【作者】 赵亮；

【导师】 郭君武；

【作者基本信息】 郑州大学 ， 影像医学与核医学， 2013， 硕士

【摘要】 背景冠状动脉粥样硬化性心脏病(CAD),是一种严重危害人类健康并危及生命的常见病,并已成为人类死亡的重要原因。在我国,冠心病的发病率不断上升,且趋向年轻化。因此,冠心病的早期诊断显得尤其重要。目前选择性冠状动脉造影术(CAG)仍被认为是冠状动脉心脏疾病的诊断的“金标准”,并被临床广泛使用和认可。但作为一种有创检查,存在一定的风险性,不适合高危人群的普查与筛选、冠心病治疗后的复查与随访。多层螺旋CT(MSCT)及心电门控技术(ECG-gating)的问世,使冠状动脉CT血管成像(CCTA)成为现实,并作为无创性心脏冠脉检查成了现今国内外研究的焦点。但由于受时间分辨率的影响,对于高心率的患者,CCTA的应用受到了一定的限制。2005年底推出的双源CT (DSCT)将CT的时间分辨率提高到了83ms,这样的时间分辨率已经可以满足临床常规应用的需要,解决了一些高心率及心律失常患者难以进行冠状动脉CT成像的问题,大大拓宽了冠状动脉CT的应用范围和应用人群,降低了心率对DSCT的检查结果的影响,并显著提高图像质量,从而明显提高了检查的成功率和准确率。特别是对高心率患者,其图像质量及诊断率较以往普通CT明显提高。2009年第二代双源CT(Somatom Definition Flash, DSCT)推出有了更大突破,它机架旋转时间仅为0.28秒／圈,扫描速度每秒43cm,使用前瞻性触发螺旋扫描技术(Flash Spiral),使整个心脏扫描只需0.25秒,曝光时间明显缩短,时间分辨率达到75ms,只需小于1mSv的辐射剂量即可完成心脏扫描,真正实现了亚mSv级辐射剂量的“绿色心脏CT检查”。第二代双源CT应用于临床以来,国内外学者采用Flash Spiral模式扫描的准确性研究主要集中在低心率病人的CCTA准确性的评价,本研究采用Flash Spiral模式对高心率患者(心率>70次／min)冠状动脉CT血管成像与回顾性心电门控模式(Spiral)相比较,评价图像质量、有效射线剂量,并与冠状动脉造影结果对比,评价冠状动脉狭窄的准确性,现对此作初步评价。目的本研究的目的是采用第二代双源CT(Somatom Definition Flash, DSCT)对于高心率患者用Flash Spiral扫描方式与回顾性心电门控扫描(Spiral)及冠状动脉造影术(CAG)相比较,评价该方式的准确性、有效射线剂量及图像质量。对象和方法1.1临床资料前瞻性分析2011年11月～2012年5月我院临床可疑冠心病患者进行第二代双源CT(Somatom Definition Flash, DSCT)冠状动脉造影检查的心率超过70次／分患者共206例。1.2.1研究方法206例患者随机分为两组,A组103例,采用Flash Spiral模式扫描,采集图像时间为RR间期20～30%,B组103例,采用回顾性心电门控模式扫描。A组中有25例于30天内行冠状动脉造影术(CAG)检查(A1组),B组中有25例行冠状动脉造影术检查(B1组)。比较两组患者一般情况、图像质量评分、图像噪声、对比信噪比(CNR)和有效射线剂量。以冠状动脉造影术结果为标准,分别计算出A1、B1两组双源CT显示冠脉病变的敏感性、特异性、准确率、阳性预测值和阴性预测值。1.2.2CCTA检查采用第二代双源CT(Somatom Definition Flash, DSCT)扫描,检查前进行呼吸训练,嘱检查者含硝酸甘油1mg于舌下。首先进行冠状动脉钙化积分扫描,选择从头向足方向,扫描范围气管分叉下1～2cm到隔顶下1cm,扫描完成后分析冠脉钙化评分,评分超过400的放弃冠脉CTA检查,评分低于400的继续进行冠脉CTA检查。用CARE Bolus技术,采用双筒高压注射器,非离子造影剂碘普罗胺(Omnipaque370,370mgI/ml)以5.0mL／s速率静脉注射60～65ml,感兴趣区为升主动脉根部,阈值为100Hu,到达峰值时间后延迟7s开始扫描,造影剂注射完成后以相同速率注射生理盐水60～65ml。扫描模式选择：A组采用Flash Spiral模式,采集图像时间为RR间期20～30%,B组病人采用Spiral模式扫描。扫描参数：管球电压100kV,管球电流220mAs／rot,CARE Dose4D打开,准直2x64x0.6mm,层厚：z-飞焦点方法采集2×128x0.6mm,旋转转速280ms／rot,螺距随患者心率变化而变化。图像重建：冠脉钙化评分重建层厚3mm,层距1.5mm。用Syngo CaScoring软件得出钙化积分。参考国外文献,积分值无钙化为0,少量钙化为1～10,轻度钙化为11～100,中度钙化为101～400,400以上为重度钙化。冠脉CTA重建层厚0.75mm,重建间隔0.4mm,卷积核B26f。血管壁钙化或有支架的患者采用B46f卷积核重建图像。扫描后图像经最大密度投影(maximum intensity projection, MIP);曲面重建(curved muhripplanar reformations, CPR):容积再现(volume rendering, VR)和心血管优化分析软件等处理后,筛选最佳CT图像用于血管评价。1.2.3评价方法使用西门子公司的Syngo multimodality workplace工作站,总结患者平扫及增强扫描时的平均心率和屏气时间,计算钙化积分平均值。在不知道心率的前提下由两位影像科医生对图像质量进行评价。根据美国心脏病协会(AHA)标准将冠状动脉分为16个节段：右冠状动脉包括1-4段,左主干和左前降支包括5～10段,回旋支包括11～15段,中间支16段。图像质量分为3级,相应评分为1～3分。质量评为1～2分的为可评价血管,3分为不可评价血管。1级为冠状动脉显示清楚,无局部中断或错位；2级为有轻度伪影,冠状动脉壁有错位或中断,但管壁显示清晰,不影响狭窄评价；3级为血管壁明显模糊,或血管明显错位或中断,影响狭窄或斑块的评价。采用国际通用的目侧直径法,冠状动脉狭窄分级：轻度为管径狭窄小于50%；中度为管径狭窄50%-75%之间；重度为管径狭窄大于等于75%,管腔闭塞100%。统计1～3分的相应3级图像的冠状动脉节段数及比例。结果1.A、B组患者一般情况比较差异无统计学意义。2.A、B组不可诊断节段基于血管节段评价分别为1.48%和1.96%,基于病人评价分别为6.8%和7.8%,差异均无统计学意义(P=0.298,P=0.834)。A、B组图像质量评分均数分别为1.059±0.332和1.0568±0.3534,差异无统计学意义(P=0.059)。A组平均图像噪声20.4+4.2HU(18～28HU),CNR11.1±5.2(5.4～24.3),B组分别为21.3+4.5HU(19～27HU),CNR12.7+5.6(6.8～26.5),两组比较差异无统计学意义。3.心率变异性：A组图像质量评分3分病例的平均心率变异性明显小于B组(16.25±11.17次／min vs.22.17±28.63次／min,P<0.05)。4.A1组、B1组与CAG比较,两组患者评价冠状动脉狭窄的敏感性、特异性差异均无统计学意义(P>0.05)。5.射线剂量：A组平均有效射线剂量显著低于B组(1.014±0.13mSv vs.7.68±1.12mSv,P=0.001)。结论采用第二代双源CT前瞻性触发螺旋扫描技术(Flash Spiral)扫描高心率患者(心率>70次／分)在收缩期RR间期20-30%成像与回顾性心电门控扫描结果相近,可以获得具有诊断意义的图像质量,但对于心率变异性较大的高心率患者扫描图像质量欠佳；对冠脉的狭窄程度的评估具有很高的准确性；有效射线剂量明显降低。更多还原

