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.
The emergence of functional MRI (fMRI) and diffusion tensor imaging (DTI) has made MRI the method of choice to study functional and structural integrity of the human brain in healthy and in diseased populations. Both fMRI and DTI rely on fast imaging techniques, which suffer from vulnerability to magnetic field inhomogeneities. The current magnetic field shimming techniques, however, are often not adequate in addressing high-order non-uniformities in local brain regions. The integrated shim and radiofrequency (RF) approach, proposed in this project, inherently combines local shimming with parallel RF reception into one single array coil, and can achieve much improved magnetic field uniformity and high sensitivity, as well as significant space savings potentially removing the need for whole-body shimming coils. We expect that our integrated solution would greatly increase the spatial fidelity and image quality of all fMRI and DTI images widely used in neuroscience applications, with a wider still applicability to other organs throughout the body. Moreover, it may lead to a design for the next-generation MRI scanner with improved imaging performance for better diagnostic accuracy, widened bore for greater patient comfort, and reduced manufacturing cost for higher economic impact - all important factors to improve the quality of our healthcare.
| Darnell, Dean; Ma, Yixin; Wang, Hongyuan et al. (2018) Adaptive integrated parallel reception, excitation, and shimming (iPRES-A) with microelectromechanical systems switches. Magn Reson Med 80:371-379 |
| Darnell, Dean; Cuthbertson, Jonathan; Robb, Fraser et al. (2018) Integrated radio-frequency/wireless coil design for simultaneous MR image acquisition and wireless communication. Magn Reson Med : |
| Darnell, Dean; Truong, Trong-Kha; Song, Allen W (2017) Integrated parallel reception, excitation, and shimming (iPRES) with multiple shim loops per radio-frequency coil element for improved B0 shimming. Magn Reson Med 77:2077-2086 |
