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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 1  |  Issue : 2  |  Page : 67-71

The diagnostic evaluation of 640 slice computed tomography angiography in the diagnosis of coronary artery stenosis


Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, China

Date of Web Publication25-Jan-2016

Correspondence Address:
Ziqiao Lei
Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province
China
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Source of Support: This project was supported by the Natural Science Foundation of Hubei Province, China, Conflict of Interest: None


DOI: 10.4103/2226-8561.144440

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  Abstract 

Objective: The aim was to evaluate diagnostic accuracy of 640 slice computed tomography angiography (640-CTCA) in diagnosis of coronary artery stenosis. Materials and Methods: Selective coronary angiography (SCA) and 640 slice CTCA were performed in 120 patients with suspected coronary artery disease (CAD) (78 male, 42 female, aged from 36 to 79 years old, with an average of 58.23 years). Various post-processing reconstructions of coronary arteries and branches, such as volumetric imaging, multi-planar reconstruction, curved planar reconstruction, maximum intensity projection were used. The coronary segments, with statistical evaluations combined with its diameter ≥1.5 mm were collected to analyze the diagnosis accuracy of 640-CTCA on coronary artery stenosis, with SCA as the reference standard. Results: About 96.91% (1535/1584) of coronary artery segments were evaluable arteries, and the sensitivity, specificity, positive and negative predictive value of 640-CTCA for detecting coronary artery stenosis were 93.44%, 99.59%, 95.00% and 99.45% respectively. 3.09% (49/1584) of coronary artery segments could not be evaluated due to motion artifact in 21 segments, calcification in 18 segments and poor display of lumen in 10 segments. There were no significant differences in the diagnostic accuracy of coronary artery stenosis between 640-CTCA and SCA. Conclusion: 640-CTCA has a higher accuracy and specificity, which is a reliable tool in the screening of CAD, coronary surgery, preoperative evaluation and the postoperative follow-up.

Keywords: Computed tomography, coronary angiography, coronary artery stenosis


How to cite this article:
Lei Z, Fu Q, Shi H, Xu H, Han P, Yu J. The diagnostic evaluation of 640 slice computed tomography angiography in the diagnosis of coronary artery stenosis. Digit Med 2015;1:67-71

How to cite this URL:
Lei Z, Fu Q, Shi H, Xu H, Han P, Yu J. The diagnostic evaluation of 640 slice computed tomography angiography in the diagnosis of coronary artery stenosis. Digit Med [serial online] 2015 [cited 2019 Sep 15];1:67-71. Available from: http://www.digitmedicine.com/text.asp?2015/1/2/67/144440


  Introduction Top


With the rapid development of multi-slice computed tomography (MSCT), CT coronary angiography (CTCA) has become an essential method for diagnosis of coronary artery disease (CAD). [1],[2] In the recent years, 640-slice volume CT has been gradually applied in clinical practice, its maximum Z-axis width of detector could reach 160 mm, making it possible to cover the entire heart and finish collecting volume data of heart within a single heart beat in a single rotation of gantry. [3] The present study has collected 120 consecutive cases, which had undergone 640-slice-CTCA in our hospital. Its diagnostic value in CAD were retrospectively analyzed compared with selective coronary angiography.


  Materials and Methods Top


General information

A total of 120 consecutive patients scanned with 640 slice computed tomography angiography (640-CTCA) were recruited from February 2014 to September 2014 in our hospital, among which 78 cases were male, 42 cases were female, aged 36-79 years, with an average age of 58.23 years. Exclusion criteria included unstable angina, renal insufficiency, iodine allergy history, seriously damaged respiratory function and heart failure.

Preparation before computed tomography scanning

Patients were requested to keep fasting for more than 4 h. For patients with a resting heart rate more than 80 bpm, they were demanded to take 25-50 mg beta blocker under condition of no contraindications and administered 0.5 mg nitroglycerin sublingually 3 min before scanning. All the patients signed informed consent and were informed with the scanning process. The patients were trained to breathe effectively, and were asked to keep chest and abdomen still when breathless.

Scanning machine and parameters

Toshiba Aquilion one 640-slice volume CT was used. Scanning tube voltage was 100 kV, tube current modulation was used according to body mass index (350-580 mA), collimation width 320 mm × 0.5 mm. Scanning ranged from 1 cm below tracheal subcarinal to diaphragmatic surface. Acquisition time window was 70% ~ 80% between R-R period when heart rate was <65 bpm, and it was 30% ~ 80% R-R interphase when heart rate was more than 65 bpm. Scanning field-of-view was 320 × 320, display matrix was 512 × 512. Double cylinder of high pressure syringe was used to inject contrast medium at a rate of 4.0-5.0 ml/s with a volume of 45-55 ml, and then 30 ml saline was injected at the same rate. Region of interest (ROI) was set in the descending aorta to monitor CT values, trigger threshold was 250 HU. When value of ROI was more than 250 HU, volume scanning would be started after breathing instructions.

