Multi-coil MR imaging with a receive array of eight microcoils

Introduction Three-dimensional microcoils are used in medical technology for high-resolution magnetic resonance analysis at the micro level. The coil sensitivity, and therefore the desired signal, is maximized when the size of the coil matches that of the sample [1]. Micro solenoids show exceptional performance compared to planar coils and due to their 3-D shape, the B1 field is stronger and more uniform [2]. Difficult 3-D processes [3] or hand-made coils [4] prevented the production of suitable, reproducible, and economical coils. As devices are often single use, low-cost solutions are required. Receive coil arrays have been introduced in MRI to take advantage of improved local SNR in their reduced active volume. Parallel techniques lead to a reduction of phase gradient steps for imaging which eventually accelerates imaging acquisition [5]. In an arrangement of coils close to each other, mutual inductance leads to coupling between the coils. Therefore, coil decoupling needs to be done carefully. In case of microcoils, the corresponding sensitive volume is small, only extending around one to two coil diameters outside the coil volume. Consequently, arranging microcoils not too close to each other, mutual coil inductance can be neglected. We present an array of eight microcoils, which was produced using MEMS technology being therefore very cost-effective. It is a suitable environment for testing parallel excitation and simultaneous detection schemes suitable for high-throughput and disposable MR analysis.