Development of a Non-Contact Sensing Method for Scratching Activity Measurement

The severity of skin diseases accompanied by itch is related to the frequency of itching; thus, the ratio of total scratching time to total measurement time (TST [%]) is a useful index for diagnosing skin diseases such as atopic dermatitis. To grasp the trend of the patient's TST [%], daily monitoring of scratching motion is effective, but it is important to carry out the measurements under unconstrained conditions so as not to burden the patient. In this paper, we propose a non-wearing sensing method for measuring scratching motions while the patient is sleeping. The sensing device used in the proposed method is composed of a piezoceramic sensor sandwiched between two metal plates and placed under the legs of the bed. This sensing device is able to measure micro-vibrations produced by the scratching motion. In carrying out the validation experiment, the TST [%] is obtained using the proposed sensing device. The results are then compared with the TST [%] obtained from conventional, more constrained measurement methods, such as electromyography, ceramic sheets, microphones, strain gauges, acceleration sensors, and gyro sensors. Therefore, the sensing device positioned near the subject's head, where the scratching points are closer together, is capable of determining the TST [%] at an accuracy nearly equal to that of the conventional method that shows the highest accuracy TST [%] among all conventional sensors.