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Noninvasive Coronary Angiography with 64-Section CT: Effect of Average Heart Rate and Heart Rate Variability on Image Quality¹

¹ From the Institute of Diagnostic Radiology (S.L., S.W., T.B., L.D., B.M., H.A.), the Clinic for Cardiovascular Surgery (A.P.), and the Cardiovascular Center (P.K., T.S., P.A.K.), University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland; and the Center for Integrative Human Physiology, University of Zurich (P.A.K.). Received August 17, 2005; revision requested October 20; revision received December 29; final version accepted February 1, 2006. Supported by the National Center of Competence in Research, Computer Aided and Image Guided Medical Interventions of the Swiss National Science Foundation and by the Georg und Bertha Schwyzer-Winiker-Stiftung, Zurich, Switzerland. Address correspondence to H.A. (e-mail: hatem.alkadhi{at}usz.ch).

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 1a: Curved multiplanar reformations of 64-section CT images of RCA in five patients illustrate use of semiquantitative five-point image quality score. (a) Image in patient with mean heart rate of 45.3 beats per minute ± 0.7 shows no motion artifacts (score 1) in all segments of the RCA. (b) Image in patient with mean heart rate of 53.9 beats per minute ± 2.1 shows mild motion artifacts (score 2) that cause mild blurring of the RCA wall. (c) Image in patient with mean heart rate of 76.5 beats per minute ± 5.9 shows moderate motion artifacts (score 3) in the proximal and middle segments of the RCA, with moderate blurring of the vessel outline. (d) Image in patient with mean heart rate of 62.4 beats per minute ± 5.9 shows severe artifacts (score 4), with discontinuity of the middle segment of the RCA leading to nondiagnostic image quality. (e) Image in patient with mean heart rate of 70.1 beats per minute ± 6.6 is nonevaluative (score 5) for the distal segment of the RCA. This image was reconstructed in midsystole (20% of the R-R interval) to provide an example for score 5. When the best reconstruction interval (at 60% of the R-R interval) was used in this patient, the image quality score was 4.

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 1b: Curved multiplanar reformations of 64-section CT images of RCA in five patients illustrate use of semiquantitative five-point image quality score. (a) Image in patient with mean heart rate of 45.3 beats per minute ± 0.7 shows no motion artifacts (score 1) in all segments of the RCA. (b) Image in patient with mean heart rate of 53.9 beats per minute ± 2.1 shows mild motion artifacts (score 2) that cause mild blurring of the RCA wall. (c) Image in patient with mean heart rate of 76.5 beats per minute ± 5.9 shows moderate motion artifacts (score 3) in the proximal and middle segments of the RCA, with moderate blurring of the vessel outline. (d) Image in patient with mean heart rate of 62.4 beats per minute ± 5.9 shows severe artifacts (score 4), with discontinuity of the middle segment of the RCA leading to nondiagnostic image quality. (e) Image in patient with mean heart rate of 70.1 beats per minute ± 6.6 is nonevaluative (score 5) for the distal segment of the RCA. This image was reconstructed in midsystole (20% of the R-R interval) to provide an example for score 5. When the best reconstruction interval (at 60% of the R-R interval) was used in this patient, the image quality score was 4.

View larger version (128K): [in this window] [in a new window] [Download PPT slide]   Figure 1c: Curved multiplanar reformations of 64-section CT images of RCA in five patients illustrate use of semiquantitative five-point image quality score. (a) Image in patient with mean heart rate of 45.3 beats per minute ± 0.7 shows no motion artifacts (score 1) in all segments of the RCA. (b) Image in patient with mean heart rate of 53.9 beats per minute ± 2.1 shows mild motion artifacts (score 2) that cause mild blurring of the RCA wall. (c) Image in patient with mean heart rate of 76.5 beats per minute ± 5.9 shows moderate motion artifacts (score 3) in the proximal and middle segments of the RCA, with moderate blurring of the vessel outline. (d) Image in patient with mean heart rate of 62.4 beats per minute ± 5.9 shows severe artifacts (score 4), with discontinuity of the middle segment of the RCA leading to nondiagnostic image quality. (e) Image in patient with mean heart rate of 70.1 beats per minute ± 6.6 is nonevaluative (score 5) for the distal segment of the RCA. This image was reconstructed in midsystole (20% of the R-R interval) to provide an example for score 5. When the best reconstruction interval (at 60% of the R-R interval) was used in this patient, the image quality score was 4.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 1d: Curved multiplanar reformations of 64-section CT images of RCA in five patients illustrate use of semiquantitative five-point image quality score. (a) Image in patient with mean heart rate of 45.3 beats per minute ± 0.7 shows no motion artifacts (score 1) in all segments of the RCA. (b) Image in patient with mean heart rate of 53.9 beats per minute ± 2.1 shows mild motion artifacts (score 2) that cause mild blurring of the RCA wall. (c) Image in patient with mean heart rate of 76.5 beats per minute ± 5.9 shows moderate motion artifacts (score 3) in the proximal and middle segments of the RCA, with moderate blurring of the vessel outline. (d) Image in patient with mean heart rate of 62.4 beats per minute ± 5.9 shows severe artifacts (score 4), with discontinuity of the middle segment of the RCA leading to nondiagnostic image quality. (e) Image in patient with mean heart rate of 70.1 beats per minute ± 6.6 is nonevaluative (score 5) for the distal segment of the RCA. This image was reconstructed in midsystole (20% of the R-R interval) to provide an example for score 5. When the best reconstruction interval (at 60% of the R-R interval) was used in this patient, the image quality score was 4.

