Freehand 3D ultrasound volume imaging using a miniature-mobile 6-DOF camera tracking system

Spatial registration of 2D ultrasound (US) scans and 3D volume reconstruction are very useful tools for clinical diagnosis. However, the existing methods for freehand US scan registration tend to be hindered by physical constraints of the equipment and patient motion artifacts. This paper describes a low-cost and unobtrusive method for spatially registering 2D US scans with six degrees of freedom (6 DoF). This method uses a lightweight camera mounted on the US probe to track skin features of the patient body for probe motion recovery, which is performed efficiently by approximating the skin surface as a planar structure. As probe position and motion are determined with respect to the body, this method is robust to patient motion and could potentially facilitate longitudinal studies. In this paper, the performance of 3D volume reconstructions in linear, tilt, and rotational scanning is quantitatively examined through in-vitro experiments.