Experimental determination of the TG‐43 dosimetric characteristics of EchoSeed™ model 6733  brachytherapy source

Meigooni, Ali S.; Dini, Sharifeh A.; Sowards, Keith; Hayes, Joshua L.; Al-Otoom, Awni

doi:10.1118/1.1470210

Cited by 14 publications

(39 citation statements)

References 16 publications

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“…There are two published papers for this model; one dealing with Monte Carlo determination by Sowards and Meigooni,15 and the other by Meigooni et al dealing with experimental dose determinations using TLDs. 16 Both of these papers report values for all the TG-43 parameters. The Monte Carlo calculations were performed both in SolidWa-ter™ ͑model 457 by Radiation Measurements Inc., of Middletown, WI͒ and in liquid water, and used the PTRAN version 7.43 Monte Carlo code.…”

Section: A Amersham Model 6733 125 I Sourcementioning

confidence: 99%

Supplement to the 2004 update of the AAPM Task Group No. 43 Report

et al. 2007

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Since publication of the 2004 update to the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report (TG-43U1), several new low-energy photon-emitting brachytherapy sources have become available. Many of these sources have satisfied the AAPM prerequisites for routine clinical use as of January 10, 2005, and are posted on the Joint AAPM/RPC Brachytherapy Seed Registry. Consequently, the AAPM has prepared this supplement to the 2004 AAPM TG-43 update. This paper presents the AAPM-approved consensus datasets for these sources, and includes the following 125I sources: Amersham model 6733, Draximage model LS-1, Implant Sciences model 3500, IBt model 1251L, IsoAid model IAI-125A, Mentor model SL-125/ SH-125, and SourceTech Medical model STM1251. The Best Medical model 2335 103Pd source is also included. While the methodology used to determine these data sets is identical to that published in the AAPM TG-43U1 report, additional information and discussion are presented here on some questions that arose since the publication of the TG-43U1 report. Specifically, details of interpolation and extrapolation methods are described further, new methodologies are recommended, and example calculations are provided. Despite these changes, additions, and clarifications, the overall methodology, the procedures for developing consensus data sets, and the dose calculation formalism largely remain the same as in the TG-43U1 report. Thus, the AAPM recommends that the consensus data sets and resultant source-specific dose-rate distributions included in this supplement be adopted by all end users for clinical treatment planning of low-energy photon-emitting brachytherapy sources. Adoption of these recommendations may result in changes to patient dose calculations, and these changes should be carefully evaluated and reviewed with the radiation oncologist prior to implementation of the current protocol.

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Section: A Amersham Model 6733 125 I Sourcementioning

confidence: 99%

Supplement to the 2004 update of the AAPM Task Group No. 43 Report

et al. 2007

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“…1͑b͔͒, introduced recently by the same manufacturer, is nearly identical to the Model 6711 source except that the titanium capsule is made with six circular grooves as opposed to a smooth surface in an effort to increase its visibility in ultrasound imaging. 23 Similar to the Model 6711 source, the Model IAI-125A Advantage source ͓Fig. 1͑c͒ manufactured by IsoAid LLC, Port Richey, FL͔ also contains a 3.0 mm long and 0.5 mm diameter silver rod as radioactivity carrier and radiographic marker.…”

Section: Iia 125 I Radioactive Sources Containing Silvermentioning

confidence: 99%

Silver fluorescent x‐ray yield and its influence on the dose rate constant for nine low‐energy brachytherapy source models

