Speckle classification for sensorless freehand 3-D ultrasound.

Despite being a valuable tool for volume measurement and the analysis of complex geometry, the need for an external position sensor is holding up the clinical exploitation of freehand 3-D ultrasound. Some sensorless systems have been developed, using speckle decorrelation for out-of-plane distance estimation, but their accuracy is still not as good as that of sensor-based systems. Here, we examine the widely held belief that accuracy can be improved by limiting the distance measurements to patches of ultrasound data containing fully developed speckle.

Sensorless freehand 3D ultrasound in real tissue: speckle decorrelation without fully developed speckle.

It has previously been demonstrated that freehand 3D ultrasound can be acquired without a position sensor by measuring the elevational speckle decorrelation from frame to frame. However, this requires that the B-scans contain significant amounts of fully developed speckle. In this paper, we show that this condition is rarely satisfied in scans of real tissue, which instead exhibit fairly ubiquitous coherent scattering.

Evaluation of visualization techniques for image-guided navigation in liver surgery.

A substantial component of an image-guided surgery system (IGSS) is the kind of three-dimensional (3D) presentation to the surgeon because the visual depth perception of the complex anatomy is of significant relevance for orientation. Therefore, we examined in this contribution four different visualization techniques, which were evaluated by eight surgeons. The IGSS developed by our group supports the intraoperative orientation of the surgeon by depicting a visualization of the spatially tracked surgical instruments with respect to intrahepatic vessels that have to be conserved vitally, the tumor, and preoperatively calculated resection planes.