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Add to EdgeEstimating Lower Body Kinematics using a Lie Group Constrained Extended Kalman Filter and Reduced IMU Count
Mar 21, 2021
Goal: This paper presents an algorithm for estimating pelvis, thigh, shank, and foot kinematics during walking using only two or three wearable inertial sensors. Methods: The algorithm makes novel use of a Lie-group-based extended Kalman filter. The algorithm iterates through the prediction (kinematic equation), measurement (pelvis position pseudo-measurements, zero-velocity update, and flat-floor assumption), and constraint update (hinged knee and ankle joints, constant leg lengths). Results: The inertial motion capture algorithm was extensively evaluated on two datasets showing its performance against two standard benchmark approaches in optical motion capture (i.e., plug-in gait (commonly used in gait analysis) and a kinematic fit (commonly used in animation, robotics, and musculoskeleton simulation)), giving insight into the similarity and differences between the said approaches used in different application areas. The overall mean body segment position (relative to mid-pelvis origin) and orientation error magnitude of our algorithm ($n=14$ participants) for free walking was $5.93 \pm 1.33$ cm and $13.43 \pm 1.89^\circ$ when using three IMUs placed on the feet and pelvis, and $6.35 \pm 1.20$ cm and $12.71 \pm 1.60^\circ$ when using only two IMUs placed on the feet. Conclusion: The algorithm was able to track the joint angles in the sagittal plane for straight walking well, but requires improvement for unscripted movements (e.g., turning around, side steps), especially for dynamic movements or when considering clinical applications. Significance: This work has brought us closer to comprehensive remote gait monitoring using IMUs on the shoes. The low computational cost also suggests that it can be used in real-time with gait assistive devices.
An Empirical Evaluation of Deep Learning for ICD-9 Code Assignment using MIMIC-III Clinical Notes
Feb 07, 2018
Code assignment is important on many levels in the modern hospital, from ensuring accurate billing process to creating a valid record of patient care history. However, the coding process is tedious, subjective, and requires medical coders with extensive training. The objective of this study is to evaluate the performance of deep learning based systems to automatically map clinical notes to medical codes. We applied the state-of-the-art deep learning methods such as Recurrent Neural Networks and Convolution Neural Networks on MIMIC-III dataset. Experiments show that the deep-learning-based methods outperform other conventional machine learning methods. Our evaluations are focused on end-to-end learning methods without manually defined rules. From our evaluations, the best models are able to predict the top 10 ICD-9 codes with 69.57% F1 and 89.67% accuracy; the top 10 ICD-9 categories with 72.33% F1 and 85.88% accuracy.