Papers by Hooman Dejnabadi
Methods in Ecology and Evolution
IEEE Access
Gait bouts (GB), as a prominent indication of physical activity, contain valuable fundamental inf... more Gait bouts (GB), as a prominent indication of physical activity, contain valuable fundamental information closely associated with human's health status. Therefore, objective assessment of the GB (e.g. detection, spatio-temporal analysis) during daily life is very important. A feasible and effective way of GB detection in real-world situations is using a wrist-mounted inertial measurement unit. However, the high degree of freedom of the wrist movements during daily-life situations imposes serious challenges for a precise and robust automatic detection. In this study, we deal with such challenges and propose an accurate algorithm to detect GB using a wrist-mounted accelerometer. Features, derived based on biomechanical criteria (intensity, periodicity, posture, and other non-gait dynamicity), along with a Bayes estimator followed by two physically-meaningful post-classification procedures are devised to optimize the performance. The proposed method has been validated against a shank-based reference algorithm on two datasets (29 young and 37 elderly healthy people). The method has achieved a high median [interquartile range] of 90.2 [80.4, 94.6] (%), 97.2 [95.8, 98.4] (%), 96.6 [94.4, 97.8] (%), 80.0 [65.1, 85.9] (%) and 82.6 [72.6, 88.5] (%) for the sensitivity, specificity, accuracy, precision, and F1-score of the detection of GB, respectively. Moreover, a high correlation (R 2 = 0.95) was observed between the proposed method and the reference for the total duration of GB detected for each subject. The method has been also implemented in real time on a low power consumption prototype. INDEX TERMS Real-world gait bout, physical activity, wrist accelerometer, machine learning, low power, and real-time.
IEEE Transactions on Biomedical Engineering
In this paper, a new vibrational modal analysis technique was developed for intraoperative cement... more In this paper, a new vibrational modal analysis technique was developed for intraoperative cementless prosthesis fixation evaluation upon hammering. Methods: An artificial bone (Sawbones)-prosthesis system was excited by sweeping of a sine signal over a wide frequency range. The exponential sine sweep technique was implemented to the response signal in order to determine the linear impulse response. Recursive Fourier transform enhancement (RFTE) technique was applied to the linear impulse response signal in order to enhance the frequency spectrum with sharp and distinguishable peak values indicating distinct high natural frequencies of the system (ranging from 15 kHz to 90 kHz). The experiment was repeated with 5 Sawbones-prosthesis samples. Upon successive hammering during the prosthesis insertion, variation of each natural frequency was traced. Results: Compared to classical Fast Fourier Transform, RFTE provided a better tracing and enhancement of frequency components during insertion. Three different types of frequency evolving trends (monotonically increasing, insensitive, and plateau-like) were observed for all samples, as confirmed by a new finite element simulation of the prosthesis dynamic insertion. Two main mechanical phenomena (i.e., geometrical compaction and compressive stress) were shown to govern these trends in opposite ways. Follow-up of the plateaulike trend upon hammering showed that the frequency shift is a good indicator of fixation. Conclusion: Alongside the individual follow-up of frequency shifts, combinatorial frequency analysis provides new objective information on the mechanical stability of Sawbone-prosthesis fixation. Significance: The proposed vibrational technique based on RTFE can provide the surgeon with a new assistive diagnostic technique during the surgery by indicating when the bone-prosthesis fixation is acceptable, and beyond of which further hammering should be done cautiously to avoid bone fracture.
IEEE Journal of Biomedical and Health Informatics
Gait speed is an important parameter to characterize people's daily mobility. For real-world spee... more Gait speed is an important parameter to characterize people's daily mobility. For real-world speed measurement, inertial sensors or Global Navigation Satellite System (GNSS) can be used on wrist, possibly integrated in a wristwatch. However, power consumption of GNSS is high and data are only available outdoor. Gait speed estimation using wrist-mounted inertial sensors is generally based on machine learning and suffers from low accuracy due to the inadequacy of using limited training data to build a general speed model that would be accurate for the whole population. To overcome this issue, a personalized model was proposed, which took unique gait style of each subject into account. Cadence and other biomechanically-derived gait features were extracted from wrist-mounted accelerometer and barometer. Gait features were fused with few GNSS data (sporadically sampled during gait) to calibrate the step length model of each subject through online learning. The proposed method was validated on 30 healthy subjects where it has achieved a median [Interquartile Range] of RMSE of 0.05 [0.04-0.06] (m/s) and 0.14 [0.11 0.17] (m/s) for walking and running respectively. Results demonstrated that the personalized model provided similar performance as GNSS. It used 50 times less training GNSS data than non-personalized method and achieved even better results. This parsimonious GNSS usage allowed extending battery life. The proposed algorithm met requirements for applications which need accurate, long, real-time, low-power, and indoor/outdoor speed estimation in daily life.
In this work we designed and tested an in-vivo measurement system of prosthetic knee joint angles... more In this work we designed and tested an in-vivo measurement system of prosthetic knee joint angles. The system included a small permanent magnet in the femoral part and three magneto resistance sensors placed in the polyethylene part. The sensor configuration was defined based on sensitivity analysis, signal to noise ratio, saturation of sensors and movements constraints. A mapping algorithm was designed to estimate the orientation of the femoral part in sagittal and coronal plane. For validation the prosthesis was placed in a mechanical simulator equipped with reflective markers tracked by optical motion capture.
