Rationale and Objectives
The aims of this study were to determine the optimal image reconstruction intervals for the systolic and diastolic phases of coronary computed tomographic angiography on 256-slice computed tomography and to assess their associated motion artifacts.
Materials and Methods
One hundred twenty-six patients were recruited (mean heart rate [HR], 72.1 beats/min; heart rate variability, 1.3 beats/min). Twenty data sets were reconstructed in 5% steps through 0% to 95% of the R-R interval. Two reviewers discriminated optimal reconstruction intervals for 15 segments distributed in three coronary arteries on the basis of motion artifacts, which were graded from 1 (no motion artifacts) to 4 (severe motion artifacts preventing diagnosis). Patients were then stratified into four HR groups for motion score comparison according to the results of a correlation analysis of HR and motion scores.
Results
The optimal systolic and diastolic reconstruction intervals were 44.4 ± 3.8% and 77.4 ± 3.7%, respectively. The mean motion scores for systolic, diastolic, and combined systolic and diastolic (S+D) reconstructions were 1.8 ± 0.3, 1.8 ± 0.5, and 1.5 ± 0.3, respectively. Combined S+D reconstruction improved diagnostic evaluability to 100% and showed fewer motion artifacts compared to single-phase reconstructions for all HR ranges (S+D vs systolic, P < .05 for HR < 85 beats/min; S+D vs diastolic, P < .05 for HRs of 73–84 beats/min). For HRs of 60 to 72 beats/min, motion artifacts were significantly lower for diastole (1.6 ± 0.3) than systole (1.8 ± 0.4) ( P < .001), and vice versa for HRs of 73 to 84 beats/min (1.7 ± 0.3 for systole vs 2.0 ± 0.5 for diastole, P < .01).
Conclusions
Optimal systolic and diastolic reconstruction intervals were determined for this 256-slice coronary computed tomographic angiographic study. Combined reconstruction showed fewer motion artifacts compared to single-phase reconstruction. In conclusion, 256-slice computed tomography has the potential to improve the diagnostic accuracy of coronary computed tomographic angiography.
Multidetector computed tomographic (CT) imaging continues to evolve as a powerful diagnostic tool for the noninvasive imaging of coronary artery disease . Both 64-slice and dual-source CT imaging enhance coronary CT angiography for patients within certain ranges of mean heart rate (HR) and HR variability (HRV) . However, because of constant cardiac motion and the short quiescent phase of the cardiac cycle, especially in patients with high HRs, multidetector CT technology with high temporal resolution and short acquisition time is essential to image the coronary arteries without substantial motion artifacts.
The recently introduced 256-slice CT technology offers superior temporal resolution, with a minimum of 135 ms, compared to 210 ms for 64-slice CT systems . Additionally, these scanners provides z -axis coverage of 80 mm, allowing an acquisition time for the whole heart as low as 5 seconds for 120-mm z -axis coverage . The currently reported scan time for single-source and dual-source 64-slice coronary CT angiography is on the order of 6 to 10 seconds .
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Materials and methods
Patient Population
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Table 1
Demographic Data of Patients
Variable Value Number of patients 126 Age (y) 56.5 ± 9.8 Women/men 49/77 Body mass index (kg/m 2 ) 25.6 ± 4.0 Heart rate range (beats/min) 53–95 Heart rate (beats/min) 72.1 ± 6.9 Heart rate variability (beats/min) 1.3 ± 0.7 Tube voltage (kV) 120.2 ± 1.8 Tube current (mA) 565.7 ± 91.7 Tube rotation time (ms) 0.27 ± 0.00 Scan time (s) 4.9 ± 0.3 Scan length (mm) 129.7 ± 13.8
Data are expressed as number, as mean ± standard deviation, or as range.
