Optimal geometry and capacitors distribution of 7T MRI surface coils

Surface coils are used widely in magnetic resonance imaging (MRI) application for their ability to operate in receive mode with high signal-to-noise ratio (SNR). In this work we show how the choice of the polygonal geometry and the number of distributed capacitors affects the coil overall performance. Several surface coils, tuned at 297.2 MHz, were designed and built, using different polygonal geometries and different number of the capacitors. Realized coils were tested and characterized by laboratory workbench in order to extract several quality indices. In addition, experiments were done in a whole body MRI scanner to evaluate the SNR. The optimal choice of coil shape and capacitors numbers allows us to obtain high-quality surface coils tuned at frequencies in the ultra-high field. According to the signal to noise ratio images, the circular shaped coil with four capacitors shows the most uniformity of the B₁⁺ RF-field.