SNR improvement and range side lobe suppression in Golay-encoded Doppler detection for ultrasound high-frequency swept-scan imaging system

摘要

Highlights•Conventional Golay decoding produces erroneous flow information due to range side lobe artifacts.•ThePRF/4 decoding can suppress the artifacts by slow-time processing in swept-scan color-flow imaging.•Golay excitation is implemented in a 40-MHz pre-clinical imaging system with thePRF/4 decoding forin-vivoevaluation.•Doppler SNR and penetration improves without artifacts when the axial motion velocity remains within ±PRF/4 limit.AbstractBackgroundGolay excitation can be utilized to improve the signal-to-noise ratio (SNR). However, its application in ultrasound Doppler detection is limited due to potential motion artifacts in conventional decoding process. In this study, the improved Golay decoding has been implemented in a commercial 40-MHz pre-clinical system and experimentally verified for its efficacy in color-flow imaging.MethodsBased on the Doppler spectral difference of half pulse-repetition-frequency (PRF) between the main lobe and range side lobe components of Golay excitation, the slow-time decoding with a low-pass filter with cut-off frequency ofPRF/4 can separate the desired main lobe from the side lobe interference. The Prospect®system has been customized to generate the Golay transmit sequence in swept-scan mode and to perform thePRF/4 decoding forin-vivoevaluation of mouse blood flow.ResultsResults indicate that thePRF/4 decoding can effectively eliminate the range side lobe artifacts in phantom experiments for flow velocity not exceeding the limit of ±PRF/4 in Doppler frequency. Forin-vivoimaging, the SNR improves by about 7dB and the Doppler penetration increases from 13.5mm to 14.2mm in mouse kidney when the transmit is switched from un-coded to Golay excitation. In mouse abdominal aorta, the Golay transmit also increases the Doppler sensitivity.ConclusionGolay-encoded color-flow imaging has been established using the pre-clinical system to achieve SNR improvement in Doppler detection without suffering from the range side lobe artifacts. To guarantee the performance ofPRF/4 decoding, the side lobe aliasing should be avoided by carefully selecting thePRFto the match the flow velocity.