Reduced Susceptibility Artifacts in Diffusion Weighted Brain Imaging Using Specialized RF and Gradient Hardware

INTRODUCTION: Diffusion Weighted Imaging (DWI) techniques have improved due to increased magnetic field strength and improved Radio Frequency (RF) and gradient coil performance[1]. Improved gradient performance is used to shorten the echotrain duration and increase the number of echoes in the same duration, thereby reducing susceptibility artifacts[2,3]. In this study, we combine a home-built insert gradient with the body gradient (BG) on our research 3T MRI scanner to create a composite gradient (CG) system with increased gradient performance (Figure 1). Because the body RF coil does not penetrate strongly through the RF shield of the insert gradient, we have developed a shielded high pass birdcage coil for use with our CG system (Figure 2). Due to the birdcage’s small size it has high SNR when compared with the body RF coil, and it deposits much less SAR over the entire body such that the patient experiences much less RF heating. To test the potential utility of this system for DWI measurement, we compare diffusion weighted images obtained using only the BG coils and using the CG system.