [PMID: 33123529 DOI: 10.1159/000508113] [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: 01/02/2020] [Accepted: 04/18/2020] [Indexed: 11/19/2022] Open
Abstract
Background/Aims The aim of this work is to compare Monte Carlo simulated absorbed dose distributions obtained from <sup>106</sup>Ru eye plaques, whose heterogeneous emitter distribution is known, with the common homogeneous approximation. The effect of these heterogeneities on segmented structures at risk is analyzed using an anthropomorphic phantom. Methods The generic CCA and CCB, with a homogeneous emitter map, and the specific CCA1364 and CCB1256 <sup>106</sup>Ru eye plaques are modeled with the Monte Carlo code PENELOPE. To compare the effect of the heterogeneities in the segmented volumes, cumulative dose-volume histograms are calculated for different rotations of the aforementioned plaques. Results For the cornea, the CCA with the equatorial placement yields the lowest absorbed dose rate while for the CCA1364 in the same placement the absorbed dose rate is 33% higher. The CCB1256 with the hot spot oriented towards the cornea yields the maximum dose rate per unit of activity while it is 44% lower for the CCB. Conclusions Dose calculations based on a homogeneous distribution of the emitter substance yield the lowest absorbed dose in the analyzed structures for all plaque placements. Treatment planning based on such calculations may result in an overdose of the structures at risk.
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Affiliation(s)
| | - Marion Eichmann
- Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
| | - Dirk Flühs
- NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany
| | - Beate Timmermann
- West German Proton Therapy Center Essen (WPE), Essen, Germany.,West German Cancer Center (WTZ), Essen, Germany.,University Hospital Essen, Essen, Germany.,German Cancer Consortium (DKTK), Essen, Germany.,Department of Particle Therapy, University Hospital Essen, Essen, Germany
| | - Lorenzo Brualla
- West German Proton Therapy Center Essen (WPE), Essen, Germany.,West German Cancer Center (WTZ), Essen, Germany.,University Hospital Essen, Essen, Germany
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Thomson RM, Furutani KM, Kaulich TW, Mourtada F, Rivard MJ, Soares CG, Vanneste FM, Melhus CS. AAPM recommendations on medical physics practices for ocular plaque brachytherapy: Report of task group 221. Med Phys 2020; 47:e92-e124. [PMID: 31883269 DOI: 10.1002/mp.13996] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 11/12/2019] [Accepted: 12/23/2019] [Indexed: 12/14/2022] Open
Abstract
The American Association of Physicists in Medicine (AAPM) formed Task Group 221 (TG-221) to discuss a generalized commissioning process, quality management considerations, and clinical physics practice standards for ocular plaque brachytherapy. The purpose of this report is also, in part, to aid the clinician to implement recommendations of the AAPM TG-129 report, which placed emphasis on dosimetric considerations for ocular brachytherapy applicators used in the Collaborative Ocular Melanoma Study (COMS). This report is intended to assist medical physicists in establishing a new ocular brachytherapy program and, for existing programs, in reviewing and updating clinical practices. The report scope includes photon- and beta-emitting sources and source:applicator combinations. Dosimetric studies for photon and beta sources are reviewed to summarize the salient issues and provide references for additional study. The components of an ocular plaque brachytherapy quality management program are discussed, including radiation safety considerations, source calibration methodology, applicator commissioning, imaging quality assurance tests for treatment planning, treatment planning strategies, and treatment planning system commissioning. Finally, specific guidelines for commissioning an ocular plaque brachytherapy program, clinical physics practice standards in ocular plaque brachytherapy, and other areas reflecting the need for specialized treatment planning systems, measurement phantoms, and detectors (among other topics) to support the clinical practice of ocular brachytherapy are presented. Expected future advances and developments for ocular brachytherapy are discussed.
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Affiliation(s)
- Rowan M Thomson
- Carleton Laboratory for Radiotherapy Physics, Physics Department, Carleton University, Ottawa, ON, K1S 5B6, Canada
| | - Keith M Furutani
- Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Theodor W Kaulich
- Department of Medical Physics, University of Tübingen, 72074, Tübingen, Germany
| | - Firas Mourtada
- Department of Radiation Oncology, Christiana Care Hospital, Newark, DE, 19713, USA
| | - Mark J Rivard
- Department of Radiation Oncology, Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | | | | | - Christopher S Melhus
- Department of Radiation Oncology, Tufts University School of Medicine, Boston, MA, 02111, USA
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Zaragoza FJ, Eichmann M, Flühs D, Wittig A, Sauerwein W, Brualla L. Monte Carlo Simulation of the Treatment of Uveal Melanoma Using Measured Heterogeneous 106Ru Plaques. Ocul Oncol Pathol 2018; 5:276-283. [PMID: 31367591 DOI: 10.1159/000492599] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 07/31/2018] [Indexed: 11/19/2022] Open
Abstract
Background/Aims Ruthenium plaques are used for the treatment of ocular tumors. The aim of this work is the comparison between simulated absorbed dose distributions tallied in an anthropomorphic phantom, obtained from ideal homogeneous plaques, and real eye plaques in which the actual heterogeneous distribution of <sup>106</sup>Ru was measured. The placement of the plaques with respect to the tumor location was taken into consideration to optimize the effectiveness of the treatment. Methods The generic CCA and CCB, and the specific CCA1364 and CCB1256 <sup>106</sup>Ru eye plaques were modeled with the Monte Carlo code PENELOPE. To compare the suitability of each treatment for an anterior, equatorial and posterior tumor location, cumulative dose-volume histograms for the tumors and structures at risk were calculated. Results Eccentric placements of the plaques, taking into account the inhomogeneities of the emitter map, can substantially reduce the dose delivered to structures at risk while maintaining the prescribed dose at the tumor apex. Conclusions The emitter map distribution of the plaque and the computerized tomography of the patient used in a Monte Carlo simulation allow an accurate determination of the plaque position with respect to the tumor with the potential to reduce the dose to sensitive structures.
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Affiliation(s)
| | - Marion Eichmann
- Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
| | - Dirk Flühs
- NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany
| | - Andrea Wittig
- Klinik für Strahlentherapie und Radioonkologie, Universitätsklinikum Jena, Jena, Germany
| | | | - Lorenzo Brualla
- West German Proton Therapy Centre Essen (WPE), Essen, Germany
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Hermida-López M, Brualla L. Absorbed dose distributions from ophthalmic 106 Ru/ 106 Rh plaques measured in water with radiochromic film. Med Phys 2018; 45:1699-1707. [PMID: 29399810 DOI: 10.1002/mp.12777] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 12/19/2017] [Accepted: 01/06/2018] [Indexed: 11/08/2022] Open
Abstract
PURPOSE Brachytherapy with 106 Ru/106 Rh plaques offers good outcomes for small-to-medium choroidal melanomas and retinoblastomas. The dose measurement of the plaques is challenging, due to the small range of the emitted beta particles and steep dose gradients involved. The scarce publications on film dosimetry of 106 Ru/106 Rh plaques used solid phantoms. This work aims to develop a practical method for measuring the absorbed dose distribution in water produced by 106 Ru/106 Rh plaques using EBT3 radiochromic film. METHODS Experimental setups were developed to determine the dose distribution at a plane perpendicular to the symmetry axis of the plaque and at a plane containing the symmetry axis. One CCA and two CCX plaques were studied. The dose maps were obtained with the FilmQA Pro 2015 software, using the triple-channel dosimetry method. The measured dose distributions were compared to published Monte Carlo simulation and experimental data. RESULTS A good agreement was found between measurements and simulations, improving upon published data. Measured reference dose rates agreed within the experimental uncertainty with data obtained by the manufacturer using a scintillation detector, with typical differences below 5%. The attained experimental uncertainty was 4.1% (k = 1) for the perpendicular setup, and 7.9% (k = 1) for the parallel setup. These values are similar or smaller than those obtained by the manufacturer and other authors, without the need of solid phantoms that are not available to most users. CONCLUSIONS The proposed method may be useful to the users to perform quality assurance preclinical tests of 106 Ru/106 Rh plaques.
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Affiliation(s)
- Marcelino Hermida-López
- NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany.,Servei de Física i Protecció Radiològica, Hospital Universitari Vall d'Hebron, Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Lorenzo Brualla
- NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany
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6
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Hermida-López M, Brualla L. Technical Note: Monte Carlo study of106Ru/106Rh ophthalmic plaques including the106Rh gamma spectrum. Med Phys 2017; 44:2581-2585. [DOI: 10.1002/mp.12248] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 02/27/2017] [Accepted: 03/21/2017] [Indexed: 11/07/2022] Open
Affiliation(s)
- Marcelino Hermida-López
- NCTeam, Strahlenklinik; Universitätsklinikum Essen; Hufelandstraße 55 D-45122 Essen Germany
- Servei de Física i Protecció Radiològica; Hospital Universitari Vall d'Hebron, Institut de Recerca (VHIR), Universitat Autònoma de Barcelona Pg. Vall d’Hebron; 119-129 08035 Barcelona Spain
| | - Lorenzo Brualla
- NCTeam, Strahlenklinik; Universitätsklinikum Essen; Hufelandstraße 55 D-45122 Essen Germany
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Heilemann G, Fetty L, Dulovits M, Blaickner M, Nesvacil N, Georg D, Dunavoelgyi R. Treatment plan optimization and robustness of 106 Ru eye plaque brachytherapy using a novel software tool. Radiother Oncol 2017; 123:119-124. [DOI: 10.1016/j.radonc.2017.01.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 12/13/2016] [Accepted: 01/11/2017] [Indexed: 02/03/2023]
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8
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Zaragoza FJ, Eichmann M, Flühs D, Sauerwein W, Brualla L. Monte Carlo Estimation of Absorbed Dose Distributions Obtained from Heterogeneous 106Ru Eye Plaques. Ocul Oncol Pathol 2017; 3:204-209. [PMID: 29071271 DOI: 10.1159/000456717] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 01/12/2017] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND The distribution of the emitter substance in 106Ru eye plaques is usually assumed to be homogeneous for treatment planning purposes. However, this distribution is never homogeneous, and it widely differs from plaque to plaque due to manufacturing factors. METHODS By Monte Carlo simulation of radiation transport, we study the absorbed dose distribution obtained from the specific CCA1364 and CCB1256 106Ru plaques, whose actual emitter distributions were measured. The idealized, homogeneous CCA and CCB plaques are also simulated. RESULTS The largest discrepancy in depth dose distribution observed between the heterogeneous and the homogeneous plaques was 7.9 and 23.7% for the CCA and CCB plaques, respectively. In terms of isodose lines, the line referring to 100% of the reference dose penetrates 0.2 and 1.8 mm deeper in the case of heterogeneous CCA and CCB plaques, respectively, with respect to the homogeneous counterpart. CONCLUSIONS The observed differences in absorbed dose distributions obtained from heterogeneous and homogeneous plaques are clinically irrelevant if the plaques are used with a lateral safety margin of at least 2 mm. However, these differences may be relevant if the plaques are used in eccentric positioning.
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Affiliation(s)
| | - Marion Eichmann
- Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
| | - Dirk Flühs
- NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany
| | | | - Lorenzo Brualla
- NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany
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9
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Sommer H, Ebenau M, Spaan B, Eichmann M. Monte Carlo simulation of ruthenium eye plaques with GEANT4: influence of multiple scattering algorithms, the spectrum and the geometry on depth dose profiles. Phys Med Biol 2017; 62:1848-1864. [DOI: 10.1088/1361-6560/aa5696] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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10
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Mangini CD, Hamby DM. SCALING PARAMETERS FOR HOT-PARTICLE BETA DOSIMETRY. RADIATION PROTECTION DOSIMETRY 2016; 172:356-366. [PMID: 26743259 DOI: 10.1093/rpd/ncv529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 10/23/2015] [Accepted: 11/25/2015] [Indexed: 06/05/2023]
Abstract
Scaling of dose-point kernel (DPK) values for beta particles transmitted by high-Z sources will overestimate dose at shallow depths while underestimating dose at greater depths due to spectral hardening. A new model has been developed based on a determination of the amount of monoenergetic electron absorption that occurs in a given source thickness through the use of EGSnrc (Electron Gamma Shower) Monte Carlo simulations. Integration over a particular beta spectrum provides the beta-particle DPK following self-absorption as a function of source thickness and radial depth in water, thereby accounting for spectral hardening that may occur in higher-Z materials. Beta spectra of varying spectral shapes and endpoint energies were used to test the model for select source materials with 7.42 ≤ Z ≤ 94. The results demonstrate that significant improvements can be made to DPK-based dosimetry models when dealing with high-Z volumetric sources. This new scaling model is currently being used to improve the accuracy of the beta-dosimetry calculations in VARSKIN 5.
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Affiliation(s)
- Colby D Mangini
- St. Jude Children's Research Hospital, 262 Danny Thomas Place (MS 730), Memphis, TN 38105, USA
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Mostafa L, Rachid K, Ahmed SM. Comparison between beta radiation dose distribution due to LDR and HDR ocular brachytherapy applicators using GATE Monte Carlo platform. Phys Med 2016; 32:1007-18. [PMID: 27499370 DOI: 10.1016/j.ejmp.2016.07.636] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 07/06/2016] [Accepted: 07/29/2016] [Indexed: 11/18/2022] Open
Abstract
Eye applicators with 90Sr/90Y and 106Ru/106Rh beta-ray sources are generally used in brachytherapy for the treatment of eye diseases as uveal melanoma. Whenever, radiation is used in treatment, dosimetry is essential. However, knowledge of the exact dose distribution is a critical decision-making to the outcome of the treatment. The Monte Carlo technique provides a powerful tool for calculation of the dose and dose distributions which helps to predict and determine the doses from different shapes of various types of eye applicators more accurately. The aim of this work consisted in using the Monte Carlo GATE platform to calculate the 3D dose distribution on a mathematical model of the human eye according to international recommendations. Mathematical models were developed for four ophthalmic applicators, two HDR 90Sr applicators SIA.20 and SIA.6, and two LDR 106Ru applicators, a concave CCB model and a flat CCB model. In present work, considering a heterogeneous eye phantom and the chosen tumor, obtained results with the use of GATE for mean doses distributions in a phantom and according to international recommendations show a discrepancy with respect to those specified by the manufacturers. The QC of dosimetric parameters shows that contrarily to the other applicators, the SIA.20 applicator is consistent with recommendations. The GATE platform show that the SIA.20 applicator present better results, namely the dose delivered to critical structures were lower compared to those obtained for the other applicators, and the SIA.6 applicator, simulated with MCNPX generates higher lens doses than those generated by GATE.
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Affiliation(s)
- Laoues Mostafa
- Laboratory of Nuclear Science and Radiation-Matter Interactions (LSNIRM) USTHB, Bab Ezzouar 16111, Algiers, Algeria; Laboratory of Theoretical Physics and Radiation-Matter Interactions (LPTHIRM) USDB, Soumaa 09000 Blida, Algeria.
| | - Khelifi Rachid
- Laboratory of Theoretical Physics and Radiation-Matter Interactions (LPTHIRM) USDB, Soumaa 09000 Blida, Algeria
| | - Sidi Moussa Ahmed
- Laboratory of Nuclear Science and Radiation-Matter Interactions (LSNIRM) USTHB, Bab Ezzouar 16111, Algiers, Algeria; Laboratory of Theoretical Physics and Radiation-Matter Interactions (LPTHIRM) USDB, Soumaa 09000 Blida, Algeria
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Heilemann G, Nesvacil N, Blaickner M, Kostiukhina N, Georg D. Multidimensional dosimetry of 106
Ru eye plaques using EBT3 films and its impact on treatment planning. Med Phys 2015; 42:5798-808. [DOI: 10.1118/1.4929564] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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13
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Asadi S, Vaez-zadeh M, Masoudi SF, Rahmani F, Knaup C, Meigooni AS. Gold nanoparticle-based brachytherapy enhancement in choroidal melanoma using a full Monte Carlo model of the human eye. J Appl Clin Med Phys 2015; 16:344–357. [PMID: 26699318 PMCID: PMC5690168 DOI: 10.1120/jacmp.v16i5.5568] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Revised: 04/15/2015] [Accepted: 04/08/2015] [Indexed: 12/20/2022] Open
Abstract
The effects of gold nanoparticles (GNPs) in 125I brachytherapy dose enhancement on choroidal melanoma are examined using the Monte Carlo simulation technique. Usually, Monte Carlo ophthalmic brachytherapy dosimetry is performed in a water phantom. However, here, the compositions of human eye have been considered instead of water. Both human eye and water phantoms have been simulated with MCNP5 code. These simulations were performed for a fully loaded 16 mm COMS eye plaque containing 13 125I seeds. The dose delivered to the tumor and normal tissues have been calculated in both phantoms with and without GNPs. Normally, the radiation therapy of cancer patients is designed to deliver a required dose to the tumor while sparing the surrounding normal tissues. However, as the normal and cancerous cells absorbed dose in an almost identical fashion, the normal tissue absorbed radiation dose during the treatment time. The use of GNPs in combination with radiotherapy in the treatment of tumor decreases the absorbed dose by normal tissues. The results indicate that the dose to the tumor in an eyeball implanted with COMS plaque increases with increasing GNPs concentration inside the target. Therefore, the required irradiation time for the tumors in the eye is decreased by adding the GNPs prior to treatment. As a result, the dose to normal tissues decreases when the irradiation time is reduced. Furthermore, a comparison between the simulated data in an eye phantom made of water and eye phantom made of human eye composition, in the presence of GNPs, shows the significance of utilizing the composition of eye in ophthalmic brachytherapy dosimetry Also, defining the eye composition instead of water leads to more accurate calculations of GNPs radiation effects in ophthalmic brachytherapy dosimetry. PACS number: 87.53.Jw, 87.85.Rs, 87.10.Rt
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Brualla L, Zaragoza FJ, Sauerwein W. Monte Carlo Simulation of the Treatment of Eye Tumors with (106)Ru Plaques: A Study on Maximum Tumor Height and Eccentric Placement. Ocul Oncol Pathol 2014; 1:2-12. [PMID: 27175356 PMCID: PMC4864522 DOI: 10.1159/000362560] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 03/31/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Ruthenium plaques are used for the treatment of ocular tumors. There is, however, a controversy regarding the maximum treatable tumor height. Some advocate eccentric plaque placement, without a posterior safety margin, to avoid collateral damage to the fovea and optic disc, but this has raised concerns about marginal tumor recurrence. There is a need for quantitative information on the spatial absorbed dose distribution in the tumor and adjacent tissues. We have overcome this obstacle using an approach based on Monte Carlo simulation of radiation transport. METHODS CCA and CCB (106)Ru plaques were modeled and their geometry embedded in a computerized tomography scan of the eye of a patient. Different tumor sizes and locations were simulated with the general-purpose Monte Carlo code PENELOPE. RESULTS Cumulative dose-volume histograms were obtained for the tumors and the tissues at risk considered. Plots of isodose lines for both plaques were obtained in a computerized tomography study. CONCLUSIONS Ruthenium eye plaques are an adequate treatment option for tumors up to around 5 mm in height. According to our results, assuming a correct placement of the plaque, a tumor of 6.5 mm apical height is about the maximum size that can be treated safely with the large CCB plaque.
