Abstract Objective To study the detective sensitivity for position of multi-leave collimators (MLC) using Delta-4. Methods First,the small positional deviation of MLC was simulated and measured using the linac (Varian,Trubeam) equipped with EPID.Then,two beam fields 2.0 cm (x)×6.0 cm (y),7.0 cm (x)×6.0 cm (y) were designed,the x1 and x2 of MLC were expanded 0.1 mm,0.2 mm,0.3 mm...0.9 mm and 1.0 mm,2.0...5.0 mm to external simultaneously,different parameters of 3 mm/3%,2.5 mm/2.5%,2 mm/2%,1.5 mm/1.5% and 1 mm/1% were used in Gamma analysis to analyze the difference between dose distribution detected by Delta-4 and original dose distribution with unexpanded MLC position derived from TPS. Results For 2.0 cm (x)×6.0 cm (y) beam field,the pass rate of original dose distribution was 100%,and that decreased to 95.5% when x1,x2 of MLC were expanded 0.3 mm to external,and decreased to 89.4% when expanded 0.5 mm at 2.5 mm/2.5% statistical standards. For 7.0 cm (x)×6.0 cm (y) beam field,the pass rate of original dose distribution was 96.5%,and that decreased to less than 95% when x2,x2 of MLC were expanded 0.3 mm to external,and passing rate was above 90% when MLC expanded less than 0.5 mm at 1.5 mm/1.5% statistical standards. Conclusions For MLC’s positional deviation in decimillimeter level,raise standards of Gamma analysis properly may improve the capability of Delta-4 for detecting small positional deviation,but it won’t detect all the positional deviation of MLC in decimillimeter level. For different size of beam field,it is proposed to use different analytical standards for Delta-4.
Ni Xinye,Gao Liugang,Lin Tao. Study of sensitivity for detecting small positional deviation of MLC by 3D Detector array Delta-4[J]. Chinese Journal of Radiation Oncology, 2016, 25(2): 168-171.
Ni Xinye,Gao Liugang,Lin Tao. Study of sensitivity for detecting small positional deviation of MLC by 3D Detector array Delta-4[J]. Chinese Journal of Radiation Oncology, 2016, 25(2): 168-171.
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