Yanaga Yumi, Awai Kazuo, Funama Yoshinori, Nakaura Takeshi, Hirai Toshinori, Roux Sebastien, Yamashita Yasuyuki
Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto, 860-8556, Japan.
AJR Am J Roentgenol. 2009 Sep;193(3):W220-9. doi: 10.2214/AJR.08.1710.
The purpose of this study was to investigate the feasibility of performance of MDCT urography with low tube voltage and an adaptive noise reduction filter.
Thirty-one patients underwent excretory phase (300 seconds after administration of 100 mL of iopamidol) 40-MDCT of the urinary tract at 120 and 80 kVp. The 80-kVp images were postprocessed with an adaptive noise reduction filter. Using a 3-point scale for homogeneity of the urinary tract and sharpness of contour, streak artifacts, and overall image quality, two radiologists evaluated coronal multiplanar reconstruction images generated from 120-kVp, unfiltered 80-kVp, and filtered 80-kVp images. Attenuation values of the abdominal aorta, renal pelvis, renal cortex, psoas muscle, vertebral body, and retroperitoneal fat and image noise of the psoas muscle were measured. The effective radiation dose was estimated for each patient.
At visual evaluation of images of the upper urinary tract, the quality of filtered 80-kVp images was comparable with that of 120-kVp images. At evaluation of images of the lower urinary tract, however, filtered 80-kVp images were of inferior quality. Except for those of fat tissue, attenuation values were significantly higher on 80-kVp than on 120-kVp images (paired Student's t test, p < 0.01). Noise values did not differ significantly between 120- and filtered 80-kVp images (Dunnett test, p = 0.37). The mean effective doses for 120- and 80-kVp scans were 7.0 and 2.9 mSv.
MDCT urography is feasible with a low-tube-voltage technique and an adaptive noise reduction filter. The technique allows reduction in radiation dose without marked degradation of image quality and can be used in clinical assessment of the renal collecting system and upper ureter. For evaluation of the pelvic ureter and urinary bladder, however, image quality is not sufficient, and a compensatory increase in tube current may be necessary.
本研究旨在探讨采用低管电压和自适应降噪滤波器进行多层螺旋CT尿路造影（MDCTU）的可行性。
31例患者分别在120 kVp和80 kVp下接受尿路排泄期（静脉注射100 mL碘帕醇后300秒）40层MDCT扫描。80 kVp图像采用自适应降噪滤波器进行后处理。两名放射科医生使用3分制对尿路均匀性、轮廓清晰度、条纹伪影及整体图像质量进行评估，评估对象为120 kVp、未滤波的80 kVp及滤波后的80 kVp图像重建的冠状面多平面图像。测量腹主动脉、肾盂、肾皮质、腰大肌、椎体、腹膜后脂肪的衰减值及腰大肌的图像噪声。估算每位患者的有效辐射剂量。
对上尿路图像进行视觉评估时，滤波后的80 kVp图像质量与120 kVp图像相当。然而，对下尿路图像进行评估时，滤波后的80 kVp图像质量较差。除脂肪组织外，80 kVp图像的衰减值显著高于120 kVp图像（配对t检验，p < 0.01）。120 kVp图像与滤波后的80 kVp图像的噪声值差异无统计学意义（Dunnett检验，p = 0.37）。120 kVp和80 kVp扫描的平均有效剂量分别为7.0 mSv和2.9 mSv。
采用低管电压技术和自适应降噪滤波器进行MDCTU是可行的。该技术可降低辐射剂量，且图像质量无明显下降，可用于肾集合系统和上输尿管的临床评估。然而，对于盆腔输尿管和膀胱评估，图像质量欠佳，可能需要适当增加管电流。
