M2 Improving arterial opacification in computed tomography for transcatheter aortic valve replacement. (7th September 2020) - Komber, Hend
Abstract : Introduction: Computed tomography (CT) prior to trans-catheter aortic valve implantation (TAVI) requires adequate vascular opacification. With expert radiographer-led contrast dosing (standard protocol), a wide variation in arterial opacification was observed. Methods: Considering the time required for the electrocardiographically (ECG)-gated and helical acquisitions (Siemens Somatom AS+ 128-slice scanner), an optimised weight-based protocol was developed using 30 s contrast bolus of iodine flux 15–19 mg/kg/s. Radiodensity [Hounsfield Units (HU)] was assessed with a circular region of interest in (a) ascending aorta (0.75 mm ECG-gated systolic acquisition) and (b) ascending, descending thoracic (at carina), infra-renal abdominal aorta and right external iliac artery (1–1.5 mm helical acquisition). Thirty-six sequential optimised scans were compared to 36 prior standard scans. All patients had adequate renal function (eGFR>45 ml/min/1.73 m 2 ). There was no difference in the CARE kV between the protocols (p=0.67). Results: The mean patient age was 78 and 80 years (standard, optimised). The male to female ratio was 47:53 and 61:39 (standard, optimised). The mean bolus durations were 25±5.3 s and 30±0.3 s (standard, optimised); a significant variation (p<0.0001). While there was no difference in the arterial radiodensity in the ECG-gated ascending aorta (p>0.9), there was a significant improvement in the arterial radiodensity at all other anatomical points in the helical scans of the optimised protocol (p<0.0001). Conclusion: Optimising contrast flux and matching bolus duration to the CT technology dramatically improves TAVI planning scans with objectively improved arterial opacification. This results in better contrast opacification for optimal assessment of aortic valve prosthesis sizing and access strategies.