Assessment of the Effect of Breast Size on Dose Distribution for 3D and Conventional Methods with TLD Dosimetry in Breast Phantoms

The complex geometry of breast tissue, variable shape, size of breasts,their lack of homogeneity and other organs at risk like the heart and lungs makedose distribution difficult, especially for cases involving large breasts. Assessmentof breast dosimetry includes homogeneity dose distribution with complete targetcoverage and the avoidance of organs at risk as much as possible. The aim of thisstudy is to assess dose distribution and coverage of the target by TLD dosimeterin slab breast phantoms. This study used a slab anatomical phantom with lung inhomogenity fortwo different breast sizes, large and small. Exposure was done with 6 MV, utilizedPTW reader, oven LTM to annulling Conventional methods were carried out witha hand generated contour, 3D treatment planning used RT Dose Plan software. There were areas with lower than 95 percent reference dose in 3D methodsdecreased in compare of conventional methods. This result for large breastswas remarkable. Received area of target for both size more than 105 percent referencedose reduce to some extent, therefore getting more homogeneity also bettercoverage for target volume for large breast. This study has shown that conventional methods are not suitable toassessment of dose distribution and coverage in target volume, especially for largebreast. Also there was not sufficient dose distribution for small breast a as result ofthe 3D method, and so can it be useful for crowded hospitals with restricted facilitycenters because they