降低小儿胸部DR摄影辐射剂量的研究

Study on reducing radiation dose in digital radiography of infant chest

目的:降低小儿胸部数字X线摄影(DR)辐射剂量,探索最优化的曝光参数。方法:通过设置附加铜滤过(0～0.3mm)和管电压(60～100kVp),采用自动曝光控制(AEC)先在等效小儿胸部的水模上放置线对卡进行卧位DR摄影,然后对各组图像进行空间分辨力、噪声水平评价,同时记录入射体表剂量和mAs。选最优化摄影参数对30例患儿进行胸部正位摄影,评价图像质量。结果:①各组图像分辨力辨认最高为2.5LP/mm,各组图像背景噪声均能接受;②采用0.3mm铜滤过入射体表剂量均低于其他滤过组,差异有统计学意义(q=5.368,q=2.29,q=2.98;P<0.05);③附加滤过相同,管电压为60～80kVp,入射体表剂量随kVp增加逐渐降低,当管电压为80～100kVp时则略有增加;④相同kVp时附加滤过增厚,入射体表剂量降低,管电流增加;⑤30例患儿胸部正位摄影图像均符合诊断标准。结论:设置管电压80kVp,0.3mm铜附加滤过,采用AEC进行小儿胸部DR为最优化摄影方案,可以降低小儿入射体表剂量。

Objective：To investigate optimal exposure parameters for reducing radiation dose in digital radiography of the infant chest.Methods：Tissue-equivalent infant chest water phantoms were divided into groups according to the different thickness of copper additional filtration （0,0.1,0.2 and 0.3mm） and Tube voltage （60～100kVp）.Then digital radiographies were taken on the phantoms with a line-pair gauge on them.Spatial resolution and noise level of images in groups were evaluated,meanwhile the incident dose on body surface and milliampere second （mAs） were recorded.Thirty infant patients underwent direct digital chest posteroanterior radiography with optimal exposure parameters and image quality were evaluated.Results：1） Background noise of images in groups may be accepted with the best resolving ability of 2.5LP/mm.2） The incident dose to body surface in the group （0.3mm;80kv） is lower than that in any other group,statistically difference was shown between any of the groups in terms of incident dose to body surface （q=5.368,q=2.29,q=2.98;P0.05）.3） Using the same additional filtration,the incident dose to body surface decreased when kilovolts peak （kVp） increased form 60 to 80,but the incident dose increased slightly when kVp increased form 80 to 100 kVp.4） With the thickness of the additional filtration,the incident dose to body surface decreased but mAs increased.5） Chest posteroanterior images of 30 infants all conformed to diagnostic criteria.Conclusion：The use of thickened additional filtration,high tube tension of 80 kVp and AEC may reduce the incident dose to body surface in digital radiography of the infant chest.