. Author manuscript; available in PMC: 2012 Aug 10.

Published in final edited form as: IEEE Trans Ultrason Ferroelectr Freq Control. 2012 Jun;59(6):1201–1211. doi: 10.1109/TUFFC.2012.2310

TABLE V.

Summary of Signal-to-Noise Ratio (SNR, in Decibels) for Different Imaging Methods.

	Measured A-scan SNR^a	Measured image SNR^a	Measured SNR gain from beamforming	Theoretical SNR gain from beamforming
Flash	14	34	53	54
CPA	14	35	54	54
SPA-0	−19^b	19	38	36
SPA-W	−19^b	18	37	35
SPA-H	−6^b	33	52	54
SPA-HW	−6^b	34	53	53

CPA = classic phased array; SPA-0 = basic synthetic phased array (SPA) without aperture weighting or multi-element firing; SPA-W = SPA with aperture weighting; SPA-H = SPA with Hadamard coding; SPA-HW = SPA with both Hadamard coding and aperture weighting.

For SNR measurements, we defined a signal window and a noise window on the A-scan or on the reconstructed image. The signal window enclosed the echo signal from the on-axis target at 13 mm depth, and the noise window was defined outside the echo signal window where the signal power is due to electronic noise alone. The signal and the noise amplitudes were then measured by calculating the rms of the A-scan or the image amplitude in the signal and the noise windows, respectively.

SNR values smaller than 0 dB were measured after averaging over multiple data sets.