Assessment of MRI issues at 7 T for 28 implants and other objects.
OBJECTIVE
Metallic implants are currently a contraindication for volunteer subjects and patients referred for 7-T examinations because of concerns related to magnetic field interactions and MRI-related heating. Artifacts may also be problematic. Therefore, the purpose of this investigation was to evaluate these MRI issues for 28 implants and other objects in association with a 7-T MR system.


METHODS
Tests were performed at 7 T using standardized procedures to evaluate magnetic field interactions (translational attraction and torque) for all 28 items. MRI-related heating and artifacts were assessed using spin-echo and gradient-echo pulse sequences, respectively, for two aneurysm clips located within a transmit-receive head radiofrequency coil.


RESULTS
Eight of the 28 items showed magnetic field interactions at levels that could pose risks to human subjects. The two aneurysm clips exhibited heating, but the temperature rise did not exceed 1°C. Artifacts were dependent on the material and dimensions of each aneurysm clip.


CONCLUSIONS
These findings show that certain implants and objects may be acceptable for human subjects undergoing MRI examinations at 7 T, whereas others may involve possible risks. This information has important implications for individuals referred for MRI examinations at 7 T.
1 Department of Radiology and Radiological Sciences, Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave S, Medical Center N, AA-1105, Nashville, TN 37232-2310.
Adrienne N
AN
Dula
John
J
Virostko
Frank G
FG
Shellock
D016477:Artifacts; D004869:Equipment Safety; D006358:Hot Temperature; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects / Q000379:methods*; D008670:Metals; D019736:Prostheses and Implants; D018570:Risk Assessment
D008670:Metals