Study on coded excitation in color flow mapping system
LI Peng1, CHEN Yu-quan1, HU Da-ke2, ZHENG Yin-fei2
1. Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China;
2. Department of Instrument Science and Technologies, Zhejiang University, Hangzhou 310027, China
To circumvent the problem that the conventional color flow map（CFM） imaging’s frame rate is seriously decreased, a new method using coded excitation to get the flow velocity estimate was proposed. The method uses a broad band coded signal as excitation instead of a narrow band pulse. The received broad band signal is divided into a number of narrow band signals by filtering with a number of band filters. As these band filters have different center frequencies, the filtered signals can be seen as a number of narrow band signals which are separated in time domain. In order to improve the vertical resolution, the narrow band signals must be pulsecompressed by matched filters. Then an improved autocorrelation approach is applied on the several narrow band signals to obtain the flow velocity estimate. Finally,all the velocity estimates from each narrow band are averaged to obtain an improved velocity estimate. The result shows that, as each excitation leads to an estimated value of the velocity, this new method substantially increases the frame rate of CFM imaging.
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