| 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. |
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