Evaluation of Scatter Contribution and Distance Error by Iterative Methods for Strength Determination of HDR 192Ir Brachytherapy Source

Srinivasan, P.; Sharma, Sunil Dutt; Subbaiah, K.V.; Mayya, Y. S.

doi:10.1016/j.meddos.2009.06.008

Cited by 2 publications

(5 citation statements)

References 17 publications

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“…The jig was placed at the centre of the room at least 1 m above the floor and at 1 m distance from any of the walls. The chamber with the build-up cap was fixed at one end of the jig while the applicator needle was moved to different distances (10,15,20,25,30,35 and 40 cm) from the chamber. Initially, electrometer readings were noted by moving the source to various dwell positions (step size of 2.5 mm) vertically along the applicator to determine the dwell position showing maximum response.…”

Section: Methodsmentioning

confidence: 99%

“…The in-air measurement of source strength using cylindrical ionization chamber requires the determination of scatter radiation from walls and floor of the room and also the offset in positioning of the chamber. Few studies [4][5][6][7][8][9][10] have been reported for determining the room scatter contribution from an 192 Ir HDR brachytherapy source. Goestch et al [4] described a method for calibrating 192 Ir HDR brachytherapy afterloading systems.…”

Section: Introductionmentioning

confidence: 99%

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Determination of contributions of scatter and distance error to the source strength of ¹⁹²Ir HDR brachytherapy source

Shwetha

Ravikumar

2016

Polish Journal of Medical Physics and Engineering

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High dose rate (HDR) brachytherapy commonly employs a 192 Ir encapsulated source to deliver high dose to the malignant tissues. Calibrations of brachytherapy sources are performed by the manufacturer using a well-type chamber or by in-air measurement using a cylindrical ionization chamber. Calibration using the latter involves measurements to be carried out at several distances and room scatter can also be determined. The aim of the present study is to estimate the scatter contribution from the walls, floor and various materials in the room in order to determine the reference air kerma rate of an 192 Ir HDR brachytherapy source by in-air measurements and also to evaluate the error in the setup distance between the source centre and chamber centre. Air kerma measurements were performed at multiple distances from 10 cm to 40 cm between the source and chamber. The room scatter correction factor was determined using the iterative technique. The distance error of -0.094 cm and -0.112 cm was observed for chamber with and without buildup cap respectively. The scatter component ranges from 0.3% to 5.4% for the chamber with buildup cap and 0.3% to 4.6% without buildup cap for distances between 10 to 40 cm respectively. Since the average of the results at multiple distances is considered to obtain the actual air kerma rate of the HDR source, the seven distance method and iterative technique are very effective in determining the scatter contribution and the error in the distance measurements.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Determination of contributions of scatter and distance error to the source strength of ¹⁹²Ir HDR brachytherapy source

Shwetha

Ravikumar

2016

Polish Journal of Medical Physics and Engineering

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“…The 7DM was suggested to determine these parameters and thereafter the strength of HDR 192 Ir brachytherapy sources. [891516] Although Kumar et al .,[2122] has described in detail the procedure for measuring the RAKR of HDR 192 Ir brachytherapy sources, a brief review of the method is given below for the sake of completeness in description.…”

Section: Methodsmentioning

confidence: 99%

“…On solving Equation 2, one may obtain the following functional form for relative distance l i between the successive measurement points (i = 1, 2,…, 6)[22]…”

Section: Methodsmentioning

confidence: 99%

“…Earlier, we have developed the analytical methods to estimate the distance error required to determine the source strength using 7 distance method by cylindrical ionization chamber. [2122] As further research in this work, an attempt has been made to apply the fuzzy set theory to estimate the subjective uncertainty associated with the distance error, which is the subject matter of this paper.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of distance error by fuzzy set theory required for strength determination of HDR ¹⁹² Ir brachytherapy sources

Datta¹,

Sharma²,

Chourasiya³

et al. 2014

J Med Phys

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Verification of the strength of high dose rate (HDR) 192Ir brachytherapy sources on receipt from the vendor is an important component of institutional quality assurance program. Either reference air-kerma rate (RAKR) or air-kerma strength (AKS) is the recommended quantity to specify the strength of gamma-emitting brachytherapy sources. The use of Farmer-type cylindrical ionization chamber of sensitive volume 0.6 cm3 is one of the recommended methods for measuring RAKR of HDR 192Ir brachytherapy sources. While using the cylindrical chamber method, it is required to determine the positioning error of the ionization chamber with respect to the source which is called the distance error. An attempt has been made to apply the fuzzy set theory to estimate the subjective uncertainty associated with the distance error. A simplified approach of applying this fuzzy set theory has been proposed in the quantification of uncertainty associated with the distance error. In order to express the uncertainty in the framework of fuzzy sets, the uncertainty index was estimated and was found to be within 2.5%, which further indicates that the possibility of error in measuring such distance may be of this order. It is observed that the relative distance li estimated by analytical method and fuzzy set theoretic approach are consistent with each other. The crisp values of li estimated using analytical method lie within the bounds computed using fuzzy set theory. This indicates that li values estimated using analytical methods are within 2.5% uncertainty. This value of uncertainty in distance measurement should be incorporated in the uncertainty budget, while estimating the expanded uncertainty in HDR 192Ir source strength measurement.

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Evaluation of Scatter Contribution and Distance Error by Iterative Methods for Strength Determination of HDR 192Ir Brachytherapy Source

Cited by 2 publications

References 17 publications

Determination of contributions of scatter and distance error to the source strength of ¹⁹²Ir HDR brachytherapy source

Determination of contributions of scatter and distance error to the source strength of ¹⁹²Ir HDR brachytherapy source

Estimation of distance error by fuzzy set theory required for strength determination of HDR ¹⁹² Ir brachytherapy sources

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Evaluation of Scatter Contribution and Distance Error by Iterative Methods for Strength Determination of HDR 192Ir Brachytherapy Source

Cited by 2 publications

References 17 publications

Determination of contributions of scatter and distance error to the source strength of 192Ir HDR brachytherapy source

Determination of contributions of scatter and distance error to the source strength of 192Ir HDR brachytherapy source

Estimation of distance error by fuzzy set theory required for strength determination of HDR 192 Ir brachytherapy sources

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Determination of contributions of scatter and distance error to the source strength of ¹⁹²Ir HDR brachytherapy source

Determination of contributions of scatter and distance error to the source strength of ¹⁹²Ir HDR brachytherapy source

Estimation of distance error by fuzzy set theory required for strength determination of HDR ¹⁹² Ir brachytherapy sources