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Optimizing MobileNet algorithms for real-time vessel detection on smartphones

October 9, 2023
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Conference Paper
Author:
Lars A. Gjesteby
…
Published in:
Proc. 2023 IEEE 19th Intl. Conf. on Body Sensor Networks, BSN, 9-11 October 2023.
Topic:
sensors
R&D area:
R&D group:

Summary

Internal bleeding due to non-compressible torso hemorrhage is the leading cause of prehospital fatalities in civilian and military trauma. A limited number of trauma surgeons are expected to be available in disaster scenarios and future large-scale combat operations. As a result, non-specialists will need to perform life-saving interventions to address internal bleeding. A first step in mitigation is ultrasound-guided central vascular access, which involves identifying a deep blood vessel in the imagery, such as the femoral vein, femoral artery, or internal jugular vein, and then placing a needle and catheter into the vessel for follow-on resuscitation. In this paper, we demonstrate machine learning algorithms for both femoral and neck vessel detection with high accuracy and real-time speed on smartphones. The algorithms are integrated with commercial ultrasound and optimized for use on low size, weight, and power devices. Coupled with custom robotics, this technology can enable rapid vascular access by non-specialist operators using a handheld platform.
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Summary

Internal bleeding due to non-compressible torso hemorrhage is the leading cause of prehospital fatalities in civilian and military trauma. A limited number of trauma surgeons are expected to be available in disaster scenarios and future large-scale combat operations. As a result, non-specialists will need to perform life-saving interventions to address...

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Optimizing MobileNet algorithms for real-time vessel detection on smartphones

Impact of haptic cues and an active ankle exoskeleton on gait characteristics

July 1, 2022
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Journal Article
Author:
Man I. Wu
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Published in:
Hum. Factors, Vol. 0, No. 0, July 2022, p. 1-12.
Topic:
sensors
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Summary

Objective This study examined the interaction of gait-synchronized vibrotactile cues with an active ankle exoskeleton that provides plantarflexion assistance. Background An exoskeleton that augments gait may support collaboration through feedback to the user about the state of the exoskeleton or characteristics of the task. Methods Participants (N = 16) were provided combinations of torque assistance and vibrotactile cues at pre-specified time points in late swing and early stance while walking on a self-paced treadmill. Participants were either given explicit instructions (N = 8) or were allowed to freely interpret (N=8) how to coordinate with cues. Results For the free interpretation group, the data support an 8% increase in stride length and 14% increase in speed with exoskeleton torque across cue timing, as well as a 5% increase in stride length and 7% increase in speed with only vibrotactile cues. When given explicit instructions, participants modulated speed according to cue timing-increasing speed by 17% at cues in late swing and decreasing speed 11% at cues in early stance compared to no cue when exoskeleton torque was off. When torque was on, participants with explicit instructions had reduced changes in speed. Conclusion These findings support that the presence of torque mitigates how cues were used and highlights the importance of explicit instructions for haptic cuing. Interpreting cues while walking with an exoskeleton may increase cognitive load, influencing overall human-exoskeleton performance for novice users. Application Interactions between haptic feedback and exoskeleton use during gait can inform future feedback designs to support coordination between users and exoskeletons.
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Summary

Objective This study examined the interaction of gait-synchronized vibrotactile cues with an active ankle exoskeleton that provides plantarflexion assistance. Background An exoskeleton that augments gait may support collaboration through feedback to the user about the state of the exoskeleton or characteristics of the task. Methods Participants (N = 16) were...

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Impact of haptic cues and an active ankle exoskeleton on gait characteristics

Estimating sedentary breathing rate from chest-worn accelerometry from free-living data

July 20, 2020
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Conference Paper
Author:
Brian A. Telfer
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Published in:
42nd Annual Intl. Conf. IEEE Engineering in Medicine and Biology Society, EMBC, 20-24 July 2020.
Topic:
sensors
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R&D group:

Summary

Breathing rate was estimated from chest-worn accelerometry collected from 1,522 servicemembers during training by a wearable physiological monitor. A total of 29,189 hours of training and sleep data were analyzed. The primary purpose of the monitor was to assess thermal-work strain and avoid heat injuries. The monitor design was thus not optimized to estimate breathing rate. Since breathing rate cannot be accurately estimated during periods of high activity, a qualifier was applied to identify sedentary time periods, totaling 8,867 hours. Breathing rate was estimated for a total of 4,179 hours, or 14% of the total collection and 47% of the sedentary total, primarily during periods of sleep. The breathing rate estimation method was compared to an FDA 510(K)-cleared criterion breathing rate sensor (Zephyr, Annapolis MD, USA) in a controlled laboratory experiment, which showed good agreement between the two techniques. Contributions of this paper are to: 1) provide the first analysis of accelerometry-derived breathing rate on free-living data including periods of high activity as well as sleep, along with a qualifier that effectively identifies sedentary periods appropriate for estimating breathing rate; 2) test breathing rate estimation on a data set with a total duration that is more than 60 times longer than that of the largest previously reported study, 3) test breathing rate estimation on data from a physiological monitor that has not been expressly designed for that purpose.
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Summary

Breathing rate was estimated from chest-worn accelerometry collected from 1,522 servicemembers during training by a wearable physiological monitor. A total of 29,189 hours of training and sleep data were analyzed. The primary purpose of the monitor was to assess thermal-work strain and avoid heat injuries. The monitor design was thus...