Image reconstruction

Volume data contained 75% of automatic reorganization period and optimal period phase. Slice thickness of reconstructed transversal images was 0.5 mm, with a 0.25 mm thickness interval. Soft tissue reconstruction algorithm was used. If preset period phase couldn't meet the needs of diagnosis, coronary arterial segments with poor display would be reconstructed to get clear transversal images according to electrocardiography editing option, then images would be sent to application software in Vitrea FX post-processing workstation to get volume rendering, maximum intensity projection, multiplanar and curved planar images coronary arteries.

Coronary segment and evaluation standard

According to the American heart association of coronary artery segmentation method, [4] the coronary arteries were divided into 15 segments, image quality was evaluated by four grades: 4 - (Optimal) continuous localized, no motion artifact, margin of blood vessels was clear; 3 - (good) localized continuously, there were minor artifacts, blood vessels had mild interference; 2 - (medium) moderate artifact, but blood vessels localized continuously; 1 - (poor) severely disturbed by artifacts, blood vessels presented double-line sign, vascular contours could not be distinguished.

Selective coronary angiography examination

Selective coronary angiography was successfully performed in all patients before or after CTCA, 3-28 days interval between the two examinations, with a mean interval of 16 days. Various perspectives were applied to observe the coronary artery, at least four perspectives to left coronary artery and two to right coronary artery.

Assessment methods

Double-blind analysis between two independent investigators of CTCA and SCA output were compared. For coronary vessel diameter ≥1.5 mm, analysis of coronary artery stenoses was done with the use of internationally accepted method of visual diameter, calculated as follows:

Degree of stenosis = (normal vessel diameter proximal to stenosis-diameter of stenosed part)/normal vessel diameter proximal to stenosis × 100%.

Grade of coronary stenosis: [5] Mild <50% diameter stenosis, moderate ≥50% to <75%, severe ≥75% and vascular occlusion 100%.

Statistical analysis

Statistical analysis was performed using SPSS 15.0 software. Compared with with the SCA results, we calculated the sensitivity, specificity, positive and negative predictive value of the 640-CTCA, using paired χ2 test to detect the differences between 640-CTCA and SCA in their ability to manifest coronary artery lesions. For all the data, P ≤ 0.05 were considered as significant.


  Discussion Top


A total of 120 patients were successfully received the dual source computed tomography (DSCT) and SCA examinations. There were 1535 (96. 91%) segments in 640-CTCA of the coronary artery that could be assessed with the diameters >1.5 mm, while, 3.09% (49/1584) segments could not be evaluated separately for the following reasons: 21 segments of motion artifact, 18 segments of dense calcification and 10 segments of negative lumen manifestation. Of the 120 patients, 1273 segments both in CTCA and SCA were ruled out lesions; in the 68 segments of mild stenosis which were manifested in SCA, 54 segments were correctly diagnosed, three segments were misdiagnosed and eight segments were overestimated (six were moderate stenosis and two were severe) in 640-CTCA. In the 56 segments of moderate, which were manifested in SCA, 49 segments were correctly diagnosed, five segments were miss diagnosed, and two segments were overestimated in DSCT. In the 122 segments of severe stenosis which were manifested in SCA, 114 segments were correctly diagnosed, eight segments were misdiagnosed and six segments were overestimated in 640-CTCA [Table 1], [Figure 1], [Figure 2], [Figure 3], and [Figure 4]. According to the results indicated above, the sensitivity, specificity, positive and negative predictive value of the 640-CTCA evaluation for the severe coronary artery stenosis were 93.44%, 99.59%, 95.00%, 99.45% respectively. By using paired χ2-test, we got the output of P > 0.05, showing no statistically significant difference between 640-CTCA and SCA on manifestation of severe coronary artery stenosis.
Figure 1: Volume rendering threshold of the right coronary showing a middle occluded right coronary artery as well as a distal severe stenosis

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Figure 2: Curved planar reconstruction of the right coronary showing a middle occluded right coronary artery as well as a distal severe stenosis

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Figure 3: The other volume rendering threshold of the right coronary showing a middle occluded right coronary artery as well as a distal severe stenosis

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Figure 4: Invasive coronary angiogram of the right coronary artery showing a middle and distal severe stenosis

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Table 1: 640-CTCA analysis of 120 patients

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640 slice computed tomography angiography correctly diagnosed 54 mild stenosis segments, 49 moderate stenosis segments, and 114 severe stenosis segments. Image quality scores of three kinds of narrow segments were shown in [Table 2]. There was no statistical difference in CT image quality among the three kinds (P > 0.05).
Table 2: Image quality evaluation of 640-CTCA analysis of 120 patients

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Features of imaging of 640-slice computed tomography coronary angiography

