Accuracy of Markerless 3D Motion Capture Evaluation to Differentiate Between On/Off Status in Parkinson's Disease After Deep Brain Stimulation

Methodology. Patients. Six patients with PD, diagnosed in accordance with the United Kingdom Parkinson's Disease Society Brain Bank Clinical Diagnostic Criteria by a certified neurologist and movement disorder specialist, were included. This is a pilot study, and sample size was chosen by convenience, accessibility and proximity to the researchers. The study was approved by the investigator's institutional research board, and the patients and controls provided written consent. In the months preceding the test, the PD patients were clinically evaluated by the same physician according to the Unified Parkinson Disease Rating Scale section III or motor section (UPDRS-III).

Instrument. Actually, there are many markerless motion capture systems in the market, with a broad range of prices, as well as a broad range of reliability. However, DARI system has been proven to be one of the best for numerous reasons. This system requires a quick calibration at the beginning of each day that the technician can complete in less than 10 minutes. It does not have to be repeated until the following day, no matter how many patients are evaluated. The system depends on a computer-based software that acquires the patient's skeleton or avatar using eighteen high-speed cameras (120 Hz) placed around the room to collect whole body data and delivers kinematic analysis almost instantly using sophisticated biomechanical algorithms.

Also, traditional motion labs use cumbersome floor-mounted pressure plates to measure the forces generated by the body. These require frequent calibration and restrict the subject's movement to a limited area. DARI's kinetic capture system does not require force plates and can measure joint torques, ground reaction forces, and other measurements without restricting the subject's natural movement.

Markerless 3D motion capture evaluation of kinematics in the PD patients and controls was performed on a rectangle room that measures 6 x 6 meters and 3 meters in height. The room has a green screen on the floor, and eighteen cameras are strategically placed on the walls, twelve are placed 2.6 meters high and 6 are on a lower level at 30 centimeters from the ground. The room has ample space, which allows for broader movements to be analyzed.

Evaluations. PD patients were asked to arrive in the morning wearing dark close-fitting clothing, to skip their last PD medication, and with DBS in Off state for least 180 minutes. On PD patients, UPDRS-III evaluation was done first. Then, to begin the markerless body motion evaluation (BME), patients and controls' weight and height were entered into the system to help establish the locations of joint centers. Once inside the green room, subjects first stood with feet apart and arms outstretched to the side, while the system created a 3D silhouette of each participant's form and a biometric skeleton was acquired; this took no more than three seconds. For the BME, all subjects performed 16 different movements. This set of movements was especially designed to evaluate PD patients and contains items that are related to three major motor symptoms in this disease: rigidity, bradykinesia and postural instability; tremor is not possible to assess. Once the BME was done, PD patients were asked to turn their DBS to On state and wait 30 minutes before repeating both UPDRS-III and BME. Controls only performed the BME, which took no more than 20 minutes. PD patients were evaluated twice (DBS state On and Off) with a 1-hour wait in between; their evaluation altogether took approximately 1.5 hours. The data files were uploaded to DARI Motion Platform where the biomechanical analysis produced full-body kinematic results and, finally, these data were exported to Excel for statistical analysis.