Sandra Hopkins Final Report.pdf - University of Surrey

70 183 67 60.7 +10.3%102 205 175 159.3 +9.9 %90 566 464 403.5 +15.0 %90 312 222 198.4 +11.9 %81 167 85 78.8 +7.9 %70 182 67 61.7 +8.6 %Table 4 : Measurements to determine the accuracy of the Skin Dose Indicator with no added Copper filters in the beamWith no additional Copper filtration in the beam the indicated skin dose is between 8% and 15%higher than the actual skin dose (table 4). Additional measurements carried out at the same kV werefor consistency or were with different amounts of attenuation to change the mA and therefore theindicated mGy/min.With various amounts of additional copper automatically added into the beam the accuracy of theskin dose indicator over reads by 15% to 22% (table 5)DisplayedkVDisplayedmA+/-2%AddedCu bysystemIndicatedmGy/min+/-5%MeasuredmGy/min+/- 4%Differencebetween indicatedand actual83.6 813 0.1 mm 226 191.7 +17.9 %87.2 817 0.1 mm 409 341.6 +19.7 %81.8 809 0.1 mm 338 286.2 +18.1 %86.7 807 0.1 mm 291 255.3 +14.0 %75.6 690 0.2 mm 189 167.2 +13.0 %83.4 681 0.2 mm 180 155.6 +15.7 %64.5 532 0.3 mm 44 38.2 +15.2 %73.5 740 0.3 mm 74 60.5 +22.3 %73.5 471 0.3 mm 60 50.3 +19.3 %64.5 492 0.3 mm 28 22.9 +22.2 %64.5 537 0.3 mm 44 38.4 +14.6 %81 492 0.3 mm 73 60.7 +20.3 %76.1 452 0.6 mm 30 25.5 +17.6 %67.4 646 0.9 mm 18 15.2 +18.4 %73.6 311 0.9 mm 9 7.5 +20 %Table 5 : Measurements to determine the accuracy of the Skin Dose Indicator with various Copper filters in the beam21