Implantable microstimulator: magnetic resonance safety at 1.5 Tesla.
OBJECTIVE
Ex vivo testing is necessary to characterize implants to determine if it is safe for the patient to undergo a magnetic resonance imaging (MRI) examination. Therefore, the objective of this study was to evaluate MR safety for an implantable microstimulator in association with a 1.5 Tesla MR system.


METHODS
A microstimulator (RF BION, Alfred E. Mann Foundation for Scientific Research, Valencia, CA) was evaluated for magnetic field interactions and MRI-related heating. The functional aspects of this implant were assessed immediately before and after exposure to MRI (15 different pulse sequences). Artifacts were also characterized.


RESULTS
Magnetic field interactions exhibited by the microstimulator will not pose a hazard after a suitable postimplantation period has elapsed. Temperature changes will not pose a risk. The function of the microstimulator was unaffected by MRI. Artifacts will only create a problem if the area of interest is in proximity to this implant (largest artifact area: T1-weighted spin echo, 2291 mm2; gradient echo, 3310 mm2).


CONCLUSIONS
The overall findings indicated that it is safe for a patient with the microstimulator to undergo MRI at 1.5 Tesla by following specific safety guidelines described herein.
Shellock
Frank G
FG
University of Southern California, Los Angeles, CA 90045, USA. frank.shellock@gte.net
Cosendai
Gregoire
G
Park
Sung-Min
SM
Nyenhuis
John A
JA
D016477:Artifacts; D004599:Electric Stimulation Therapy / Q000295:instrumentation*; D004574:Electromagnetic Fields / Q000009:adverse effects; D004869:Equipment Safety; D006358:Hot Temperature; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects* / Q000295:instrumentation* / Q000592:standards; D008839:Microelectrodes; D009422:Nervous System Diseases / Q000628:therapy; D019047:Phantoms, Imaging; D019736:Prostheses and Implants