不同摄影源像距对小儿胸部数字X线技术辐射剂量图像质量的影响

Effects of different image distance of photographic sources on radiation dose and image quality of children chest digital radiography

目的不同摄影源像距对小儿胸部数字X线技术(DR)辐射剂量、图像质量的影响。方法选取我院2017至2018年收治的60例行胸部X线(DR)检查的患儿为研究对象开展回顾性分析,首先进行体模预实验曝光,采用同一管电压和不同摄影源像距(SID)(80~150 cm),其中10 cm为1组,记录每次曝光的毫安秒和入射体表剂量(ESD)。选取体模预实验中ESD相对低剂量和剂量适中的2组(90 cm和110 cm)开展临床试验。所有患儿住院期间采用同一X线机对同一患儿进行胸部DR的初查和复查,并分为初查组和复查组,初查组采用SID=110 cm,复查组采用SID=90 cm,由3位影像学专家采用5分法对图像质量进行打分。结果通过影像学专家评判,80~150 cm的DR曝光图像质量无差异,且不同的SID下实施胸部体模DR,得到的毫安秒与辐射剂量不相同,同一体模在相同曝光指数下,随着SID的增大,毫安秒与辐射剂量均逐渐增大;初查组的图像质量评分为(4.9±1.0)分,复查组的图像质量评分为(4.9±1.0),2组的图像质量评分比较差异无统计学意义(P>0.05)。结论患儿DR胸部摄影中不同SID,其体表辐射剂量具有明显差异,SID为90 cm时能够大幅度地降低X线管的输出剂量,减少体表辐射剂量,延长X线管的使用寿命。

Objective The explore effects of different image distance of photographic sources on radiation dose and image quality of children chest digital radiography. Methods Sixty children who underwent chest DR and were admitted to the hospital from 2017 to 2018 were enrolled and retrospective analysis was conducted. First,phantom pre-experimental exposure was performed. The same tube voltage and different source image distance(SID)(80~150 cm) of photographic sources were applied. 10 cm distance was defined as a group. The milliampere second and entrance surface dose(ESD) at each exposure time were recorded. The two groups with ESD at relatively low dose and moderate dose(90 cm and 110 cm) level in phantom pre-experiment were chosen to conduct clinical experiment. The same children were given preliminary examination and reexamination of chest DR by the same X-ray machine during their hospitalized period. They were divided into preliminary examination group and reexamination group. The preliminary examination group was given SID of 110 cm, while reexamination group was given SID of 90 cm. The 5-scoring method was applied by 3 imaging experts to score image quality. Results By judgement of imaging experts, there was almost no significant difference in images quality with DR exposure of 80 cm^150 cm.When chest phantom DR was implemented under different SID, obtained milliampere second and radiation dose were different. When the same phantom was under the same exposure index, with the increase of SID, milliampere second and radiation doses were gradually increased. There was no significant difference in image quality score between preliminary examination group and reexamination group [(4.9±1.0) points vs(4.9±1.0) points](P>0.05). Conclusion There are significant differences in radiation doses under different image distance of photographic sources in children chest DR. When SID is equaled to 90 cm, output dose of X-ray tube can be greatly reduced, radiation dose of body surface can be reduced, and service life of X-ray tube can be prolonged.