Designing and Fabrication of a New Radiofrequency Planar microcoil for mini-Nuclear Magnetic Resonance

Introduction Radiofrequency planar microcoils are used to increase the resolution of magnetic resonance images of small samples. In this study, we aimed to design and fabricate a spiral planar microcoil constructed on a double-sided printed circuit board (PCB). It has four rings with an internal diameter of 241 microns tuned and matched at 63.8 MHz. Materials and Methods To achieve the maximum signal-to- noise ratio (SNR) and quality factor of the coil, its geometry was optimized based on parameters such as width (w) and thickness (h) of the copper rings, the distance between the rings, inner radius of the microcoil  (Ri), and the number (N) of coil rings by using COMSOL, ADS, and MATLAB software packages. Results Our findings indicated that the Q factor and SNR of the coil at resonance frequency of 63.8 MHz are 63.149 and 168.23, respectively, which are higher than the equivalent features of the pervious coils. In addition, to evaluate the function of matching and tuning circuit, reflection coefficient factor (S11) of the coil was experimentally measured to be -48 dB at resonance frequency of 63.8 MHz, which is consistent with the simulated value. Conclusion In this study, a new microcoil was designed and fabricated to produce images of very small samples and volumes in microliter dimensions. The results showed that this new microcoil has superior capability in imaging very small samples compared to the conventional coils applied in magnetic resonance imaging devices.