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Affiliation(s)
- Lorenzo Brualla
- NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany
| | - Francisco J. Zaragoza
- Institut de Tècniques Energètiques, Universitat Politècnica de Catalunya, Barcelona, Spain
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Barbosa N, da Rosa L, Menezes A, Reis J, Facure A, Braz D. Assessment of ocular beta radiation dose distribution due to 106Ru/106Rh brachytherapy applicators using MCNPX Monte Carlo code. INTERNATIONAL JOURNAL OF CANCER THERAPY AND ONCOLOGY 2014. [DOI: 10.14319/ijcto.0203.8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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Alva-Sánchez MS, de Oliveira LN, Petchevist PC, Moreira MV, de Almeida A. Beta planar source quality assurance with the Fricke xylenol gel dosimeter. Radiat Phys Chem Oxf Engl 1993 2014. [DOI: 10.1016/j.radphyschem.2013.08.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Fuss M, Sanz A, Muñoz A, Blanco F, Brunger M, Buckman S, Limão-Vieira P, García G. Current prospects on Low Energy Particle Track Simulation for biomedical applications. Appl Radiat Isot 2014; 83 Pt B:159-64. [DOI: 10.1016/j.apradiso.2013.01.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 12/28/2012] [Accepted: 01/09/2013] [Indexed: 10/27/2022]
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Therapies for neovascular age-related macular degeneration: current approaches and pharmacologic agents in development. BIOMED RESEARCH INTERNATIONAL 2013; 2013:830837. [PMID: 24319688 PMCID: PMC3844201 DOI: 10.1155/2013/830837] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 09/30/2013] [Indexed: 12/27/2022]
Abstract
As one of the leading causes of blindness, age-related macular degeneration (AMD) has remained at the epicenter of clinical research in ophthalmology. During the past decade, focus of researchers has ranged from understanding the role of vascular endothelial growth factor (VEGF) in the angiogenic cascades to developing new therapies for retinal vascular diseases. Anti-VEGF agents such as ranibizumab and aflibercept are becoming increasingly well-established therapies and have replaced earlier approaches such as laser photocoagulation or photodynamic therapy. Many other new therapeutic agents, which are in the early phase clinical trials, have shown promising results. The purpose of this paper is to briefly review the available treatment modalities for neovascular AMD and then focus on promising new therapies that are currently in various stages of development.
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Hermida-López M. Calculation of dose distributions for 12 106
Ru/106
Rh ophthalmic applicator models with the PENELOPE Monte Carlo code. Med Phys 2013; 40:101705. [DOI: 10.1118/1.4820368] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Koivunoro H, Siiskonen T, Kotiluoto P, Auterinen I, Hippelainen E, Savolainen S. Accuracy of the electron transport in mcnp5 and its suitability for ionization chamber response simulations: A comparison with the egsnrc and penelope codes. Med Phys 2013; 39:1335-44. [PMID: 22380366 DOI: 10.1118/1.3685446] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In this work, accuracy of the mcnp5 code in the electron transport calculations and its suitability for ionization chamber (IC) response simulations in photon beams are studied in comparison to egsnrc and penelope codes. METHODS The electron transport is studied by comparing the depth dose distributions in a water phantom subdivided into thin layers using incident energies (0.05, 0.1, 1, and 10 MeV) for the broad parallel electron beams. The IC response simulations are studied in water phantom in three dosimetric gas materials (air, argon, and methane based tissue equivalent gas) for photon beams ((60)Co source, 6 MV linear medical accelerator, and mono-energetic 2 MeV photon source). Two optional electron transport models of mcnp5 are evaluated: the ITS-based electron energy indexing (mcnp5(ITS)) and the new detailed electron energy-loss straggling logic (mcnp5(new)). The electron substep length (ESTEP parameter) dependency in mcnp5 is investigated as well. RESULTS For the electron beam studies, large discrepancies (>3%) are observed between the MCNP5 dose distributions and the reference codes at 1 MeV and lower energies. The discrepancy is especially notable for 0.1 and 0.05 MeV electron beams. The boundary crossing artifacts, which are well known for the mcnp5(ITS), are observed for the mcnp5(new) only at 0.1 and 0.05 MeV beam energies. If the excessive boundary crossing is eliminated by using single scoring cells, the mcnp5(ITS) provides dose distributions that agree better with the reference codes than mcnp5(new). The mcnp5 dose estimates for the gas cavity agree within 1% with the reference codes, if the mcnp5(ITS) is applied or electron substep length is set adequately for the gas in the cavity using the mcnp5(new). The mcnp5(new) results are found highly dependent on the chosen electron substep length and might lead up to 15% underestimation of the absorbed dose. CONCLUSIONS Since the mcnp5 electron transport calculations are not accurate at all energies and in every medium by general clinical standards, caution is needed, if mcnp5 is used with the current electron transport models for dosimetric applications.