With the rapid development of MSCT technology, CTCA has become a noninvasive method to diagnose CAD. But previous MSCT has not completely solved the main problems of cardiac CT examination: Image quality of CAD diagnosis was influenced by motion artifacts. So previous MSCT CA results had certain disparity compared with results of the SCA. [6] 640-slice volume CTCA has several features as follows: (1) Its maximum Z-axis width of detector could reach 160 mm, making it possible to cover the entire heart and finish collecting volume data of heart within a single heart beat in a single rotation of gantry. At the same time, the sequence helps avoid stair-step artifact and banded artifact. Therefore, results of CTCA have high accuracy. Even in patients with atrial fibrillation, the available ratio of vascular segments also can achieve 96%. [7],[8] (2) Less of the cardiac cycles are enough for image collection, for heart rate <65 bpm only collect one cardiac cycle, the heart rate >65 bpm only collect 2 or above of the cardiac cycles, which can effectively reduce patient radiation dose and dosage of contrast medium. (3) 640 CT can automatically screen out the abnormal exposures, which ensures image quality in patients with arrhythmia. (4) Its spatial resolution has increased to 0.31 mm, helping with clear observation of lumen wall, structure of the plaques and stents. Our research showed that there's no significant difference between CTCA and SCA in the accuracy of the evaluation of coronary arterial stenosis. The evaluable coronary artery segments reached 96.91%. At the same time, there was no statistically significant difference in image quality between them.

Implications of 640-computed tomography coronary angiography in the diagnosis of coronary artery stenosis

Several researches at home and abroad showed that 640 CT has a better consistency than SCA for the diagnosis of coronary artery lesions. 640 CT can show the vast majority of coronary artery stenosis, and can accurately judge the degree of luminal stenosis. [3],[9],[10] We compared results of CTCA and SCA, showing that CCTA can clearly show diameter ≥1.5 mm or coronary artery branch of 2-3 grades and coronary arterial distribution. The present study selected these coronary arteries as evaluation objects, because when there are coronary stenosis, vascular reconstruction treatment can be achieved. [11] Through this research, we can draw the following conclusions: (1) CCTA has a high diagnostic value in evaluation of coronary artery of severe stenosis. Sensitivity, specificity, positive and negative predictive value of the 640-CTCA evaluation for the severe coronary artery stenoses were 93.44%, 99.59%, 95.00%, 99.45% respectively. (2) This study found that CCTA have a higher negative predictive value for coronary artery stenosis, basically meaning that for patients with negative 640-CT examination, SCA checks can be avoided. However, positive predictive value of mild stenosis was a little low. (3) Artifacts were retrospectively analyzed (21 segments caused by CT cardiac motion artifacts, 18 segments dense calcifications and 10 segments poor lumen enhancement. Although 640 slice CT examination has no obvious requirement for arrhythmia, but image quality of the patients still have been influenced by rapid heart rate. Evaluation of degree of luminal stenosis with coronary arterial calcification couldn't be assessed accurately due to the partial volume effect with 640 slice CT. 640 slice CT showed mild stenosis for dot calcified plaque of coronary artery wall, while SCA showed no obvious stenosis. Measurement accuracy of 640 slice CT for diffuse mixed plaques was not high. For severe diffuse coronary artery calcification plaques, often accompanied by vascular positive remodeling, lumen showed no significant stenosis, so 640 slice CT examination tended to overestimate the degree of stenosis. From this study we can find that similar to other MSCT studies, [12],[13],[14] coronary artery calcification is still the main factor influencing the accuracy of 640 slice CTCA, for it is different to distinguish high density calcification from vascular cavity, leading to evaluation error of luminal stenosis degree. It was reported that the sensitivity, specificity, positive and negative predictive value of 640 slice CT for severe calcification (>400) coronary artery stenosis were 93%, 67%, 93% and 67% respectively. [15] Although diagnostic accuracy of 640 slice CT is still affected by severe calcification, the accuracy has improved a lot compared with other noninvasive coronary artery examinations. Poor lumen development was related with the amount of contrast medium and injection rate, the scan delay time, and stenosis degree of the recent relevant narrowed coronary arteries. [16],[17],[18] Our group can't evaluate by developing light 10 section that is in coronary arteries caused by severe stenosis. (4) Of 120 cases of patients, a total of 25 stents were evaluated, 640 slice CT examination can clearly display the stent lumen and presence of plaques. Stent restenosis detection and classification of diagnostic results were all consistent with SCA results, meaning that 640 slice CTCA has higher accuracy in the diagnosis of stent restenosis, which was similar to that of reported by Das. [19]

In short, 640 slice CTCA for noncalcified coronary arteries shows a higher reliability and diagnostic value. The sensitivity, specificity, positive and negative predictive values, for evaluating the degree of stenosis, all meet the clinical requirements. Hence, 640-CTCA can be used as the preferred method in preoperative screening for SCA in patients with suspicion of CAD or postoperative coronary stent implantation or patients on follow-up after coronary artery bypass grafting surgery.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2]


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