Magnetic Resonance Induced Heating in a Vascular Stent
Chaudhury, Ankur; Khasnavis, Siddharth; Russell, Matthew; Sarathy, Vijay
It is standard hospital practice to remove metallic objects from patients prior to MRIs. Since magnetic resonance imaging employs changing magnetic fields, even everyday items such as jewelry or keys run the risk of overheating due to induced currents leading to Joule heating. A potential problem arises, however, when the metal is subcutaneously located in the form of a medical implant. The present study evaluated this scenario by using finite element analysis to model a vascular stent under the influence of a standard MRI field. COMSOL Multiphysics software was used to conduct finite element analysis on two different stent sizes, each in the presence and absence of blood flow. The stents were modeled as stainless steel (type 316L) with internal diameters of 5mm and 8mm, length of 40mm, and wall thicknesses of 0.18mm and 0.22mm. The tests revealed that under the influence of blood cooling, the stents modeled did not overheat or cause arterial damage. Specifically, the large stent resulted in a maximum temperature of 310.807 K and the smaller stent led to 310.230 K, each after 30 minutes of heating. In the unrealistic absence of blood flow, the large and small stents reached maximum temperatures of 318.851 K and 312.297 K respectively. Ultimately, given variance in blood flow the true solutions lie somewhere in between the blood perfusion and static flow models.
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