Evaluations of the MRI RF-Induced Heating for Helical Stents Under a 1.5T MRI System

This paper investigates the radio frequency (RF)-induced heating for helical stents under 1.5T magnetic resonance imaging (MRI) birdcage RF coil electromagnetic emission.The effects of design parameters, such as pitch, gap, winding pattern, overall length, and diameter, on RF-induced heating are investigated. It is found that these parameters can have different levels of impacts on the overall heating of tissue near the stents. The peak 1 g averaged specific absorption rate (SAR), a parameter that is closely related to the RF-induced heating, is strongly influenced by the stent length and the worst-case peak 1 g averaged SAR often occurs when the stent length is around the half-wavelength of the incident electric field. The increasing diameter reduces the SAR values. At the same stent length and diameter, a higher RF-induced heating occurs for the stent with a larger pitch and a smaller gap. In addition, stents that have longer equivalent electrical lengths could reduce the heating. The SAR and current distributions are also extracted from simulation results to demonstrate the heating mechanism. Experimental measurements are performed to validate the results from simulation investigations.