低剂量CT扫描在新生儿缺氧缺血性脑病中的应用和防护价值

目的 探讨多层螺旋CT低剂量扫描在新生儿缺氧缺血性脑病（HIE）中的应用和防护价值.方法 前瞻性选取临床拟诊HIE 60例,随机等分成两组.扫描参数：管电压120 kV,层厚、层间距6 mm,管电流常规剂量组250 mAs、低剂量组50 mAs行全颅脑扫描.对比两种剂量扫描产生的加权CT剂量指数（CTDIw）、全头颅扫描剂量长度乘积（DLP）;图像噪声的比较采用模拟儿童头颅的水模扫描,计算并比较两种剂量下的CT值均数与标准差;盲式评判两组扫描剂量的图像质量.结果 ①低剂量扫描组的mAs、CTDIw和DLP仅为常规剂量组的20%;②低剂量组水模噪声较常规剂量组大,两者差异有统计学意义（t=34.533,P＜0.01）.③低剂量组图像质量以较好为主,较常规剂量组稍差,但未出现差级图像,不影响HIE诊断.结论 低剂量CT扫描在HIE诊断中的应用是完全可行的,既能明确诊断又能有效地保护新生儿,符合医用辐射防护最优化原则.

The application and shielding value of low-dose CT scanning in hypoxic ischemic encephalopathy of neonate

Objective To investigate the application and shielding value of multi-slice spiral CT scanning with low-dose in hypoxic ischemic encephalopathy (HIE) of neonate. Methods 60 neonates with HIE diagnosed by clinic were prospectively selected and randomly divided into two groups averagely. The technical parameters were tube tension 120 kV, slice thickness and gap 6 mm, conventional tube current 250 mAs and low dose 50 mAs. Weighted CT dose index (CTDI_w) and dose length product (DLP) were compared to each other. The image noise were analyzed with water phantom of children's skull. The mean and standard deviation of CT value were statistically analyzed. The image quality was blindly evaluated in two different dose groups. Results (1) The mAs, CTDI_w and DLP in low dose group were 20% of conventional dose group; (2) The noise of water phantom in low dose group was larger than in conventional dose group with the significant difference (t=34.533, P<0.01); (3) The imaging quality in low dose group was mostly better,but inferior to conventional dose group, while there is no poor images to influence the diagnosis of HIE. Conclusions The low dose scanning will be practical in diagnosis of HIE, and beneficial to protect the newborn which corresponds to the optimizing principle of ICRP in medical radiation protection.