Manual versus automatic detection of aortic annulus plane in a computed tomography scan for transcatheter aortic...

Precise measurements of aortic annulus dimensions are crucial for prosthesis size selection in patients undergoing transcatheter aortic valve implantation (TAVI). The so-called effective diameter (derived from area) measured in multislice computed tomography (MSCT) images has evolved to be the most precise measurement tool. Usually, the operator must manually adjust the aortic annular plane. Syngo Aortic ValveGuide (Siemens Healthcare) is a new software tool that allows for automatic aortic root reconstruction and annular plane detection. The aim of this study was to compare the effective diameter measured in automatically detected and manually adjusted annular plane.

Seventy-three raw image datasets of preoperative TAVI MSCT scans were analysed using our institutional gold standard (3Mensio Valves™) with manual annular plane adjustment and using Aortic ValveGuide with automatic annular plane detection. The aortic annular circumference was manually marked for both software tools, and the effective diameter was calculated using the formula: effective diameter = 2 × √(circumferential area/π).

Automatic annulus plane detection using Syngo Aortic ValveGuide worked well in all MSCT scans. Minor manual adjustment of the detected plane was necessary in only 3 patients. The mean effective aortic annulus diameter was 23.1 ± 2.4 mm for 3Mensio and 23.3 ± 2.4 mm for Syngo Aortic ValveGuide. Bland-Altman analysis of both imaging software tools showed good agreement (mean difference of 0.16 mm and limits of agreement of -0.48 to 0.80 mm).

Effective aortic annulus diameter measured with Syngo Aortic ValveGuide, as a new imaging software that allows for automatic aortic annular plane detection, shows good agreement to gold standard measurements. Automatic annulus plane detection might reduce the effort for MSCT analysis and may lead to more reproducible aortic annulus measurements. Aortic ValveGuide is part of the DynaCT and in future aortic annulus dimension measurements may be feasible during intraoperatively acquired DynaCT.