Revue de Chirurgie Orthopédique et Traumatologique, 2011
2011 IEEE International Conference on Automation Science and Engineering, 2011
IEEE Transactions on Biomedical Engineering, 2006
A new method of estimating lower limbs orientations using a combination of accelerometers and gyr... more A new method of estimating lower limbs orientations using a combination of accelerometers and gyroscopes is presented. The model is based on estimating the accelerations of ankle and knee joints by placing virtual sensors at the centers of rotation. The proposed technique considers human locomotion and biomechanical constraints, and provides a solution to fusing the data of gyroscopes and accelerometers that yields stable and drift-free estimates of segment orientation. The method was validated by measuring lower limb motions of eight subjects, walking at three different speeds, and comparing the results with a reference motion measurement system. The results are very close to those of the reference system presenting very small errors (Shank: rms = 1 0, Thigh: rms = 1 6) and excellent correlation coefficients (Shank: r = 0 999, Thigh: r = 0 998). Technically, the proposed ambulatory system is portable, easily mountable, and can be used for long term monitoring without hindrance to natural activities. Finally, a gait analysis tool was designed to visualize the motion data as synthetic skeletons performing the same actions as the subjects.
IEEE Transactions on Biomedical Engineering, 2005
A new method of measuring joint angle using a combination of accelerometers and gyroscopes is pre... more A new method of measuring joint angle using a combination of accelerometers and gyroscopes is presented. The method proposes a minimal sensor configuration with one sensor module mounted on each segment. The model is based on estimating the acceleration of the joint center of rotation by placing a pair of virtual sensors on the adjacent segments at the center of rotation. In the proposed technique, joint angles are found without the need for integration, so absolute angles can be obtained which are free from any source of drift. The model considers anatomical aspects and is personalized for each subject prior to each measurement. The method was validated by measuring knee flexion-extension angles of eight subjects, walking at three different speeds, and comparing the results with a reference motion measurement system. The results are very close to those of the reference system presenting very small errors (rms = 1 3, mean = 0 2, SD = 1 1 deg) and excellent correlation coefficients (0.997). The algorithm is able to provide joint angles in real-time, and ready for use in gait analysis. Technically, the system is portable, easily mountable, and can be used for long term monitoring without hindrance to natural activities.
Gait & Posture, 2005
Chapter 13. Biomechanics and orthopaedic disorders Methods: 8 ACL patients walked and crossed obs... more Chapter 13. Biomechanics and orthopaedic disorders Methods: 8 ACL patients walked and crossed obstacles of 3 heights (10, 20 and 30% leg lengths) before and 3 months after ACLR. Kinematic and kinetic data were measured using a motion analysis system (Vicon, Oxford Metrics, U.K.) and two force plates (AMTI, U.S.A.). An asymmetry index (AI, difference between sound and affected limbs/average of both limbs) was used to investigate the asymmetry of the joint kinematics and kinetics. Paired-t test was used for before after reconstruction comparisons (¢~ 0.05). Results: Significantly bigger AI values were found in the trailing knee crossing flexion angles and leading knee crossing flexor moments as well as the peak hip internal rotator moments of both limbs for all heights after ACLR. Discussion and Conclusion: The results suggest that ACLR did not help reduce the biomechanical asymmetry 3 months post-op. It may be associated with the persistent deficit of the muscle strength after surgery. Rehabilitation for a longer period of time may be needed to achieve better inter-limb coordination.
Citeseer
A new method of estimating lower limbs orientations using a combination of accelerometers and gyr... more A new method of estimating lower limbs orientations using a combination of accelerometers and gyroscopes is presented in this chapter. The model is based on estimating the accelerations of ankle and knee joints by placing virtual sensors at the centers of rotation. The proposed technique considers human locomotion and biomechanical constraints, and provides a solution to fusing the data of gyroscopes and accelerometers that yields stable and drift-free estimates of segment orientation. The method was validated by measuring lower limb motions of eight subjects, walking at three different speeds, and comparing the results with a reference motion measurement system. The results are very close to those of the reference system presenting very small errors (Shank: rms = 1.0, Thigh: rms = 1.6 deg) and excellent correlation coefficients (Shank: r = 0.999, Thigh: r = 0.998). Technically, the proposed ambulatory system is portable, easily mountable, and can be used for long term monitoring without hindrance to natural activities.
différences d'inclinaison acétabulaire de 6 à 20° et d'orientation des cols prothétiques de 5 à 1... more différences d'inclinaison acétabulaire de 6 à 20° et d'orientation des cols prothétiques de 5 à 17°. DISCUSSION ET CONCLUSION. L'analyse d'une PTH est généralement baséee sur un cliché de face standardisé. Les clichés en situation fonctionnelle éclairent de façon originale les conflits et les subluxations surtout en cas d'enraidissement lombo-sacré.
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Papers by Hooman Dejnabadi