Hagihara Yoshiaki, Umehara Takayoshi, Matsumoto Kazuma, Fujita Tomoko, Ikeuchi Youko, Fujikawa Keita, Takahashi Yoshiyuki, Kotoura Noriko
Department of Radiological Technology, Hyogo College of Medicine College Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2017;73(2):96-103. doi: 10.6009/jjrt.2017_JSRT_73.2.96.
Determination of X-ray fluoroscopy radiation dose and contrast with angiographic system automatically depending on the objects, and to control setting manually, which is difficult for the measurement of characteristics. Therefore, we examined the method to adjust the conditions of fluoroscopy and measured the input-output characteristics.
To adjust and fix the condition of fluoroscopy, the exposure adjustment area at the center of the irradiation field was moved to the left side and attached the copper plates to regulate the exposure dose. The area to measure the digital value was selected at the center of the irradiation field, and the dosimeter was placed at the right side of the area, which was selected to measure the digital value. To regulate the entrance dose progressively, the acryl plates were inserted into the irradiation field except for the exposure adjustment area. We obtained a characteristic curve from the measured dose and the digital value. Difference of lookup table (LUT), dose dependency, and tube voltage dependency were checked by the digital characteristic curves.
Each LUT showed different curves, but they all saturated with 4095, which is the maximum value of 12 bits. Dose dependency was measured as an increase in the permitted dose level with an increase in the setting dose. Tube voltage dependency improved with the tube voltage rises. Each characteristic curve became same by converting the relative exposure dose. As a result, measuring the shape of LUT would be possible.
The method is useful for measuring the characteristic curve with the X-ray fluoroscopy of angiographic system.
根据物体自动确定X射线荧光透视的辐射剂量并与血管造影系统进行对比，同时手动控制设置，这对于特性测量来说较为困难。因此，我们研究了调整荧光透视条件的方法并测量了输入输出特性。
为了调整和固定荧光透视条件，将照射野中心的曝光调整区域移到左侧，并附上铜板以调节曝光剂量。在照射野中心选择测量数字值的区域，并将剂量计放置在该区域右侧，该区域被选来测量数字值。为了逐步调节入射剂量，除曝光调整区域外，将丙烯酸板插入照射野。我们从测量的剂量和数字值中获得了一条特性曲线。通过数字特性曲线检查查找表（LUT）的差异、剂量依赖性和管电压依赖性。
每个LUT都显示出不同的曲线，但它们都在4095处饱和，4095是12位的最大值。剂量依赖性表现为随着设置剂量的增加，允许剂量水平也增加。管电压依赖性随着管电压升高而改善。通过转换相对曝光剂量，每条特性曲线变得相同。结果，测量LUT的形状将成为可能。
该方法对于用血管造影系统的X射线荧光透视测量特性曲线是有用的。
