Evaluation Of Coronary Artery Image With 64-slice Helical CT: Clinical And Experimental Study

Background and purpose: Recently, with the development of living standard, coronary artery disease has been the most frequent cause of morbidity and mortality. Conventional invasive coronary angiography(CCA) is still the gold standard for the assessment of coronary artery disease (CAD) . However, the technique is limited by its invasive characteristics and related complications. Since the majority of all diagnostic invasive coronary angiographias are not followed by therapeutic interventions, there is a growing interest in non-invasive technologies to visualize coronary artery tree and to diagnose CAD. Recently,with the development of CT equipment and exploration of software,scan speed has been greatly increased. Movement organ may be clearly imaged. Multi- slice helical CT (MSCT) coronary artery angiography has been a key-point of present radiological study.MSCT systems provides for routine submillimeter cardiac imaging at short breath-hold times. Even with remarkable results reported on the diagnostic accuracy of this scanner generation, however, a number of limitations remained,hindering the full acceptance of this promising noninvasive technology as an established diagnostic tool in the routine clinical workup of CAD. 64-MSCT system improve data sampling along the z-axis. This way, spatial resolution in the longitudinal direction is increased.In this clinical and experimental study , we try to define the clinical value of 64-MSCT coronary angiography (64SCTCA)and to investigate the factors that could influence the quality of coronary angiography.The first part: Experimental studyObjective To explore the main influence factors (heart rate, rotation speed,and reconstruction algorithm) on the image quality of coronary artery with 40mm VCT (64-detector row helical CT) using a pulsating cardiac phantom.. Methods An adjustable pulsating cardiac phantom (GE) containing predetermined simulated coronary arteries was scanned using a 40mm VCT (GE LightSpeed VCT) with cardiac pulsating rates of 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100,105,110, and 115 beats per minute (bpm). The variable rotation speeds technique of 0.35s, 0.4s and 0.45s were used respectively. The raw data were reconstructed using both one-sector and multi-sector reconstruction algorithm at optimal window of the R-R interval . The image quality score(IQS) were evaluated by two radiologist according to the same evaluative standard of reformated image. The correlation between heart rate(HR), roation speed ,reconstruction algorithm and IQS were analyzed. The IQS as independent variable and the HR, rotation speed, reconstruction algorithm as dependent variables were analyzed by multiple linear regression analysis.Results. The heart rate have significant with IQS, The reconstruction algorithm have significant with IQS, The rotation speed(0.35s,0.4s,0.45s) didn't have significant with IQS.There was linear regression relationship between heart rate, reconstruction algorithm and IQS(p<0.01). The equation of multiple regression was IQS=5.154-0.046×(HR)+ 0.500×(reconstruction algorithm). The multi-sector reconstruction algorithm improved the image quality than one-sector did.Conclusion It can evaluate the main influence factors on the image quality of coronary artery with 40mm VCT using a pulsating cardiac phantom .It plays an important role in clinical research and application.The second part:Clinical studyStudy 1 Objective To study the superiority of 64-detector spiral CT in coronary artery image and the effect of heart rate(HR) on image quality. Methods Sixty-six patients were examed by 64-detector spiral CT in coronary artery image. We recorded the scan time,heart rate ,difference of heart rate ,then analyzed the ablity of displaying the coronary artery vessels and the lesions of coronary artery .66 patients were divided into 4 groups(groupⅠ,heart rate≤60 bpm; groupⅡ,61 bpm≤heart rate≤70 bpm;groupⅢ, 71 bpm≤heart rate≤80 bpm;groupⅣ,> 80 bpm).Then image quality's score in different groups were compared using an unpaired Student t test. Results 64-detector spiral CT in coronary artery image showed improvement in scan time, difference of heart rate, displaying the coronary artery vessels and lesions of coronary artery. The image quality's score of GroupⅣwere significantly lower than those of groupⅠ,Ⅱ,Ⅲ(p<0.05)Conclusion 64-detector spiral CT in coronary artery image is better than 16-detector spiral CT.But heart rate (>80 bpm) still affect the image quality.Study 2 Objective To analyze the fluctuation of heart rate during the scanning and its influence on image quality in coronary artery angiography with 64-detector spiral CT. Methods A retrospective study was undertaken in 138 cases which had 64-detector spiral CT scan in coronary artery angiography. Fluctuation of heart rate during the scanning was recorded. 