低剂量螺旋CT在青少年阻生牙诊断中的应用

目的探讨低剂量螺旋CT在青少年口腔阻生牙诊断中的应用价值。方法选择因阻生牙、多生牙或牙列不齐等口腔疾病在本院进行螺旋CT检查，并确诊为阻生牙的153例患儿为研究对象。按照口腔颌面部接受螺旋CT检查时的管电流时间乘积、扫描层厚度和准直器宽度3个参数不同进行分组：A组（n=30，330 mAs、6×0.75 mm和3.0 mm），B组（n=30，140 mAs、6×0.75 mm和3.0 mm），C组（n=30，80 mAs、6×0.75 mm和3.0 mm），D组（n=31，80 mAs、6×1.50 mm和5.0 mm）及E组（n=32，50 mAs、6×1.50 mm和5.0 mm）。各组患者间性别与年龄等一般临床资料差异均无统计学意义（ P>0.05）。使用美国Victoreen公司的76-410高对比分辨率模体与76-421EX低对比分辨率模体（直径均为16 cm），分别对各组螺旋CT检查结果的空间分辨率与密度分辨率进行评价。记录5组患儿进行螺旋CT检查时的剂量长度乘积（DLP），计算CT的电离辐射剂量（有效剂量，ED），并对ED值进行统计学分析，同时对图像质量评分进行比较。结果 ①各组CT图像的空间分辨率均为1.0 mm，密度分辨率分别为2.0、3.0、4.5、4.5及6.0 mm。② 5组间ED值差异有统计学意义（F=1 064.119， P=0.000），E组患儿的ED值最低，为0.19 mSv，分别较A组、B组、C组和D组降低86.52％、67.24％、45.71％与38.71％。5组间任意两组ED值相比，差异均有统计学意义（ P<0.05）。③5组CT摄片按照CT图像清晰度质量等级评分标准的结果均≥3分，各组间差异无统计学意义（F=1.978， P>0.05），且螺旋CT诊断结果与患者接受正畸手术的结果一致。结论采用低剂量螺旋CT诊断阻生牙时，可获得满足临床诊断要求的CT图像质量，又可有效降低螺旋CT检查对患儿口腔颌面部的电离辐射剂量。低剂量螺旋CT可用于青少年阻生牙诊断。

英文摘要:

Objective To determine the value of low dose spiral CT scanning in diagnosing impacted teeth of children and adolescents. Methods A total of 153 children and adolescents with confirmed impacted teeth in West China Second University Hospital, Sichuan University were enrolled in this study. They were divided into 5 groups according to the different spiral CT scan parameters (tube current time product, scanning thickness and collimation value): Group A (n=30, 330 mAs, 6×0.75 mm and 3.0 mm), Group B (n=30, 140 mAs, 6×0.75 mm and 3.0 mm), Group C (n=30, 80 mAs, 6×0.75 mm and 3.0 mm), Group D (n=31, 80 mAs, 6×1.50 mm and 5.0 mm), and Group E (n=32, 50 mAs, 6×1.50 mm and 5.0 mm). There were no significant differences in general clinical features ( P>0.05) among the participants of the five groups. The phantoms were used to measure spatial resolution and contrast resolution of the scan images. Dose length product (DLP) was recorded during CT scanning for calculating effective dose (ED) of exposure. The quality of images was evaluated using a list of quality scoring criteria. Results ① Under 330, 140, 80, 80 and 50 mAs, the images had a spatial resolution of 1.0 mm, with contrast resolution of 2.0, 3.0, 4.5, 4.5 and 6.0 mm, respectively. ② Significant differences in ED values were found among the five groups (F=1 064.119, P=0.000) and between every two of those groups ( P<0.05). Group E had the lowest ED (0.19 mSv), 86.52％, 67.24％, 45.71％, and 38.71％ lower than that in Group A, B, C and D, respectively ( P<0.05). ③ All of the five groups obtained an image quality score above 3, and no statistical differences appeared among the 5 groups （F=1.978, P>0.05）. The diagnostic results of the spiral CT were consistent with those of orthodontic surgery. Conclusion Low dose spiral CT scanning can meet the image quality requirements for diagnosing impacted teeth, minimizing radiation exposure effectively.

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