Development of a chirp radar-type microwave computed tomography with the rotational scanner used for animal experiments

研制了用于人体无创测温的线性调频雷达型微波CT原型系统。在本研究中，通过在层析测量中引入旋转扫描，尝试了CP-MCT的高速成像。原型系统，它使用的线性调频脉冲信号从1 GHz到2 GHz，通过重复的平移扫描和旋转扫描的一对发射和接收天线收集投影数据。原型系统的空间分辨率估计约为1cm和0.7度的温度变化已经可视化，虽然它需要大约100分钟的数据acquisition.The开发的旋转扫描器是由一个发射天线，这是介质加载的发射天线和接收阵列天线，这是由21个小偶极子天线。从1 GHz到2 GHz的啁啾脉冲信号从发射天线照射到浸没在盐水溶液中的目标。由于介质加载波导天线的增益图案相当宽，因此确保了扇形波束投影。发射天线和接收天线以282 mm的距离彼此面对。每个偶极子与相邻偶极子天线的距离为14.7 mm，以减少相互耦合效应。其中，扫描器的扇形角变为60度。所开发的扫描器的空间分辨率与预测的空间分辨率相同，但由于旋转扫描器的采样间隔较粗，因此比原型系统的空间分辨率差。然而，这使我们能够开发新的旋转扫描仪与41个小偶极天线的动物实验。除了高速成像外，还发展了利用FD-TD方法计算点扩散函数的图像去模糊技术。

The prototype system of the chirp radar-type microwave computed tomography (CP-MCT) was developed for noninvasive thermometry of the human body. High speed imaging of CP-MCT has been attempted in this study by introducing the rotational scan in the tomographic measurement. The prototype system, which uses the chirp pulse signal from 1 GHz to 2 GHz, collects projection data by repeating the translational scan and rotational scan of a pair of the transmitting- and receiving-antenna. The spatial resolution of the prototype system is estimated at approximately 1cm and 0.7 degree temperature variation has been visualized, although it takes approximately 100 minutes for data acquisition.The developed rotational scanner is composed of a transmitting antenna that is the dielectric loaded transmitting antenna and a receiving array antenna, which is composed of 21 small dipole antennas. Chirp pulse signal from 1 GHz to 2 GHz is irradiated from the transmitting antenna to a target immersed in saline solution. Since gain pattern of the dielectric-loaded waveguide antenna is fairly broad so that, fan beam projection is secured. The transmitting- and receiving-antenna are facing each other at a distance of 282 mm. Each dipole is arranged at a distance of 14.7 mm from adjacent dipole antennas to reduce the mutual coupling effect. Where, fan angle of the scanner becomes 60 degrees.Spatial resolution of the developed scanner is the same value with the predicted one that is worse than that of the prototype system due to its coarse sampling interval of the rotational scanner. However, this enabled us to develop the new rotational scanner with 41 small dipole antennas for animal experiments. It requires only 90 seconds for data acquisition.In addition to high speed imaging, image deblurring technique has also been developed by using the point spread function computed by FD-TD method.