Sensitivity analysis of synthetic aperture focusing based on the virtual source point for high-frequency ultrasound imaging

In a previous work we investigated the use of the synthetic aperture focusing technique based on a virtual point source (VSAFT) for high frequency ultrasound-based tooth surface reconstruction in the context of CAD/CAM-based dental restorations. However, discrepancies between real and assumed values of the transducer´s and coupling media´s parameters could affect the performance of the VSAFT. In the framework of this work an analysis has been conducted to investigate the influence of wrong assumptions concerning speed of sound and location of the virtual point source (VPS) with respect to spatial resolution and SNR after processing with VSAFT in case of using a focused (f#=2) high frequency (75MHz) ultrasound probe. Additionally, a comparison between common apodization windows (Hamming, triangle and cosine) and the coherence factor method (CF) has been carried out. The results show that already 3% deviation of the VPS position from their real value causes a significant deterioration of the achieved 6-dB lateral resolution after VSAFT processing. The best lateral resolution and SNR have been achieved with the CF method. Furthermore, the acoustic focus is more appropriate for VSAFT compared to the geometric pendant.