Thermal and Electrical Characterization of PAA and HEC Gel Used in MRI Testing of Active and Passive Medical Implants

Holly Moschiano¹, Warren Dabney¹, Robert S. Johnson¹, Lana Placek¹

Polyacrylic acid (PAA) gel has been used historically as the phantom material in MRI testing of passive and active medical implants. However, PAA exhibits undesirable variability in bulk electrical and thermal properties due to the presence of crystallites. Hydroxyethyl Cellulose (HEC) gel has been referenced in the most recent version of ASTM F 2182-02a as an acceptable substitute for PAA gel. HEC gel has similar electrical, thermal, and materials properties as PAA gel. Variations in electrical conductivity and specific heat capacity can greatly affect the amount of temperature rise seen in a test phantom in an MRI environment.