デジタルポータルイメージング装置を用いた治療照合システム : スクリーン/フィルム・システムとの比較

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A digital portal imaging (DPI) system for megavoltage photon beams was installed recently in our department. The purpose of this study is to evaluate the image quality of this system. We have analyzed the following properties of the system; relationship between measured dose-rate and pixel values of the DPI, spatial resolution, detectability of low-contrast objects and setup errors. The results were compared with those of conventional screen-film systems. As a result, the relationship between the measured dose-rate and the pixel value of the DPI was found to be linear in the dose-rate range between 100 and 400cGy/min. Spatial resolution was 1.25 and 0.5mm for the DPI and the screen-film systems, respectively. The slope of the contrast-detail curves differed between the DPI and the screen-film systems. The contrast thresholds were 0.6 and 0.3% for the DPI and the screen-film systems, respectively. The detectability of a setup error of 1mm and 2mm for the DPI was lower than that by the screen-film systems, although the difference was not very significant. In conclusion, the image quality of the DPI at present time is slightly inferior to the conventional screen-film systems. However, notable advantages of the DPI system are that any positional changes in patients during irradiation can be detected very quickly, and that quantitative analysis of the setup variation can be obtained. The image quality of the DPI will be improved as the technology regarding advances. Therefore, this verification system using the DPI device, is expected to be used for clinical radiation therapy in the future.
社団法人日本放射線技術学会の論文
1994-09-01

デジタルポータルイメージング装置を用いた治療照合システム : スクリーン/フィルム・システムとの比較

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