Robot integrated ultrasound geometry-scanning for trackerless bone cement detection in RTHR

Detection and removal of intra-femoral bone-cement in the context of revision total hip replacement (RTHR) can be a time-consuming and risky intervention. Within the framework of computer and robot assisted surgery a system for integrated intraluminal ultrasound based cement detection using a modular mini-robot is being developed. One challenge of an ultrasound based approach is that refraction and wave mode conversion at the water-cement interface will cause refraction distortion and artefacts respectively. In order to minimize measurement errors a scanning concept aiming on an almost perpendicular beam direction with respect to the local water cement interface scanning has been developed. Bone cement prepared ex-vivo femora have been ultrasound scanned and the results have been compared with golden standard CT data. The ultrasound integrated geometry scanner, the detection algorithms as well as the ex-vivo evaluation is presented as part of this contribution.