Surgery implants: compatibility in MRI environments

The evaluation of medical devices, when subjected to magnetic fields, will permit the determination of image artifacts, magnetically induced displacement torque and force, and radiofrequency induced heating. Such evaluation is essential to assure safety and efficacy of active and non-active surgical implants, as established in ABNT ISO/TR 14283 and ABNT NBR ISO 14630.

The standards methods ASTM F2119, ASTM F2182, ASTM F2052 and ASTM F2213 are intended to assist the implant manufacturer in terms of tests, information and requirements to prove the safety and effectiveness for MRI envinronment.

The clinical success of an implant involves aspects related to the design, handling of components from storage to surgical centers, implantation procedures, the expertise of the professional responsible for the surgical procedure, and the health status of the patient.

In addition, it is also important to consider aspects related to the design and quality of ancillary components, as well as other associated components, which include instrumental and auxiliary components.

The main issues affecting the safety and compatibility of non-active implants in a magnetic resonance environment are related to magnetically induced force/torque, radiofrequency heating, and the presence of image artifacts.

Static fields in magnetic resonance environments induce displacement forces and torques on magnetic materials, and radiofrequency heating of bodies is a consequence of currents induced by excitation pulses applied during magnetic resonance scanning. The scientific literature presents some cases of death and severely burned patients during an MRI scan.

On the other hand, the presence of an implant can produce an image artifact that can appear as an empty region or as a geometric distortion of the true image. If the imaging artifact is close to an area of interest, the artifact can lead to an inaccurate clinical diagnosis, potentially resulting in inappropriate medical actions.

For most of the  clinical applications the MRI procedure is performed with 1.5 T or 3.0 T equipments. It is important to note that an implant characterized as safe in a 1.5 T field may not be in a system with a higher or lower static magnetic field (eg, 3T or 1T).

Standards

ASTM F2052 (2015) – Standard Test Method for Measurement of Magnetically Induced Displacement Force on Medical Devices in the Magnetic Resonance Environment

ASTM F2119 (2007) – Standard Test Method for Evaluation of MR Image Artifacts from Passive Implants

ASTM F2182 (2019) – Standard Test Method for Measurement of Radio Frequency Induced Heating On or Near Passive Implants During Magnetic Resonance Imaging

ASTM F2213 (2017) – Standard Test Method for Measurement of Magnetically Induced Torque on Medical Devices in the Magnetic Resonance Environment

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