The motivation for this STTR project is to improve the application of MRI technology by reducing scan times and improving spatial resolution. We intend to accomplish this by taking advantage of a neurophysiological loophole: the threshold for bio-effects due to gradient fields can be significantly raised by dramatically shortening magnetic field rise-times. In Phase I, we constructed an ultra-fast gradient driver and coil apparatus using novel pulsed-power techniques. These methods allowed us to test bio-effects in several invertebrate models, using magnetic slew rates that were 200,000 times higher than those used in typical clinical systems. In Phase II we will follow up these initial experiments with even higher slew rates, in order to conduct pre- clinical heart studies in a 4.7 Tesla MRI. These animal heart studies will measure specific absorption rate, establish thresholds for fibrillation, assess image quality, and detect any histological changes that might occur at ultra-high slew rates. For subsequent human volunteer experiments, we will set a maximum slew rate for exposure at a level significantly below the lowest threshold found to induce fibrillation in the animal hearts. In this human subject pilot study, we will adapt our ultra-fast gradient system to fit in a 3T MRI system, to determine the threshold for discomfort, and to assess image quality in MR carotid arteriograms. Our clinical progress will set the stage for dissemination of the technology into the marketplace, while our technical efforts will prepare for high-resolution fast Phase III neonatal cardiac studies. Clinically, our effort will be coordinated with a leading pediatric research center (Children's National Medical Center) and the nation's pre-eminent Historically Black University (Howard University) to deliver a product of particular relevance to the pediatric population, a segment recognized as under-served by the NIH. The regulatory and scientific aspects of this study are expected to be ground-breaking, revealing bio-effect data about gradient regimes never studied experimentally. These findings will likely be of great interest to all MRI system manufacturers and users once they are validated.
MRI scans are widely used to examine blood vessels. Many groups are trying to study the heart with MRI. An important factor in the quality of MRI images is the speed at which magnetic fields can be changed. Unfortunately, high speeds are limited because of side-effects. We have shown in animals that side effects can be eliminated with certain techniques. We will study this phenomenon in humans.
| Weinberg, Irving N; Stepanov, Pavel Y; Fricke, Stanley T et al. (2012) Increasing the oscillation frequency of strong magnetic fields above 101 kHz significantly raises peripheral nerve excitation thresholds. Med Phys 39:2578-83 |
