Objective To study the method of measuring the position accuracy and the step distance accuracy of afterloading system with192Ir source by using flushing-free film.Methods The position accuracy and the step distance accuracy of a China-made afterloading system with192Ir source was measured by using GAFCHROMIC (R) EBT3 flushing-free film.The film was scanned to proper image format,required by dose analysis software,by EPSON PREFACTION V700 PHOTO scanner.Then images are analyzed by using film dose analysis software in SNC Patient 5.2.Results With focus on the center of active section of source,the position accuracy of this afterloading system with192Ir source was-0.75 mm.Using film analysis could make the step point to tell apart if the step distance was 5 mm away by the method of film analysis,but couldnot make it to tell apart if the step distance was 2.5 mm away.The 2.5 mm step distance accuracy could be judged if the distance between the 1 st point and the 3rd point was 5 mm,then the 2.5 mm step distance could be deemed to no deviation.The 5 mm step distance of this afterloading system had no deviation in continuous 9 step points measured by flushing-free film.The indirect measuring results of the 2.5 mm step distance had no deviation as well.The position accuracy of this afterloading system measured with the flushing-free film accorded with the national standards.Conclusions The method of measuring the position accuracy and the step distance accuracy of the afterloading system with192Ir source by using flushing-free film is technically feasible.
Key words:
Flushing-free film; Afterloading systems; 192Ir source; Position accuracy; Step distance accuracy