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KMID : 1164220080200010037
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Journal of Korean Society for Radiotherapeutic Technology
2008 Volume.20 No. 1 p.37 ~ p.43
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A Dosimetric Evaluation of Large Pendulous Breast Irradiation in Prone Position
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Hong Chae-Seon
Ju Sang-Gyu
Park Ju-Young
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Abstract
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Purpose: To evaluate dosimetry results of three different techniques for whole breast irradiation after conservative
surgery of large pendulous breast patient.
Materials and Methods: Planning computed tomography (CT) scans for three techniques were performed on a GE Hi-speed advantage CT scanner in the supine (SP), supine with breast supporting Device (SD) and prone position
on a custom prone mattress (PP). Computed tomography images were acquired at 5 mm thickness. The clinical target volumes (CTV), ipsilateral lung and heart were delineated to evaluate the dose statistic, and all techniques were planned with the tangential photon beams (Pinnacle3, Philips Medical System, USA). The prescribed dose was 50 Gy delivered in 25 fractions. To evaluate the dose coverage for CTV, we analysed percent volume of CTV receiving minimum of 95%, 100%, 105%, and 110% of prescription dose (V95, V100, V105, and V110) and minimal dose covering 95% (D95) of CTV. The dosimetric comparison for heart and ipsilateral lung was analysed using the minimal dose covering 5% of each organs (D5) and the volume that received ＞18 Gy for the heart and ＞20 Gy for the ipsilateral lung.
Results: Target volume coverage (V95 and V100) was not significantly different for all technique. The V105 was lower for PP (1.2% vs. 4.4% for SP, 11.1% for SD). Minimal dose covering 95% (D95) of target was 47.5 Gy, 47.7 Gy and 48 Gy for SP, SD and PP. The volume of ipsilateral lung received ＞20 Gy was 21.7%, 11.6% and 4.9% for SP, SD and PP. The volume of heart received ＞18 Gy was 17.0%, 16.1% and 9.8% for SP, SD and PP.
Conclusion: Prone positioning of patient for large pendulous breast irradiation enables improving dose uniformity
with minimal heart and lung doses.
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KEYWORD
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large pendulous breast, prone position
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