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目的探讨计算机X线摄影(computed radiography,CR)的合理曝光条件。材料与方法以10mAs、20mAs、40mAs档,分别从50～150kV、步长为2kV对实验猪胸部进行系列曝光,用剂量计记录每次曝光的入射点的入射X线剂量、肺野和纵隔处的透射X线剂量,得到三个序列的X线剂量与kV的关系数据,绘制入射剂量、透射剂量与kV的关系图,然后用相同的步骤进行系列胸部正位CR摄影,以噪声不影响观察为前提,找出曝光量最低的CR图像及其对应的合理曝光剂量,分析合理曝光剂量与曝光条件的关系。结果(1)合理曝光条件对透射剂量有很强的依从关系,不管如何改变kV和mAs的组合,合理透射剂量均是一个相对的恒定值,三个序列间合理剂量差异性比较均无统计学意义(P>0.05);(2)合理曝光剂量相对应的入射剂量,低mAs高kV组合要比高mAs低kV组合的入射剂量低,三个序列间差异比较具有统计学意义(P<0.01);(3)入射点剂量与mAs呈正相关。结论(1)对于CR来说,透射剂量是合理曝光条件唯一考量的参数;(2)提高kV对降低患者辐射剂量有意义。
Objective To explore the reasonable exposure conditions of computed radiography (CR). MATERIALS AND METHODS A series of exposures of experimental pigs from 50 to 150 kV and 2 kV steps were exposed serially in 10 mAs, 20 mAs and 40 mAs, respectively. The incident X-ray dose at each exposure point was recorded with a dosimeter, Of the transmission X-ray dose, the relationship between the three series of X-ray dose and kV data were drawn, the incidence of injection dose, transmission dose and kV relationship diagram, and then use the same sequence of chest X-ray photography, noise does not affect the observation As the premise, find out the lowest exposure CR images and the corresponding reasonable exposure dose, analyze the relationship between reasonable exposure dose and exposure conditions. Results (1) Reasonable exposure conditions have a strong dependence on the transmitted dose. Regardless of how to change the combinations of kV and mAs, the reasonable transmitted dose is a relatively constant value. There is no statistically significant difference in the reasonable dose among the three sequences (P> 0.05). (2) For the dose corresponding to reasonable exposure dose, the low mAs high kV combination was lower than that of the high mAs low kV combination, the difference between the three sequences was statistically significant (P <0.01) ); (3) The incidence of dose and mAs was positively correlated. CONCLUSIONS (1) For CR, the transmitted dose is the only parameter to be considered for reasonable exposure conditions; (2) Increasing kV is significant for reducing the patient’s radiation dose.