Verification of treatment planning algorithms using optically stimulated luminescent dosimeters in a breast phantom

Abstract

Aim:The aim of this study is to measure and compare the surface dose of treated breast and contralateral breast with the treatment planning system (TPS) calculated dose using calibrated optically stimulated luminescent dosimeter (OSLD) in an indigenous wax breast phantom.Materials and Methods:Three-dimensional conformal plans were generated in eclipse TPS v. 13 to treat the left breast of a wax phantom for a prescribed dose of 200 cGy. The plans were calculated using anisotropic analytical algorithm (AAA) and Acuros algorithm with 1-mm grid size. Calibrated OSLDs were used to measure the surface dose of treated and contralateral breasts.Results:Large differences were observed between measured and expected doses when OSLDs were read in “reading mode” compared to the “hardware mode.” The consistency in the responses of OSLDs was better (deviation <±5%) in the “hardware mode.” Reasonable agreement between TPS dose and measured dose was found in regions inside the treatment field of treated breast using OSLDs for both algorithms. OSLD measured doses and TPS doses, for the points where the angle of incidence was almost normal, were in good agreement compared to all other locations where the angle of incidence varied from 45° to 70°. The maximum deviation between measured doses and calculated doses with AAA and with Acuros were 2.2% and-12.38%, respectively, for planning target volume breast, and 76% and 77.51%, respectively, for the opposite breast.Conclusion:An independent calibration factor is required before using the OSLDs for in vivo dose measurements. With reference to measured doses using OSLD, the accuracy of skin dose estimation of TPS with AAA was better than with Acuros for both the breasts. In general, a reasonable agreement between TPS doses calculated using AAA and measured doses exists in regions inside treatment field, but unacceptable differences were observed for the points lateral to the opposite breast for both AAA and Acuros.

Comparison of skin doses of treated and contralateral breasts during whole breast radiotherapy for different treatment techniques using optically stimulated luminescent dosimeters

“…During the planning of whole breast radiotherapy, even if a wedge plan is the choice, a plan with an enhanced dynamic wedge (EDW) ought to be used as the dose to the peripheral regions is greatly reduced with the use of an EDW as reported by our study. 15…”

“…14 The procedure adopted for the calibration of nanoDot OSLDs used in our study is discussed elsewhere. 15 The 'hardware' mode and 'high dose' setting in the reader were selected for the readout of exposed OSLDs. The calibration factors (cGy/counts) were obtained as the ratio of reference dose delivered to the OSLDs to the net counts from the corresponding OSLDs.…”

Evaluation of DIBH and VMAT in Hypofractionated Radiotherapy for Left-Sided Breast Cancers After Breast-Conserving Surgery: A Planning Study

“…Dynamic wedge filters and/or the field in field technique were used to obtain a homogeneous dose distribution. 6,7 In 3DCRT, 42.4 Gy in 16 fractions of 2.65 Gy was prescribed to the isocenter. A VMAT plan used dual partial arcs of 40° to 50° with a collimator angle of 30° and treatment couch angle of 0°, rotating in opposite directions.…”