a comparison of dose distribution parameters between conventional and mono isocentric methods of breast irradiation in phantom by gafchromic ebt2 films

background : this study was set to determine the optimal technique of breast cancer with supraclavicular fossa irradiation. methods : three techniques was compared in this study. techniques were two point symmetric (2p-sym), two point asymmetric (2p-asym) and single point (sp). in 2p-sym all of beams were symmetric, in 2p-asym tangential beams were symmetric and supra was asymmetric, in sp all of beams were asymmetric. this study performed in 2 parts. in one part three techniques were compared in thirty patients and in second part was done dosimetry by gafchromic film in phantom. techniques were analyzed by dvhs treatment’s volumes and organ at risk (oar) volumes. result : there are no notable differences between dose distributions in three techniques but hot spot in the junction of treatment’s beams in single point (sp) technique was 115% and 118% for other techniques. the analysis of dvhs showed a decrease in oar’s doses with sp technique. there was a significant difference of v20%, v20, v30 for lungs and v10, v40 for heart in sp technique compared to other techniques. the profiles of dose that obtained from films showed a gap in matchline, while matchline’s dose distribution in software was right and there was no gap. conclusion : observed gap in gafchromic films was created because of mechanical limitations in accelerators. correction methods for this limitation was offered in articles. sp technique is optimal technique compared to other techniques if correction methods are done. it seems that iranian radiotherapy clinics don't pay attention to this correction methods.