Numerical Thermal Analysis of a Wireless Cortical Implant with Two-Body Packaging

Abstract

This article presents the numerical analysis of temperature elevation in the head due to the operation of a wireless cortical implant. The thermal analyses are done by using a finite-difference time-domain simulation tool and a high-resolution 3-D head phantom with 22 different tissues. The effects of the power dissipation level, size, location, and packaging of the implant on the temperature distribution in the head are investigated by using a generic silicon chip. Furthermore, the distribution of the power consumption in the implant by using multiple integrated circuits is discussed. In order not to exceed the safety precaution limit of 1 • C, maximum allowable power dissipation in a chip of size 2 × 2 × 0.5 mm 3 is found to be 5.3 mW, whereas it is 9.3 mW for an implant with two chips of the same size separated by 10 mm. Additionally, the thermal analysis of a wireless cortical implant is also done by using a two-body cortical implant prototype. Maximum allowable power consumption for the two-body implant is found as 35 mW, whereas the unibody implant can only dissipate 17.5 mW without exceeding the safety precaution limit. By using the two-body implant, the maximum allowable power consumption in the implant can be increased or the temperature elevation in the tissues can be decreased.

Power Budget of a Skull Unit in a Fully-Implantable Brain-Computer Interface: Bio-Heat Model

“…Previous studies have demonstrated the predictive value of numerical bio-heat transfer models for several active head implants, including active microelectrode arrays (MEA) [18], deep brain stimulators [19], an MEA-based cortical implant [20], and a retinal prosthesis [21]. However, due to the unique features of our SU implant, including its ability to simultaneously record and stimulate, the findings from these previous studies do not generalize to our SU design.…”

System-Level Modeling of a Safe Autonomous Closed-loop Epileptic Seizure Control Implant

“…The safety of patients in a long-term is the priority of IMDs. The power dissipation of the implant results in temperature elevation of the human brain which must be continuously kept less than 1℃ to prevent tissue damage [6]. Furthermore, the size and location of the implant are regarded as the critical parameters of temperature elevation in the brain.…”

“…Furthermore, the size and location of the implant are regarded as the critical parameters of temperature elevation in the brain. According to [6], the peak δ factor is 0.083 ℃ for a typical implant dimension of 4×4×0.5 𝑚𝑚 located at the right lobe of the brain. The δ factor is the slope of the plot of temperature elevation versus power consumption.…”