Noninvasive pressure monitoring using acoustic resonance spectroscopy and machine learning
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Engineering studies of vectorcardiographs in blood pressure measuring systems
The following projects involving cardiovascular instrumentation were conducted: (1) the development and fabrication of a three-dimensional display measurement system for vectorcardiograms, (2) the development and fabrication of a cardiovascular monitoring system to noninvasively monitor beat-by-beat the blood pressure and heart rate using aortic pulse wave velocity, (3) the development of software for an interactive system to analyze systolic time interval data, and (4) the development of microprocessor-based physiologic instrumentation, focussing initially on EKG rhythm analysis. Brief descriptions of these projects were given.
Mark, R. G.↗
Engineering studies of vectorcardiographs in blood pressure measuring systems, appendix 2
The development of a cardiovascular monitoring system to noninvasively monitor the blood pressure and heart rate using pulse wave velocity was described. The following topics were covered: (1) pulse wave velocity as a measure of arterial blood pressure, (2) diastolic blood pressure and pulse wave velocity in humans, (3) transducer development for blood pressure measuring device, and (4) cardiovascular monitoring system. It was found, in experiments on dogs, that the pulse wave velocity is linearly related to diastolic blood pressure over a wide range of blood pressure and in the presence of many physiological perturbations. A similar relationship was observed in normal, young human males over a moderate range of pressures. Past methods for monitoring blood pressure and a new method based on pulse wave velocity determination were described. Two systems were tested: a Doppler ultrasonic transducer and a photoelectric plethysmograph. A cardiovascular monitoring system was described, including operating instructions.
Mark, R. G.↗
Monitoring Temperatures Indirectly in Cooled Combustors
Noninvasive monitoring of temperatures on inner surface of combustion liner of cooled combustor increases liner life, thereby increasing combustor reliability and performance. Technique used in furnaces, reactors, jet engines, rocket engines, stationary turbines, combustors, and heat exchangers. Growth of internal overheating streaks monitored using output from array of thermocouples on outside wall of combustor. Computer analysis of output indicates temperature pattern on combustor lining. Use of data enables timely liner maintenance or overhaul.
Wagner, W.↗
Wearable Beat-to-Beat Blood Pressure Monitor
Linea Research Corporation has developed a wearable noninvasive monitor that provides continuous blood pressure and heart rate measurements in extreme environments. Designed to monitor the physiological effects of astronauts' prolonged exposure to reduced-gravity environments as well as the effectiveness of various countermeasures, the device offers wireless connectivity to allow transfer of both real-time and historical data. It can be modified to monitor the health status of astronaut crew members during extravehicular missions.
Lee, Yong Jin↗
Monitoring Object Library Usage and Changes
The NASA Ames Numerical Aerodynamic Simulation program Aeronautics Consolidated Supercomputing Facility (NAS/ACSF) supercomputing center services over 1600 users, and has numerous analysts with root access. Several tools have been developed to monitor object library usage and changes. Some of the tools do "noninvasive" monitoring and other tools implement run-time logging even for object-only libraries. The run-time logging identifies who, when, and what is being used. The benefits are that real usage can be measured, unused libraries can be discontinued, training and optimization efforts can be focused at those numerical methods that are actually used. An overview of the tools will be given and the results will be discussed.
Owen, R. K.↗
UV–Vis–NIR Reflectance Spectroscopy and Chemometrics for Monitoring Pu Directly on an Ion Exchange Column
Here, we present a fiber-optic UV–vis–NIR reflectance spectroscopy method for direct, noninvasive monitoring of Pu(IV) in a glass ion exchange column during dynamic loading and elution in a glovebox. A movable probe enables spatially resolved spectral acquisition along the column axis, capturing distinct features associated with Pu(IV) nitrate complexes during loading and free ions during elution. Principal component analysis was applied to extract the dominant spectral variance and resolve relative concentration profiles without requiring precise knowledge of optical penetration depth or species identity. This in situ approach reveals spatial gradients and speciation dynamics in real time, which provides actionable insight into Pu(IV) ion migration, resin saturation, and breakthrough behavior under evolving flow conditions. The method offers a practical, fiber-compatible strategy to monitor glass column–based separations for Pu and other lanthanides or actinides and to characterize metal–resin interactions in flow-through systems.
