超音波(Ultrasound)成像因為具有較好的時間解析度以及相對低的成本，對於監測高能量聚焦超音波(HIFU)的治療手術有很好的潛力。然而，超音波引導HIFU治療監測經常會受到強烈的HIFU干擾，這種干擾會蓋過成像陣列接收到的回音訊號使得監測無法順利進行。為了避免干擾，在我們先前研究方法中，使用了格雷編碼(Golay-encoded)結合脈衝反向(Pulse-inversion subtraction)技術來達成消除HIFU干擾。其中消除干擾的部分，是透過脈衝反向的過程來消除HIFU干擾，並藉由格雷編碼激發的特性，透過格雷解碼(Golay-decoding)來增強影像信號。
本論文提出了只需使用格雷編碼激發並透過調整格雷編碼位元長度就能夠達成消除HIFU干擾的效果。也因為採用了格雷編碼激發，在消除干擾的同時能有效的增強影像信號。且除去了脈衝反向過程的額外發射，對於運動偽影(motion artifact)的影響應能有效的降低。其中格雷編碼位元長度需調整與發射HIFU 波形週期為特定比例，在本研究中分別以Case I (四分之一的奇數倍)與Case II (四分之一的偶數倍)統稱。
研究結果顯示使用4位元格雷編碼發射時，能在Case I以及Case II將HIFU干擾信號有效的消除，且峰值訊雜比(PSNR)在經過格雷解碼過後，能有效提升大約20 dB。值得注意的是，在HIFU諧波消除的部分，Case I中僅能消除奇數階諧波信號，而在Case II當中則可以消除所有HIFU諧波信號。
此外，本研究提出的方法也適用於HIFU連續波傳輸，相較於脈衝波傳輸，HIFU信號整體強度會因改成連續波傳輸而有所提升，HIFU諧波信號影響可由連續波傳輸實驗結果清楚的觀察到在Case II中因消除所有HIFU諧波信號，表現得比Case I還理想。

Ultrasound (US) imaging has high potential in monitoring high-intensity focused ultrasound (HIFU) treatment due to its superior temporal resolution and relatively low cost. However, US monitoring is often hindered by strong HIFU interference which overwhelms the echoes received by the imaging array. In order to avoid the HIFU interference, in our previous study, we have proposed a Golay-encoded US-gHIFU method by combining Golay excitation with PI subtraction for real-time US monitoring of HIFU treatment. It eliminates HIFU interference in the process of the PIS and enhances the image signal through the Golay decoding.
In this study, we propose only using the Golay-encoded by adjusting the bit length of Golay code for eliminating HIFU interference. Due to adapting Golay excitation, it effectively eliminates HIFU interference patterns in real-time US imaging and also enhances the image signal. In addition, the extra emissions in the process of PIS is removed. It should effectively reduce the motion effect. In the method, the bit length of Golay code needs to be relative to the period of HIFU. For convenience, we will call Case I (odd integer multiples of the HIFU quarter period) and Case II (even integer multiples of the HIFU quarter period).
Experimental results show that 4-bit Golay transmit in Case I and Case II can eliminate the HIFU interference and increase the PSNR of US monitoring image by about 20 dB. It should be noted that, however, the result of eliminating HIFU harmonics in the Case I and Case II. In Case I, it only eliminates odd-order HIFU harmonics. In contrast, it not only eliminates odd-order HIFU harmonics but also even-order HIFU harmonics.
In addition, the proposed method is also works for continuous-wave HIFU transmission. Compared with pulse-wave HIFU transmission, the HIFU signal intensity will be higher. Obviously, in the continuous-wave HIFU transmission experiment, the performance in Case II markedly outperforms Case I by eliminating all HIFU harmonics.

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民國107年。
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