Refraction Correction in Full Angle Spatial Image Compounding

Currently there is a growing interest on Full Angle Spatial Compounding (FASC) for breast cancer detection. This technique obtains tomograms at coronal planes of a hanging breast immersed in a water tank and surrounded by ring of ultrasonic transducers. The tomograms are obtained by compounding sector images taken from different orientations in 360º. The well known advantages of the technique include improved contrast-to-noise ratio, high and uniform resolution and the possibility of obtaining 3D images by stacking several tomograms. Since FASC is applied in immersion, refraction at the skin due to different propagation velocities in water and tissue deteriorates significantly the image if not taken into account. Image compounding in presence of refraction is more complicated than in the homogeneous case. This work addresses this problem by proposing an algorithm that performs the required interpolation of many scan lines in the compounding region, taking into account the refraction at the interface.