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   evaluating the impact of various parameters on the gamma index values of 2d diode array in imrt verification  
   
نویسنده jabbari keyvan ,pashaei fakhereh ,ay mohammad r. ,amouheidari alireza ,tavakoli mohammad b.
منبع journal of medical signals and sensors - 2018 - دوره : 8 - شماره : 1 - صفحه:31 -38
چکیده    Background: mapcheck2 is a two-dimensional diode arrays planar dosimetry verification system. dosimetric results are evaluated with gamma index. this study aims to provide comprehensive information on the impact of various factors on the gamma index values of mapcheck2, which is mostly used for imrt dose verification. methods: seven fields were planned for 6 and 18 mv photons. the azimuthal angle is defined as any rotation of collimators or the mapcheck2 around the central axis, which was varied from 5 to −5°. the gantry angle was changed from −8 to 8°. isodose sampling resolution was studied in the range of 0.5 to 4 mm. the effects of additional buildup on gamma index in three cases were also assessed. gamma test acceptance criteria were 3%/3 mm. results: the change of azimuthal angle in 5° interval reduced gamma index value by about 9%. the results of putting buildups of various thicknesses on the mapcheck2 surface showed that gamma index was generally improved in thicker buildup, especially for 18 mv. changing the sampling resolution from 4 to 2mmresulted in an increase in gamma index by about 3.7%. the deviation of the gantry in 8° intervals in either directions changed the gamma index only by about 1.6% for 6 mv and 2.1% for 18 mv. conclusion: among the studied parameters, the azimuthal angle is one of the most effective factors on gamma index value. the gantry angle deviation and sampling resolution are less effective on gamma index value reduction.
کلیدواژه gamma index ,intensity modulated radiation therapy verification ,mapcheck2 ,twodimensional array
آدرس isfahan university of medical sciences, department of medical physics, iran, isfahan university of medical sciences, department of medical physics, iran, tehran university of medical sciences, department of medical physics and biomedical engineering, iran. university of medical sciences, medical image and signal processing research center, iran, isfahan milad hospital, department of radiation oncology, iran, isfahan university of medical sciences, department of medical physics, iran
پست الکترونیکی mbtavakoli@mui.ac.ir
 
     
   
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