Low-cost Sensor-enabled Freehand 3D Ultrasound

Volumetric 3D ultrasound provides intuitive visualization and spatial context, but most implementations are expensive, using a sophisticated probe design or a cumbersome position-tracking setup requiring calibration. In this work, we implemented freehand 3D ultrasound using low-cost sensors. A custom probe attachment with a pivoting head was made to accommodate IMUs and optical surface-tracking sensors, plus a microcontroller with USB connection. An external laptop with a custom graphical user interface synchronously acquired sensor data and 2D ultrasound images using a Siemens 9L4 probe (depth = 4 cm) and S2000 scanner with a video capture device. Sensor data was stabilized with a gradient descent orientation filter and used to reconstruct a 3D image volume from 500 2D frames, acquired over an irregular path in an abdominal phantom over 15 seconds. The 3D reconstruction time was 30 seconds, and the quality of the 3D image volume was comparable to that of the raw 2D images. These results demonstrate that freehand 3D ultrasound can be practically achieved using low-cost sensors.