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Chiu-Tsao ST, Astrahan MA, Finger PT, Followill DS, Meigooni AS, Melhus CS, Mourtada F, Napolitano ME, Nath R, Rivard MJ, Rogers DWO, Thomson RM. Dosimetry of (125)I and (103)Pd COMS eye plaques for intraocular tumors: report of Task Group 129 by the AAPM and ABS. Med Phys 2012; 39:6161-84. [PMID: 23039655 DOI: 10.1118/1.4749933] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Dosimetry of eye plaques for ocular tumors presents unique challenges in brachytherapy. The challenges in accurate dosimetry are in part related to the steep dose gradient in the tumor and critical structures that are within millimeters of radioactive sources. In most clinical applications, calculations of dose distributions around eye plaques assume a homogenous water medium and full scatter conditions. Recent Monte Carlo (MC)-based eye-plaque dosimetry simulations have demonstrated that the perturbation effects of heterogeneous materials in eye plaques, including the gold-alloy backing and Silastic insert, can be calculated with reasonable accuracy. Even additional levels of complexity introduced through the use of gold foil "seed-guides" and custom-designed plaques can be calculated accurately using modern MC techniques. Simulations accounting for the aforementioned complexities indicate dose discrepancies exceeding a factor of ten to selected critical structures compared to conventional dose calculations. Task Group 129 was formed to review the literature; re-examine the current dosimetry calculation formalism; and make recommendations for eye-plaque dosimetry, including evaluation of brachytherapy source dosimetry parameters and heterogeneity correction factors. A literature review identified modern assessments of dose calculations for Collaborative Ocular Melanoma Study (COMS) design plaques, including MC analyses and an intercomparison of treatment planning systems (TPS) detailing differences between homogeneous and heterogeneous plaque calculations using the American Association of Physicists in Medicine (AAPM) TG-43U1 brachytherapy dosimetry formalism and MC techniques. This review identified that a commonly used prescription dose of 85 Gy at 5 mm depth in homogeneous medium delivers about 75 Gy and 69 Gy at the same 5 mm depth for specific (125)I and (103)Pd sources, respectively, when accounting for COMS plaque heterogeneities. Thus, the adoption of heterogeneous dose calculation methods in clinical practice would result in dose differences >10% and warrant a careful evaluation of the corresponding changes in prescription doses. Doses to normal ocular structures vary with choice of radionuclide, plaque location, and prescription depth, such that further dosimetric evaluations of the adoption of MC-based dosimetry methods are needed. The AAPM and American Brachytherapy Society (ABS) recommend that clinical medical physicists should make concurrent estimates of heterogeneity-corrected delivered dose using the information in this report's tables to prepare for brachytherapy TPS that can account for material heterogeneities and for a transition to heterogeneity-corrected prescriptive goals. It is recommended that brachytherapy TPS vendors include material heterogeneity corrections in their systems and take steps to integrate planned plaque localization and image guidance. In the interim, before the availability of commercial MC-based brachytherapy TPS, it is recommended that clinical medical physicists use the line-source approximation in homogeneous water medium and the 2D AAPM TG-43U1 dosimetry formalism and brachytherapy source dosimetry parameter datasets for treatment planning calculations. Furthermore, this report includes quality management program recommendations for eye-plaque brachytherapy.
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Accurate estimation of dose distributions inside an eye irradiated with 106Ru plaques. Strahlenther Onkol 2012; 189:68-73. [DOI: 10.1007/s00066-012-0245-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 09/17/2012] [Indexed: 10/27/2022]
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Brualla L, Sempau J, Sauerwein W. Comment on Monte Carlo calculation of the dose distributions of two 106Ru eye applicators [Radiother Oncol 49 (1998) 191–196]. Radiother Oncol 2012; 104:267-8. [DOI: 10.1016/j.radonc.2012.07.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 07/05/2012] [Accepted: 07/08/2012] [Indexed: 11/25/2022]
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Gueli A, Mannino G, Troja S, Asero G, Burrafato G, De Vincolis R, Greco C, Longhitano N, Occhipinti A, Pansini F, Stella G. 3D dosimetry on Ru-106 plaque for ocular melanoma treatments. RADIAT MEAS 2011. [DOI: 10.1016/j.radmeas.2011.07.032] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Energy deposition by a 106Ru/106Rh eye applicator simulated using LEPTS, a low-energy particle track simulation. Appl Radiat Isot 2011; 69:1198-204. [DOI: 10.1016/j.apradiso.2011.04.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 04/18/2011] [Accepted: 04/19/2011] [Indexed: 11/24/2022]
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Kaneko TS, Sehgal V, Skinner HB, Al-Ghazi MSAL, Ramisinghani NS, Keyak JH. Evaluation of a radiation transport modeling method for radioactive bone cement. Phys Med Biol 2010; 55:2451-63. [PMID: 20371905 DOI: 10.1088/0031-9155/55/9/002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Spinal metastases are a common and serious manifestation of cancer, and are often treated with vertebroplasty/kyphoplasty followed by external beam radiation therapy (EBRT). As an alternative, we have introduced radioactive bone cement, i.e. bone cement incorporated with a radionuclide. In this study, we present a Monte Carlo radiation transport modeling method to calculate dose distributions within vertebrae containing radioactive cement. Model accuracy was evaluated by comparing model-predicted depth-dose curves to those measured experimentally in eight cadaveric vertebrae using radiochromic film. The high-gradient regions of the depth-dose curves differed by radial distances of 0.3-0.9 mm, an improvement over EBRT dosimetry accuracy. The low-gradient regions differed by 0.033-0.055 Gy/h/mCi, which may be important in situations involving prior spinal cord irradiation. Using a more rigorous evaluation of model accuracy, four models predicted the measured dose distribution within the experimental uncertainty, as represented by the 95% confidence interval of the measured log-linear depth-dose curve. The remaining four models required modification to account for marrow lost from the vertebrae during specimen preparation. However, the accuracy of the modified model results indicated that, when this source of uncertainty is accounted for, this modeling method can be used to predict dose distributions in vertebrae containing radioactive cement.
