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RISS 인기검색어
- 검색키워드
- 저자 : Jinbum Kang (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Kang, Jinbum,Jang, Won Seuk,Yoo, Yangmo Institute of Physics in association with the Ameri 2018 Physics in medicine & biology Vol.63 No.4
<P>Ultrafast compound Doppler imaging based on plane-wave excitation (UCDI) can be used to evaluate cardiovascular diseases using high frame rates. In particular, it provides a fully quantifiable flow analysis over a large region of interest with high spatio-temporal resolution. However, the pulse-repetition frequency (PRF) in the UCDI method is limited for high-velocity flow imaging since it has a tradeoff between the number of plane-wave angles (<I>N</I>) and acquisition time. In this paper, we present high PRF ultrafast sliding compound Doppler imaging method (HUSDI) to improve quantitative flow analysis. With the HUSDI method, full scanline images (i.e. each tilted plane wave data) in a Doppler frame buffer are consecutively summed using a sliding window to create high-quality ensemble data so that there is no reduction in frame rate and flow sensitivity. In addition, by updating a new compounding set with a certain time difference (i.e. sliding window step size or <I>L</I>), the HUSDI method allows various Doppler PRFs with the same acquisition data to enable a fully qualitative, retrospective flow assessment. To evaluate the performance of the proposed HUSDI method, simulation, <I>in vitro</I> and <I>in vivo</I> studies were conducted under diverse flow circumstances. In the simulation and <I>in vitro</I> studies, the HUSDI method showed improved hemodynamic representations without reducing either temporal resolution or sensitivity compared to the UCDI method. For the quantitative analysis, the root mean squared velocity error (RMSVE) was measured using 9 angles (−12° to 12°) with <I>L</I> of 1–9, and the results were found to be comparable to those of the UCDI method (<I>L</I> = <I>N</I> = 9), i.e. ⩽0.24 cm s<SUP>−1</SUP>, for all <I>L</I> values. For the <I>in vivo</I> study, the flow data acquired from a full cardiac cycle of the femoral vessels of a healthy volunteer were analyzed using a PW spectrogram, and arterial and venous flows were successfully assessed with high Doppler PRF (e.g. 5 kHz at <I>L</I> = 4). These results indicate that the proposed HUSDI method can improve flow visualization and quantification with a higher frame rate, PRF and flow sensitivity in cardiovascular imaging.</P>
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Jinbum Kang,Yeajin Kim,Wooyoul Lee,Yangmo Yoo IEEE 2017 and Frequency Control Vol.64 No.11
<P>Chirp-coded excitation can increase the signal-to-noise ratio (SNR) without degrading the axial resolution. Effective pulse compression (PC) is important to maintain the axial resolution and can be achieved with radio frequency (RF) and complex baseband (CBB) data (i.e., PCRF and PCCBB, respectively). PCCBB can further reduce the computational complexity compared to PCRF; however, PCCBB suffers from a degraded SNR due to tissue attenuation. In this paper, we propose a new dynamic CBB PC method (PCCBB-Dynamic) that can improve the SNR while compensating for tissue attenuation. The compression filter coefficients in the PCCBB-Dynamic method are generated by dynamically changing the demodulation frequencies along with the depth. For PC, the obtained PCCBB-Dynamic coefficients are independently applied to the in-phase and quadrature components of the CBB data. To evaluate the performance of the proposed method, simulation, phantom, and in vivo studies were conducted, and all three studies showed improved SNR, i.e., maximally 3.87, 7.41, and 5.75 dB, respectively. In addition, the measured peak range sidelobe level of the proposed method yielded lower values than the PCRF and PCCBB, and it also derived a suitable target location, i.e., a <0.07-mm target location error, while maintaining the axial resolution. In an in vivo abdominal experiment, the PCCBB-Dynamic method depicted brighter and clearer features in the hyperechoic region because highly correlated signals were produced by compensating for tissue attenuation. These results demonstrated that the proposed method can improve the SNR of chirp-coded excitation while preserving the axial resolution and the target location and reducing the computational complexity.</P>
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