Comparing interpolation schemes in dynamic receive ultrasound beamforming.

In medical ultrasound interpolation schemes are of- ten applied in receive focusing for reconstruction of image points. This paper investigates the performance of various interpolation scheme by means of ultrasound simulations of point scatterers in Field II. The investigation includes conventional B-mode imaging and synthetic aperture (SA) imaging using a 192-element, 7 MHz linear array transducer with λ pitch as simulation model. The evaluation consists primarily of calculations of the side lobe to main lobe ratio, SLMLR, and the noise power of the interpolation error. When using conventional B-mode imaging and linear interpolation, the difference in mean SLMLR is 6.2 dB. With polynomial interpolation the ratio is in the range 6.2 dB to 0.3 dB using 2nd to 5th order polynomials, and with FIR interpolation the ratio is in the range 5.8 dB to 0.1 dB depending on the filter design. The SNR is between 21 dB and 45 dB with the polynomial interpolation and between 37 dB and 43 dB with FIR filtering. In the synthetic aperture imaging modality the difference in mean SLMLRrangesfrom14dBto33dBand6dBto31dBforthe polynomial and FIR filtering schemes respectively. By using a proper interpolation scheme it is possible to reduce the sampling frequency and avoid a decrease in performance. When replacing linear interpolation with a more advanced interpolation scheme it is possible to obtain a reduction of 18 dB and 33 dB in the SLMLR for the B-mode and SA imaging, respectively, and an improvement in SNR of 24 dB