Mayo J R, Hartman T E, Lee K S, Primack S L, Vedal S, Müller N L
Department of Radiology, University of British Columbia, Vancouver, Canada.
AJR Am J Roentgenol. 1995 Mar;164(3):603-7. doi: 10.2214/ajr.164.3.7863879.
We wanted to determine minimal tube current (mAs) required for consistently good image quality on conventional 10-mm collimation chest CT and effect of tube current reduction on detection of mediastinal and lung abnormalities. Tube current reduction is desirable to reduce patient radiation dose.
Prospectively, 30 consecutive patients (mean weight, 68 kg; range, 34-93 kg) older than 45 undergoing conventional chest CT with standard technique (120 kVp, 400 mAs) had four additional sections imaged at reduced tube current (200, 140, 80, 20 mAs) at two levels (tracheal carina and left atrium). CT scans were evaluated in random order by two independent observers who were blinded to technical factors used. Subjective image quality was graded on a five-point scale from non-diagnostic to excellent. Visualization of mediastinal adenopathy (n = 18), pleural plaques (n = 17), effusions (n = 28), lung parenchymal nodules (n = 37), and emphysema (n = 15) were assessed. The 400 mAs scan was considered the reference standard.
When compared with the reference technique (400 mAs), the first and second (200 mAs and 140 mAs) reduction levels showed no significant difference (p > .05) in subjective image quality. A significant difference (p < .001) was seen at the third and fourth (80 mAs and 20 mAs) reduction levels. However, no significant difference (p > .05) was seen in detection of mediastinal or lung parenchymal abnormalities with different tube currents.
A twofold reduction in tube current (400-140 mAs) and resultant radiation dose did not cause a significant change in subjective image quality or in detection of mediastinal or lung abnormalities with conventional chest CT. One hundred forty milliampere-seconds is the minimal tube current required to provide good image quality in patients of average weight.
我们想确定在传统的10毫米准直胸部CT上获得始终良好的图像质量所需的最小管电流（毫安秒），以及管电流降低对纵隔和肺部异常检测的影响。降低管电流有助于减少患者的辐射剂量。
前瞻性地，对30例年龄大于45岁、采用标准技术（120千伏峰值，400毫安秒）进行传统胸部CT检查的连续患者（平均体重68千克；范围34 - 93千克），在气管隆突和左心房两个层面，以降低的管电流（200、140、80、20毫安秒）额外成像四个层面。由两名对所使用的技术因素不知情的独立观察者以随机顺序评估CT扫描。主观图像质量按从非诊断性到优秀的五点量表进行分级。评估纵隔淋巴结肿大（n = 18）、胸膜斑（n = 17）、胸腔积液（n = 28）、肺实质结节（n = 37）和肺气肿（n = 15）的可视化情况。400毫安秒的扫描被视为参考标准。
与参考技术（400毫安秒）相比，第一和第二降低水平（200毫安秒和140毫安秒）在主观图像质量上无显著差异（p > 0.05）。在第三和第四降低水平（80毫安秒和20毫安秒）观察到显著差异（p < 0.001）。然而，不同管电流下在纵隔或肺实质异常检测方面未观察到显著差异（p > 0.05）。
管电流降低两倍（400 - 140毫安秒）以及由此产生的辐射剂量，在传统胸部CT中并未导致主观图像质量或纵隔及肺部异常检测的显著变化。140毫安秒是为平均体重患者提供良好图像质量所需的最小管电流。
