Jung K J, Lee K S, Kim S Y, Kim T S, Pyeun Y S, Lee J Y
Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Invest Radiol. 2000 Sep;35(9):557-63. doi: 10.1097/00004424-200009000-00007.
The aim of our study was to assess the image quality, radiation dose, and clinical applicability of low-dose, volumetric helical CT in the evaluation of bronchiectasis.
Volumetric helical CT scans (120 kVp, 3-mm collimation, pitch of 2, and reconstruction interval of 2 mm) were obtained through the thorax at four levels of tube current: 150, 100, 70, and 40 mA. There were a total of 12 patients who underwent CT scan either for suspected bronchiectasis or for lung cancer screening, with three patients allocated to each current level. Five radiologists assessed and compared image quality of the helical CT scans obtained at the various exposure levels. Radiation doses of helical CT performed with four different current settings and of high-resolution CT (120 kVp, 170 mA, 1-mm collimation, and 10-mm intervals) were measured. The diagnostic usefulness of the 40-mA helical CT images was compared with that of high-resolution CT by two observers in 52 patients with known or suspected airway diseases.
With helical CT, there was no significant difference in image quality among the four different levels of current (P > 0.05). Radiation doses associated with the 40-, 70-, 100-, and 150-mA helical techniques were 3.21 mGy (range, 3.02-3.57), 4.81 mGy (range, 3.89-5.93), 6.46 mGy (range, 6.01-7.31), and 10.4 mGy (range, 8.93-12.1), respectively, whereas that of high-resolution CT was 2.17 mGy (range, 1.90-2.67). Of 52 patients, 44.5 and 47 patients (the mean of positive interpretations by the five observers) were diagnosed with bronchiectasis at high-resolution and low-dose helical CT, respectively. Of 928 segments, bronchiectasis was seen in 152.5 segments on high-resolution CT and in 193.5 segments on helical CT. The interobserver agreement (k-values) was acceptable for both techniques.
With acceptable images and similar radiation dose, low-dose volumetric helical CT at 40 mA may offer more information than does high-resolution CT in the evaluation of bronchiectasis.
我们研究的目的是评估低剂量容积螺旋CT在支气管扩张评估中的图像质量、辐射剂量及临床适用性。
在四个管电流水平（150、100、70和40 mA）下，对胸部进行容积螺旋CT扫描（120 kVp，3 mm准直，螺距2，重建间隔2 mm）。共有12例因疑似支气管扩张或肺癌筛查而接受CT扫描的患者，每个电流水平分配3例患者。五名放射科医生评估并比较了在不同曝光水平下获得的螺旋CT扫描的图像质量。测量了在四种不同电流设置下进行的螺旋CT以及高分辨率CT（120 kVp，170 mA，1 mm准直，10 mm间隔）的辐射剂量。两名观察者在52例已知或疑似气道疾病的患者中，比较了40 mA螺旋CT图像与高分辨率CT图像的诊断效用。
对于螺旋CT，四个不同电流水平之间的图像质量无显著差异（P>0.05）。与40、70、100和150 mA螺旋技术相关的辐射剂量分别为3.21 mGy（范围3.02 - 3.57）、4.81 mGy（范围3.89 - 5.93）、6.46 mGy（范围6.01 - 7.31）和10.4 mGy（范围8.93 - 12.1），而高分辨率CT的辐射剂量为2.17 mGy（范围1.90 - 2.67）。在52例患者中，高分辨率CT和低剂量螺旋CT分别有44.5例和47例（五名观察者阳性解读的平均值）被诊断为支气管扩张。在928个节段中，高分辨率CT上可见152.5个节段有支气管扩张，螺旋CT上可见193.5个节段有支气管扩张。两种技术的观察者间一致性（k值）均可接受。
在图像质量可接受且辐射剂量相似的情况下，40 mA的低剂量容积螺旋CT在支气管扩张评估中可能比高分辨率CT提供更多信息。