View larger version (177K): [in this window] [in a new window] [Download PPT slide]   Figure 1e: Curved multiplanar reformations of 64-section CT images of RCA in five patients illustrate use of semiquantitative five-point image quality score. (a) Image in patient with mean heart rate of 45.3 beats per minute ± 0.7 shows no motion artifacts (score 1) in all segments of the RCA. (b) Image in patient with mean heart rate of 53.9 beats per minute ± 2.1 shows mild motion artifacts (score 2) that cause mild blurring of the RCA wall. (c) Image in patient with mean heart rate of 76.5 beats per minute ± 5.9 shows moderate motion artifacts (score 3) in the proximal and middle segments of the RCA, with moderate blurring of the vessel outline. (d) Image in patient with mean heart rate of 62.4 beats per minute ± 5.9 shows severe artifacts (score 4), with discontinuity of the middle segment of the RCA leading to nondiagnostic image quality. (e) Image in patient with mean heart rate of 70.1 beats per minute ± 6.6 is nonevaluative (score 5) for the distal segment of the RCA. This image was reconstructed in midsystole (20% of the R-R interval) to provide an example for score 5. When the best reconstruction interval (at 60% of the R-R interval) was used in this patient, the image quality score was 4.

View larger version (17K): [in this window] [in a new window] [Download PPT slide]   Figure 2: Linear regression plot of mean image quality scores for all coronary artery segments in each patient (y-axis) against average heart rate during CT scanning (x-axis). Dotted lines represent 95% confidence limits. Linear correlation indicates no significant dependence of image quality on average heart rate (Pearson correlation, r = 0.22; P = not significant [n.s.]).

View larger version (17K): [in this window] [in a new window] [Download PPT slide]   Figure 3: Linear regression plot of mean image quality scores for all coronary artery segments in each patient (y-axis) against standard deviation of heart rate during CT scanning (x-axis). Dotted lines represent 95% confidence limits. Linear correlation indicates significantly degraded image quality with increasing heart rate variability (Pearson correlation, r = 0.75; P < .001).

View larger version (15K): [in this window] [in a new window] [Download PPT slide]   Figure 4: Linear regression plot between percentage of coronary segments with best image quality in diastole or systole (y-axis) and average heart rate (x-axis). Dotted lines represent 95% confidence limits. At 85.5 beats per minute, the optimal time for image reconstruction shifted from diastole to systole for more than 50% of the coronary segments.

View larger version (10K): [in this window] [in a new window] [Download PPT slide]   Figure 5a: (a) Box plot shows mean heart rate in patients receiving and those not receiving ß-blockers. Mean heart rate did not differ significantly between these groups (repeated-measures analysis of variance, P = not significant [n.s.]). Box = 1st–3rd quartiles, bold line = median, whiskers = minimum and maximum values, = outlier. (b) Box plot shows standard deviation of heart rate in patients receiving and those not receiving ß-blockers. Heart rate variability was significantly decreased in patients receiving ß-blockers (repeated-measures analysis of variance, P < .05). Box = 1st–3rd quartiles, bold line = median, whiskers = minimum and maximum values, = outlier.

View larger version (11K): [in this window] [in a new window] [Download PPT slide]   Figure 5b: (a) Box plot shows mean heart rate in patients receiving and those not receiving ß-blockers. Mean heart rate did not differ significantly between these groups (repeated-measures analysis of variance, P = not significant [n.s.]). Box = 1st–3rd quartiles, bold line = median, whiskers = minimum and maximum values, = outlier. (b) Box plot shows standard deviation of heart rate in patients receiving and those not receiving ß-blockers. Heart rate variability was significantly decreased in patients receiving ß-blockers (repeated-measures analysis of variance, P < .05). Box = 1st–3rd quartiles, bold line = median, whiskers = minimum and maximum values, = outlier.