【Abstract】 BackgroundCHD is a common disease which is really harmful to human health and even human life, and has been a major reason for human death.The incidence of coronary heart disease in China shows the tendency to be younger. Therefore, the early diagnosis on the coronary artery disease is especially important. Currently The Selective Coronary Angiography (CAG) is still considered the "Gold Standard" to diagnose the coronary heart disease, and it is widely recognized and used in clinical. But certain risk exists to serve as an invasive examination, and it is not suitable for surveying and screening of high-risk groups as well as review and follow-up after coronary heart disease treatment. The advent of Multislice CT and ECG-gating technology enables the Coronary CT Angiography (CCTA) to become a reality, and acting the focus of research at home and abroad currently by being non-invasive examination of coronary heart. However, CCTA application on patients with high heart rate is subject to certain restrictions due to the impact time resolution. The Dual-source computerized tomography (DSCT) introduced at the end of2005increased the temporal resolution of CT to be83ms, in this way the time resolution already met the need of clinical routine application, and settle the difficulty of CT angiography of coronary artery in some patients with high heart rate and arrhythmia, greatly broadening the application scope of coronary CT and application groups, reducing the impact of heart rate on test results of DSCT and significantly improving image quality, thereby significantly improving the success rate and accuracy of examination. Especially for patients with high heart rate, and the quality and diagnostic accuracy of them are significantly improved when compared to ordinary CT previously.The introduction of second-generation of dual-source CT (Somatom Definition Flash) delivered greater breakthroughs, it rotation time of gantry only hit0.28seconds/circle, and the scanning speed per second only hits43cm, the use of Flash Spiral realizes that the whole heart scanning just takes0.25seconds, the exposure time is significantly shortened, time resolution hits75ms, and only radiation dose less than lmSv can complete heart scan, truly realizing’Green Heart CT Scan’ of sub mSv radiation dose level.Since clinical application of second-generation dual-source CT, the accuracy studies of Flash Spiral pattern scanning made by scholars at home and abroad focused on CCTA accuracy evaluation of patients with a low heart rate, the Flash Spiral mode is used in this research compares to coronary CT angiography and retrospective ECG gating mode of patients with high heart rate (heart rate>70times/min) to evaluate the image quality, effective radiation dose, and compares to the results of coronary angiography to evaluate the accuracy of coronary artery stenosis, now the preliminary evaluation is made hereto.ObjectiveThe purpose of the research is to compare the way high heart rate patients using Flash Spiral with that using retrospective electrocardiographically-gated scanning and that using coronary artery angiography under the help of the second generation dual-source CT (Somatom Definition Flash). So the accuracy, effective radiation dose and the quality of pictures of the method can be evaluated.Object and Methods1.1Clinical data: From November,2011to May,2012, through