雙頻諧波影像與傳統單頻諧波影像相比可有效利用成像系統頻寬並且可利用頻域複合技術來增強影像對比度；雙頻諧波影像雖然可以利用特殊啾聲編碼方式來增加諧波訊雜比以改善影像穿透度，並同時維持信號頻寬與解析度，但啾聲編碼在雙頻諧波中會受限於兩影像頻帶互干擾產生的中央旁瓣問題。本研究利用格雷互補對的相位編碼特性來避免影像頻帶互干擾產生之旁瓣假影，並且發展反相消除法由另一組特殊設計的格雷編碼與原有格雷編碼結合以消除三倍頻帶諧波干擾與對應之旁瓣假影，本研究也發展出利用格雷編碼正交特性的三倍頻旁瓣消除法來抑制旁瓣信號且不喪失幀率。由水聽筒實驗結果顯示，格雷編碼較啾聲編碼的壓縮品質好，並可利用干擾消除法進一步提升壓縮品質分別達13.9%及11.3%。仿體實驗結果顯示經過特殊設計之格雷編碼波形能夠提高雙頻諧波影像的訊雜比達10 dB，並可大幅抑制影像的旁瓣強度達7.5dB；且因格雷互補對是相位編碼，在儀器上的產生也較容易實現。

Compared with conventional single-frequency counterpart, dual-frequency harmonic imaging (DHI) , can effectively use the system bandwidth for enhancement of contrast-to-noise ratio (CNR) by frequency compounding. Though particular Chirp-encoded excitation can achieve high signal-to-noise ratio (SNR) for penetration together with wide signal bandwidth for resolution, it suffers from the central side-lobes because of the mutual interference between two imaging bands. In this study, we take advantage of the phase encoding of complementary Golay pairs to alleviate the mutual interference. Particular Golay combined with the original Golay code to suppress the range side-lobes from second-order interference. To maintain the frame rate another side-lobe suppression technique is also developed using the orthogonality between Golay pairs. Hydrophone experiments show that, the Golay waveform improves the compression quality in DHI as compared to the Chirp counterpart by 13.9% and 11.3%. B-mode phantom imaging show that, the proposed Golay waveform can improves the SNR by 10 dB and effectively eliminates the Side-lobes magnitude (SLM) by 7.5 dB.

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