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KMID : 1164220120240020183
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Journal of Korean Society for Radiotherapeutic Technology
2012 Volume.24 No. 2 p.183 ~ p.188
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Evaluation of Scattered Dose to the Contralateral Breast by Separating Effect of Medial Tangential Field and Lateral Tangential Field: A Comparison of Common Primary Breast Irradiation Techniques
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Ban Tae-Joon
Jeon Soo-Dong
Kwak Jung-Won
Back Geum-Mun
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Abstract
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Purpose: The concern of improving the quality of life and reducing side effects related to cancer treatment has been a subject of interest in recent years with advances in cancer treatment techniques and increasing survival time. This study is an analysis of differing scattered dose to the contralateral breast using common different treatment techniques.
Materials and Methods: Eclipse 10.0 (Varian, USA) based 30o EDW (Enhanced dynamic wedge) plan, 15o wedge plan, 30o wedge plan, Open beam plan, FiF (field in field) plan were established using CT image of breast phantom which in our hospital. Each treatment plan were designed to exposure 400 cGy using CL-6EX (VARIAN, USA) and we measured scattered dose at 1 cm, 3 cm, 5 cm, 9 cm away from medial side of the phantom at 1 cm depth using ionization chamber (FC 65G, IBA). We carried out measurement by separating effect of medial tangential field and lateral tangential field and analyze.
Results: The evaluation of scattered dose to contralateral breast, 30o EDW plan, 15o wedge plan, 30o wedge plan, Open beam plan, FIF plan showed 6.55%, 4.72%, 2.79%, 2.33%, 1.87% about prescription dose of each treatment plan. The result of scattered dose measurement by separating effect of medial tangential field and lateral tangential field results were 4.94%, 3.33%, 1.55%, 1.17%, 0.77% about prescription dose at medial tangential field and 1.61%, 1.40%, 1.24%, 1.16%, 1.10% at lateral tangential field along with measured distance.
Conclusion: In our experiment, FiF treatment technique generates minimum of scattered dose to contralateral breast which come from mainly phantom scatter factor. Whereas 30o wedge plan generates maximum of scattered doses to contralateral breast and 3.3% of them was scattered from gantry head. The description of treatment planning system showed a loss of precision for a relatively low scatter dose region. Scattered dose out of Treatment radiation field is relatively lower than prescription dose but, in decision of radiation therapy, it cannot be ignored that doses to contralateral breast are related with probability of secondary cancer.
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KEYWORD
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breast cancer, tangential field, contralateral breast dose, scatter dose, Sc factor, Sp factor
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