Thermal Simulation of Artery Occlusion in the Lower Limb
Kuokkanen, Emppu (2025)
2025
Teknis-luonnontieteellinen DI-ohjelma - Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Hyväksymispäivämäärä
2025-06-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202506066882
https://urn.fi/URN:NBN:fi:tuni-202506066882
Tiivistelmä
Changes in skin temperature can indicate circulatory disorders, which may progress into serious conditions such as chronic lower limb ischemia. Bioheat models describing heat transfer in human tissues have been developed for inspecting physiological processes. These models can also be applied to simulate the effects of circulatory impairments, such as analyzing the distribution of skin surface temperatures. In this thesis, the thermal profile of a three-dimensional lower limb model was investigated through simulation using the Pennes bioheat model. The aim was to evaluate the relationship between circulatory changes and skin temperature. A blockage was introduced into the medial plantar artery, and the results were compared to those of a normal lower limb model, both with and without an external heat source. Simulated results were compared to experimentally measured mean temperatures of angiosomes.
The thesis consists of a literature review, modification of a 3D model based on computed tomography (CT) data, comparison of simulation results to thermal camera measurements, and the attempt to import a magnetic resonance imaging (MRI) -based model into the COMSOL Multiphysics software. Literature review covers lower limb anatomy, heat transfer and fluid dynamics physics, and medical imaging techniques. The MRI-based model includes veins and adipose tissue in addition to the bones, arterial network, skin, and combined soft tissues that are also present in the CT-based model.
Simulation results show that the CT-based model generally produced higher temperatures than the experimental measurements, and the results did not align. Mean temperatures of angiosomes are further examined by adjusting three parameters: blood velocity, inlet blood temperature, and thermal conductivity of the combined soft tissues. Of these, changes in blood inlet temperature had the greatest effect, increasing the mean temperature of angiosomes by 1.5–2.5°C, which is more than twice the impact of the other two parameters.
The assembly of the MRI-based model into a single solid geometry in COMSOL failed due to the irregular geometry of the adipose tissue and mesh overlap issues at vein intersections. Consequently, the effects of adipose tissue and veins on the lower limb thermal profile could not be evaluated using this model. However, the impact of adipose tissue on skin surface temperature was investigated using a simplified cylindrical model. It is assumed that a more advanced model including veins and adipose tissue could improve the accuracy and comparability of results to experimental measurements. Alternative bioheat models based on porous media theory may offer more realistic results compared to the Pennes model.
The thesis consists of a literature review, modification of a 3D model based on computed tomography (CT) data, comparison of simulation results to thermal camera measurements, and the attempt to import a magnetic resonance imaging (MRI) -based model into the COMSOL Multiphysics software. Literature review covers lower limb anatomy, heat transfer and fluid dynamics physics, and medical imaging techniques. The MRI-based model includes veins and adipose tissue in addition to the bones, arterial network, skin, and combined soft tissues that are also present in the CT-based model.
Simulation results show that the CT-based model generally produced higher temperatures than the experimental measurements, and the results did not align. Mean temperatures of angiosomes are further examined by adjusting three parameters: blood velocity, inlet blood temperature, and thermal conductivity of the combined soft tissues. Of these, changes in blood inlet temperature had the greatest effect, increasing the mean temperature of angiosomes by 1.5–2.5°C, which is more than twice the impact of the other two parameters.
The assembly of the MRI-based model into a single solid geometry in COMSOL failed due to the irregular geometry of the adipose tissue and mesh overlap issues at vein intersections. Consequently, the effects of adipose tissue and veins on the lower limb thermal profile could not be evaluated using this model. However, the impact of adipose tissue on skin surface temperature was investigated using a simplified cylindrical model. It is assumed that a more advanced model including veins and adipose tissue could improve the accuracy and comparability of results to experimental measurements. Alternative bioheat models based on porous media theory may offer more realistic results compared to the Pennes model.