EAGER: Design of an Active Voice Box Prosthesis with Embedded Actuation

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

The most effective treatment for advanced cancer of the larynx, commonly called the voice box, is often the removal of the entire organ, i.e., a "total laryngectomy." Loss of the vocal folds, commonly called vocal cords, which were housed in the larynx, leads to significant complications in all three of the critical physiological functions that the vocal folds enabled: respiration, swallowing, and voice production. Breathing and swallowing have received considerable attention for patients with laryngectomy, but vocalization still presents unresolved issues due to the complexity and variability of the vocal fold dynamics. Current laryngectomy treatment options employ unnatural speech production methods and require breathing through a redirected airway. This project addresses this limitation by investigating the feasibility of creating an artificial voice box that can recreate the dynamic behavior or replace the functionality of healthy vocal fold tissue. Based on studies of the properties of pig vocal folds, a 3D printing technique has been developed to produce synthetic vocal folds that can be fine-tuned to have desired movement properties. Vibrations will be created by embedding piezoelectric actuators (small motors that can convert energy into motion) in the printed vocal folds. A minimally invasive, closed-loop control system will be developed to generate appropriate signals and control the synthetic vocal fold behavior. Efforts will also be made to control the artificial voice box remotely using EEG (electroencephalogram), i.e. brain signals, from a healthy subject to estimate the subject's intent to move the vocal folds. The proposed research offers the possibility of improving the quality of life of laryngectomy patients who could develop a profound sense of isolation from their inability to communicate. Development of an EEG-driven robust control strategy will also provide a framework for guiding rehabilitation strategies for other impairments. Results obtained will be disseminated through conference and journal papers and be made available using dedicated websites such as Connexions and the National Science Digital Library. The goal of this exploratory project is to investigate the feasibility of developing an artificial voice-box, with embedded actuation, that uses biofeedback via EEG and leverages novel adaptive control algorithms to restore full vocal function to patients requiring a laryngectomy. Unlike current laryngectomy treatment options that employ unnatural speech production methods and require breathing through a redirected airway, this approach focuses on creating, controlling, and dynamically testing an artificial voice box that can recreate the dynamic behavior or replace the functionality of healthy vocal fold tissue. Preliminary work focused on identifying continuous model parameters for porcine vocal folds and the additive manufacturing techniques necessary to produce synthetic vocal folds serves as the foundation for the project. The Research Plan is organized under six tasks. TASK 1) Dynamic testing to evaluate vocal fold vibration of both excised porcine vocal folds and the synthetic vocal fold models. Frequencies of vibration will be recorded as the samples are dynamically loaded. Digital images captured at 3000 frames per second will enable the determination of strain fields and deformation on the superior surface of the samples. TASK 2) Comparison and iterative design of synthetic vocal fold in order to understand how the fundamental frequencies change while the samples are loaded. The spatial properties of the synthetic vocal fold model will be iteratively adjusted by tuning manufacturing process parameters in order to achieve a desired frequency response during dynamic tests. PZT (piezoelectric) actuation will be embedded into the printed vocal folds with the goal of modulating the vocal fold vibration during dynamic testing. TASK 3) Controlling vocal folds without a human in the Loop through development of an Output Based Control algorithm that will address effects such as time delays, actuator amplitude and rate saturation limitations, and partial and noisy measurements. TASK 4) Controlling vocal folds using EEG signals from a healthy subject, for the purpose of changing the pitch of the sound produced when a constant flow of air is passed across the synthetic vocal folds. TASK 5) Data post-processing and performance evaluation of the data collected in Tasks 3 and 4. The closed loop results obtained using standard controllers and the Output Based controller will be compared. A performance index, based on the ease of implementation, tuning and actual performance of the closed loop system will be developed and used to assess the performance of the control with respect to existing algorithms. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.