低剂量螺旋CT扫描在口腔正畸中的应用

Clinical application of low-dose spiral CT for orthodontics

目的探讨牙齿螺旋CT扫描时降低kV、mA值患者接受的射线剂量及其对图像质量的影响。方法随机表法将30例口腔正畸患者分为常规剂量组（120kV、200mA）、低kV组（80kV、200mA）和低mA组（120kV、80mA）。扫描时记录容积CT剂量指数（CTDI）及扫描长度，并计算出平均剂量长度乘积（DLP）。对不同扫描参数的图像质量评分进行统计学分析。结果常规剂量组、低kV组和低mA组的CTDI值分别为43．6、15．0和17．5mGy，DLP分别为（375．40±13．99）、（128．10±6．30）和（151．90±6．00）mGy·cm，各组图像质量评分差异无统计学意义。结论牙齿低剂量螺旋CT扫描技术，尤其是低kV扫描，既显著减少辐射剂量，又能保证图像质量。

Objective To determine the effect of reducing the value of mA or kV on the image quality and the radiation dose of the patients undergoing low-dose spiral CT for orthodontics. Methods Thirty patients were divided into three groups, each group has 10 patients. They were group 1（80 kV and 200 mA）, group 2 （120 kV and 80 mA）, group 3 （120 kV and 200 mA） The volume CT dose index （CTDI） was recorded and the average dose-length produce （DLP） was calculated in three groups, respectively. Image quality of three groups were compared and scored by two radiologists, and the results were statistically analysed. Results The CTDI and DLP of 80 kV group （group 2） were 8.7 mGy and （36.80 ± 3.60）mGy＇cm, respectively, those of 80 mA group （group 3 ） were 19.6 mGy and （ 82.14 ± 7.18） mGy· cm, respectively, and those of conventional-dose group （group 1 ） were 19.6 mGy and （82.14 ± 7.18） mGy· cm, respectively. There was no significant difference among three groups in diagnostic image quality. Conclusions Low-dose spiral CT for orthodontics, especially the low-kV scan, may decrease the radiation exposure and guarantee the image quality.