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Dosimetric Verification of the Enhanced Dynamic Wedges Using a 2D Ion Chamber Array


S Kim

S.A. Oh, S.K. Kim*, M.K. Kang, J.W. Yea, Yeungnam University Medical Center, Daegu, korea

SU-E-T-357 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
Wedge filters are commonly used to achieve dose uniformity in the target volume in radiotherapy and can be categorized as the physical wedge (PW) and the enhanced dynamic wedge (EDW. The EDW generates PW-like dose profiles while moving the upper jaw in the Y directions with a varying dose rate in the treatment beams. Task Group 53 of the AAPM (American Association of Physicists in Medicine) recommended that the dynamic wedge should be verified before implementation in the radiation treatment planning (RTP) system in order to ensure the same capabilities between the PW and the dynamic wedge. The aim of this study was to verify the dose profiles of the EDWs manufactured by Varian with the ImRT MatriXX.

Methods:
The ImRT MatriXX was used to compare the dose distributions between PW and EDW with wedge angles of 15°, 30°, 45° and 60° in the axial plane. The passing criteria of DD and the DTA were selected as 1%/1mm, 2%/2mm and 3%/3mm. The gamma evaluations were performed with the calculated and measured dose distributions for the varied wedge angle in EDW.

Results:
The gamma index of the calculations and the measurements for the EDWs were 84.84% and 86.54% in 2%/2mm tolerance, and 99.47% and 99.64% in 3%/3mm tolerance for the wedge angles of 15°, 30°, 45° and 60°, respectively. The dose distributions differed between the treatment planning system (TPS) calculations and the measurements in the penumbra and the outer beam regions of the wedge fields.

Conclusion:
We confirmed that the dosimetric verifications of the EDW were acceptable with an acceptability criterion for external beam dose calculations of Task Group 53.

Funding Support, Disclosures, and Conflict of Interest: This work has supported by the Yeungnam University Academic Research Fund (212A380146).

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