Diagnostic accuracy of coronary 320 slice CT angiography using retrospective electrocardiogram gated acquisition compared with virtual prospective electrocardiogram gated acquisition with and without padding

Abstract

Purpose: To reduce radiation-exposure, prospective-ECG-gating without padding is preferable. To evaluate diagnostic-accuracy of coronary 320-slice-CT angiography using various-acquisition-methods, we compared retrospective-ECG-gated with dose-modulation and "virtual" prospective-ECG-gating with and without padding.

Materials-and-methods: We retrospectively selected seventy-seven consecutive symptomatic subjects (52-males, 62 ± 12 years) with normal-sinus-rhythm who underwent both retrospective-ECG-gated 320-slice-CT and conventional-coronary-angiograms (CCAG) within 3-months. CT images were reconstructed at 5% from 0 to 95% of RR-interval. Three-methods were used to assess >50% coronary-stenosis; 1) using only 75% of data named virtual prospective-ECG-gating without padding, 2) using 70-100% of data if heart-rate (HR) was <66 beats/minute (bpm), or using 35-100% of data if HR was >65 bpm, named as virtual prospective-ECG-gating with padding, and 3) using all-phase-data named retrospective-ECG-gating.

Results: In 42-subjects with HR <66 bpm, there were zero unevaluable-segments in virtual prospective-ECG-gating with and without padding and retrospective-ECG-gating. But in 35-subjects with HR >65 bpm, the percentage of unevaluable-segments were significantly-higher in virtual prospective-ECG-gating without padding (13.6 ± 27.9%) than in virtual prospective-ECG-gating with padding (0.7 ± 3.1%), and retrospective-ECG-gating (0.7 ± 3.1%) (both P = 0.012). Using only evaluable-lesions, in 35-subjects with HR >65 bpm, sensitivity, specificity, positive-predictive-value and negative-predictive-value of CT for detecting >50% luminal-stenosis compared with CCAG were 82%, 94%, 60%, and 98%, respectively, for virtual prospective-ECG-gating without padding, 97%, 96%, 73%, and 100%, respectively, for virtual prospective-ECG-gating with padding, and 97%, 96%, 73%, and 100%, respectively, for retrospective-ECG-gating (all P = not-significant).

Conclusion: Virtual prospective-ECG gating at 75% of RR-interval without padding had significantly-more unevaluable-segments than virtual prospective-ECG-gating with padding and retrospective-ECG-gating only in subjects with HR >65 bpm.

Keywords: Coronary 320-slice CT angiography; Diagnostic accuracy; Padding; Retrospective ECG-gating; Virtual prospective ECG-gating.