Synthetic Aperture Focusing for a Single Element Transducer undergoing Helix Motion

This paper describes the application of 3D synthetic aperture focusing (SAF) to a single element trans-rectal ultrasound transducer. The transducer samples a 3D volume by simultaneous rotation and translation giving a helix motion. Two different 3D SAF methods are investigated, a direct and a two-step approach. Both methods perform almost identical for simulated scatterers and give a significant improvement in azimuth resolution and a constant resolution in elevation. Sidelobes below -60 dB is achievable for both methods. Validation of the method is achieved by scanning a simple wire phantom and a complex phantom containing wires in azimuth and elevation. The simple wire phantom shows the same results as that found through simulation. The complex phantom shows simultaneous focusing in azimuth and elevation for the wire scatterers. Considerations on processing requirements for both 3D SAF methods show that the two-step approach can give equivalent performance using an order of magnitude lower calculations. This reduction requires a temporary storage of 9.1 GB of data for the investigated setup.