retrospective analysis, the number of clinical suspected CHD patients who have been conducted DSCT coronary artery angiography and the heart rate is over67times per minute is206.1.2.1Methods:The206patients is divided into two groups. Group A with103patients is scanned in prospectively ECG-triggered spiral acquisition mode (Flash Spiral mode), and the time of image capture is20%to30%of RR interphase. Group B with103patients is in retrospectively ECG-gated spiral acquisition mode (Spiral mode). There are25patients in Group A (A1) who have been examined with coronary artery angiography while in Group B (B1) there are25patients. The author will compare general situation, the score of pictures’quality, noise, CNR and effective radiation dose. And then the result of CAG will be used as the golden standard to calculate the susceptibility, specificity, accuracy rate, positive and negative predictive value of coronary artery lesion which were showed by Flash DSCT in Group A1and Group B1respectively.1.2.2CCTA examination:Adopt the second generation dual-source CT (Somatom Definition Flash) as the respiratory training before scanning. The common content of nitroglycerin under the tone is lmg. Firstly, conduct CACS scanning, and the scanning scope is1-2cm below the furcation of tracheae to lcm below septum, from top to toe. Then analyze the scores for CACS after scanning. Give up the CTA examination if the score is over400, and keep on CTA examination if the score is below400. With the skill of CARE Bolus and nonionic contrast medium—Omnipaque370(370mgI/mL)60-65ml, use double-syringe power injector to inject into patients’vena5ml per second and make the root of aorta the region of interest (threshold100Hu). Star to scan7seconds after peak time, and then inject60-65ml normal saline at the same speed after the injection of contrast medium. Scan mode selection:for Group A is Flash Spiral mode and the time of image capture is20%to30%of RR period. And for Group B, the scanning mode is Spiral. Scanning parameter:The voltage of the tube is100KV, the current is220m As/rot, with CARE Dose4D on. Collimation is2×64×0.6mm. Thickness:z-flying focus, collecting method is2x128x0.6mm, the revolving speed is280ms/rot. The screw pitch changes with patients’heart rate. The reestablishment of pictures:the thickness of CACS reestablishment is3mm, the distance between layers is1.5mm. Using Syngo CaScoring to get CACS. According to foreign literature, the integral value without calcification is0,1-10means with little calcification,11-100means mild calcification,101-400means moderate calcification, and over400means serious calcification. The thickness of the reestablished picture is0.75mm, the interval is0.4mm, and the soft tissue convolution kernel is (B26f). Patients whose vascular wall is calcified or those with scaffold will use sharp organization convolution kernels to reestablish pictures (B46) for the compensation of pseudomorphism. After maximum intensity projection, curved muhripplanar reformations, volume rendering and cardiovascular optimization analysis, choose the best CT pictures from the scanned ones for vessel evaluation.1.2.3Evaluation methodsWith the help of Syngo multimodality workplace of Siemens, the author will summarize the average heart rate and breath-holding time of those patients after they have been scanned