actinide↗
Evaluation of the Accuracy of Astroskin as a Behavioral Health Self-Monitoring System for Spaceflight
In space, there is a need to monitor astronauts' vital signs and assess their readiness to perform specific tasks during a mission. Currently, NASA does not have the capability to noninvasively monitor crew for extended periods of time. The Canadian Space Agency is working with the Psychophysiology Lab at NASA ARC to determine if the Astroskin could be used as a solution to this problem. Astroskin, a commercially available garment with built-in biosensors, can be comfortably worn under clothing or a spacesuit and relay information to the crewman's own mobile device. Data can also be sent wirelessly to the on-board Exploration Medical System. To determine if Astroskin meets requirements for health monitoring, it must first be validated in spaceflight analog environments. In the current study Astroskin data will be compared to traditional biomedical instrument measures of electrocardiography (ECG), respiration rate, and systolic blood pressure. The data will be recorded during Autogenic Feedback Training Exercise (AFTE), which is a type of physiological self-regulation training designed for astronauts. The data will also be recorded during simulations of the Orion spacecraft re-entry. The results to date suggest that Astroskin is a suitable ambulatory monitoring system that allows astronauts to self-diagnose and self-regulate adverse autonomic nervous system responses to sustained exposure to microgravity of spaceflight.
biomedical↗
Engine materials characterization and damage monitoring by using x ray technologies
X ray attenuation measurement systems that are capable of characterizing density variations in monolithic ceramics and damage due to processing and/or mechanical testing in ceramic and intermetallic matrix composites are developed and applied. Noninvasive monitoring of damage accumulation and failure sequences in ceramic matrix composites is used during room-temperature tensile testing. This work resulted in the development of a point-scan digital radiography system and an in situ x ray material testing system. The former is used to characterize silicon carbide and silicon nitride specimens, and the latter is used to image the failure behavior of silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. State-of-the-art x ray computed tomography is investigated to determine its capabilities and limitations in characterizing density variations of subscale engine components (e.g., a silicon carbide rotor, a silicon nitride blade, and a silicon-carbide-fiber-reinforced beta titanium matrix rod, rotor, and ring). Microfocus radiography, conventional radiography, scanning acoustic microscopy, and metallography are used to substantiate the x ray computed tomography findings. Point-scan digital radiography is a viable technique for characterizing density variations in monolithic ceramic specimens. But it is very limited and time consuming in characterizing ceramic matrix composites. Precise x ray attenuation measurements, reflecting minute density variations, are achieved by photon counting and by using microcollimators at the source and the detector. X ray computed tomography is found to be a unique x ray attenuation measurement technique capable of providing cross-sectional spatial density information in monolithic ceramics and metal matrix composites. X ray computed tomography is proven to accelerate generic composite component development. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results from one-, three-, five-, and eight-ply ceramic composite specimens show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber-matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. In situ film radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction-bonded silicon nitride matrix. It is concluded that pretest, in situ, and post-test x ray imaging can provide greater understanding of ceramic matrix composite mechanical behavior.
Baaklini, George Y.↗
X ray attenuation measurements for high-temperature materials characterization and in-situ monitoring of damage accumulation
The scope of this dissertation is to develop and apply x ray attenuation measurement systems that are capable of: (1) characterizing density variations in high-temperature materials, e.g., monolithic ceramics, ceramic and intermetallic matrix composites, and (2) noninvasively monitoring damage accumulation and failure sequences in ceramic matrix composites under room temperature tensile testing. This dissertation results in the development of: (1) a point scan digital radiography system, and (2) an in-situ x ray material testing system. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. Further in-situ radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction bonded silicon nitride matrix. It is concluded that pretest, in-situ, and post test x ray imaging can provide for greater understanding of ceramic matrix composite mechanical behavior.
Baaklini, George Y.↗
Wearable Health Monitoring Systems
The shrinking size and weight of electronic circuitry has given rise to a new generation of smart clothing that enables biological data to be measured and transmitted. As the variation in the number and type of deployable devices and sensors increases, technology must allow their seamless integration so they can be electrically powered, operated, and recharged over a digital pathway. Nyx Illuminated Clothing Company has developed a lightweight health monitoring system that integrates medical sensors, electrodes, electrical connections, circuits, and a power supply into a single wearable assembly. The system is comfortable, bendable in three dimensions, durable, waterproof, and washable. The innovation will allow astronaut health monitoring in a variety of real-time scenarios, with data stored in digital memory for later use in a medical database. Potential commercial uses are numerous, as the technology enables medical personnel to noninvasively monitor patient vital signs in a multitude of health care settings and applications.
Bell, John↗
Devices Would Detect Drugs In Sweat
Proposed devices worn on skin detect such substances as methamphetamine, morphine, tetrahydrocannabinol (THC), and cocaine in wearers' sweat and transmits radio signals in response to computer queries. Called Remote Biochemical Assay Telemetering System (R-BATS), commonly referred to as "drug badge," attached to wearer by use of adhesive wristband. Used for noninvasive monitoring of levels of prescribed medications in hospital and home-care settings and to detect overdoses quickly.
