MRI compatibility and visibility assessment of implantable medical devices.

We have developed a protocol to evaluate the magnetic resonance (MR) compatibility of implantable medical devices. The testing protocol consists of the evaluation of magnetic field-induced movement, electric current, heating, image distortion, and device operation. In addition, current induction is evaluated with a finite element analysis simulation technique that models the effect of radiofrequency fields on each device. The protocol has been applied to several implantable infusion pumps and neurostimulators with associated attachments. Experiments were performed using a 1.5-T whole-body MR system with parameters selected to approximate the intended clinical and worst case configuration. The devices exhibited moderate magnetic field-induced deflection and torque but had significant image artifacts. No heating was detected for any of the devices. Pump operation was halted in the magnetic field, but resumed after removed. Exposure to the magnetic field activated some of the neurostimulators.

Use of magnetic resonance imaging to analyze the performance of hollow-fiber bioreactors.

Preliminary experiments were described that demonstrate that MRI is an effective tool for the noninvasive study of hollow-fiber bioreactors. Flow-compensated velocity-encoding pulse sequences were successively applied to analyze the velocity patterns in a module operated without cells, with an artificially induced flow field perturbation. Diffusion damping pulse sequences were also used to spatially resolve regions of cell growth in a bioreactor. These experiments provide the necessary basis from which future flow and spectroscopic studies can be conducted.