Figure 3

Shear layer detection (JSLD) and single plane velocity truncation (SPVT) methods for the determination of EOA by CMR. The velocity map is isolated along cardiac cycle by a semi-automatic detection of vessel borders. Once the velocity map at peak systole is isolated, both CMR_JSLD and CMR_SPVT methods can be applied. Panel A describes the CMR_JSLD method: i) the isolated velocity map is used to compute normalized vorticity map and acoustical source term map, which is an amplification of vorticity map by local velocity magnitude; ii) a semi-automated algorithm that detects the peaks of AST shear layers corresponding to maximal noise production due to vorticity; iii) pixels inside the computed contour area are counted to estimate valve EOA. Panel B describes CMR_SPVT method: i) the isolated velocity map is normalized with respect to its maximal velocity; ii) a threshold of 0.65 is used to truncate the normalized velocity profile; iii) pixels inside the threshold area are counted to estimate valve EOA. These algorithms could be also applied throughout systole.