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KMID : 0364920140390040168
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Journal of Radiation Protection and Research
2014 Volume.39 No. 4 p.168 ~ p.175
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USEFULNESS OF SIMPLE SHIELDING TECHNIQUE USING MULTILEAF COLLIMATOR IN BREAST RADIATION THERAPY
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Lee Kyu-Chan
Lee Seok-Ho
Lee Seung-Heon
Sung Ki-Hoon
Ahn So-Hyun
Choi Jin-Ho
Dong Sang-Kap
Kim Jin-Hyo
Chun Yong-Seon
Park Heung-Kyu
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Abstract
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This study was designed to assess whether the conventional tangential technique, using a multileaf collimator (MLC), allows a reduced dose to the organs at risk (OAR) in breast radiation therapy. A total of forty right and left 20 for each breast cancer patients that underwent radiation therapy after breast conserving surgery were included in this study. For each patient, the planning target volume (PTV) and OAR (heart, left anterior descending artery (LAD), liver and lung) were defined and dose distribution were produced for conventional tangential beams using 6 MV photons. The treatment plans were made using the following two techniques for all patients. For the first plan (P1), MLC was designed to shield as much of OAR as possible without compromising the coverage of PTV. In the second plan (P2), the treatment plan was created without using MLC. Dose-volume histograms for OARs were calculated for all plans. For left breast cancer, the percentage of maximum dose (Dmax%) and mean dose (Dmean%) of OARs (heart and LAD) were calculated, and for right breast cancer, the percentage of the mean dose (Dmean%) of the liver was calculated. The Dmean% of the lung was calculated in all patients. The mean values of Dmax% of the heart (86.9±19.5% range, 35.1-100.6%) in P1 were significantly lower than in P2 (98.3±3.4% range, 91.7-105.2%) (p=0.001). The mean values of Dmax% of LAD (78.4±22.5% range, 26.5-99.7%) in P1 was significantly lower than in P2 (93.3±8.1% range, 67.9-102.1%) (p<0.001). In P1, the mean values of Dmean% of the liver (4.8±2.0%) were significantly lower than in P2 (6.2±2.5%) (p<0.001). The mean values of Dmean% of the lung were significantly lower in P1 (9.3±2.3%) than in P2 (9.7±2.4%) (p<0.001). P1, by using MLC, allows a significantly reduced dose to OAR compared with P2. We can suggest that it is reasonable to routinely use MLC in the conventional tangential technique for breast radiation therapy considering the primary tumor location.
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KEYWORD
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Breast cancer, Multileaf collimator, Organs at risk
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