Monitoring Of Freezing Research Articles

Assessing inertial measurement unit locations for freezing of gait detection and patient preference

BackgroundFreezing of gait, a common symptom of Parkinson’s disease, presents as sporadic episodes in which an individual’s feet suddenly feel stuck to the ground. Inertial measurement units (IMUs) promise to enable at-home monitoring and personalization of therapy, but there is a lack of consensus on the number and location of IMUs for detecting freezing of gait. The purpose of this study was to assess IMU sets in the context of both freezing of gait detection performance and patient preference.MethodsSixteen people with Parkinson’s disease were surveyed about sensor preferences. Raw IMU data from seven people with Parkinson’s disease, wearing up to eleven sensors, were used to train convolutional neural networks to detect freezing of gait. Models trained with data from different sensor sets were assessed for technical performance; a best technical set and minimal IMU set were identified. Clinical utility was assessed by comparing model- and human-rater-determined percent time freezing and number of freezing events.ResultsThe best technical set consisted of three IMUs (lumbar and both ankles, AUROC = 0.83), all of which were rated highly wearable. The minimal IMU set consisted of a single ankle IMU (AUROC = 0.80). Correlations between these models and human raters were good to excellent for percent time freezing (ICC = 0.93, 0.89) and number of freezing events (ICC = 0.95, 0.86) for the best technical set and minimal IMU set, respectively.ConclusionsSeveral IMU sets consisting of three IMUs or fewer were highly rated for both technical performance and wearability, and more IMUs did not necessarily perform better in FOG detection. We openly share our data and software to further the development and adoption of a general, open-source model that uses raw signals and a standard sensor set for at-home monitoring of freezing of gait.

Role of synthetic antifreeze agents in catalyzing ice nucleation

Nature endows antifreeze (glyco)proteins (AF(G)Ps) with the excellent capability of inhibiting ice crystal growth. Recent years have also witnessed the emergence of many potent AF(G)P mimics such as poly (vinyl alcohol) (PVA). As researchers are revealing the molecular mechanisms of inhibiting ice crystal growth by AF(G)Ps and their synthetic substitutes, there remains no agreement about their effect on ice nucleation. In this study, we report the observation of ice nucleation catalyzed by PVA of different polymerization degrees using a freeze-on-a-chip platform which allows the monitoring of freezing and melting events over hundreds of monodisperse, picoliter-sized aqueous droplets. Aqueous droplets made of 1 mg/ml PVA solution exhibit a median freezing temperature of around −36 °C, two degrees higher than the observed homogeneous nucleation temperature of water. The findings in our study bring useful insights into the different roles of synthetic antifreeze agents in controlling ice formation.