TUTCRIS - Tampereen teknillinen yliopisto


Inductively Powered Implantable System with Far-field Data Transmitter for an Intracranial Pressure Monitoring Application: Design and Performance Validation



KustantajaTampere University of Technology
ISBN (elektroninen)978-952-15-4155-1
ISBN (painettu)978-952-15-4152-0
TilaJulkaistu - 7 kesäkuuta 2018
OKM-julkaisutyyppiG5 Artikkeliväitöskirja


NimiTampere University of Technology. Publication
ISSN (painettu)1459-2045


Monitoring of the intracranial pressure (ICP) is an essential activity for many brain diseases and injuries. For an adult, ICP value is between 7 mmHg to 15 mmHg . However, for a critically ill patient, the ICP should be maintained below 20 mmHg. Therefore, continuous monitoring of ICP is a life-saving activity. Several invasive and non-invasive methods have been proposed for monitoring of the ICP. However, invasive methods cannot be used for continuous monitoring of the ICP due to the risk of infection. Moreover, non-invasive methods lack in accuracy.

Therefore, many researchers reported battery-powered or fully passive implantable systems. However, a battery-powered implant has limited life and large size. On the other hand, in a fully passive implant the readout distance is relatively small in comparison with a battery-powered implant due to its zero-power operation.

In contrast, this work presents the development of an inductively powered implantable system equipped with a data transmission unit for an ICP monitoring application. The developed system has three main parts: an implant or in-body unit, an on-body unit and an off-body unit. The on-body unit powers the implant through inductive near-field link. After the activation, the implant, consists of a piezoresistive pressure sensor and a data transmission unit, transmits the pressure signal at the industrial, scientific, and medical radio (ISM) band of 2.45 GHz. The off-body unit receives the transmitted signal from the implant and estimates the pressure value.

The simulation and the measurement results of both near-filed and far-field links are presented. After the development of the system, the pressue readout measurement results have been presented in the air, water and in a setting mimicking the human head dielectric properties. For biocompatibility, the implant is coated with biocompatible adhesive silicone. The effect of coating on both wireless links has also been studied.

Finally, this work also presents the effect of misalignment between the inductively coupled antennas on the pressure readout accuracy of the developed ICP monitoring system and discusses the solution to overcome this impact. The thesis also presents the response of the developed ICP monitoring system with the change in the temperature.

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