141 Twenty out of 81 TVUS recordings from IVF patients had to be excluded because of improper imaging window. These were all part of the retrospective IMPLANT 1 study, while no recording had to be excluded from the prospective Ghent study. This suggests the relevance of instructing the sonographers on the acquisition requirements. The proposed speckle tracking method is based on TVUS B-mode images. This approach has the advantage of being easily transferred to different ultrasound scanners, However, more accurate results can in principle be obtained by the employment of the raw radio frequency (RF) signals, although conflicting results are reported [32]. In future work, when access to the RF signals is available, speckle tracking based on RF signals could be implemented and evaluated. In this study, the TMs were positioned in the junctional zone close to the subendometrial line, which is the region where UP is mostly observed. However, from a physiological perspective, uterine motion should be mostly ascribed to myometrial cells [33]. Therefore, the initial positions of the TMs might have an impact on the UP characterization in relation to the physiological structure of the uterus. As we only investigated the UP characteristics close to the endometrium within the junctional zone, it would be interesting in the future to extend the investigation to the myometrium, where uterine motion originates, to obtain a more comprehensive analysis of UP. D. Future Perspectives Our proposed method for uterine strain analysis is designed to keep constant distances between the TMs over time and good alignment with the uterine anatomy while mitigating the effect of decorrelation due to OOP motion. These conditions enable our proposed spatial–temporal analysis. However, strong in-plane deformation of the endometrium might in principle lead to misalignment between the endometrial walls and the TM grid. To overcome these problems, automatic segmentation of the endometrial walls may be considered in the future [31], [34], possibly enabling improved grid placement and strain rate localization with respect to the uterine anatomy. The promising novel features for the characterization of different uterine activity and associated UP patterns, such as UP velocity and coordination,
RkJQdWJsaXNoZXIy MTk4NDMw