Monte Carlo dosimetry of the eye plaque design used at the St. Erik Eye Hospital for 125I brachytherapy

Karlsson, Mattias; Nilsson, Josef; Lundell, Marie; Tedgren, Åsa Carlsson

doi:10.1016/j.brachy.2014.05.018

Cited by 7 publications

(2 citation statements)

References 20 publications

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“…When using the TPS for calculation of dose, the stent and the medium around it are simulated as water, ignoring the structure inhomogeneities with only limited dose uncertainties. [25] The TPS in this study calculated the dose using point source simulations, which in fact agreed to be within about 2% with the full geometric simulations at all distances between 1 cm and 10 cm;[26] thus, within this practical range, TPS agrees very well with the TLD measurements and MCNPX. Therefore, the TPS utilized by us can be reliably used for clinical applications involving biliary stents.…”

Section: Discussionsupporting

confidence: 67%

In vitro Dosimetric Study of Biliary Stent Loaded with Radioactive 125I Seeds

Yao

Wang

Shang

et al. 2017

Chinese Medical Journal

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Background:A novel radioactive 125I seed-loaded biliary stent has been used for patients with malignant biliary obstruction. However, the dosimetric characteristics of the stents remain unclear. Therefore, we aimed to describe the dosimetry of the stents of different lengths — with different number as well as activities of 125I seeds.Methods:The radiation dosimetry of three representative radioactive stent models was evaluated using a treatment planning system (TPS), thermoluminescent dosimeter (TLD) measurements, and Monte Carlo (MC) simulations. In the process of TPS calculation and TLD measurement, two different water-equivalent phantoms were designed to obtain cumulative radial dose distribution. Calibration procedures using TLD in the designed phantom were also conducted. MC simulations were performed using the Monte Carlo N-Particle eXtended version 2.5 general purpose code to calculate the radioactive stent's three-dimensional dose rate distribution in liquid water. Analysis of covariance was used to examine the factors influencing radial dose distribution of the radioactive stent.Results:The maximum reduction in cumulative radial dose was 26% when the seed activity changed from 0.5 mCi to 0.4 mCi for the same length of radioactive stents. The TLD's dose response in the range of 0–10 mGy irradiation by 137Cs γ-ray was linear: y = 182225x − 6651.9 (R2= 0.99152; y is the irradiation dose in mGy, x is the TLDs’ reading in nC). When TLDs were irradiated by different energy radiation sources to a dose of 1 mGy, reading of TLDs was different. Doses at a distance of 0.1 cm from the three stents’ surface simulated by MC were 79, 93, and 97 Gy.Conclusions:TPS calculation, TLD measurement, and MC simulation were performed and were found to be in good agreement. Although the whole experiment was conducted in water-equivalent phantom, data in our evaluation may provide a theoretical basis for dosimetry for the clinical application.

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Section: Discussionsupporting

confidence: 67%

In vitro Dosimetric Study of Biliary Stent Loaded with Radioactive 125I Seeds

Yao

Wang

Shang

et al. 2017

Chinese Medical Journal

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“…It offers equivalent tumor control and better quality of life such as eye preservation and vision retention in comparison to enucleation [ 3 – 5 ]. Various plaque designs were proposed and are clinically used in major institutions [ 6 – 8 ]. Nonetheless, Collaborative Ocular Melanoma Study (COMS) plaques have been widely used in most clinics since the COMS established standardized methods of plaque brachytherapy for medium-sized choroidal melanomas [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

A practical approach to estimating optic disc dose and macula dose without treatment planning in ocular brachytherapy using 125I COMS plaques

2018

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BackgroundIt has been reported that proximity of the tumor to the optic disc and macula, and radiation dose to the critical structures are substantial risk factors for vision loss following plaque brachytherapy. However, there is little dosimetry data published on this. In this study, therefore, the relationship between distance from tumor margin and radiation dose to the optic disc and macula in ocular brachytherapy using 125I Collaborative Ocular Melanoma Study (COMS) plaques was comprehensively investigated. From the information, this study aimed to allow for estimation of optic disc dose and macula dose without treatment planning.MethodsAn in-house brachytherapy dose calculation program utilizing the American Association of Physicists in Medicine Task Group-43 U1 formalism with a line source approximation in a homogenous water phantom was developed and validated against three commercial treatment planning systems (TPS). Then optic disc dose and macula dose were calculated as a function of distance from tumor margin for various tumor basal dimensions for seven COMS plaques (from 10 mm to 22 mm in 2 mm increments) loaded with commercially available 125I seeds models (IAI-125A, 2301 and I25.S16). A prescribed dose of 85 Gy for an irradiation time of 168 h was normalized to a central-axis depth of 5 mm. Dose conversion factors for each seed model were obtained by taking ratios of total reference air kerma per seed at various prescription depths (from 1 mm to 10 mm in 1 mm intervals) to that at 5 mm.ResultsThe in-house program demonstrated relatively similar accuracy to commercial TPS. Optic disc dose and macula dose decreased as distance from tumor margin and tumor basal dimension increased. Dose conversion factors increased with increasing prescription depth. There existed dose variations (<8%) among three 125I seed models. Optic disc dose and macula dose for each COMS plaque and for each seed model are presented in a figure format. Dose conversion factors for each seed model are presented in a tabular format.ConclusionsThe data provided in this study would enable clinicians in any clinic using 125I COMS plaques to estimate optic disc dose and macula dose without dose calculations.Electronic supplementary materialThe online version of this article (10.1186/s13014-018-1166-z) contains supplementary material, which is available to authorized users.

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AAPM recommendations on medical physics practices for ocular plaque brachytherapy: Report of task group 221

et al. 2020

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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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Monte Carlo dosimetry of the eye plaque design used at the St. Erik Eye Hospital for 125I brachytherapy

Cited by 7 publications

References 20 publications

In vitro Dosimetric Study of Biliary Stent Loaded with Radioactive 125I Seeds

In vitro Dosimetric Study of Biliary Stent Loaded with Radioactive 125I Seeds

A practical approach to estimating optic disc dose and macula dose without treatment planning in ocular brachytherapy using 125I COMS plaques

AAPM recommendations on medical physics practices for ocular plaque brachytherapy: Report of task group 221

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