Heating of metallic biliary stents during magnetic hyperthermia of patients with pancreatic ductal adenocarcinoma: an in silico study

Abstract

Objective

To investigate the eddy current heating that occurs in metallic biliary stents during magnetic hyperthermia treatments and to assess whether these implants should continue to be an exclusion criterion for potential patients.

Methods

Computer simulations were run on stent heating during the hyperthermia treatment of local pancreatic tumors (5–15 mT fields at 300 kHz for 30 min), considering factors such as wire diameter, type of stent alloy, and field orientation. Maxwell’s equations were solved numerically in a bile duct model, including the secondary field produced by the stents. The heat exchange problem was solved through a modified version of the Pennes’ bioheat equation assuming a temperature dependency of blood perfusion and metabolic heat.

Results

The choice of alloy has a large impact on the stent heating, preferring those having a lower electrical conductivity. Only for low field intensities (5 mT) and for some of the bile duct tissue layers the produced heating can be considered safe. The orientation of the applied field with respect to the stent wires can give rise to the onset of regions with different heating levels depending on the shape that the stent has finally adopted according to the body’s posture. Bile helps to partially dissipate the heat that is generated in the lumen of the bile duct, but not at a sufficient rate.

Conclusion

The safety of patients with pancreatic cancer wearing metallic biliary stents during magnetic hyperthermia treatments cannot be fully assured under the most common treatment parameters.

Keywords:

• Biliary stent
• magnetic hyperthermia
• eddy currents
• electromagnetic dosimetry
• in silico

Acknowledgments

We are indebted to Drs. Teresa Macarulla, Helena Verdaguer and Raquel Pérez from Vall d’Hebron Institute of Oncology (VHIO) for their support, as well as the Gastrointestinal Tumors Service of the Medical Oncology Service at the University Hospital of Vall d’Hebron for providing the medical images used in this study. We also thank the Systems Unit of the Information Systems Area of the University of Cádiz for computer resources and technical support. Finally, we gratefully acknowledge the support of NVIDIA Corporation through the GPU Grant Program with the donation of the Quadro P6000 GPU used for this research.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work has been supported by the NoCanTher project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 685795. The authors acknowledge support from the COST Association through the COST action “MyWAVE” (CA17115). D.O. and I.R.R. acknowledge financial support from the Community of Madrid under Contract No. PEJD-2017-PRE/IND-3663. We acknowledge support under grant PID2020-117544RB-I00, CEX2020-001039-S, RED2018-102626-T and MAT2017-85617-R funded by MCIN/AEI/ 10.13039/501100011033, and grant RYC2018-025253-I funded by MCIN/AEI/ 10.13039/501100011033 and by “FEDER A way of making Europe”. The Authors also acknowledge the 18NET05 MATHMET project. This project has received funding from the EMPIR Programme, co-financed by the Participating States and from the European Union’s Horizon 2020 Research and Innovation Programme.