Magnetic Resonance Imaging Technology Development

National Institute Of Neurological Disorders And Stroke

Investigators

Linked publications, trials & patents

Abstract

The magnet of the new human 11.7 T MRI system that was damaged during testing in December 2011 is still out for repair and is slated to return around the end of 2013. Major factors that have held up its repair have been the worldwide helium shortage (about 20,000 liters are required to cool it down) and the decision of the manufacturer to cease production of large MRI magnets. As a result of not having the 11.7 T system available, development of high field technology in MRI has occurred at a lower pace. Chiefly, refinements were made to methods to map the transmit field, and to the transmit coil that will be used for whole head MRI. In addition, elements were put in place to facilitate the monitoring of RF power deposition, including appropriate head phantoms, simulation software, temperature probes, and MRI techniques that enable temperature monitoring. In addition, an initial version of a multi-channel transmit system to be used at 11.7 T has been designed and some of its critical components have been tested on LFMIs animal 11.7 T MRI. Development of acquisition techniques has continued on the 7 T MRI with the main goal of investigating magnetic susceptibility contrast in the human brain. Multi-echo techniques with navigators were developed that allow characterization of the complex signal decay at high field with reduced sensitivity to head motion and respiration-induced signal instability. Some initial applications of this technique are detailed in the accompanying 2012-2013 report for NS003027-07. In parallel with the high field developments, AMRI has continued to develop methods for concurrent EEG-functional MRI (fMRI) acquisition. Over the last year the emphasis has been on developing and testing novel approaches for combined analysis. One example is to correlate fMRI signals with a condensed version of EEG signals that preserves much of their spatial and temporal information. This method was demonstrated to provide novel information about spontaneous brain activity in normal subjects.