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Affiliation(s)
- T S Kaneko
- Department of Radiological Sciences, B170 Med Sci I, University of California, Irvine, CA 92697, USA.
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Sherbini S, DeCicco J, Gray AT, Struckmeyer R. Verification of the VARSKIN beta skin dose calculation computer code. HEALTH PHYSICS 2008; 94:527-538. [PMID: 18469586 DOI: 10.1097/01.hp.0000308500.98525.99] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The computer code VARSKIN is used extensively to calculate dose to the skin resulting from contaminants on the skin or on protective clothing covering the skin. The code uses six pre-programmed source geometries, four of which are volume sources, and a wide range of user-selectable radionuclides. Some verification of this code had been carried out before the current version of the code, version 3.0, was released, but this was limited in extent and did not include all the source geometries that the code is capable of modeling. This work extends this verification to include all the source geometries that are programmed in the code over a wide range of beta radiation energies and skin depths. Verification was carried out by comparing the doses calculated using VARSKIN with the doses for similar geometries calculated using the Monte Carlo radiation transport code MCNP5. Beta end-point energies used in the calculations ranged from 0.3 MeV up to 2.3 MeV. The results showed excellent agreement between the MCNP and VARSKIN calculations, with the agreement being within a few percent for point and disc sources and within 20% for other sources with the exception of a few cases, mainly at the low end of the beta end-point energies. The accuracy of the VARSKIN results, based on the work in this paper, indicates that it is sufficiently accurate for calculation of skin doses resulting from skin contaminations, and that the uncertainties arising from the use of VARSKIN are likely to be small compared with other uncertainties that typically arise in this type of dose assessment, such as those resulting from a lack of exact information on the size, shape, and density of the contaminant, the depth of the sensitive layer of the skin at the location of the contamination, the duration of the exposure, and the possibility of the source moving over various areas of the skin during the exposure period if the contaminant is on protective clothing.
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Affiliation(s)
- Sami Sherbini
- US Nuclear Regulatory Commission, Washington, DC 20555, USA.
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Ali Nedaie H, Mosleh-Shirazi M, Gharaati H, Shariari M, Allahverdi M. Assessment of different MCNP Monte Carlo codes in electron absorbed dose. Rep Pract Oncol Radiother 2006. [DOI: 10.1016/s1507-1367(06)71075-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Schueler AO, Flühs D, Anastassiou G, Jurklies C, Sauerwein W, Bornfeld N. Beta-Ray Brachytherapy of Retinoblastoma: Feasibility of a New Small-Sized Ruthenium-106 Plaque. Ophthalmic Res 2005; 38:8-12. [PMID: 16166817 DOI: 10.1159/000088259] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Accepted: 02/24/2005] [Indexed: 11/19/2022]
Abstract
UNLABELLED A non-comparative case observation study estimated the feasibility of brachytherapy for retinoblastoma with a newly designed ruthenium-106 plaque (label: CXS) with an 8-mm diameter of the irradiation zone. METHODS The new CXS plaque was used between 2001 and 2003 for brachytherapy of 13 retinoblastomas. Indications were recurrences after preceding local treatment or endophytic retinoblastoma with an impending vitreous tumour cell seeding. The prescribed radiation dose at the apex was 88 Gy (NIST-calibrated dosimetry). RESULTS The mean age at brachytherapy was 1.2 years (standard deviation, SD: 1.1 years), and the mean follow-up was 1.7 years (SD: 0.6 years). The treated tumours had a mean diameter of 2.3 mm (SD: 0.7 mm) and a mean height of 1.5 mm (SD: 0.6 mm) with a mean distance to the optic disc of 9.9 mm (SD: 2.2 mm). The mean duration of irradiation was 29.3 h (SD: 9.9 h) with a mean dose at the sclera of 213 Gy (SD: 80 Gy). Surgery was uneventful in all cases. Complete regression developed after 3.1 months (SD: 2.8 months) in all cases without a recurrence or a progression of the vitreous tumour cell seeding. The eyes developed no further side-effects besides a temporary circumscribed intra-ocular haemorrhage that emerged from the regressive tumour remnants. CONCLUSION Brachytherapy with the CXS plaque seems to be a safe and reliable treatment option for small-sized retinoblastoma when laser or cryocoagulation failed to control the tumour growth or for small retinoblastoma with an incipient local tumour cell seeding on the tumour surface.
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Kaulich TW, Zurheide J, Haug T, Nüsslin F, Bamberg M. Clinical quality assurance for 106Ru ophthalmic applicators. Radiother Oncol 2005; 76:86-92. [PMID: 15972240 DOI: 10.1016/j.radonc.2005.05.001] [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] [Received: 08/30/2004] [Revised: 04/17/2005] [Accepted: 05/09/2005] [Indexed: 11/25/2022]
Abstract
BACKGROUND AND PURPOSE Episcleral brachytherapy using 106Ru/106Rh ophthalmic applicators is a proven method of therapy of uveal melanomas sparing the globe and in many cases sparing the vision. In the year 2001, an internal clinical quality assurance procedure revealed that part of the ophthalmic applicators leaked and that the calibration was erroneous. Consequently, the producer modernized its production procedures and, in May 2002, introduced a dose rate calibration that is traceable to the NIST standard. This NIST calibration confirmed that the previous calibration had been incorrect. In order to study the effects of the producer's new internal quality assurance procedures on the ophthalmic applicators, applicators of this new generation were submitted to a newly improved internal clinical acceptance test. PATIENTS AND METHODS The internal clinical acceptance test consists of a leakage test and a dosimetric test of the ophthalmic applicators. The leakage test simulates contact of the ophthalmic applicators with chloride containing body fluid. The dosimetric tests measure depth dose curves and dose rate with a plastic scintillator dosimetric system and compare them with the indications in the producer's certificate. Furthermore, the depth dose profile of the most frequently used applicator (type CCB) was compared with published data. RESULTS The internal clinical leakage test showed that all of the tested ophthalmic applicators belonging to the new generation (n=17) were tight and not contaminated. The dosimetric acceptance tests applied to seven different types of applicators revealed that the relative depth dose profiles in the therapeutically relevant range (up to a depth of <or=7 mm) deviate from the producer's indications only by -2.7 to +3.2%. The acceptance test of the dose rate values of the ophthalmic applicators at a distance of 2mm from the surface of the applicators resulted in a coefficient of variation of 1.7% (n=17). In the evaluation of the depth dose profile of the type CCB applicator the producer's indications and the results of the entrance test conformed very well to published data. CONCLUSIONS The internal clinical quality assurance procedure has proved successful in three ways. (1) It had a catalytic effect that led to the development of a new generation of ophthalmic applicators. (2) It could be demonstrated that this new generation of applicators is up to the state of the art in brachytherapy. (3) With this new generation of 106Ru/106Rh ophthalmic applicators it is possible for the first time in the history of their use to apply the dose that is prescribed by the radiooncologist.
