Pasquier A, Le Diraison Y, Serfaty S, Joubert P-Y
Annu Int Conf IEEE Eng Med Biol Soc. 2020 Jul;2020:4105-4108. doi: 10.1109/EMBC44109.2020.9175769.
The aim of this paper is to experimentally assess the capacity of radio-frequency flexible sensors to localize a dielectric object inside a fluid, which could be used as a non contact sensor detected to the detection or the monitoring a local modification of a tissue, such as a tumor or a lesion. The used sensor is an MRI-like antenna, which consists in a flat, flexible and low cost multi-turn split resonator (MTLR), which features a geometrically pre-determined resonance frequency. The MTLR is used here as a transmit and receive sensor monitored by a distant loop coil. The complex impedance changes observed at the ends of the monitoring coil is known to be linked to the dielectric properties of the resonator environment. If a dielectric object is placed close to the resonator, the complex impedance is altered. In this work, an experimental set up is used to assess the relevance of such a measurement scheme to detect the presence of a dielectric inclusion embedded in another dielectric medium. The setup includes a spherical object of 1.5 cm diameter filled with various NaCl solutions moved vertically inside a tank filled with deionized water by means of a three axis robotic arm, to create an electrical conductivity contrast between the inclusion and the media, and three 2 cm diameter MTLR sensors featuring 30, 47 and 70 MHz resonance frequencies, respectively. The sensors are operated through the use of monitoring coils connected to a network analyzer, and measurements are carried out at each position of the spherical object. The resulting sensor responses are plotted and used for the assessment of sensor performances. In addition, a method to combine the multi-frequency data provided by the three different sensors is proposed. Two different metrics regarding the spatial resolution (SR) and the peak signal to noise ratio (PSNR) are computed to characterize the single sensor performances, as well as the enhancement provided by the proposed multi-frequency approach.
本文的目的是通过实验评估射频柔性传感器在流体中定位介电物体的能力，该传感器可作为非接触式传感器用于检测或监测组织的局部变化，如肿瘤或病变。所使用的传感器是一种类似MRI的天线，它由一个扁平、柔性且低成本的多匝分裂谐振器（MTLR）组成，其具有几何上预先确定的谐振频率。这里MTLR用作由远距离环形线圈监测的发射和接收传感器。已知在监测线圈末端观察到的复阻抗变化与谐振器环境的介电特性有关。如果将介电物体放置在靠近谐振器的位置，复阻抗就会改变。在这项工作中，使用了一个实验装置来评估这种测量方案检测嵌入另一种介电介质中的介电内含物的相关性。该装置包括一个直径为1.5厘米的球形物体，内部填充有各种NaCl溶液，通过三轴机器人手臂在装满去离子水的水箱中垂直移动，以在内含物和介质之间产生电导率对比，以及三个直径为2厘米的MTLR传感器，其谐振频率分别为30、47和70兆赫。传感器通过连接到网络分析仪的监测线圈进行操作，并在球形物体的每个位置进行测量。绘制得到的传感器响应并用于评估传感器性能。此外，还提出了一种组合由三个不同传感器提供的多频数据的方法。计算了关于空间分辨率（SR）和峰值信噪比（PSNR）的两个不同指标，以表征单个传感器的性能以及所提出的多频方法提供的增强效果。
