Retrospectively ECG-Gated Multi-Detector Row CT of the Chest: Does ECG-Gating Improve Three-Dimensional Visualization of the Bronchial Tree?

Zusammenfassung

Ziel: Untersuchung des Einflusses der retrospektiven EKG-Synchronisierung auf die dreidimensionale Darstellung des Bronchialbaumes und die virtuelle Bronchoskopie. Material und Methode: Bei 25 Patienten wurden eine EKG-synchronisierte und eine nicht-EKG-synchronisierte CT-Untersuchung des Thorax durchgeführt. Aus beiden Bilddatensätzen wurde eine dreidimensionale Oberflächenrekonstruktion SSD (shaded surface display) generiert, die für eine virtuelle Bronchoskopie verwendet wurde. Die Darstellbarkeit kleiner Bronchien im 3D-Datensatz wurde durch drei Radiologen verglichen. Die effektive Strahlendosis und das Signal-zu-Rausch-Verhältnis wurden ermittelt. Ergebnisse: Die Visualisierung der einzelnen Segmente des Bronchialbaumes war für die beiden Akquisitionsmethoden nicht signifikant unterschiedlich. Bei Summation der Scores zeigte sich eine signifikant bessere Bronchialbaumvisualisierung mit der nicht-EKG-synchronisierten Akquisitionstechnik (p < 0,05). Die effektive Strahlendosis, aber auch das Signal-zu-Rausch-Verhältnis waren signifikant höher bei der EKG-synchronisierten Akquisition (p < 0,05). Schlussfolgerung: Der Bronchialbaum kann signifikant besser mit nicht-EKG-synchronisierten Datensätzen visualisiert werden. Mit den aktuellen Rekonstruktionsalgorithmen bringt die EKG-synchronisierte Akquisition keinen zusätzlichen Vorteil.

Abstract

Purpose: To determine the impact of retrospectively ECG-gated multi-detector row CT (MDCT) on three-dimensional (3D) visualization of the bronchial tree and virtual bronchoscopy (VB) as compared to non-ECG-gated data acquisition. Materials and Methods: Contrast-enhanced retrospectively ECG-gated and non-ECG-gated MDCT of the chest was performed in 25 consecutive patients referred for assessment of coronary artery bypass grafts and pathology of the ascending aorta. ECG-gated MDCT data were reconstructed in diastole using an absolute reverse delay of - 400 msec in all patients. In 10 patients additional reconstructions at - 200 msec, - 300 msec, and - 500 msec prior to the R-wave were performed. Shaded surface display (SSD) and virtual bronchoscopy (VB) for visualization of the bronchial segments was performed with ECG-gated and non-ECG-gated MDCT data. The visualization of the bronchial tree underwent blinded scoring. Effective radiation dose and signal-to-noise ratio (SNR) for both techniques were compared. Results: There was no significant difference in visualizing single bronchial segments using ECG-gated compared to non-ECG-gated MDCT data. However, the total sum of scores for all bronchial segments visualized with non-ECG-gated MDCT was significantly higher compared to ECG-gated MDCT (P < 0.05). The summary scores for visualization of bronchial segments for different diastolic reconstructions did not differ significantly. The effective radiation dose and the SNR were significantly higher with the ECG-gated acquisition technique (P < 0.05). Conclusion: The bronchial tree is significantly better visualized when using non-ECG-gated MDCT compared to ECG-gated MDCT. Additionally, non-ECG-gated techniques require less radiation exposure. Thus, the current retrospective ECG-gating technique does not provide any additional benefit for 3D visualization of the bronchial tree and VB.

Key words

Shaded surface display - virtual bronchoscopy - ECG-gated MDCT

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