Low dose contrast CT for transcatheter aortic valve replacement assessment: Results from the prospective SPECTACULAR study (spectral CT assessment prior to TAVR)

Background: Computed tomographic angiography (CTA) based planning for transcatheter aortic valve replacement (TAVR) is essential for reduction of periprocedural complications. Spectral CT based imaging provides several advantages, including better contrast/signal to noise ratio and increased soft tissue contrast, permitting better delineation of contrast filled structures at lower doses of iodinated contrast media. The aim of this prospective study was to assess the initial feasibility of a low dose iodinated contrast protocol, utilizing monoenergetic 40 keV reconstruction, using a dual-layer CT scanner (DLCT) for CTA in patients undergoing TAVR planning. Methods: 116 consecutive TAVR patients underwent a gated chest and a non-gated CTA of the abdomen and pelvis. 40 keV virtual monoenergetic images (VMI) were reconstructed and compared with conventional polychromatic images (CI). The proximal aorta and access vessels were scored for image quality by independent experienced cardiovascular imagers. Results: Proximal aortic image quality as assessed by signal to noise (SNR) and contrast to noise ratio (CNR), were significantly better with 40 keV VMI relative to CI (SNR 14.65 +/- 7.37 vs 44.16 +/- 22.39, p < 0.001; CNR 15.84 +/- 9.93 vs 59.8 +/- 40.83, p < 0.001). Aortic root dimensions were comparable between the two approaches with a bias towards higher measurements at 40 keV (Bland Altman). SNR and CNR in all access vessel segments at 40 keV were substantially better (p < 0.001 for all peripheral access vessel segments) with comparable image quality. Conclusion: 40 keV VMI with low dose contrast dose spectral imaging is feasible for comprehensive pre-procedural evaluation of access vessels and measurements of aortic root dimensions in patients undergoing TAVR.