Frank G. Shellock

Purpose. To assess the MRI issues at 3 Tesla for a metallic tissue marker used to localize removal areas of tissue abnormalities.Materials and Methods. A newly designed, metallic tissue marker (Achieve Marker, CareFusion, Vernon Hills, IL) used to mark biopsy sites, particularly in breasts, was assessed for MRI issues which included standardized tests to determine magnetic field interactions (i.e., translational attraction and torque), MRI-related heating, and artifacts at 3 Tesla. Temperature changes were determined for the marker using a gelled-saline-filled phantom. MRI was performed at a relatively high specific absorption rate (whole body averaged SAR, 2.9-W/kg). MRI artifacts were evaluated using T1-weighted, spin echo and gradient echo pulse sequences.Results. The marker displayed minimal magnetic field interactions (2-degree deflection angle and no torque). MRI-related heating was only 0.1°C above background heating (i.e., the heating without the tissue marker present). Artifacts seen as localized signal loss were relatively small in relation to the size and shape of the marker.Conclusions. Based on the findings, the new metallic tissue marker is acceptable or “MR Conditional” (using current labeling terminology) for a patient undergoing an MRI procedure at 3 Tesla or less.

This article is intended to provide guidelines for the minimum level of safety and operational knowledge that an MR system operator should exhibit in order to safely perform an MR procedure in a human subject in a research setting. This article represents the position of the International Society for Magnetic Resonance in Medicine (ISMRM) regarding this important topic and was developed by members of this society's MR Safety Committee. J. Magn. Reson. Imaging 2015;41:899–902.

Hypothesis Ossicular implants made from metallic materials may be acceptable or pose hazards for patients referred for magnetic resonance imaging (MRI) examinations, depending on the outcome of proper MRI testing procedures. Background Using a 3-T MR system, 2 ossicular implants were tested for magnetic field interactions, heating, and artifacts. Materials and Methods Two different ossicular implants (Stainless Steel/Fluoroplastic Sanna-Type Piston [6 mm in length] and the Offset ALTO Total Prosthesis [15 mm in length, titanium/silicone]; Grace Medical, Memphis, TN, USA) were selected for testing, which represented the largest metallic mass and materials with the highest magnetic susceptibilities, with the intent of applying the MRI findings to other ossicular implants. The implants were evaluated at 3-T for magnetic field interactions, heating, and artifacts using standard previously described techniques. Results Each ossicular implant showed relatively minor magnetic field interactions that will not be associated with movement in situ. Heating was not excessive (highest temperature change, ≤1.6°C; background temperature change, 1.5°C). Artifacts, although relatively small, may create issues for diagnostic imaging if the area of interest is in the same area or close to these ossicular implants. Conclusion The results of this investigation demonstrated that it would be acceptable (i.e., “MR conditional” using current terminology) for patients with these ossicular implants to undergo MRI examinations at 3 T or less. In consideration of the materials and dimensions of the implants that underwent testing, these findings pertain to many other similar ossicular implants from the same manufacturer.

OBJECTIVE. A newly developed CSF shunt valve that incorporates a magnetically adjustable mechanism designed to resist unintended setting changes was evaluated for problems during 3-T MRI. MATERIALS AND METHODS. Standardized protocols were used to assess magnetic field interactions, MRI-related heating, artifacts, and functional changes related to multiple exposures and various MRI conditions in nine different samples at 3 T. RESULTS. The magnetic field interactions were not excessive. MRI-related heating, which was studied at a relatively high, MRI system–reported whole body–averaged specific absorption rate (2.9 W/kg), was at a level that should not pose a hazard to a patient. Although artifacts were large in relation to the dimensions of this programmable CSF shunt valve, the results were consistent with similar devices containing permanent magnets. Multiple exposures and various MRI conditions at 3 T did not damage or affect the functional aspects of the devices, and no unintentional changes to the val...