Heating effects of metallic implants by MRI examinations

Area of Science:

• Biomedical Engineering
• Medical Physics
• Materials Science

Background:

• Magnetic resonance imaging (MRI) utilizes radiofrequency (RF) fields that can induce electrical currents in metallic implants.
• These induced eddy currents pose a potential risk of localized tissue heating due to implant warming.
• Understanding and quantifying this heating effect is crucial for patient safety in MRI procedures involving implants.

Purpose of the Study:

• To investigate and quantify the temperature rise in metallic implants during MRI examinations.
• To validate theoretical calculations of RF power deposition and joule heating in implants.
• To assess the safety of MRI for patients with common metallic implants.

Main Methods:

• Solving Maxwell's equations to theoretically predict RF power deposition and joule heating.
• Conducting in vitro worst-case experiments using a large, thin aluminum sheet in a 1.5-T MRI scanner.
• Performing in vitro experiments with a hip joint prosthesis and an osteosynthetic plate under MRI conditions.

Main Results:

• A thermally insulated aluminum sheet showed a minimal temperature rise of only 0.08°C after a 15-minute MRI at 64 MHz.
• No measurable temperature increase was observed in the aluminum sheet when immersed in saline solution.
• Experiments with a hip prosthesis and osteosynthetic plate confirmed theoretical predictions, showing no significant temperature rise.

Conclusions:

• Metallic implants, including hip prostheses and osteosynthetic plates, exhibit negligible temperature increases during MRI examinations.
• Theoretical calculations and in vitro experiments confirm that induced eddy currents do not cause clinically significant heating of implants.
• The findings support the safety of MRI procedures for patients with common metallic implants, mitigating concerns about thermal injury.