The example focuses on the thermal analysis of a hip implant in an MRI system.

During an experimental safety test setup, an implant is placed in an ASTM-2009 phantom designed according to the ASTM F2182-09 standard.1 The phantom is filled with a gel that has averaged material properties similar to those of human tissue. The implant is positioned near the edge of the phantom, where the field gradients are high to emulate a potential worst-case scenario. The phantom with the implant is placed in an MRI scanner and the temperature rise is monitored.

Figure 1. Phantom with a hip implant in a 1.5 T MRI coil (the RF coil shielding is not shown).
The specific absorption rate (SAR) results at 64 MHz when the MRI coil accepts a power of 38 W of which 30 W is absorbed in the phantom gel, shows the implant has a strong influence on the fields. Localised peaks in the SAR distribution can be seen at the tips of the implant.

Figure 2. SAR distribution at 64 MHz.
1 Standard F2182–09, “Standard Test Method for Measurement of Radio Frequency Induced Heating Near Passive Implants During Magnetic Resonance Imaging”, ASTM International, http://%E2%81%A0www.astm.org.