Mintz, Fredrick W.↗
New optical scheme for a polarimetric-based glucose sensor
A new optical scheme to detect glucose concentration in the aqueous humor of the eye is presented. The ultimate aim is to apply this technique in designing a new instrument for, routinely and frequently, noninvasively monitoring blood glucose levels in diabetic patients without contact (no index matching) between the eye and the instrument. The optical scheme exploits the Brewster reflection of circularly polarized light off of the lens of the eye. Theoretically, this reflected linearly polarized light on its way to the detector is expected to rotate its state of polarization, owing to the presence of glucose molecules in the aqueous humor of a patient's eye. An experimental laboratory setup based on this scheme was designed and tested by measuring a range of known concentrations of glucose solutions dissolved in water. (c) 2004 Society of Photo-Optical Instrumentation Engineers.
Evaluation Studies↗
A quantitative comparison of simultaneous BOLD fMRI and NIRS recordings during functional brain activation
Near-infrared spectroscopy (NIRS) has been used to noninvasively monitor adult human brain function in a wide variety of tasks. While rough spatial correspondences with maps generated from functional magnetic resonance imaging (fMRI) have been found in such experiments, the amplitude correspondences between the two recording modalities have not been fully characterized. To do so, we simultaneously acquired NIRS and blood-oxygenation level-dependent (BOLD) fMRI data and compared Delta(1/BOLD) (approximately R(2)(*)) to changes in oxyhemoglobin, deoxyhemoglobin, and total hemoglobin concentrations derived from the NIRS data from subjects performing a simple motor task. We expected the correlation with deoxyhemoglobin to be strongest, due to the causal relation between changes in deoxyhemoglobin concentrations and BOLD signal. Instead we found highly variable correlations, suggesting the need to account for individual subject differences in our NIRS calculations. We argue that the variability resulted from systematic errors associated with each of the signals, including: (1) partial volume errors due to focal concentration changes, (2) wavelength dependence of this partial volume effect, (3) tissue model errors, and (4) possible spatial incongruence between oxy- and deoxyhemoglobin concentration changes. After such effects were accounted for, strong correlations were found between fMRI changes and all optical measures, with oxyhemoglobin providing the strongest correlation. Importantly, this finding held even when including scalp, skull, and inactive brain tissue in the average BOLD signal. This may reflect, at least in part, the superior contrast-to-noise ratio for oxyhemoglobin relative to deoxyhemoglobin (from optical measurements), rather than physiology related to BOLD signal interpretation.
Non-NASA Center↗
Real-time non-invasive eyetracking and gaze-point determination for human-computer interaction and biomedicine
Eyetracking is one of the latest technologies that has shown potential in several areas including human-computer interaction for people with and without disabilities, and for noninvasive monitoring, detection, and even diagnosis of physiological and neurological problems in individuals.
image processing hardware↗
Ambient-Light-Canceling Camera Using Subtraction of Frames
The ambient-light-canceling camera (ALCC) is a proposed near-infrared electronic camera that would utilize a combination of (1) synchronized illumination during alternate frame periods and (2) subtraction of readouts from consecutive frames to obtain images without a background component of ambient light. The ALCC is intended especially for use in tracking the motion of an eye by the pupil center corneal reflection (PCCR) method. Eye tracking by the PCCR method has shown potential for application in human-computer interaction for people with and without disabilities, and for noninvasive monitoring, detection, and even diagnosis of physiological and neurological deficiencies. In the PCCR method, an eye is illuminated by near-infrared light from a lightemitting diode (LED). Some of the infrared light is reflected from the surface of the cornea. Some of the infrared light enters the eye through the pupil and is reflected from back of the eye out through the pupil a phenomenon commonly observed as the red-eye effect in flash photography. An electronic camera is oriented to image the user's eye. The output of the camera is digitized and processed by algorithms that locate the two reflections. Then from the locations of the centers of the two reflections, the direction of gaze is computed. As described thus far, the PCCR method is susceptible to errors caused by reflections of ambient light. Although a near-infrared band-pass optical filter can be used to discriminate against ambient light, some sources of ambient light have enough in-band power to compete with the LED signal. The mode of operation of the ALCC would complement or supplant spectral filtering by providing more nearly complete cancellation of the effect of ambient light. In the operation of the ALCC, a near-infrared LED would be pulsed on during one camera frame period and off during the next frame period. Thus, the scene would be illuminated by both the LED (signal) light and the ambient (background) light during one frame period, and would be illuminated with only ambient (background) light during the next frame period. The camera output would be digitized and sent to a computer, wherein the pixel values of the background-only frame would be subtracted from the pixel values of the signal-plus-background frame to obtain signal-only pixel values (see figure). To prevent artifacts of motion from entering the images, it would be necessary to acquire image data at a rate greater than the standard video rate of 30 frames per second. For this purpose, the ALCC would exploit a novel control technique developed at NASA s Jet Propulsion Laboratory for advanced charge-coupled-device (CCD) cameras. This technique provides for readout from a subwindow [region of interest (ROI)] within the image frame. Because the desired reflections from the eye would typically occupy a small fraction of the area within the image frame, the ROI capability would make it possible to acquire and subtract pixel values at rates of several hundred frames per second considerably greater than the standard video rate and sufficient to both (1) suppress motion artifacts and (2) track the motion of the eye between consecutive subtractive frame pairs.
