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FPGA Based Experimental Platform for High Frequency Ultrasound B-Mode Imaging |
School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China |
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Abstract High frequency ultrasound imaging has been extensively applied to smallscale tissue observation in clinic and biomedical research area because of its high-resolution. New processing algorithms have ceaselessly been proposed in this area to improve the image quality. A flexible experimental platform which function can be changed by programming is needed to test the new algorithms. This kind of platform should have the ability to adapt different frequencies of the probes. It also needs to provide sufficient resources to host the algorithms under test and of course the convenient debugging tool is another necessity. We recently developed a Field Programmable Gate Array (FPGA) based experimental platform for these purposes. It scans the tissue by single element probe which central frequency is between 10 MHz and 50 MHz. The platform features an independent scanning control unit to ensure that data acquiring process is always right and the resulting realtime B-mode images are displayed on a screen no matter the algorithm under test works well or not. There is a largescale FPGA on board to host the algorithm under test, and many general purpose processing modules, such as bandpass filter, orthogonal demodulation, down sampling, amplitude detecting and logarithmic compression modules are prepared in the FPGA. In addition, we developed a debug tool. With this tool one can read RAMs outside the FPGA at any addresses and move the data into a computer connected to the FPGA by JTAG. The software based on the MATLB can plot the data on the computer screen as a waveform or a B-mode image depends on the dimensionality of the data that are under check. We tested the platform by scanning the volunteers’ eyes with a 10 MHz probe. Results show that the band-pass filter is effective in reducing the RF noise. It is also showed that, in the condition of 50 MHz clock rate, the total time from the data is sampled to demodulated is only 85.34 μs for each A-line of 64 mm deep, while amplitude detection and logarithmic compression take 340 ns only.
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