Article

Optimal transmit phasing on tissue background suppression in contrast harmonic imaging

Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
Ultrasound in medicine & biology (Impact Factor: 2.1). 07/2008; 34(11):1820-31. DOI: 10.1016/j.ultrasmedbio.2008.04.010
Source: PubMed

ABSTRACT Ultrasonic harmonic imaging provides superior image quality than linear imaging and has become an important diagnostic tool in many clinical applications. Nevertheless, the contrast-to-tissue ratio (CTR) in harmonic imaging is generally limited by tissue background signal comprising both the leakage harmonic signal and the tissue harmonic signal. Harmonic leakage generally occurs when a wideband transmit pulse is used for better axial resolution. In addition, generation of tissue harmonic signal during acoustic propagation also decreases the CTR. In this paper, suppression of tissue background signal in harmonic imaging is studied by selecting an optimal phase of the transmit signal to achieve destructive cancellation between the tissue harmonic signal and the leakage harmonic signal. With the optimal suppression phase, our results indicate that the tissue signal can be significantly reduced at second harmonic band, whereas the harmonic amplitude from contrast agents shows negligible change with the selection of transmit phase. Consequently, about 5-dB CTR improvement can be achieved from effective reduction of tissue background amplitude in optimal transmit phasing.

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    • "shen et al. proposed a technique transmitting a fundamental and a phase-shifted third-harmonic wave simultaneously to cancel the second harmonic [12], [13]. The same group also used the harmonic leakage signal to produce the secondharmonic reduction signal [14], [15]. all of the aforementioned methods are single-pulse techniques, and many multi-pulse techniques have also been proposed to increase the cTr. "
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    • "Currently, only the experimental transducers with interleaved high-and low-frequency elements are available (Bouakaz et al 2004, van Neer et al 2010). An alternative method to improve the ATR 2 by reducing P tis 2 was introduced by Shen and Hsieh (2008), who proposed to use the harmonic leakage signal to generate the second harmonic reduction signal. The imaging protocol was based on a constant phase shift between the emitted fundamental pulse and the leakage signal. "
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