Development of pathological evaluating system of tremor disease by a tablet PC and accelerometers

A tremor of Parkinson’s disease (PD) or Essential tremor (ET) disease affects the patient’s movement such as writing the letter or pouring tea into a cup. Specifically, the handwritten performance is important of their daily life. Most of the patients with PD or ET have the diseased tremors. We aim to control these diseased tremors using a biofeedback technique. To investigate the effect of the biofeedback training, we need a system which evaluates the pathology of the subject. In this study, we have constructed the pathological evaluating system with a tablet PC and 3-axis accelerometers to quantify the handwritten performance. Using this system, we measured the handwriting and the upper limbs accelerations while the subject was drawing spirals. All subjects were 17 ET patients and 13 PD patients. The accelerometers were attached on the subject’s index fingers. The subjects sat on the chair and traced the spiral on the tablet PC comfortably. We instructed the subject to trace the spiral correctly. For evaluating the handwritten performance, we have analyzed the accelerations of the index fingers and the shape of the traced figure. We experimented under four conditions; a clockwise or a counter clockwise spiral and presence or absence of the handwriting. The position of the pen tip on the display and the accelerations of the fingers were measured continuously during drawing the spiral. We calculated the tremor frequency and amplitude using the measured acceleration data. The standard deviation of drawing spiral was calculated. The drawings of the healthy elder subject were smooth in the all conditions. We have found some disorders in the figure of the spirals in PD and ET patients. This result suggests that this system is effective in the evaluation of the handwritten performance.