Morookian, John Michael↗
Hemodynamic and symptomatic effects of acute interventions on tilt in patients with postural tachycardia syndrome
A variety of approaches have been used to alleviate symptoms in postural tachycardia syndrome (POTS). Drugs reported to be of benefit include midodrine, propranolol, clonidine, and phenobarbital. Other measures used include volume expansion and physical countermaneuvers. These treatments may influence pathophysiologic mechanisms of POTS such as alpha-receptor dysfunction, beta-receptor supersensitivity, venous pooling, and brainstem center dysfunction. The authors prospectively studied hemodynamic indices and symptom scores in patients with POTS who were acutely treated with a variety of interventions. Twenty-one subjects who met the criteria for POTS were studied (20 women, 1 man; mean age, 28.7 +/- 6.8 y; age range, 14-39 y). Patients were studied with a 5-minute head-up tilt protocol, ECG monitoring, and noninvasive beat-to-beat blood pressure monitoring, all before and after the administration of an intervention (intravenous saline, midodrine, propranolol, clonidine, or phenobarbital). The hemodynamic indices studied were heart rate (ECG) and systolic, mean, and diastolic blood pressure. Patients used a balanced verbal scale to record any change in their symptoms between the tilts. Symptom scores improved significantly after the patients received midodrine and saline. Midodrine and propranolol reduced the resting heart rate response to tilt (p <0.005) and the immediate and 5-minute heart rate responses to tilt (p <0.002). Clonidine accentuated the immediate decrease in blood pressure on tilt up (p <0.05). It was concluded that midodrine and intravenous saline are effective in decreasing symptoms on tilt in patients with POTS when given acutely. Effects of treatments on heart rate and blood pressure responses generally reflected the known pharmacologic mechanisms of the agents.
Non-NASA Center↗
Use of Otoacousticemission Phase Change to Evaluate Countermeasures for Spaceflight-Associated Neuro-Ocular Syndrome
Spaceflight-associated neuro-ocular syndrome (SANS) is a human spaceflight risk recognized by NASA. Elevated intracranial pressure (ICP) has been implicated as a root cause of many SANS signs and symptoms, yet there is no reliable noninvasive means of monitoring ICP. We have developed a noninvasive method of monitoring ICP change that exploits ear canal acoustic and otoacoustic emission (OAE) measurements. Changed ICP alters pressure in the inner ear, leading to changes in the tension and position of middle ear (ME) components; tension of these components determines the phase of the stimulus in the ear canal and the OAE response sound transmission back through the ME. The OAE method has been validated in several studies, including our own experiments as part of the NASA Fluid Shifts study. Systematic OAE phase changes demonstrating increased ME tension (an ICP indicator) are observed as posture is changed from seated to supine to head-down tilt (HDT). This effect can be substantially mitigated by lower body negative pressure (LBNP). The OAE technique has also been used on International Space Station (ISS) crewmembers, providing evidence that ICP in microgravity is similar to that seen on the ground in the supine position. The OAE method is also a rapid and noninvasive means of assessing the effectiveness of SANS countermeasures. Here we report results from two studies which used OAEs. In the most recent study (Venous Congestion Countermeasures - VCCM), three promising countermeasures [LBNP, an impedance threshold device (ITD), and veno-occlusive thigh cuffs (VTC)] were applied individually and in combination. In our previous ITD-only study, ITD was investigated for its ability to reduce ICP and cephalic venous congestion in supine and various HDT postures. Internal jugular vein (IJV) ultrasound showed a clear decongestive effect at all postures, however OAE data showed that ITD only caused a phase decrease (tension decrease) in HDT postures. In supine, ITD appeared to INCREASE tension. This paradox leads us to hypothesize that the OAE method is not accurately representing ICP changes with countermeasures (CM), which can alter ME tension through other means, such as ME pressure (MEP) changes. More generally, the exact mechanism for observed OAE response and stimulus phase shifts are not clearly understood, specifically with regard to the effects of MEP. The VCCM study examined the effects of externally-applied MEP on OAE recordings to document the relationship between these parameters. Analysis of these data provide new insights to these OAE mechanisms, in addition to results on CM effectiveness.
Kemp, D.↗