Optimizing of the Tangential Technique and Supraclavicular Fields in 3 Dimensional Conformal Radiation Therapy for Breast Cancer

Radiotherapy plays an essential role in the management of breast cancer. three-dimensional conformal radiation therapy (3d-crt)is applied based on 3d image information of anatomy of patients. in 3d-crt for breast cancer one of the common techniques istangential technique. in this project, various parameters of tangential and supraclavicular fields are optimized. this project has beendone on computed tomography images of 100 patients in isfahan milad hospital. all patients have been simulated and all the importantorgans have been contoured by radiation oncologist. two techniques in supraclavicular region are evaluated including: 1-a singlefield (anterior posterior [ap]) with a dose of 200 cgy per fraction with 6 mv energy. this is a common technique. 2?two parallel opposedfields (ap?posterior anterior [pa]). the dose of ap was 150 cgy with 6 mv energy and pa 50 cgy with 18 mv. in the second part of theproject, the tangential fields has been optimized with change of normalization point in five points: (1) isocenter (confluence of rotationgantry axis and collimator axis) (2) middle of thickest part of breast or middle of inter field distance (ifd) (3) border between the lungand chest wall (4) physician’s choice (5) between ifd and isocenter. dose distributions have been compared for all patients in differentmethods of supraclavicular and tangential field. in parallel opposed fields average lung dose was 4% more than a single field and themaximum received heart dose was 21.5% less than a single field. the average dose of planning tumor volume (ptv) in method 2 is 2%more than method 1. in general ap?pa method because of a better coverage of ptv is suggested. in optimization of the tangential fieldall methods have similar coverage of ptv. each method has spatial advantages and disadvantages. if it is important for the physician toreduce the dose received by the lung and heart, fifth method is suggested since in this method average and maximum received dose toheart and lung have been reduced few percent in comparison to other methods. if a better coverage of ptv is important for the physiciansecond method can be an optimized method. in this method, average and maximum received dose to ptv have been increased fewpercent in comparisons of physician’s choice method and three other methods. in optimizing of supraclavicular field ap?pa method dueto better coverage of ptv is suggested. in optimizing of tangential all methods are similar. each method has special advantages anddisadvantages. the physicians can change the depth of the normalization point in the breast to get the desired average dose.