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CT Acquisition Protocol
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CT Data Postprocessing and Image Analysis
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Statistical Analysis
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Results
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Motion Artifacts of Coronary Artery Segments in Their Optimal Systolic Reconstruction Interval
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Table 2
Optimal Reconstruction Interval, Motion Score, Its Correlation with Mean Heart Rate and Heart Rate Variability: Systolic Phase
Variable Total RCA LAD LCX Optimal systolic reconstruction (%) 44.4 ± 3.8 45.1 ± 3.8 44.0 ± 3.8 44.0 ± 3.8 Median systolic reconstruction (%) 45 45 45 45 Overall image quality score 1.8 ± 0.3 1.8 ± 0.5 1.7 ± 0.4 1.9 ± 0.5 1 31.5% (519/1649 ∗ ) 32.6% (159/488) 36.1% (249/690) 24.2% (104/429) 2 58.4% (963/1649) 53.9% (263/488) 57.1% (394/690) 63.4% (272/429) 3 10.1% (167/1649) 13.5% (66/488) 6.8% (47/690) 12.4% (53/429) 4 0.0 (0/1649) 0.0 (0/488) 0.0 (0/690) 0.0 (0/429) Correlation ( r ) with mean heart rate ( P ) −0.07 (.44) 0.01 (.89) −0.09 (.32) −0.07 (.46) Correlation ( r ) with heart rate variability ( P ) 0.01 (.99) −0.07 (.47) 0.08 (.35) −0.03 (.75)
The right coronary artery (RCA) includes segments 1 to 4, the left anterior descending coronary artery (LAD) includes segments 5 to 10, and the left circumflex coronary artery (LCX) includes segments 11 to 15.
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Motion Artifacts of Coronary Artery Segments in Their Optimal Diastolic Reconstruction Interval
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Table 3
Optimal Reconstruction Interval, Motion Score, Its Correlation with Mean Heart Rate and Heart Rate Variability: Diastolic Phase
Variable Total RCA LAD LCX Optimal diastolic reconstruction (%) 77.4 ± 3.7 77.1 ± 4.4 77.4 ± 3.4 77.7 ± 3.5 Median diastolic reconstruction (%) 78 78 78 78 Overall image quality score 1.8 ± 0.5 2.0 ± 0.7 1.7 ± 0.5 1.8 ± 0.6 1 37.0% (610/1649 ∗ ) 28.3% (138/488) 44.6% (308/690) 34.3% (147/429) 2 48.6% (801/1649) 45.7% (223/488) 45.4% (313/690) 56.4% (242/429) 3 12.8% (211/1649) 21.5% (105/488) 9.4% (65/690) 9.1% (39/429) 4 1.6% (26/1649) 4.3% (21/488) 0.6% (4/690) 0.2% (1/429) Correlation ( r ) with mean heart rate ( P ) 0.55 (<.001) 0.55 (<.001) 0.42 (<.0001) 0.51 (<.001) Correlation ( r ) with heart rate variability ( P ) −0.09 (.32) −0.11 (.21) −0.06 (.51) −0.06 (.51)
The right coronary artery (RCA) includes segments 1 to 4, the left anterior descending coronary artery (LAD) includes segments 5 to 10, and the left circumflex coronary artery (LCX) includes segments 11 to 15.
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Motion Artifacts of Coronary Artery Segments in the Combined Reconstruction Interval
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Table 4
Motion Score and Its Correlation with Mean Heart Rate and Heart Rate Variability: Combined Systolic and Diastolic Phase
Total RCA LAD LCX Overall image quality score 1.5 ± 0.3 1.6 ± 0.4 1.4 ± 0.3 1.6 ± 0.4 1 50.6% (835/1649 ∗ ) 44.3% (216/488) 58.4% (403/690) 45.7% (196/429) 2 46.8% (771/1649) 49.8% (243/488) 40.4% (279/690) 52.9% (227/429) 3 2.6% (43/1649) 5.9% (29/488) 1.2% (8/690) 1.4% (6/429) 4 0.0% (0/1649) 0.0% (0/488) 0.0% (0/690) 0.0% (0/429) Correlation ( r ) with mean heart rate ( P ) 0.37 (<.0001) 0.29 (<.01) 0.27 (<.01) 0.39 (<.00001) Correlation ( r ) with heart rate variability ( P ) −0.07 (.43) −0.07 (.43) −0.07 (.44) −0.02 (.82)
The right coronary artery (RCA) includes segments 1 to 4, the left anterior descending coronary artery (LAD) includes segments 5 to 10, and the left circumflex coronary artery (LCX) includes segments 11 to 15.
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Motion Artifact Comparison for Different HR Ranges
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Discussion
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Conclusions
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Acknowledgment
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