A Non-Invasive Measurement System for Larynx Motion Developed for Swallowing Rehabilitation

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1) Design and development of a larynx-motion measurement systemSensing device of the system consists of twelve photo-reflective sensors spatially arranged in line, which are mounted on subject's frontal neck. The photo-reflective sensor is a combination of an infrared LED and a photodiode, capable of detecting reflected light from a reflective surface located in front of the sensor. Using the principle of the reflective-light intensity being inversely proportional to the square distance between the sensor and the reflective surface, we can estimate the distance from sensor output. Then, the one-dimensional (1-D) array of the photo-reflective sensor located in front of the target surface can detect the 1-D surface contour. The larynx position can be detected as the peak position of the frontal neck contour. If such measurement is done at a high sampling rate, we can digitize the larynx motion non-invasively.2) Measurement and analysis of water-swallowing motionFive healthy volunteers, w … More ho completely understand the purpose and procedure of the experiment and agreed with all of them, were asked to drink a 10[ml] of natural water at a single draft. We measured subject's larynx motion generated by this swallowing using the developed system at a rate of 400[Hz]. The onset of swallowing was defined as the time denoted as to when the digastric muscles started to be activated. We measured temporal parameters t_1, t_2, t_3 and t_4 at which the larynx was located at the position 5[mm], 10[mm], 15[mm] and 20[mm] distant from the initial position at to, respectively. Motion parameters were t_<0,1>, t_<1,2>, t_<2,3> and t_<3,4> defined as t_<i, j> =t_j-t_j The measurement was done five times for each subject, and the average value of each motion parameter was defined as the subject's representative value of the parameter. The average and standard deviation of the parameters with respect to all subjects were to_<0,1>: 0.31±0.09[s], t_<1,2>: 0.11±0.07[s], t_<2,3>: 0.06±0.03[s] and t_<3,4>: 0.04±0.02[s]. These results coincided well with our previous finding that the larynx ascending motion was accelerated. Less