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Kovacević N, Vrtar M, Vekić B. A simple calibration method for 106Ru–106Rh eye applicators. Radiother Oncol 2005; 74:293-9. [PMID: 15763310 DOI: 10.1016/j.radonc.2004.12.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 10/25/2004] [Accepted: 12/10/2004] [Indexed: 10/26/2022]
Abstract
Ru-Rh eye applicators are used for the radiotherapy of eye malignancies such as melanomas. We present a method of dosimetry of these beta particle emitting applicators. Method is based on a Plexiglas phantom (constructed for this purpose) containing spherical shells and very small, 1x1x1mm3 thermoluminescent dosimeters (TLD) as dosimeters. We determined 3-D depth doses and interpolated depth dose functions. Surface dose rate inhomogeneities and the consequences were considered and discussed. A possible influence of photon component of the emission on the results was analysed. The method has overall combined uncertainty + or -6% which is comparable, and slightly better, than other recent dosimetric methods.
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Affiliation(s)
- Nenad Kovacević
- Clinic of Oncology, University Hospital Centre Rebro, Kispatićeva 12, 10000 Zagreb, Croatia
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Mourtada F, Horton JL. Dose perturbation of a novel cobalt chromium coronary stent on P32 intravascular brachytherapy: A Monte Carlo study. Med Phys 2005; 32:268-74. [PMID: 15719978 DOI: 10.1118/1.1833592] [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: 11/07/2022] Open
Abstract
Intravascular brachytherapy has been adopted for the indication of in-stent restenosis on the basis of results of clinical trials using mainly stainless steel stents. Recently, a new stent made of cobalt-chromium L-605 alloy (CoCr, p=9.22 g/cm3) (MULTI-LINK VISION) was introduced as an alternative to the 316L stainless steel stent design (SS, p=7.87 g/cm3) (MULTI-LINK PENTA). In this work, we used the Monte Carlo code MCNPX to compare the dose distribution for the 32P GALILEO source in CoCr and SS 8 mm stent models. The dose perturbation factor (DPF), defined as the ratio of the dose in water with the presence of a stent to the dose without a stent, was used to compare results. Both stent designs were virtually expanded to diameters of 2.0, 3.0, and 4.0 mm using finite element models. The complicated strut shapes of both the CoCr and SS stents were simplified using circular rings with an effective width to yield a metal-to-tissue ratio identical to that of the actual stents. The mean DPF at a 1 mm tissue depth, over the entire stented length of 8 mm, was 0.935 for the CoCr stent and 0.911 for the SS stent. The mean DPF at the intima (0.05 mm radial distance from the strut outer surface), over the entire stented length of 8 mm, was 0.950 for CoCr, and 0.926 for SS. The maximum DPFs directly behind the CoCr and SS struts were 0.689 and 0.644, respectively. All DPF estimates have a standard deviation of +/-0.6%(k=2), approximating the 95% confidence interval. Although the CoCr stent has a higher effective atomic number and greater density than the SS stent, the DPFs for the two stents are similar, probably because the metal-to-tissue ratio and strut thickness of the CoCr stent are lower than those of the SS stent.
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Affiliation(s)
- Firas Mourtada
- Department of Radiation Physics, The University of Texas M D Anderson Cancer Center, Houston, Texas 77030, USA.
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Yoriyaz H, Sanchez A, dos Santos A. A new human eye model for ophthalmic brachytherapy dosimetry. RADIATION PROTECTION DOSIMETRY 2005; 115:316-9. [PMID: 16381737 DOI: 10.1093/rpd/nci105] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The present work proposes a new mathematical eye model for ophthalmic brachytherapy dosimetry. This new model includes detailed description of internal structures that were not treated in previous works, allowing dose determination in different regions of the eye for a more adequate clinical analysis. Dose calculations were determined with the MCNP-4C Monte Carlo particle transport code running n parallel environment using PVM. The Amersham CKA4 ophthalmic applicator has been chosen and the depth dose distribution has been determined and compared to those provide by the manufacturer. The results have shown excellent agreement. Besides, absorbed dose values due to both 125I seeds and 60Co plaques were obtained for each one of the different structures which compose the eye model and can give relevant information in eventual clinical analyses.
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Affiliation(s)
- Hélio Yoriyaz
- Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, Av. Lineu Prestes, 2242, Cidade Universitária, P.O. Box 11049, 05508-000 São Paulo, Brazil.
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Mourtada F, Koch N, Newhauser W. 106Ru/106Rh plaque and proton radiotherapy for ocular melanoma: a comparative dosimetric study. RADIATION PROTECTION DOSIMETRY 2005; 116:454-60. [PMID: 16604677 DOI: 10.1093/rpd/nci266] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The objective of this study was to perform comparative dosimetric studies of both 106Ru/106Rh plaque brachytherapy and external beam proton therapy proposed for ocular treatments at the University of Texas M. D. Anderson Cancer Center, Houston, TX, USA. These modalities were also compared with traditional 125I plaque brachytherapy. Using a standardised eye model with a representative ocular melanoma tumour, the relative dose distributions within the tumour and surrounding tissue were calculated using the Monte Carlo code MCNPX. Published absorbed dose distributions benchmarked the Monte Carlo models. Results indicate that the proton beam provided superior dose uniformity within the tumour volume, whereas the dose distribution from 106Ru/106Rh was more heterogeneous. Relative to 125I COMS plaque, both 106Ru/106Rh and protons have shown more confined dose distributions to the tumour volume in this situation, thus sparing other critical ocular structures. For protons, it has been shown that only doses lower than the maximum dose are delivered outside the tumour volume. Depending on the clinical situation, this may aid in the sparing of critical structures located in the sclera and optic disc boundary. The Monte Carlo model's statistical uncertainties of the mean dose estimates for the 106Ru/106Rh plaque and proton beam were 3 and 2.5%, respectively.
