Sakabe Daisuke, Funama Yoshinori, Murazaki Hiroo, Tochihara Syuichi, Ono Michiaki, Tokuda Masaki, Kai Noriyuki, Nakato Kengo, Hashida Masahiro
Department of Radiology, Kumamoto University Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2012;68(8):970-8. doi: 10.6009/jjrt.2012_jsrt_68.8.970.
The purpose of our study was to measure the reduction rate of radiation dose and variability of image noise using the angular beam modulation (ABM) on computed tomography (CT) fluoroscopy. The Alderson-Rando phantom and the homemade phantom were used in our study. These phantoms were scanned at on-center and off-center positions at -12 cm along y-axis with and without ABM technique. Regarding the technique, the x-ray tube is turned off in a 100-degree angle sector at the center of 12 o'clock, 10 o'clock, and 2 o'clock positions during CT fluoroscopy. CT fluoroscopic images were obtained with tube voltages, 120 kV; tube current-time product per reconstructed image, 30 mAs; rotation time, 0.5 s/rot; slice thickness, 4.8 mm; and reconstruction kernel B30s in each scanning. After CT scanning, radiation exposure and image noise were measured and the image artifacts were evaluated with and without the technique. The reduction rate for radiation exposure was 75-80% with and without the technique at on-center position regardless of each angle position. In the case of the off-center position at -12 cm, the reduction rate was 50% with and without the technique. In contrast, image noise remained constant with and without the technique. Visual inspection for image artifacts almost have the same scores with and without the technique and no statistical significance was found in both techniques (p>0.05). ABM is an appropriate tool for reducing radiation exposure and maintaining image-noise and artifacts during CT fluoroscopy.
我们研究的目的是使用计算机断层扫描（CT）透视中的角束调制（ABM）来测量辐射剂量的降低率和图像噪声的变异性。我们的研究中使用了Alderson-Rando体模和自制体模。这些体模在y轴上-12 cm处的中心和偏心位置进行扫描，扫描时使用和不使用ABM技术。关于该技术，在CT透视期间，X射线管在12点、10点和2点位置的中心处以100度角扇形关闭。CT透视图像在管电压120 kV、每个重建图像的管电流-时间乘积30 mAs、旋转时间0.5 s/rot、切片厚度4.8 mm以及每次扫描使用重建核B30s的条件下获得。CT扫描后，测量辐射暴露和图像噪声，并评估使用和不使用该技术时的图像伪影。无论角度位置如何，在中心位置使用和不使用该技术时，辐射暴露的降低率均为75%-80%。在-12 cm的偏心位置，使用和不使用该技术时的降低率均为50%。相比之下，使用和不使用该技术时图像噪声保持不变。对图像伪影的视觉检查在使用和不使用该技术时几乎具有相同的分数，并且两种技术均未发现统计学意义（p>0.05）。ABM是在CT透视期间降低辐射暴露并保持图像噪声和伪影的合适工具。
