A comparison of dose distribution parameters between conventional and mono isocentric methods of breast irradiation in phantom by gafchromic EBT2 films

This study was set to determine the optimal technique of breast cancerwith supraclavicular fossa irradiation. Three techniques were compared in this study. Techniques were two pointsymmetric (2p-sym), two point asymmetric (2p-asym) and single point (SP). In 2p-symall of beams were symmetric, in 2p-asym Tangential and supraclavicular beams respectivelywere symmetric and asymmetric, in SP all of beams were asymmetric. In this studyhas been done dosimetry by gafchromic films in phantom with compact accelerator. Techniqueswere analyzed by DVHs treatment’s volumes and organ at risk (OAR) volumes. There are no notable differences between dose distributions in three techniquesbut 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 doseswith SP technique. There was a significant difference of V20%, V20, V30 for lungs andV10, V40 for heart in SP technique compared to other techniques. The profiles of dosethat obtained from films showed a gap in matchline, while matchline’s dose distributionin software was right and there was no gap. Observed gap in gafchromic films was created because of mechanical limitationsin accelerators. Correction methods for this limitation were offered in many articles. SP technique is optimal technique compared to other techniques if correctionmethods are done. It seems that Iranian radiotherapy clinics don’t pay attention tothis correction methods.