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| An efficient quadrature demodulator for medical ultrasound imaging |
| Hao Zhou, Yin-fei Zheng |
| MOE Key Laboratory for Biomedical Engineering, Zhejiang University, Hangzhou 310027, China |
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Abstract Quadrature demodulation is used in medical ultrasound imaging to derive the envelope and instantaneous phase of the received radio-frequency (RF) signal. In quadrature demodulation, RF signal is multiplied with the sine and cosine wave reference signal and then low-pass filtered to produce the base-band complex signal, which has high computational complexity. In this paper, we propose an efficient quadrature demodulation method for B-mode and color flow imaging, in which the RF signal is demodulated by a pair of finite impulse response filters without mixing with the reference signal, to reduce the computational complexity. The proposed method was evaluated with simulation and in vivo experiments. From the simulation results, the proposed quadrature demodulation method produced similar normalized residual sum of squares (NRSS) and velocity profile compared with the conventional quadrature demodulation method. In the in vivo color flow imaging experiments, the time of the demodulation process was 5.66 ms and 3.36 ms, for the conventional method and the proposed method, respectively. These results indicated that the proposed method can maintain the performance of quadrature demodulation while reducing computational complexity.
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Received: 10 June 2014
Published: 03 April 2015
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用于医学超声成像的高效正交解调器
目的：针对数字化医学超声成像时信号解调操作运算量较大的问题，简化正交解调操作，减少信号解调运算量。
创新点：设计一对正交解调数字滤波器，省去传统解调方法中回波信号与载波信号相乘的操作，从而提高解调操作效率，并保证超声成像结果不变。
方法：1.针对正交解调表达式特点，将混频操作与低通滤波操作相融合，从而提升正交解调运算效率（图1b）；2.利用有限冲激响应滤波器系数对称特性，设计系数对称的解调滤波器（图2）；3.进行仿真与在体（in vivo）实验，评估正交解调器效率与精度。
结论：针对医学超声成像，提出一种高效的正交解调方法，在降低运算量的同时保证成像精度与传统正交解调方法相近。同传统正交解调方法一样，该方法还可用于旋转相位波束合成技术中。
关键词：
B型超声成像,
彩色血流成像,
正交解调,
有限冲激响应滤波器
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