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Facha - The Facial Nerve Surgical Monitoring Device

Introduction

Facha - The Facial Nerve Surgical Monitoring Device is designed to prevent damage to the patient's facial nerve during Ear, Nose, and Throat (ENT) surgeries. The device is particularly useful when the nerve is located close to the operating area, or in cases where its morphology makes it challenging to assess the risk prior to surgery.

The solution

This solution enables the surgeon to monitor the proximity of the surgical cutting tool to the facial nerve by measuring myoelectric response.

The surgeon stimulates with a controlled electrical current the operating area, where a myoelectric response is simultaneously measured. The surgeon then uses heuristics based on the shape of the signal to estimate the distance between the surgical cutting tool and the facial nerve.

The device

The solution is comprised of: (a) an application on a laptop running Windows or MacOS X, (b) an external unit that amplifies the myoelectric signals and sends the signal samples to the laptop, (c) an electric current pulse stimulator.

The pulse stimulator produces an electrical current with controlled width and intensity, which is injected into the patient's operating area using the surgical cutting tool.

The signal is measured from the muscle's contracting response of the orbicularis oris and orbicularis oculi muscles. A metric is obtained heuristically from the shape and size of the response. Several responses can be selected and captured during surgery for later analysis.

The application

The application has capabilities similar to those provided by digital or analog oscilloscopes. A few control knobs enable the surgeon assistant to control auto sweep, triggered sweep, variable trigger threshold, variable sweep velocity, variable trigger hold-off time, variable sampling rate, and a persistent signal storage.

The application is written entirely in the Java language. It uses the JavaFX GUI library for displaying purposes, and the Java Sound Library to acquire the signal coming from two separate analog channels. Those analog channels come through a USB connection between the laptop and the input amplifiers/samplers.

The application uses real time linear and nonlinear digital filtering on the signal. The signal processing library is included in this repository. The signal conditioning process features the Widrow's adaptive normalized LMS filter in order to remove the power line noise from the useful signal, without damaging its temporal shape. This task would be impossible using linear filtering, as the spectrum of the signal and the noise overlap.

Hardware units

The specifications for the biological signal amplifier and the pulse stimulator are located below:

./notes/manuals/Manual*.doc

Building and deploying the application

The repository contains the production source code, the unit test code and the gradle/bash building scripts. The build output artifacts consist of both a distribution .zip file for MacOS X, and an installation executable for Windows.

For building and unit testing, please refer to the documentation below:

./notes/software/how-to-build-and-test.md

The source code repository, the continuous integration, and the download of installation executables are hosted below:

https://bitbucket.org/claudio_ortega/monitoreo

License

A copy of the license for this project is included in:

./LICENSE.txt

Credits to the original team

This project was sponsored by FundaciĆ³n Arauz - http://www.farauzorl.org.ar, and driven entirely by an interdisciplinary team, based in Argentina and USA.

Project medical direction - Santiago Luis Arauz, MD, ENT Surgeon
Product management and QA - Ing. Marcelo Ortega
Hardware implementation - Ing. Esteban Castro
Software construction - Ing. Claudio Ortega

Contact

For contributing to this project, or to use it as is, please contact me at:

claudio.alberto.ortega@gmail.com

Screenshots

Monitor screen, complete

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Settings screen, upper portion

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Settings screen, lower portion

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