Nath¹,

Chen²

2007

Medical Physics

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The physical characteristics of the photons emitted by a low-energy brachytherapy source are strongly dependent on the source's construction. Aside from absorption and scattering caused by the internal structures and the source encapsulation, the photoelectric interactions occurred in certain type of source-construction materials can generate additional energetic characteristic x rays with energies different from those emitted by the bare radionuclide. As a result, the same radionuclide encapsulated in different source models can result in dose rate constants and other dosimetric parameters that are strikingly different from each other. The aim of this work was to perform a systematic study on the yield of silver fluorescent x rays produced in nine 125I sources that are known to contain silver and its impact on the dose-rate constant. Using a high-resolution germanium spectrometer, the relative 125I spectra emitted by the nine sources on its bisector were measured and found to be similar to each other (the maximum variation in the 125I-Kbeta relative intensity was less than 4%). On the other hand, the measured silver fluorescent x-ray spectra exhibited much greater variations from model to model; the maximum change in the measured Ag-Kalpha relative intensity was over 95%. This larger variation in the measured silver fluorescent x-ray yield was caused by (1) the different amount of silver that was directly exposed to the 125I radionuclide in different source models and (2) the stronger influence of the source's internal geometry on the silver fluorescent x rays. Because the addition of silver fluorescent x rays can significantly alter the photon characteristics emitted by the radioactive sources, a precise knowledge on the silver fluorescent x-ray yield is needed in theoretical calculations of the sources' intrinsic dosimetric properties. This study concludes that the differences in silver fluorescent yield are the primary causes of the variable dose rate constant observed among these source models.

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“…In recent years there have been an increasing number of studies written in relation to this topic. These are based on experimental measurements ͑mainly TLD͒ [3][4][5] or Monte Carlo ͑MC͒ 6-15 methods, which combine the advantages of both methodologies to solve the problems faced in BT dosimetry due to the high dose gradient. It has been well established that, the weak points in experimental BT dosimetry are caused by positioning errors at small distances from the source and the signal-to-noise ratio of the detectors at large distances.…”

Section: Introductionmentioning

confidence: 99%

“…The question is as follows: what is the optimum phantom diameter to be used in MC calculations or experimental measurements, in order to establish the reference dose rate distributions on photon BT source dosimetry studies used as input and benchmark data in computerized TPS for clinical dosimetry? Presently, there are recommended dataset with available limited phantom size ͑for example the data included in the TG43 Report 1 for the steel-clad 192 Ir seed͒ and most published MC dosimetry studies have been obtained using a spherical phantom with a radius of 15 cm [3][4][5][6][7][8]14,15 or a cylinder phantom of 40 cm ϫ40 cm. [9][10][11][12][13] The TG43U1 Report recommends that MC primary dosimetry calculations should be performed in a 30 cm diameter liquid water in order to produce dosimetry results extending out to rϷ10 cm for I-125 and Pd-103 dosimetry calculations.…”

Section: Introductionmentioning

confidence: 99%

Phantom size in brachytherapy source dosimetric studies

2004

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An important point to consider in a brachytherapy dosimetry study is the phantom size involved in calculations or experimental measurements. As pointed out by Williamson [Med. Phys. 18, 776-786 (1991)] this topic has a relevant influence on final dosimetric results. Presently, one-dimensional (1-D) algorithms and newly-developed 3-D correction algorithms are based on physics data that are obtained under full scatter conditions, i.e., assumed infinite phantom size. One can then assume that reference dose distributions in source dosimetry for photon brachytherapy should use an unbounded phantom size rather than phantom-like dimensions. Our aim in this paper is to study the effect of phantom size on brachytherapy for radionuclide 137Cs, 192Ir, 125I and 103Pd, mainly used for clinical purposes. Using the GEANT4 Monte Carlo code, we can ascertain effects on derived dosimetry parameters and functions to establish a distance dependent difference due to the absence of full scatter conditions. We have found that for 137Cs and 192Ir, a spherical phantom with a 40 cm radius is the equivalent of an unbounded phantom up to a distance of 20 cm from the source, as this size ensures full scatter conditions at this distance. For 125I and 103Pd, the required radius for the spherical phantom in order to ensure full scatter conditions at 10 cm from the source is R = 15 cm. A simple expression based on fits of the dose distributions for various phantom sizes has been developed for 137Cs and 192Ir in order to compare the dose rate distributions published for different phantom sizes. Using these relations it is possible to obtain radial dose functions for unbounded medium from bounded phantom ones.

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Experimental determination of the TG‐43 dosimetric characteristics of EchoSeed™ model 6733 brachytherapy source

Cited by 14 publications

References 16 publications

Supplement to the 2004 update of the AAPM Task Group No. 43 Report

Supplement to the 2004 update of the AAPM Task Group No. 43 Report

Silver fluorescent x‐ray yield and its influence on the dose rate constant for nine low‐energy brachytherapy source models

Phantom size in brachytherapy source dosimetric studies

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