An In–Laboratory Validity and Reliability Tested System for Quantifying Hand–Arm Tremor in Motions

Despite the advancement of the tremor assessment systems, the current technology still lacks a method that can objectively characterize tremors in relative segmental movements. This paper presents a measurement system, which quantifies multi-degrees-of-freedom coupled relative motions of hand–arm tremor, in terms of joint angular displacement. In-laboratory validity and reliability tests of the system algorithm to provide joint angular displacement was carried out by using the two-degrees-of-freedom tremor simulator with incremental rotary encoder systems installed. The statistical analyses show that the developed system has high validity results and comparable reliability performances using the rotary encoder system as the reference. In the clinical trials, the system was tested on 38 Parkinson’s disease patients. The system readings were correlated with the observational tremor ratings of six trained medical doctors. The moderate to very high clinical correlations of the system readings in measuring rest, postural and task-specific tremors add merits to the degree of readiness of the developed tremor measurement system in a routine clinical setting and/or intervention trial for tremor amelioration.