Key Technology Study And Implementation Of Implantable Intracranial Pressure Continuous Monitoring System

Intracranial pressure is an important medical indicator.Continuous intracranial pressure monitoring is of great value clinically,which is beneficial to early detection and timely treatment of risen intracranial pressure and intracranial diseases.Traditional invasive monitoring using the external ventricular drainage technique is the most widely used intracranial pressure monitoring method,which is considered the ‘gold standard’ of intracranial pressure monitoring.However,this method can easily lead to the monitored patients’ infection and restrictions on patients’ freedom of movement.Therefore,it is necessary to study the intracranial pressure monitoring devices that can be implanted and adopt wireless data transmission.There are many implantable intracranial pressure monitoring schemes up to now,but these schemes often have the following shortcomings: poor human biocompatibility,low resolution and bad accuracy.In order to overcome the shortcomings of the existing implantable intracranial pressure monitoring schemes,this paper proposes an implantable intracranial pressure monitoring system,which is based on a low-power System-on-a-Chip(SoC)and pressure sensing air pouch.The system mainly consists of three parts: an implanted intracranial pressure monitoring device,an off-body wireless data recorder,intracranial pressure monitoring user software on the computer.The research focuses on the implantable intracranial pressure monitoring device.The research process can be divided into two stages.Stage 1: build a multi-chips-based prototype system,which is composed of a 400 MHz RF transmitter chip,a commercial SCP1000 sensor and a main control chip EPM570ZM100.In the liquid pressure measurement experiment based on this system,the pressure measurement error doesn’t exceed ± 1 mmHg within the range of 0 and 32 mmHg,validating the feasibility of the air-pouch-based implantable intracranial pressure monitoring scheme.Stage 2: design a SoC chip to achieve high integration,small size and low power consumption of the implantable monitoring device.The SoC is composed of wakeup controller,power management unit,400 MHz RF transmitter,a 24 MHz crystal oscillator,a 20 kHz RC oscillator,digital baseband,sensor interface and workflow control circuit.And a complete prototype of implantable intracranial pressure monitoring system based on the SoC is built.The average current consumption of the implantable device based on SoC is about 300 μA.The implanted device is 24 mm long,19 mm wide and 8 mm thick.Within the range of-20 mmHg and 150 mmHg,the measurement error of the implanted device is smaller than ±0.4 mmHg.Finally,the feasibility of implanting the intracranial pressure monitoring device into the animal body was verified by animal(goat)experiment.