A MEMS intracranial pressure device for monitoring brain injuries and disorders

University Of Michigan At Ann Arbor, Ann Arbor MI

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Abstract

DESCRIPTION (provided by applicant): Intracranial pressure (ICP) monitoring is an essential diagnostic tool for the efficient treatment of patients with brain injuries (e.g. traumatic brain injuries (TBIs)) and cerebrospinal fluid outflow disorders (e.g. hydrocephalus). Clinical trials have shown that ICP monitoring decreases the mortality rate and minimizes secondary injuries. Various ICP monitoring systems have been successful so far in accurately monitoring ICP, but: (a) they have high probability of infection (up to 15%), (b) they do not allow long-term ICP monitoring and (c) they are not MRI (Magnetic Resonance Imaging) compatible. Taking advantage of recent developments in the MicroElectroMechanical Systems (MEMS) field, we propose an 'Intracranial Pressure Micro Stick'(IP<S) technology that overcomes the aforementioned limitations. The technology is based on a fully implantable (cable-free), optical, MEMS device that 'color'codes ICP changes: ICP is converted to a ratiometric optical signal in the near infrared (NIR) wavelength. The device consists of a tunable microlens that focuses light into a quantum-dot bilayer. Each of the two layers contains NIR quantum dots of a unique wavelength. The focal length of the microlens is altered when the ICP changes, resulting in a change in the ratiometric intensity of the two wavelengths. A non-implantable, portable optical unit is used to excite the microlens/quantum dot assembly and collect the emitted NIR spectrum. The electronic- free (and thus power-free) IP<S device enables prolonged ICP monitoring, eliminates the risk of infection, allows patient's comfort and mobility and it is MRI compatible. We propose a research plan with the following specific aims: (a) Optimization of the tunable microlens/quantum dot bilayer assembly: the tunable microlens/quantum dot bilayer assembly will be optimized with respect to the microlens collection efficiency, internal microlens pressure resolution, dynamic range, and quantum dot bilayer thickness;(b) Microfabrication and testing of the integrated IP<S device: an IP<S prototype will be microfabricated and its specifications will be established (ICP range, resolution, time response);(c) In-vitro Studies: We will perform in vitro studies by immersing the integrated device in a bath containing cerebrospinal fluid (CSF). The pressure of the CSF will be externally adjusted to represent a real ICP monitoring scenario and the long term durability and zero drift of the device will be determined. The proposed technology will help in efficiently managing and treating brain injuries and CSF outflow disorders, and it will inaugurate the development of implantable and power-free, miniaturized devices that can be used in a variety of pressure monitoring biomedical applications. PUBLIC HEALTH RELEVANCE: Intracranial pressure (ICP) monitoring is an important diagnostic tool for accessing the pathological condition of patients with traumatic brain injury (TBI), congenital or acquired hydrocephalus or mass lesions. This work aims to develop a new class of implantable ICP monitoring devices that will provide better management and efficient treatment of patients with elevated ICP.