GAF chromic dosimetryの特性とPDD, OCR曲線への利用

概要

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GAF Chromic Dosimetry Media(GAF Media, Nuclear Associates Co.Ltd.)has been newly developed for the purpose of absorbed dose measurements with ionizing radiation. GAF Media is colorless and transparent before radiation exposure, and it changes progressively to a darker blue color with exposure. In contrast to conventional film, GAF Media can be used in room light and does not require any other procedure to develop or fix the image. In this study, we used a microdensitometer to evaluate the relationship between the absorbed dose and optical density of GAF Media types MD-55 and HD-810. We discuss the possibility of application of GAF Media as a simple dosimeter of percent depth dose(PDD)and off-center ratio(OCR) in the field of quality assurance(QA)of radiotherapy. The optical density derived by GAF Media could be converted into absorbed dose by using an approximation curve. However, the elevation of baseline density, the "fog effect", according to time was too great to be neglected. To measure the absorbed spectrum of GAF Media a microdensitometer attached with a Band Pass Filter, which selectively absorbed the spectrum at 671 nm, was useful. The PDD and OCR curves derived by GAF Media were accurate enough for QA of radiotherapy. GAF Media was simple to use, but further investigation will be required before applying it in other fields.
社団法人日本放射線技術学会の論文
2001-11-20