Magnetic resonance imaging with inherent local shimming

Duke University, Durham NC

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Abstract

? DESCRIPTION (provided by applicant): Magnetic resonance imaging (MRI) is perhaps the most dominant imaging technique for modern neuroscience research because of its high spatial resolution, noninvasiveness, and versatile imaging contrasts. However, MRI is susceptible to main magnetic field (B0) inhomogeneities, as such virtually all MRI scanners are equipped with extensive capabilities for B0 shimming. The traditional whole-body shimming coils, which are used by all leading MRI manufacturers today, often cannot adequately correct for imaging artifacts due to high-order or local B0 inhomogenneities. These artifacts are especially apparent when fast imaging techniques are used such as in functional MRI (fMRI, used to image brain function) and diffusion tensor imaging (DTI, used to image brain connectivity). Recently proposed multi-coil local shimming strategy can perform better in the presence of high-order and local nonuniformities, however, it requires a separate array of shim coils, typically within th RF coil, to be effective and efficient, thus taking up considerable room within the already confined space for subjects. In addition, the shim array would create undesirable electromagnetic interferences and shielding effects, compromising the RF sensitivity and also reducing the flexibility and performance of the local shimming. In practice it would also require the RF coil to be enlarged, further reducing the signal-to-noise ratio (SNR). To address all these limitations and provide greatly improved B0 homogeneity without compromising any RF performance, we propose here to further develop a promising new hardware platform that enables inherent local shimming and parallel RF reception within a single unified coil array. Specifically, extending from our successful preliminary results demonstrating a 16- channel implementation, we will 1) develop and construct a 32-channel head coil array with inherent local shimming and RF reception, and 2) incorporate the newly integrated 32-channel head coil into a GE MR750 3T MRI scanner and validate the many advantages in vivo for fMRI and DTI applications. We anticipate that this new technology, inherently combining RF and shimming components within a single unified coil array, will achieve greatly improved magnetic field homogeneity and high SNR, without the need for separate sets of coils. Moreover, this innovation could be further expanded to image other organs throughout the body, thereby removing the need for whole-body shimming coils altogether and significantly widening the scanner bore to increase patient comfort and reduce manufacturing costs.