Measurement system of finger-tapping contact force for quantitative diagnosis of Parkinson´s disease

The purpose of this study was to develop a measuring system of contact force in finger-tapping of Parkinson´s disease patients and to show its effectiveness for quantitative diagnosis. This system was composed of a pair of 3-axis accelerometers, a touch sensor an analog to digital converter and a personal computer (PC). Firstly, a transfer function representing relation between the contact force and the accelerometer output during the finger contact phase of finger-tapping was determined. This means that the finger-tapping contact force could be estimated from the measured acceleration by using the determined transfer function. Secondly the developed system was applied to 27 normal subjects and 16 Parkinson´s diseases subjects. Score of UPDRS finger tap test was evaluated for each subject by a neurologist. Finally, these sensors were attached to subject´s index finger and thumb, and sensor signals were recorded and processed within the PC. The subjects were asked to execute continuous finger taps movement for 60 s. It was shown that the contact force was smaller as the subject was with the larger UPDRS score of tap test.