1.School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China 2.Department of Medical Engineering, University of South Florida, Florida 33612, USA
Fund Project:Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61701076) and the Key Research and Development Program of Science and Technology Planning Project of Sichuan Province, China (Grant Nos. 2019YFS0119, 2019YFS0127)
Received Date:01 July 2020
Accepted Date:04 August 2020
Available Online:08 December 2020
Published Online:20 December 2020
Abstract:Thermoacoustic imaging (TAI) is an emerging biomedical imaging method in which microwave is used as an excitation source to generate acoustic signals. The TAI possesses the advantages of high contrast of microwave imaging and high resolution of ultrasound imaging, which is also noninvasive. While the signal-to-noise ratio (SNR) of TAI is often very low. It is usually required by averaging the thermoacoustic signal many times to improve the SNR. However, averaging the signal to improve the SNR can significantly reduce the TAI’s time resolution, which hinders the development of rapid TAI. Here in this paper, we propose to reduce the cost and improve the time resolution of TAI based on multi-channel amplifier and additive circuit. The received thermoacoustic signals are divided into 4 channels and then entered into 4 amplifiers simultaneously.After being amplified, the signals are added and collected by the data acquisition system for reconstructing the image. The phantom results indicate that the time resolution of TAI increases 5 times and the SNR rises from 6 dB to 12 dB, with the multi-channel amplifier and additive circuit adopted. The method proposed in this paper is helpful in promoting the development and clinical application of TAI, especially it has a great significance for developing the ultra-fast TAI. Keywords:thermoacoustic imaging/ low cost/ additive circuit/ time resolution
4.实验结果与讨论实验对象为浓度2%的NaCl 溶液, 溶液分别装在5个直径为3 mm的薄壁塑料管中作为吸收体. 首先进行如图1(b)所示的采集方案, 热声信号分成四路进入四通道放大器放大, 放大后的信号输入到加法电路进行累加后进行采集, 完成四通道加法电路数据采集后, 保持吸收体不动, 将图1(b)所示采集方式切换至图1(a)完成单通道的采集. 在图4中展示了两种采集方法在平均50次时采集的热声信号. 定性比较两种采集方法, 四通道信号的信噪比要明显优于单通道. 在图5中绘制了四通道加法电路和单通道的成像结果. 图 4 平均 50 次单通道和四通道加法电路信号对比图 Figure4. Fifty times averaged signal amplitudes measured using the single-channel and four-channel amplifier and additive-circuit methods.
图 5 仿体重建热声图 (a) 四通道加法电路不平均; (b) 四通道加法电路平均 25 次; (c) 四通道加法电路平均 50次; (d) 单通道不平均; (e) 单通道平均25次; (f) 单通道平均50次 Figure5. Recovered TA images from phantom experimental data using the four-channel amplifier and additive circuit without average (a), the four-channel amplifier and additive circuit with 25 times average (b), the four-channel amplifier and additive circuit with 50 times average (c), the single channel without average (d), the single channel with 25 times average (e), and the single channel with 50 times average (f).