Experimental characterization of a novel fiber-optic accelerometer for the quantitative assessment of rest tremor in Parkinsonian patients

A novel fiber-optic accelerometer has been developed for the quantitative assessment of parkinsonian tremor at rest. The transducers is based on a fiber-optic sensing technique, that reduce some important drawbacks of biomedical applications, such as patient electrical safety and electromagnetic interference, and allows a non-invasive solution for monitoring of human movement, due to their limited mass. The sensing principle is based on the measurement of the transversal displacement of an emitting optical fiber cantilever due to the acceleration, conducted by means of a photodiode array: the detection of the light intensity profile makes the developed measurement system less sensitive to the light intensity variations independent from acceleration than intensity-based sensors. A dynamic calibration of the optical fiber accelerometer has been performed and a linear relationship between the lateral displacement of the fiber cantilever and acceleration has been experimentally evaluated. Moreover, a flat frequency response function between 3 Hz and 7 Hz (i.e. typical frequency range in which tremor at rest occurs in parkinsonian patients) and an high sensitivity in this frequency range (about 14 pixel/m.s-2) have been experimentally derived. These metrological features confirm that the proposed measurement system is particularly suitable for the quantitative assessment of parkinsonian tremor at rest.