Pulsed microwave induced thermoacoustic imaging takes advantage of the depth penetration of microwave energy and the resolution of acoustic waves. The microwave source generally employed in thermoacoustic imaging has a pulse width of sub-microsecond, with the energy density of several mJ/cm2 . The excited thermoacoustic wave has a main frequency of 2 MHz, and a resolution of 500 μm can be obtained. With the development of thermoacoustic imaging toward clinical application, it is very important to effectively reduce the radiation dose and improve the imaging resolution, which is a key factor for the successful application of thermoacoustic imaging system. In this paper, we designed a ultra-short microwave induced thermoacoustic imaging system, the experimental results show that this system can improve the generation efficiency of thermoacoustic waves with two orders of magnitude, and the resolution can approximately reach up to about 100 μm.%微波热声成像综合了微波成像和超声成像的优点,具有很好的穿透深度及较高的图像分辨率.热声成像的激发源通常为基于脉冲调制的亚微秒级脉冲微波,激发能量密度约为几mJ/cm2,激发出的热声信号主频通常为2 MHz,成像分辨率约为500 μm.随着热声成像向着临床应用方向发展,能否有效的减小辐射剂量并提高成像分辨率,是热声成像系统设计成败的一个关键因素.为了有效改善微波热声成像中热损伤及分辨率,设计开发了超短脉冲微波热声成像系统,实验结果表明该系统提高了热声转化效率约两个数量级,成像分辨率达到105 μm,为热声成像的临床应用铺平了道路.
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