Neurostimulation systems: Assessment of magnetic field interactions associated with 1.5- and 3-Tesla MR systems

Purpose: To evaluate magnetic field interactions at 1.5-and 3-Tesla for implantable pulse generators (IPGs) and radiofrequency (RF) receivers used for implantable neurostimulation systems. Materials and Methods: Measurements of magnetically induced displacement force and torque were determined for 10 devices (seven IPGs, three RF receivers) used for neurostimulation systems. Displacement force and torque were assessed at various positions in 1.5- and 3-Tesla MR systems using standardized techniques. Results: Four IPGs exhibited force ratios (magnetic attraction force/device weight) greater than 1.0, with the overall magnitude of the force ratio increasing significantly when comparing the 1.5-Tesla to the 3-Tesla MR system. Of the seven IPGs tested, one exhibited a torque ratio (magnetic induced torque/product of the device weight and length) greater than 1.0. The RF receivers displayed relatively strong magnetic field interactions at both 1.5- and 3-Tesla, exhibiting force and torque ratios greater than 1.0. Conclusions: The neurostimulation implants tested exhibited varying degrees of magnetic field interactions, with four of the seven IPGs and the three RF receivers exhibiting at least one MR-induced force or torque value greater than the effect of gravity. These findings have important implications for patients with these implants who are referred for MRI examinations.