【作者】 黄桂玲；

【导师】 孙戈新；

【作者基本信息】 吉林大学 ， 临床医学， 2011， 硕士

【摘要】 目的:随着多层螺旋CT冠状动脉成像(MSCTCA)成功率和图像质量的提高,其临床应用也越来越广泛,但是其较高的辐射剂量也引起了人们的注意。文献报道前置心电门控冠状动脉成像采取轴位扫描技术,在满足临床诊断所需的图像质量的同时能有效降低辐射剂量。但以往关于心脏冠状动脉CT成像低剂量技术的研究多基于64层螺旋CT。具有8厘米超宽探测器的飞利浦256层螺旋CT已经投入临床使用,但关于其辐射剂量方面的研究尚不多。本研究应用飞利浦256层螺旋CT对两组分别接受前置心电门控扫描和后置心电门控扫描的受检者进行辐射剂量及图像质量的评估。方法:收集2010年10～12月来我院行256层螺旋CT冠状动脉成像扫描的患者60例,随机分为两组,每组30例,对两组患者分别进行前置心电门控扫描和后置心电门控扫描,并评估辐射剂量及图像质量。记录由计算机生成的容积CT剂量指数(CTDIVOL),用CTDIVOL乘以扫描长度得出剂量长度乘积(DLP),再计算有效剂量(ED)。用有效剂量表达受检者所受到的射线剂量。对两组的平均有效剂量进行统计学分析,判断其差异是否具有统计学意义。图像质量的评估分为主观评价和客观评价。客观评价指在冠状动脉横断面图像上分别选取适当的感兴趣区,并分别测量感兴趣区的平均CT,即升主动脉、右冠状动脉、左主干及左前降支的平均CT值,并对平均CT值进行统计学分析,判断其差异是否具有统计学意义。主观评价为评估冠状动脉节段的显示程度。按照美国心脏协会( AHA )的分类方法将冠状动脉分为16个节段。由两名有经验的影像诊断医师以双盲法对两组图像进行评分,记录各组分值,进行统计学分析,判断两组图像质量评分差异是否具有统计学意义。评分有分歧时由两人共同商讨后达成一致。结果:本次研究得出,前门控组和后门控组的有效放射剂量平均值分别为(3.7±0.9) mSv和( 18.0±6.5) mSv。两组间比较差异有统计学意义(t=-11.82,p=0.00<0.05),前门控低于后门控79.0%。前门控组和后门控组客观图像质量评估结果为:两组升主动脉感兴趣区平均CT值分别为(342.0±47.5)HU和(322.6±37.7)HU,两组间比较差异无统计学意义(t=1.75,p=0.08>0 . 05) ;两组右冠状动脉感兴趣区平均CT值分别为(323.2±71.8)HU和(306.9±72.4)HU,两组间比较差异无统计学意义(t=-0.87,p=0.38>0.05);两组左主干感兴趣区平均CT值分别为(353.6±57.6)HU和( 326.0±72.2 ) HU ,两组间比较差异无统计学意义(t=1.63,p=0.10>0 . 05) ;两组左前降支感兴趣区平均CT值分别为(307.8±76.8)HU和(280.8±75.5)HU,两组间比较差异无统计学意义(t=1.37,p=0.17>0.05)。两组间冠状动脉图像平均CT值经t检验差异无统计学意义(P>0.05)。两组间主观图像质量评分经非参数检验(Mann-Whitney检验)差异无统计学意义(U=-1.2,P=0.19>0.05);两组图像质量均能满足诊断要求。结论:与后置心电门控比较,前置心电门控在保持冠脉成像质量的同时降低了辐射剂量。更多还原

【Abstract】 Objective:Computed tomography (CT) coronary angiography has been widely used since the introduction of multi-slice scanners technology, but high radiation doses have been reported. Prospective ECG-gating using‘step- and- shoot’axial scanning protocol has been shown to reduce radiation exposure effectively while maintaining diagnostic accuracy. 256-slice scanners with 80 mm detector coverage have been currently introduced into practice, but their impact on radiation exposure has not been adequately studied. The aim of this study was to assess radiation doses associated with CT coronary angiography using a 256-slice CT scanner. radiation doses were estimated for 60 patients scanned with either prospective or retrospective ECG-gating.Methods:Our initial study cohort included 60 patients who were referred for CTCA at our department . Radiation dose estimates were expressed in the volume CT dose index (CTDIvol), dose–length product (DLP) and effective dose (ED).The CTDIvol was provided by the CT scanner.The dose–length product is defined as the CTDIvol multiplied by scan length.To obtain the effective dose, dose–length product was multiplied by an appropriate gender and body habitus averaged conversion coefficient for the adult thorax (k =0.014 mSv mGy?1 cm?1).Image quality was assessed objectively in terms of mean CT attenuation at selected regions of interest on axial coronary images and subjectively by coronary segment quality scoring.Results:It was found that radiation doses associated with prospective ECG-gating were significantly lower than retrospective ECGgating (3.7±0.9 mSv versus 18.0±6.5 mSv),reducing radiation dose by 79%. No statistically significant differences in image quality were observed between the two scanning protocols for both objective and subjective quality assessments.Conclusion:With the use of PT CTCA , radiation dose is markedly reduced and optimal image quality is maintained.更多还原