138 cases were divided into 4 groups(group A, fluctuation of heart rate was 0 - 4/ min; group B, fluctuation of heart rate was 5 -9/ min ; group C, fluctuation of heart rate was 10 - 20/ min ; group D, fluctuation of heart rate>20/ min ).The image quality of branches or segments of coronary arteries (total 1104) were compared in different groups. Results There were 88,35,8 and 7 cases in group A,B,C and D respectively. There was no significant differences( p>0.05)in image quality's score between group A,B,C in the display of RCA1,RCA3,PDA,LMA,LAD,LCX1and LCX2.The image quality's score in group D was significantly lower than those in group A,B,C in the display of RCA1,RCA3,PDA,LMA,LAD,LCX1 and LCX2. The image quality's score in RCA2 was significant different among different groups (p<0.05) Conclusion The fluctuation of heart rate in coronary artery angiography with 64-detector spiral CT is minor.The image quality of coronary artery begins to be poor when the fluctuation of heart rate is greater than 20/min especially RCA2. Study 3 Objective To explore the optimal reconstruction phase of coronary artery imaging with 64-slice helical CT in different heart rates.METHODS: 112 patients underwent coronary angiography using 64-slice helical CT. Raw helical CT data were reconstructed at 10 % - 90 % of the cardiac cycle with increments of 10 % .112 patients were divided into 4 groups: groupⅠ(n=25) with heart rates less than 60 bpm; groupⅡ(n=38) with heart rates between 60 bpm～69 bpm; groupⅢ(n=29) with heart rates between 70 bpm～79 bpm; and groupⅣ(n=20) with heart rates more than 80 bpm. Image quality for each coronary was scored as 1,2,3,4or 5 (IQS:5: best; 1:worst;≥3: Diagnosis Available).Evaluated the image quality of coronary artery in different reconstruction phases for different groups. RESULTS: The optimal reconstruction phase could be achieved at 80% image reconstruction window of cardiac cycle for groupⅠⅡⅢ. In groupⅣ, the optimal reconstruction phase of RCA was at 50%, and the the optimal reconstruction phase of LMA , LAD, LCX were at 40%. Heart rate didn't have correlation with image quality of coronary in 40% cardiac cycle. CONCLUSION: In different heart rate, the the optimal reconstruction phase of coronary artery are different .The reconstructed image of 40%, 50% cardiac cycle can be used for diagnosis when the image quality of 80% degrade in high heart rates.Study 4 Objective The aim of our study was to evaluate consistency of estimating the degree of stegnosis in calcification and noncalcification coronary by the 64-slice spiral computed tomography coronary angiography (64SCTCA) and the conventional coronary angiography(CCA). METHODS : 64SCTCA was performed in 67 cases (37 male, 30 female; mean age 61 years) with suspected coronary artery disease and compared with invasive coronary angiography(CCA). The stegnosis degree( no stegnosis ,diameter reduction≤50%, 51%～75% and 76%～100% respectively) of vessels were identified by the 64SCTCA and CCA. All vessels were divided into two groups(calcification, noncalcification) according to the CT scan.The consistency of stegnosis degree were compared by two methods in calcification and noncalcification group. The results were analysed by Kappa Value. RESULTS: Of 67 cases, 804 segments could be evaluated. There were 90 and 714 segments in calcification and noncalcification group. The consistency coefficient Kappa(K) was 0.145 and 0.643 of two group respectively. CONCLUSIONS: Compared with CCA, our results indicate high quantitative and qualitative diagnostic accuracy of 64SCTCA in noncalcifiation coronary.In calcification coronary, the consistency of estimating the degree of stegnosis between 64SCTCA and CCA is weak.