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Dual-Source CT: Effect of Heart Rate, Heart Rate Variability, and Calcification on Image Quality and Diagnostic Accuracy¹

¹ From the Departments of Diagnostic Radiology (H.B., I.T., A.R., C.D.C., M.H., A.F.K.) and Cardiology (C.B., S.S.), Eberhard-Karls-University, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany. Received May 24, 2007; revision requested July 31; revision received September 9; accepted October 9; final version accepted October 29. Address correspondence to H.B. (e-mail: h.brodoefel{at}t-online.de)

Purpose: To prospectively evaluate the effect of heart rate, heart rate variability, and calcification on dual-source computed tomography (CT) image quality and to prospectively assess diagnostic accuracy of dual-source CT for coronary artery stenosis, by using invasive coronary angiography as the reference standard.

Materials and Methods: This study had local Ethics Committee approval; all patients gave informed consent. Patients who underwent bypass surgery were excluded; patients with coronary artery stent-grafts were included. One hundred patients (20 women, 80 men; mean age, 62 years ± 10 [standard deviation]) known to have or suspected of having coronary artery disease underwent dual-source CT and invasive coronary angiography. Image quality was assessed. Accuracy of dual-source CT in depiction or exclusion of significant stenosis (50%) was evaluated on a per-segment and per-patient basis. Effects of heart rate, heart rate variability, and calcification on image quality and accuracy were analyzed by using multivariate regression and were analyzed between subgroups of predictor variables. Simple regression was performed to calculate thresholds for adequate image quality.

Results: Mean heart rate was 64.9 beats per minute ± 13.2, mean variability was 23.6 beats per CT examination ± 36.2, and mean Agatston score was 786.5 ± 965.9. Diagnostic image quality was obtained in 90.2% of segments. Sensitivity, specificity, and positive and negative predictive values for the presence of significant stenosis were, respectively, 91.1%, 92.0%, 75.4%, and 97.5% by segment and 100%, 81.5%, 93.6%, and 100% by patient. Image quality was significantly related to heart rate variability (P = .015) and calcification (P < .001); the number of nondiagnostic segments was significantly affected by calcification only. Calcification was the single factor with significant impact on diagnostic accuracy (P = .001).

Conclusion: While dual-source CT resulted in heart-rate independent image quality, image quality remained prone to heart rate variability and calcification.

© RSNA, 2008