SNR Variability with Frontal Coil Plate Displacement in 3T Head MRI

In head MRI applications, flexible RF receive-only head coils can offer improved SNR and patient comfort. In our work, we achieve partial, but sufficient, flexibility by decomposing an average head surface into movable, semi-flexible plates that comfortably adapt to the surface of the head. As a result, we can include a larger number of smaller elements, pushing the boundary of achievable SNR while still being able to resolve brain areas. In order to test the viability of the design, we investigate the SNR variability of two 12-channel frontal plate arrays when they are adapted to fit differently sized heads. The elements were constructed on a 3D-printed thermoplastic polyurethane (TPU) flexible substrate, with conductive loops on the inside surface to minimize their distance to the head. Experiments were conducted in an MRI scanner in which a spherical phantom was imaged by the frontal plate arrays together at four positions. We demonstrate that SNR decreases, as expected, as the gap between the plates increases, but in an acceptable range. The overall range of inter-plate distance results in SNR variability of approximately 15%. These results support the overall feasibility of the larger head coil composed of eight movable plates: the mechanical gaps that would appear for larger heads would not compromise the SNR and, therefore, signal integrity and would still outperform a similar fixed-size head coil.