or scanned intensively, and then calculate the average calcification score.Two doctors from imaging department will evaluate the pictures before they know the heart rate. According to AHA, coronary artery can be divided into16segments:the first to the forth segments are the right coronary artery, the5th to the10th segments are the left trunk and the left anterior descending branch, the11th to the15th segments are LCX, the16th is the intermediate branch. The quality of pictures can be divided into3degrees, and the score for each is from1to3. The quality score from1to2is the evaluable vessel, and score3is the vessel which can not be evaluated. The first degree means that coronary artery is showed clearly without local interrupt or malposition. The second degree means that there are mild artifacts. Though the vessel wall of coronary artery has malposition or interrupt, the vessel wall is shown clearly without influence on stenosis evaluation. The3rd degree means that the vessel wall is obviously indistinct, or the vessel wall is clearly in disposition or is interrupted, which has influence on stenosis or plaque evaluation. According to the international eye-measurement of diameter, the stenosis is classified by degree of narrowing:the mild narrow means the stenosis of diameter of the vessel is less than50%, the moderate means the stenosis is between50%and75%, and the severe means the stenosis is equal to or above75%, and the lumen is totally obstructed. And then, the author will count the segments and rate of the related3rd degree pictures of coronary artery which is scored from1to3.Results1. There is no statistic value to compare the general situation between Group A and Group B.2. Segments in Group A and Group B, which can not be diagnosed are1.48%and1.96%based on vessel wall segments evaluation, and6.8%and7.8%based on patients’evaluation. All the differences have no statistic value (P=0.298, P=0.834). The average scores of pictures’quality of Group A and Group B are1.059±0.332and1.0568±0.3534respectively, which have no statistic value(P=0.059. The average picture noise of Group A is20.4±4.2HU (18-28HU), CNR11.1±5.2(5.4-24.3). Group B is21.3±4.5HU (19-27HU), CNR12.7±5.6(6.8-26.5), The comparative differences between the two groups have no statistic value.3. Heart rate variability:the average heart rate variability of Group A in which the quality of pictures scored3is obviously less than Group B (16.25±11.17beats/min vs.22.17±28.63beats/min, P<0.05)4. Compare Group A1and Group B1to CAG, the evaluations of the susceptibility and specificity of coronary artery stenosis among the patients in two groups have no statistic value.(P>0.05)5. Radiation dose:the average effective radiation dose of Group A is obviously inferior to that of Group B (1.01±0.13mSv vs.7.68±1.12mSv, P=0.001).ConclusionAdopt the second dual-source Flash Spiral mode to scan patients with high heart rate (heart rate>70beats/min) during systole RR period, and the result is that20%to30%of the images are similar to the result of Spiral mode. The image quality which has diagnostic value is achieved, but the scanned image quality of high heart rate patients with lager heart rate variability is below the average; the evaluation for the degree of coronary artery stenosis is highly accurate; effective radiation dose is significantly reduced.更多还原