Analysis of biotelemetric interrogation of chronically implantable intracranial capacitive pressure sensor

Intractranial pressure (ICP) may increase due to an illness or an injury. Increased ICP causes severe brain damages and leads to life-threatening situations. Therefore, the ICP of patients with possibly high ICP must be monitored continuously. In this paper, we study the design of a subdural ICP sensor consisting of a MEMS capacitive pressure sensor connected to an inductive loop forming an LC circuit. An external LC circuit, whose loop antenna is inductively coupled to the sensor side loop antenna, can detect the resonance frequency of the implanted sensor LC circuit. We analyze for the first time different design aspects and factors affecting the sensitivity of the system to the changes of the capacitance of a pressure sensor implanted inside human head. In simulations, we used anatomical ANSYS Human Body Model. By considering different loss factors and optimizing the system for best sensitivity, we achieved a system with the sensitivity of 5.1 MHz/pF.