Development of the dose distribution measurement equipment for Gafchromic film in radiotherapy

点击翻译按钮获取中文摘要

The purpose of our research is the development of inexpensive and high-speed measurement equipment for the improvement of dose distribution measurement accuracy of Gafchromic film in high energy x-rays. First, the measurement light source of the transmission unit of a general-purpose flat-bed scanner, ES-2200 (EPSON) was converted into the wavelength of 670 nm for Gafchromic film MD-55 and HS in 2005. Moreover, since EBT model was also put on the market in addition to Gafchromic film MD-55 and HS, the transmission unit of measurement wavelength 630 nm is ordered. Performance evaluation of the scanner to Gafchromic film MD-55, HS and EBT was performed. The outline of the result is summarized to below.1. Match to the measurement light source wavelength of the scanner to Gafchromic filmsGafchromic film MD-55 and HS have the absorption spectrum with a maximum absorption band centered at 670 nm and Gafchromic film EBT has the absorption spectrum with a maximum absorption band centered at 636 run. For two wavelengths, the form that consists of one body of a general-purpose flat-bed scanner and two exchange transmission units with different measurement LED light source was chosen. Thereby, the inexpensive scanner of a multiple use way has been realized.2. Improvement in measurement sensitivityFrom having adjusted to the measurement light source with the maximum absorption wavelength to each Gafchromic film, the density measurement system of high sensitivity of 1.5-1.8 was able to be completed as compared with use of the conventional general-purpose flat-bed scanner. Furthermore, when performing the measure against a noise well, it became possible to raise measurement accuracy.