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Estimating sedentary breathing rate from chest-worn accelerometry from free-living data

Integrative sensor networks, informatics, and modeling for precision and preventative medicine

July 1, 2020
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Journal Article
Author:
Wei Wei Chen
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Published in:
IEEE J. Biomed. Health, Vol. 24, No. 7, July 2020, pp. 1858-1859.
Topic:
sensors
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R&D group:

Summary

The topics of integrative sensor networks, informatics and modeling bring together the tightly coupled and rapidly developing fields of biomedical and health informatics and body sensor networks. Biomedical and health informatics encompasses methods to extract and communicate information from data in order to impact health, healthcare, life sciences and biomedicine. Body sensor networks provide one means to measure the needed data, through continuous monitoring in both clinical and free-living environments. Developments in these areas were highlighted at two co-located conferences: the 2019 IEEE-EMBS International Conferences on Biomedical and Health Informatics (BHI'19) and Wearable and Implantable Body Sensor Networks (BSN'19). BHI and BSN are long-standing IEEE EMBS conferences that provide a forum for researchers and leaders from academia, government and industry to share technical advances and new initiatives in these important areas. Through an open call for this special issue, eleven papers have been included for publication. The majority were presented in an initial form at the 2018 or 2019 BHI and BSN conferences. Nine of the papers were selected through a rigorous peer review. In addition, two keynote speakers from BHI'19 and BSN'19 have provided short position papers.
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Summary

The topics of integrative sensor networks, informatics and modeling bring together the tightly coupled and rapidly developing fields of biomedical and health informatics and body sensor networks. Biomedical and health informatics encompasses methods to extract and communicate information from data in order to impact health, healthcare, life sciences and biomedicine...

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Integrative sensor networks, informatics, and modeling for precision and preventative medicine

Large-format Geiger-mode avalanche photodiode arrays and readout circuits

March 1, 2018
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Journal Article
Author:
Brian F. Aull
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Published in:
IEEE J. Sel. Top. Quantum Electron., Vol. 24, No. 2, March/April 2018, 3800510.
Topic:
photonics
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R&D group:

Summary

Over the past 20 years, we have developed arrays of custom-fabricated silicon and InP Geiger-mode avalanche photodiode arrays, CMOS readout circuits to digitally count or time stamp single-photon detection events, and techniques to integrate these two components to make back-illuminated solid-state image sensors for lidar, optical communications, and passive imaging. Starting with 4 × 4 arrays, we have recently demonstrated 256 × 256 arrays, and are working to scale to megapixel-class imagers. In this paper, we review this progress and discuss key technical challenges to scaling to large format.
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Summary

Over the past 20 years, we have developed arrays of custom-fabricated silicon and InP Geiger-mode avalanche photodiode arrays, CMOS readout circuits to digitally count or time stamp single-photon detection events, and techniques to integrate these two components to make back-illuminated solid-state image sensors for lidar, optical communications, and passive imaging...

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Large-format Geiger-mode avalanche photodiode arrays and readout circuits

Flexible glucose sensors and fuel cells for bioelectronic implants

August 6, 2017
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Conference Paper
Author:
Todd A. Thorsen
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Published in:
IEEE 60th Int. Midwest Symp. on Circuits and Systems, MWSCAS, 6-9 August 2017.
Topic:
sensors
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Summary

Microfabrication techniques were developed to create flexible 24 um thick glucose sensors on polyimide substrates. Measurements of the sensor performance, recorded as voltage potential, were carried out for a range of glucose concentrations (0 – 8 mM) in physiological saline (0.1 M NaCl, pH 7.4). The sensors show rapid response times (seconds to stable potential) and good sensitivity in the 0 – 4 mM range. Additionally, we demonstrate that the sensors can operate as fuel cells, generating peak power levels up to 0.94 uW/cm2. Such flexible devices, which can be rolled up to increase surface area within a fixed volume, may enable ultra-low-power bio-electronic implants for glucose sensing or glucose energy harvesting in the future.
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Summary

Microfabrication techniques were developed to create flexible 24 um thick glucose sensors on polyimide substrates. Measurements of the sensor performance, recorded as voltage potential, were carried out for a range of glucose concentrations (0 – 8 mM) in physiological saline (0.1 M NaCl, pH 7.4). The sensors show rapid response...

