High resolution ultrasound imaging using frequency domain interferometry-suppression of interference using adaptive frequency averaging

We have reported that frequency domain interferometry (FDI) imaging with the Capon method has the potential to acquire high range-resolution ultrasound images. The reported method employed uniform frequency averaging to suppress coherent interferences. In atmospheric radar imaging, adaptive averaging has proposed to perfectly suppress coherent interference. In the present study, we applied adaptive frequency averaging to the FDI imaging method and investigated its image quality in a simulation study, where the -6 dB bandwidth of the echo returned from an interface was 2.6 MHz. When two targets 0.1 mm apart from each other were located in a region of interest the FDI imaging method using uniform frequency averaging succeeded in estimating the interface ranges correctly; however, the estimated echo intensity was 6.3 dB lower than the true echo intensity. In contrast, the FDI imaging method using adaptive frequency averaging successfully estimated the interface ranges, and the estimated echo intensity was only 0.049 dB higher than the true one. These results indicate that the FDI imaging method using adaptive frequency averaging has excellent accuracy in the measurement of echo intensity, under the condition that the echo waveform returned from each target is the same as the waveform of the reference signal.