Characterization of infants’ general movements based on a single RGB-Depth camera: a feasibility study

Abstract

Movements in infants have age-specific characteristics which could be quantified by extracting specific metrics based on the kinematics of General Movements (GM). For this purpose, a number of metrics have been proposed [1,2]. However the latter have been often obtained using complex and expensive experimental setups. The aim of this study was to evaluate if a simple experimental setup associated (RGB-D camera) with a suitable signal processing (a purposely modified markerless method - MLM) can be used to characterize the GM with the above-mentioned metrics. Data from three typically developing infants sitting in a baby seat were acquired at 3, 4 and 5 months from birth with a single RGB-D camera with depth obtained from a stereoscopic view of two infrared sensors (Intel RealSense D435). Each acquisition lasted three minutes. First, the video and depth data alignment was guaranteed using a purposely developed method, then an automatic tracking algorithm (DeepLabCut [3]) was used to estimate the locations of six points of interest (PoI) for both left and right upper body sides (shoulder, elbow and wrist). The 3D position of PoIs tracked in the RGB images was obtained by exploiting the depth data. Erroneous values were found when one or more of the following situations occurred: 1) a residual spatial misalignment between RGB and depth images, 2) a ‘black’ area in the depth images caused by the different points of view of the two infrared sensors and 3) PoIs were occluded by a body segment. Such erroneous values were replaced by applying a cubic spline interpolation to obtain the 3D trajectories of the PoIs. The periodicity index of the wrist trajectories, the area in which the wrist velocity profiles fall outside the standard deviation band of their moving average and the skewness of the wrist velocity were then determined [1]. Results are shown in Table 1. This work has shown that the infants’ GM could be characterized with a simple experimental setup, therefore giving parents the possibility of performing such evaluations at home with a higher frequency than currently possible in clinical facilities. This would allow an earlier detection of the appearance of GM anomalies. Additional work is needed to streamline the process and reduce the processing time while developing protocols for improving the acceptance and reliability of parents’ participation.