婴幼儿耳部低剂量CT三维成像研究

目的探讨低剂量CT在婴幼儿内、中耳容积再现（VR）重建中应用价值。方法 60例被怀疑耳部疾病患儿,其中男性36例,女性24例,年龄15天～3岁。分为常规剂量组和低剂量组,各随机选择30例CT诊断解剖结构正常、临床检查未见异常的健侧耳为研究对象。常规剂量组男性17例,女性13例,平均年龄为1岁8个月;低剂量组男性19例,女性11例,平均年龄为1岁5个月。用75mAs（常规剂量组）和15mAs（低剂量组）的剂量分别扫描婴幼儿颞骨,行VR重建,比较不同剂量对骨迷路和听骨链三维结构再现能力的影响。结果 60例中除镫骨板、镫骨脚和半规管外,其余结构均100%完整再现。常规剂量组中,镫骨脚、镫骨板的完整再现率分别为63.3%（19/30）、26.7%（8/30）,完整再现率最低的半规管为上半规管73.3%（22/30）;低剂量组中,镫骨脚、镫骨板的完整再现率分别为60.0%（18/30）和26.7%（8/30）,完整再现率最低的半规管为外半规管70.0%（21/30）。两组图像上述部位完整再现率比较差异均无统计学意义（P〉0.05）。结论 15mAs为目前颞骨CT扫描的最低剂量值,能获得理想的婴幼儿骨迷路和听骨链三维图像,可应用于临床。

Study on three-dimensional reconstructions of low-dose CT in infant ear

Objective To explore the value of low-dose CT with volume rendering（VR） reconstruction in infant ear.Methods A total of 60 cases were enrolled,male 36,female 24,aged 15-day to 3-year,divided into conventional dose group（male 17,female 13,mean age 1-year-8-month） and low-dose group（male 19,female 11,mean age 1-year-5-month）.The temporal bones of infant were scanned with 75 mAs（conventional dose group） and 15 mAs（low-dose group） respectively.Thirty cases of health inner-middle ear in each group were performed VR reconstruction.The rendering ability of 3D structures of ossicular chain and osseous labyrinth were compared in 2 groups.Results Except for crus stapedis,stapedial plate and semicircular canal,the other structures were rendered completely.In conventional dose group,the complete rendering rate of crus stapedis and stapedial plate were 63.3 %（19/30） and 26.7 %（8/30） respectively,the complete rendering rate of anterior semicircular canal was lower than other semicircular canals;In low-dose group,the complete rendering rate of crus stapedis and stapedial plate were 63.0 %（18/30） and 26.7 %（8/30） respectively,the complete rendering rate of lateral semicircular canal was lower than other semicircular canals.There was no significant difference between 2 groups（P 0.05）.Conclusion It is demonstrated that the lowest dose of temporal bone CT scanning is 15 mAs,it could be used to obtain ideal quality VR images in infant inner-middle ear.