Improvement of DTI measurement using the Composite Gradient Systems on a Clinical 3T MRI System: DTI study of ex vivo Dog's Heart

INTRODUCTION: Diffusion Tensor Imaging (DTI) techniques have improved due to increased magnetic field strength and improved RF and gradient coil performance. Further improvement in gradient performance could be used to shorten the echotrain duration or increase the number of echoes in the same duration and thereby be of substantial benefit for high resolution DTI acquisition. Although, insert gradient coils can improve gradient performance for the benefit of EPI, diffusion and short TE imaging, their use typically requires that the insert gradients replace the body gradients, which is a logistically difficult process. The ideal MRI system may allow insert gradients to be used in concert with the whole-body gradients so that the best qualities of each gradient system can be dynamically selected for each acquisition. We have implemented hardware on our research 3T MRI scanner to allow simultaneous operation of two gradient systems. To test the potential utility of this system for DTI measurement, we have acquired diffusion weighted images of phantoms, tissue samples, and an excised dog heart using a combination of local insert and standard whole body gradients. Here, we report on the results of DTI of the excised dog heart.