Safety assessment of patients with one-dimensionally structured passive
implants, like cranial plates or stents, exposed to low or medium frequency
magnetic fields, like those generated in magnetic resonance imaging or magnetic
hyperthermia, can be challenging, because of the different length scales of the
implant and the human body. Most of the methods used to estimate the heating
induced near such implants neglect the presence of the metallic materials
within the body, modeling the metal as thermal seeds. To overcome this
limitation, a novel numerical approach that solves three-dimensional and
one-dimensional coupled problems is proposed. This method leads to improved
results by modelling the thermal diffusion through the highly conductive
metallic implants. A comparison of the proposed method predictions with
measurements performed on a cranial plate exposed to the magnetic field
generated by a gradient coil system for magnetic resonance imaging is
presented, showing an improved accuracy up to 25 % with respect to the method
based on thermal seeds. The proposed method is finally applied to a magnetic
hyperthermia case study in which a patient with a cranial plate is exposed to
the magnetic field generated by a collar-type magnetic hyperthermia applicator
for neck tumour treatment, predicting a temperature increase in proximity of
the implant that is 10 % lower than the one overestimated by relying on thermal
seeds.

Questo articolo esplora i giri e le loro implicazioni.

Scarica PDF: