联合低电压和自动管电流调节技术降低婴幼儿胸部增强CT扫描剂量

目的 在婴幼儿胸部增强CT扫描中联合应用低电压和自动管电流调节技术在降低射线剂量的同时获得临床认可的诊断图像并提高血管结构显示程度。方法 69例3岁以下因各种不同胸部疾患进行64排螺旋CT增强检查的患儿（38个男孩、31个女孩）并随机分成三组：低电压结合自动管电流调节技术并噪声指数设置为9（A组）或10（B组），标准扫描序列为120kVp结合120mA固定毫安（C组）。三组均采用相同的增强程序。测量强化主动脉和外周肌肉CT值及噪声，并计算信号噪声比和对比噪声比。记录三组CT剂量指数值（CTDIvol）。采用5分制由两名儿科放射医生对图像质量进行评估，用Kappa方法评价观察者间的一致性。信号噪声比、对比噪声比进行统计学分析。结果 三组主动脉强化程度分别为495.32±14.74HU, 485.85±18.96HU 和 299.28±8.67HU，相应的肌肉平均CT值和图像背景噪声分别是 (54.71±4.52, 9.08±0.63), (46.33±4.79, 9.29±0.76) 和 (57.49±3.61, 4.93±0.54)。SNR分别为55.23±4.98，53.39±5.62和58.64±5.17，CNR分别为48.74±6.15, 47.56±5.35和51.17±6.84，均无统计学差异。所有图像均获得满足临床诊断要求的质量。A组和B组比常规扫描序列C组CTDIvol 分别降低了74 % 和77 %。结论 在婴幼儿64排螺旋CT增强扫描中联合应用低电压（80kVp）和ATCM技术可以获得临床接受的图像质量和良好的对比，并明显降低了射线剂量。

Dose reduction for contrast-enhanced chest CT scanning in infants with low tube voltage and automatic tube current modulation technique

Objective To observe the value of combining low tube voltage and automatic tube current modulation (ATCM) technique for reducing radiation dose and improving contrast vascular structures for contrast-enhanced chest CT scanning in infants. Methods All 69 patients aged <3 years were assigned into three groups for contrast-enhanced MSCT scanning, i.e. low kVp and ATCM technique with noise index 9 (group A) or 10 (group B), respectively, and a standard 120 kVp with fixed tube current of 120 mA (group C). Aorta contrast enhancement and surrounding muscle CT values and noises were measured, SNR and contrast-to-noise ratio (CNR) were calculated. The CT dose index of volume (CTDIvol) values were recorded. Imaging quality was assessed by two radiologists using a five-point scale, and the degree of interobserver concordance was evaluated with Kappa statistics. Results Compared with group C, the aorta significantly enhanced in group A and group B, increased by 196.04 HU (65.51%) and 186.57 HU (62.34%), respectively, and the average background noise increased 4.15 HU and 4.36 HU in group A and group B, respectively. SNR and CNR were not statistically different among three groups. Compared with group C, CTDIvol reduced by 73.71% and 77.00% in group A and group B, respectively. Conclusion Combining low tube voltage (80 kVp) with ATCM technique for contrast-enhanced chest CT scanning in infants can obtain good image quality and clinically acceptable contrast degree, and significantly reduce radiation dose.