Cardiac pacemakers and implantable cardioverter defibrillators are unaffected by operation of an extremity MR imaging system.
OBJECTIVE
The objective of our investigation was to determine whether an MR imaging system designed to obtain images of the extremities affects the safety and functionality of pacemakers or that of implantable cardioverter defibrillators (ICDs).


METHODS
Ex vivo experiments were conducted in which seven pacemakers and seven ICDs were exposed to a 0.2-T extremity MR imaging system. Magnetic field attraction was assessed at three positions relative to the MR imaging system. In addition, the devices were placed into a test apparatus that was oriented parallel and perpendicular relative to the MR imaging system while imaging was performed on a phantom using T1-weighted spin-echo and gradient-echo sequences. Various functional aspects of the pacemakers and ICDs were evaluated before, during (pacemakers only), and after MR imaging.


RESULTS
Magnetic field attraction was relatively minor for all devices. The quality of the MR images was unaffected by the devices. Operation of this MR system did not alter any of the functional aspects of the pacemakers or ICDs evaluated in this study.


CONCLUSIONS
According to these data and in consideration of how patients are positioned during examinations--that is, positioned so that the thorax (where the pacemaker or ICD and the corresponding leads are located) does not enter the magnet bore--the results suggest that it should be safe to perform MR imaging in patients with the pacemakers and ICDs evaluated in this study.
Shellock
F G
FG
Department of Radiology, University of Southern California, and Shellock R & D Services, Inc., Los Angeles 90045, USA.
O'Neil
M
M
Ivans
V
V
Kelly
D
D
O'Connor
M
M
Toay
L
L
Crues
J V
JV
D001132:Arm; D017147:Defibrillators, Implantable; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008280:Magnetics; D010138:Pacemaker, Artificial; D019047:Phantoms, Imaging; D011187:Posture