Page 47 - Fisica In Medicina n° 1/2017

As regards the diode-diamond OFs comparison, corrected diode OFs curves show a very good agreement with the diamond ones (Δmax<2%, except for the 5 mm cone at SAD = 650 mm,^Äëíê~Åí=cáëáÅá= =Fixed OFsSAD = 800 mm5mm7,5 mm10 mm12,5 mm15 mmPTW 60017 raw0,6930,8490,8920,9250,945PTW 60017 corrected0,6620,8230,8750,9150,940PTW 600190,6550,8340,8820,9200,942deviation PTW 60017/PTW 60019 (%)1,046-1,226-0,816-0,494-0,278IRIS OFsSAD = 800 mm5mm7,5 mm10 mm12,5 mm15 mmPTW 60017 raw0,5070,8090,8870,9200,940PTW 60017 corrected0,4870,7860,8700,9120,936PTW 600190,4920,7860,8790,9170,940deviation PTW 60017/PTW 60019 (%)-0,964-0,084-1,102-0,545-0,410Table 1. OFs comparisonwhich exhibits Δ=3.78%). The comparisonbetween treatment plans calculated with thesame beams number, directions, weights, and monitor units, shows a slight dose underestimation when raw OFs were adopted. In particular a deviation within 1.15% is registered in accordance with MC correction factors values.ConclusionThe application of MC correction factors allowed to obtain corrected diode OFs values improving the dosimetric accuracy level in very small fields dosimetry with consequent clinical implications. This consideration is confirmed by the very low deviations between corrected diode and diamond OFs values. Thus the diamond seems to be particularly suitable for OFs measures in small field dosimetry confirming this as free correction detector.38