Robustness of 7T-MRI flexible array coil behaviour

Magnetic resonance imaging (MRI) strongly relies on signal-to-noise ratio (SNR) parameter that must be as high as possible. The electrical performance of the RF coil is critical to achieve this purpose. Using higher magnetic fields is the most common way to increase the amount of detectable nuclear magnetization, but this generates more complex interactions between the RF field and the subject. This, forces to find the best coil design to obtain an optimal RF signal, for example using a device that fits the very variable anatomies in dimension and shape, leading to the develop of coils that are geometrically adjustable to the subject to analyse. Moreover, the need to have a bigger field of view (FOV) without losing significant SNR, is usually reached increasing the number of coils for the signal detection. The main challenges of designing a flexible array coil is to develop geometry-achieved decoupling for the coil elements. In fact, mutual inductance among coil elements varies with the coil size, thus the flexibility of the coil creates even more complicated decoupling issues. Furthermore, to fit high-density receiver arrays for MRI closely around individual target anatomies, there is a need to provide a high degree of geometric adjustability with ease of handling and patient comfort. In this work is first performed an electrical characterization of the coil to evaluate the RF sensitivity of these flexible devices. Then, this work focuses on the advantages of an array of two smaller coils over a single larger coil, on the decoupling issues performing an MRI simulation over a saline and body-like phantom, measuring the magnetic field penetration with a high frequency (7T) experiment.