双源CT冠状动脉成像时间窗设置与辐射剂量关系的探讨

目的：双源CT冠状动脉成像时,通过对心率与全剂量时间窗关系的研究分析,来有效的降低患者的辐射剂量。方法：双源CT在心脏序列DEMO模式下,对插有左冠状动脉的胸部模体（RS-330）进行扫描。扫描参数中,只有全剂量时间窗的宽度从15%、20%、25%、35%、40%到48%不断增加,其他参数均固定不变。记录每次扫描的辐射剂量（容积CT剂量指数CTDIvol、及剂量长度乘积DLP）,每种全剂量时间窗的宽度重复扫描5次,计算5次剂量的平均值。利用SPSS11.5,得到DLP与全剂量时间窗的宽度（W）的拟合方程及拟合曲线。随机统计日常双源CT冠状动脉检查者200例,分析200例患者的心率与最佳重组期相的关系。结果：全剂量时间窗的宽度从15%、20%、25%、35%、40%到48%,其对应的DLP分别为643±7.07mGy、680±10.44mGy、712±14.58mGy、786±13.04mGy、821±9.12mGy、878±9.57mGy。利用spss得出的拟合方程及拟合曲线均为线性的。通过对200例患者的统计,心率≤65bpm时,最佳重组期相在65%～75%之间;心率≥85bpm时,最佳重组期相在35%～50%之间;心率介于65bpm～85bpm之间时,最佳重组期相在35%～75%之间。结论：全剂量时间窗的宽度越宽,患者的辐射剂量越高;患者的心率不同,则最佳重组期相不同,心率越快,最佳重组期相在一个心动周期内的位置越靠前。

The study of pulsing window and dose in coronary artery CTA of DSCT

Objective：To reduce radiation dose effectively on patients by studying the relationship of heart rate and pulsing window in dual-source CT of coronary artery angiography.Methods：The lung phantom（RS-330） inserted left coronary artery was scanned in the heart DEMO mode of DSCT.Scanning parameters were fixed except pulsing window.The pulsing window was continually increased from 15%,20%,25%,35%,40% to 48%.The radiation dose（volume computed tomography dose index（CTDIvol）,dose length product（DLP） were recorded.Every pulsing window was scanned 5 times and calclulated average value.The fitted eqution and curve of DLP and pulsing window were got by spss 11.5.200 patients examined by DSCT were analyzed to get the relation of heart rate and optimal recon pulse in coronary artery CTA of DSCT.Results：Dose length product of lung phantom was 643±7.07 mGy,680±10.44 mGy,712±14.58 mGy,786 ±13.04 mGy,821±9.12 mGy,878±9.57 mGy,corresponding to the pulsing window width of 15%,20%,25%,35%,40%,48%.The relationship of DLP and pusing window was lineaar by spss.At low heart rate（≤65 bpm）,the optimal recon pulse was in the period of 65%～75%;At high heart rate（≥85 bpm）,the optimal recon pulse was in the period of 35%～50%;At middle heart rate（65～85） bpm,the optimal recon pulse was in the period of 35%～75%.Conclusion：The wider the width of pulsing window the higher the radiation dose of patient.As the heart rate is diffferent,the optimal reconstrction pulse is different.The higher patient＇s heart rate,the more anterior the optimal recon pulse of cardiac cycle.