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Affiliation(s)
- F Mourtada
- Radiation Physics Department, Box 94, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030, USA.
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Astrahan MA. A patch source model for treatment planning of ruthenium ophthalmic applicators. Med Phys 2003; 30:1219-28. [PMID: 12852546 DOI: 10.1118/1.1573971] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Beta-ray emitting Ru-106/Rh-106 ophthalmic applicators have been used for close to 4 decades in the treatment of choroidal melanoma. The form factor of these applicators is a spherically concave silver bowl with an inner radius of curvature between 12 and 14 mm, and a total shell thickness of 1 mm. The radioactive nuclide is deposited in a layer 0.1 mm below the concave surface of the applicator. Calculation of dose distributions for clinical treatment planning purposes is complicated by the concave nature of the distributed source, the asymmetric shape of the active region of some applicators, imperfections in the manufacturing process which can result in an inhomogeneous distribution of activity across the active surface, and absorption and scatter in the 0.1 mm layer of silver which seals and protects the radioactive layer. A semi-empirical method of calculating dose distributions for these applicators is described which is fundamentally compatible with treatment planning systems that use the AAPM TG43 brachytherapy formalism. Dose to water is estimated by summing a "patch source" dose function over a discrete number of overlapping patches uniformly distributed over the active surface of the applicator. The patch source dose function differs conceptually from a point source dose function in that it is intended to represent the macroscopic behavior of a small, disk-like region of the applicator. The patch source dose function includes an anisotropy term to account for angular variation in absorption and scatter as particles traverse the 0.1 mm silver window. It geometrically models the nearfield of a patch with properties akin to both a small disk and infinite plane, and models the farfield as if the patch were a point. This allows a manageable number of discrete patches (300 to 1000) to provide accuracy appropriate for clinical treatment planning. This approach has the advantages of using familiar concepts and data structures, it is computationally quick, and it readily adapts to asymmetric applicator shapes and inhomogeneities in the radionuclide distribution. A method for optimizing the patch source dose function parameters is presented, and the dosimetric calculations are compared with published Monte Carlo calculations and measurements.
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Affiliation(s)
- Melvin A Astrahan
- Department of Radiation Oncology, University of Southern California School of Medicine, Los Angeles, California 90033, USA.
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Schaart DR, Jansen JTM, Zoetelief J, de Leege PFA. A comparison of MCNP4C electron transport with ITS 3.0 and experiment at incident energies between 100 keV and 20 MeV: influence of voxel size, substeps and energy indexing algorithm. Phys Med Biol 2002; 47:1459-84. [PMID: 12043813 DOI: 10.1088/0031-9155/47/9/303] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The condensed-history electron transport algorithms in the Monte Carlo code MCNP4C are derived from ITS 3.0, which is a well-validated code for coupled electron-photon simulations. This, combined with its user-friendliness and versatility, makes MCNP4C a promising code for medical physics applications. Such applications, however, require a high degree of accuracy. In this work, MCNP4C electron depth-dose distributions in water are compared with published ITS 3.0 results. The influences of voxel size, substeps and choice of electron energy indexing algorithm are investigated at incident energies between 100 keV and 20 MeV. Furthermore, previously published dose measurements for seven beta emitters are simulated. Since MCNP4C does not allow tally segmentation with the *F8 energy deposition tally, even a homogeneous phantom must be subdivided in cells to calculate the distribution of dose. The repeated interruption of the electron tracks at the cell boundaries significantly affects the electron transport. An electron track length estimator of absorbed dose is described which allows tally segmentation. In combination with the ITS electron energy indexing algorithm, this estimator appears to reproduce ITS 3.0 and experimental results well. If, however, cell boundaries are used instead of segments, or if the MCNP indexing algorithm is applied, the agreement is considerably worse.
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Affiliation(s)
- Dennis R Schaart
- Interfaculty Reactor Institute, Delft University of Technology, The Netherlands.
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Reynaert N, Hafeli U. Response to Dr. Janicki's Letter to the Editor [Med. Phys. 29, 260 (2002)]. Med Phys 2002. [DOI: 10.1118/1.1446106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Soares CG, Vynckier S, Järvinen H, Cross WG, Sipilä P, Flühs D, Schaeken B, Mourtada FA, Bass GA, Williams TT. Dosimetry of beta-ray ophthalmic applicators: comparison of different measurement methods. Med Phys 2001; 28:1373-84. [PMID: 11488568 DOI: 10.1118/1.1376441] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
An international intercomparison of the dosimetry of three beta particle emitting ophthalmic applicators was performed, which involved measurements with radiochromic film, thermoluminescence dosimeters (TLDs), alanine pellets, plastic scintillators, extrapolation ionization chambers, a small fixed-volume ionization chambers, a diode detector and a diamond detector. The sources studied were planar applicators of 90Sr-90Y and 106Ru-106Rh, and a concave applicator of 106Ru-106Rh. Comparisons were made of absolute dosimetry determined at 1 mm from the source surface in water or water-equivalent plastic, and relative dosimetry along and perpendicular to the source axes. The results of the intercomparison indicate that the various methods yield consistent absolute dosimetry results at the level of 10%-14% (one standard deviation) depending on the source. For relative dosimetry along the source axis at depths of 5 mm or less, the agreement was 3%-9% (one standard deviation) depending on the source and the depth. Crucial to the proper interpretation of the measurement results is an accurate knowledge of the detector geometry, i.e., sensitive volume and amount of insensitive covering material. From the results of these measurements, functions which describe the relative dose rate along and perpendicular to the source axes are suggested.
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Affiliation(s)
- C G Soares
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
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