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

我们的研究目的是开发廉价、高速的测量设备，以提高红外致变色膜在高能x射线下的剂量分布测量精度。首先，于2005年将通用平板扫描仪ES-2200 （EPSON）传输单元的测量光源转换为670 nm波长，用于Gafchromic薄膜MD-55和HS。此外，由于除了Gafchromic薄膜MD-55和HS外，还有EBT型号上市，因此订购了测量波长630 nm的传输单元。对该扫描仪对MD-55、HS和EBT薄膜进行了性能评价。结果概要总结如下。与扫描仪对Gafchromic薄膜的测量光源波长相匹配，Gafchromic薄膜MD-55和HS具有以670 nm为中心的最大吸收带的吸收光谱，Gafchromic薄膜EBT具有以636 nm为中心的最大吸收带吸收光谱。对于两个波长，选择了由一个通用平板扫描仪主体和两个具有不同测量LED光源的交换传输单元组成的形式。从而实现了多用途的廉价扫描仪。测量灵敏度的提高通过对每块变色膜调整到最大吸收波长的测量光源，与使用传统的通用平板扫描仪相比，可以完成1.5-1.8高灵敏度的密度测量系统。此外，当对噪声井进行测量时，可以提高测量精度。

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.