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Flexible glucose sensors and fuel cells for bioelectronic implants

Covariance estimation in terms of Stokes parameters with application to vector sensor imaging

November 6, 2016
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Conference Paper
Author:
Ryan Volz
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Published in:
2016 Asilomar Conf. on Signals, Systems and Computers, Asilomar 2016, 6-9 November 2016.
Topic:
sensors
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Summary

Vector sensor imaging presents a challenging problem in covariance estimation when allowing arbitrarily polarized sources. We propose a Stokes parameter representation of the source covariance matrix which is both qualitatively and computationally convenient. Using this formulation, we adapt the proximal gradient and expectation maximization (EM) algorithms and apply them in multiple variants to the maximum likelihood and least squares problems. We also show how EM can be cast as gradient descent on the Riemannian manifold of positive definite matrices, enabling a new accelerated EM algorithm. Finally, we demonstrate the benefits of the proximal gradient approach through comparison of convergence results from simulated data.
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Summary

Vector sensor imaging presents a challenging problem in covariance estimation when allowing arbitrarily polarized sources. We propose a Stokes parameter representation of the source covariance matrix which is both qualitatively and computationally convenient. Using this formulation, we adapt the proximal gradient and expectation maximization (EM) algorithms and apply them in...

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Covariance estimation in terms of Stokes parameters with application to vector sensor imaging

HF vector sensor for radio astronomy: ground testing results

September 13, 2016
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Conference Paper
Author:
Mary Knapp
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Published in:
AIAA Space 2016 Conf. and Exposition, 13-16 September 2016.
Topic:
sensors
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Summary

The radio sky below ~10 MHz is largely unexplored due to the inability of ground-based telescopes to observe near or below the ionospheric plasma frequency, or cut-off frequency. A space-based interferometric array is required to probe the portion of the electromagnetic (E-M) spectrum below 10 MHz with sufficient angular resolution and sensitivity to be scientifically useful. Multi-spacecraft constellations scale quickly in cost and complexity as the number of spacecraft increases, so minimizing the number of required spacecraft for an interferometric array (while maintaining performance) is critical for feasibility. We present the HF (High Frequency, 3 to 30 MHz) Vector Sensor as a high performance spacecraft instrument in a future space-based interferometric array. The HF Vector Sensor is composed of three orthogonal dipoles and three orthogonal loop antennas with a common phase center. These six elements fully measure the E-M field of incoming radiation. We present the design of two prototype HF Vector Sensors, ground-based data collection at frequencies above the ionospheric cut-off, and imaging results using several different algorithms.
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Summary

The radio sky below ~10 MHz is largely unexplored due to the inability of ground-based telescopes to observe near or below the ionospheric plasma frequency, or cut-off frequency. A space-based interferometric array is required to probe the portion of the electromagnetic (E-M) spectrum below 10 MHz with sufficient angular resolution...

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HF vector sensor for radio astronomy: ground testing results

Liquid crystal uncooled thermal imager development

August 28, 2016
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Conference Paper
Author:
Harry R. Clark Jr
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Published in:
SPIE, Vol. 9974, Infrared Sensors, Devices, and Applications VI, 28 August 2016.
Topic:
sensors
R&D area:
R&D group:

Summary

An uncooled thermal imager is being developed based on a liquid crystal (LC) transducer. Without any electrical connections, the LC transducer pixels change the long-wavelength infrared (LWIR) scene directly into a visible image as opposed to an electric signal in microbolometers. The objectives are to develop an imager technology scalable to large formats (tens of megapixels) while maintaining or improving the noise equivalent temperature difference (NETD) compared to microbolometers. The present work is demonstrating that the LCs have the required performance (sensitivity, dynamic range, speed, etc.) to enable a more flexible uncooled imager. Utilizing 200-mm wafers, a process has been developed and arrays have been fabricated using aligned LCs confined in 20-20-um cavities elevated on thermal legs. Detectors have been successfully fabricated on both silicon and fused silica wafers using less than 10 photolithographic mask steps. A breadboard camera system has been assembled to test the imagers. Various sensor configurations are described along with advantages and disadvantages of component arrangements.
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Summary

An uncooled thermal imager is being developed based on a liquid crystal (LC) transducer. Without any electrical connections, the LC transducer pixels change the long-wavelength infrared (LWIR) scene directly into a visible image as opposed to an electric signal in microbolometers. The objectives are to develop an imager technology scalable...

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Liquid crystal uncooled thermal imager development

Geiger-mode avalanche photodiode arrays integrated to all-digital CMOS circuits

April 8, 2016
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Journal Article
Author:
Brian F. Aull
Published in:
Sensors, Vol. 16, No. 495, 2016, doi:10.3390/s16040495.
Topic:
photonics
R&D area:
R&D group:

Summary

This article reviews MIT Lincoln Laboratory's work over the past 20 years to develop photon-sensitive image sensors based on arrays of silicon Geiger-mode avalanche photodiodes. Integration of these detectors to all-digital CMOS readout circuits enable exquisitely sensitive solid-state imagers for lidar, wavefront sensing, and passive imaging.
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Summary

This article reviews MIT Lincoln Laboratory's work over the past 20 years to develop photon-sensitive image sensors based on arrays of silicon Geiger-mode avalanche photodiodes. Integration of these detectors to all-digital CMOS readout circuits enable exquisitely sensitive solid-state imagers for lidar, wavefront sensing, and passive imaging.

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Geiger-mode avalanche photodiode arrays integrated to all-digital CMOS circuits
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