Thermal Analysis of Heat Transfer from Catheters and Implantable Devices to the Blood Flow

Abstract

Implantable devices, ultrasound imaging catheters, and ablation catheters (such as renal denervation catheters) are biomedical instruments that generate heat in the body. The generated heat can be harmful if the body temperature exceeds the limit of almost 315 K. This paper presents a heat-transfer model and analysis, to evaluate the temperature rise in human blood due to the power loss of medical catheters and implantable devices. The dynamic of the heat transfer is modeled for the blood vessel, at different blood flow velocities. The physics and governing equations of the heat transfer from the implanted energy source to the blood and temperature rise are expressed by developing a Non-Newtonian Carreau–Yasuda fluid model. We used a Finite Element method to solve the governing equations of the established model, considering the boundary conditions and average blood flow velocities of 0–1.4 m/s for the flow of the blood passing over the implanted power source. The results revealed a maximum allowable heat flux of 7500 and 15,000 W/m2 for the blood flow velocities of 0 and 1.4 m/s, respectively. The rise of temperature around the implant or tip of the catheter is slower and disappeared gradually with the blood flow, which allows a higher level of heat flux to be generated. The results of this analysis are concluded in the equation/correlation T=310+H3000(1+e−7V), to estimate and predict the temperature changes as a function of heat flux, H, and the blood flow velocity, V, at the implant/catheter location.

Temperature Dependence of Thermal Properties of Ex Vivo Porcine Heart and Lung in Hyperthermia and Ablative Temperature Ranges

“… 12 Among the various physical parameters, thermal properties have gained a huge interest due to their utilization in critical fields in which the quantitative understanding of short- and long-term thermal effects on tissues is pivotal for the optimal design of monitoring and therapeutic devices, and a deeper investigation of the biological phenomena. Indeed, tissue thermal properties are widely employed in simulations of hyperthermal and thermal ablation procedures for cancer treatment, 13 , 44 analysis of the heat transfer between implantable devices, ablation catheters and the body, 32 , 36 , 38 , 60 modeling of the heat transport during physiological mechanisms 30 , 54 and to realize tissue-mimicking phantoms. 6 …”

Dependence of Temperature Rise on the Position of Catheters and Implants Power Sources Due to the Heat Transfer into the Blood Flow

“…Figure 1 shows the conceptual schematic of the catheters and implantable devices for various applications at the different human body positions. Based on the study presented in [23], the local heat generated by the implants in the human body is significantly proportional to the blood velocity across the implants. On the other hand, the blood velocity is sented in [23], the local heat generated by the implants in the human body is significantly proportional to the blood velocity across the implants.…”

“…Based on the study presented in [23], the local heat generated by the implants in the human body is significantly proportional to the blood velocity across the implants. On the other hand, the blood velocity is sented in [23], the local heat generated by the implants in the human body is significantly proportional to the blood velocity across the implants. On the other hand, the blood velocity is not constant everywhere in a blood vessel (it reduces to zero velocity near the vessel wall).…”

“…On the other hand, the blood velocity is not constant everywhere in a blood vessel (it reduces to zero velocity near the vessel wall). Therefore, the position of the implant in the blood vessel is an essential parameter for safety considerations and adds extra limits to the design by reducing the maximum allowable power that the implants can consume [16,23]. In this work, we have changed the location of implants in a blood vessel model (from the center to near the wall) with small steps, using COMSOL Multiphysics ® software (version 5.6, Stockholm, Sweden) and evaluated the local temperature rise in the human body.…”

“…A comprehensive analysis of heat transfer is done by comparing the temperature rises at different implants positions. As a result, we have modified the temperature rise prediction equation presented in [23] by adding the new parameter of the implant's position into it. Section 2 presents an overview of the design and system modeling method.…”