Supercamera is used to study voice production

A videolaryngoscope utilized by USP researchers can capture 4,000 images per second and allows for visualization of vocal cord vibrations in slow motion.

By Karina Toledo

Agência FAPESP – To produce sound, the vocal folds in the human larynx vibrate between 100 and 400 times per second. This phenomenon, impossible to observe with the naked eye, can be seen in slow motion thanks to a device: the videolaryngoscope, which can capture up to 4,000 images per second.

The technology has allowed researchers from Universidade de São Paulo (USP) to better understand how vocal folds work and study the pathologies that affect their vibration. The device has also made it possible to evaluate objective criteria such as the impact of surgery and speech therapy treatments for voice production.

Unprecedented in the country, the equipment was acquired with resources from a FAPESP-funded project that is coordinated by Professor José Carlos Pereira of USP’s São Carlos Engineering School.

Through a partnership with a team of otorhinolaryngologists from the Medical School, coordinated by professor Domingos Hiroshi Tsuji, the machinery was donated to the Hospital das Clínicas (HC) in São Paulo, where it is being used in exams that have already resulted in two master’s dissertations, in addition to five doctorates and one ongoing post-doctoral project.

“As this equipment is new, the first step was to define how vocal cords normally work. To do so, we created a protocol,” explains Arlindo Neto Montagnoli, a researcher and mentor for the master’s degree project undertaken by speech therapist Regina Aparecida Pimenta, who is a FAPESP fellow.

In the study, Pimenta evaluated the vocal fold vibrations of 30 volunteers who had no problems with their voices—12 men and 18 women—before and after they participated in phonoaudiological exercises. “It proved that that the exercises improve, for example, the mobility and amplitude of the vibration of vocal folds. With this, people had less wear and tear [on their vocal cords] to speak. It’s like a work out for the voice,” she explained.

Another master’s degree project that has already been concluded is that of speech therapist Paula Belini, who compared the functioning of vocal folds in healthy patients with those of people with vocal fold nodules.

A team of engineers coordinated by Montagnoli developed software that stimulates the movement of vocal folds and measures different parameters (such as fold vibration cycles and the duration of the closed stage) to conduct these evaluations. The project resulted in the doctoral thesis of Alan Petrônio Pinheiro, who should be defending it in 2012.

“We intend to create a computer model to test surgical techniques virtually. This will give doctors an idea of how a patient’s voice will be after an operation,” explains Montagnoli.

The researcher had already worked with the concept of virtual surgery in his doctoral studies, but the software was perfected thanks to information provided by the new videolaryngoscope. “The model was one dimensional before. Now, we’ve developed a three-dimensional version,” he explains.

An “electrocardiogram” of the voice

In the post-doctoral project of speech therapist and FAPESP fellow Maria Eugênia Dajer, which is being conducted under the guidance of Tusji, the objective is to create graphs that allow for quick evaluation of how vocal folds are working.

“It’s a like an electrocardiogram for the voice. The doctor looks and already knows whether it is normal or not,” explains Montagnoli. The new equipment is being used to validate the results of this analysis.
“The idea is to attempt to identify standards. The doctor would look at the graph and would already know if changes are caused by a cyst or a nodule, for example,” explains otorhinolaryngologist Adriana Hachiya, who is responsible for the Voice Research Center, where exams with the high-speed videolaryngoscope are conducted.

Hachiya is also participating in a project in partnership with the USP Medical School’s Department of Speech Therapy, Physical Therapy and Occupational Therapy to study cord vibration in patients over 65. “Vocal folds are formed by a muscle and mucous. With age, the muscle tone diminishes. That is why the voices of elderly people are weaker and shakier. We will apply exercises and evaluate the improvement,” he explains.

There is also a pilot project that seeks to investigate the physiology and the pathologies that affect classical singers and an ongoing study that works with the larynx of cadavers. “We placed an air flow that simulates air from the lungs. The vocal folds vibrate and produce sound,” explains Hachiya.

USP researchers will utilize this resource to test surgical techniques and simulate pathologies. “One of the projects simulates paralysis of vocal folds. We will use the videolaryngoscope to evaluate what vibration is like in these conditions,” she comments.