Itoh S, Koyama S, Tusaka M, Maekoshi H, Satake H, Ishigaki T
Department of Radiology, Nagoya Memorial Hospital.
Nihon Igaku Hoshasen Gakkai Zasshi. 1996 Nov;56(13):961-6.
In order to develop ultra-low-dose helical CT for lung cancer screening, the effect of reduction of the tube current to 20mA and application of a 10mm thick aluminium filter upon radiation dose and image quality was evaluated with a phantom. Exposure dose at the center of a gantry and absorbed dose at the center of an acrylic phantom at 20mA with the filter were 15% and 29% of the dose at 50mA without the filter, respectively. For reduction of absorbed dose, reduction of the tube current was more useful than application of the filter. Image noise at 20mA with the filter was double that at 50mA without the filter. Neither reduction of the tube current nor application of the filter changed full width at half maximum on section sensitivity of the Z-axis. Although reduction of the tube current did not affect the difference in CT values between an acrylic sphere and styroform, application of the filter caused a reduction of 4.5% in the difference in CT values. Neither reduction of the tube current nor application of the filter affected the contrast resolution of the high-contrast phantom; however, that of the low-contrast phantom deteriorated. Although improvement of the filter and evaluation of clinical images are necessary, reduction of the tube current to 20mA and application of the aluminium filter appear to be a promising method for ultra-low-dose helical CT of the lung.
为了开发用于肺癌筛查的超低剂量螺旋CT，使用体模评估了将管电流降低至20mA以及应用10mm厚铝滤过器对辐射剂量和图像质量的影响。使用滤过器时，在20mA下机架中心的照射剂量和丙稀酸体模中心的吸收剂量分别是无滤过器时50mA剂量的15%和29%。对于吸收剂量的降低，降低管电流比应用滤过器更有效。使用滤过器时20mA的图像噪声是无滤过器时50mA图像噪声的两倍。降低管电流和应用滤过器均未改变Z轴截面灵敏度的半高宽。虽然降低管电流不影响丙稀酸球和聚苯乙烯之间的CT值差异，但应用滤过器会使CT值差异降低4.5%。降低管电流和应用滤过器均不影响高对比度体模的对比分辨率；然而，低对比度体模的对比分辨率变差。虽然有必要改进滤过器并评估临床图像，但将管电流降低至20mA并应用铝滤过器似乎是一种有前景的肺部超低剂量螺旋CT方法。
