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

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

目的评价联合应用低电压和自动管电流调节(ATCM)技术在婴幼儿胸部增强CT扫描中降低辐射剂量、提高血管结构对比的价值。方法对69例3岁以下患儿行64排MSCT增强检查,并分为低电压结合ATCM并噪声指数为9(A组)或10(B组)及标准扫描序列为120kVp结合120mA固定毫安(C组);测量强化主动脉和外周肌肉CT值及噪声,计算SNR和对比噪声比(CNR)。记录容积CT剂量指数(CTDIvol)。采用5分法评估图像质量;以Kappa方法评价观察者间的一致性。结果A组和B组主动脉强化明显,分别较C组增高196.04 HU(65.51%)和186.57 HU(62.34%),A、B组背景噪声平均值较C组分别增加4.15HU和4.36HU;3组间SNR及CNR差异无统计学意义。A组和B组比C组CTDIvol分别降低73.71%和77.00%。结论在婴幼儿64排MSCT增强扫描中联合应用低电压(80kVp)和ATCM技术可获得临床接受的图像质量和良好的对比,并明显降低辐射剂量。

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 interob-server 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.