Preterm birth (PTB) is a critical global health concern, contributing to over 35% of 3.1 million neonatal deaths annually. PTB is linked to various developmental complications, including neurological disorders, cognitive impairment, and gestational difficulties. Our primary objective in this study is to investigate pregnant cervix remodeling using the Self Validating Mueller Matrix Micro-mesoscope (SAMMM). Departing from conventional methods, our research emphasizes visualizing the entire cervix through large field of view mesoscopic imaging and high-resolution microscopic imaging. By employing SAMMM, we aim to visualize the extracellular matrix (ECM) structure in spatially defined cervical sections, from the internal os to the distal cervix, at different gestational stages in mice. This research has significant potential to improve PTB risk assessment and maternal-neonatal healthcare outcomes on a global scale, contributing to enhanced understanding and targeted interventions for better maternal and neonatal health.
Cardiovascular disease is one of the leading causes of death in the United States and over 40% of the population lives with cardiovascular conditions including hypertension. We have developed a dynamic pulsatile phantom for PPG signal evaluation towards creating a non-invasive, wearable, point-of-care health device for monitoring cardiovascular health. This phantom has the capabilities to generate and control a pressurized pulsatile waveform ranging from 30mmHg to 200mmHg. The phantom manufacturing process allows control of the optical properties, interfaces and geometrical form factors which are known to change due to both skin tone and obesity to influence the captured PPG signature.
SignificancePreterm birth is defined as a birth before 37 weeks of gestation and is one of the leading contributors to infant mortality rates globally. Premature birth can lead to life-long developmental impairment for the child. Unfortunately, there is a significant lack of tools to diagnose preterm birth risk, which limits patient care and the development of new therapies.AimTo develop a speculum-free, portable preterm imaging system (PPRIM) for cervical imaging; testing of the PPRIM system to resolve polarization properties of birefringent samples; and testing of the PPRIM under an IRB on healthy, non-pregnant volunteers for visualization and polarization analysis of cervical images.ApproachThe PPRIM can perform 4×3 Mueller-matrix imaging to characterize the remodeling of the uterine cervix during pregnancy. The PPRIM is built with a polarized imaging probe and a flexible insertable sheath made with a compatible flexible rubber-like material to maximize comfort and ease of use.ResultsThe PPRIM device is developed to meet specific design specifications as a speculum-free, portable, and comfortable imaging system with polarized imaging capabilities. This system comprises a main imaging component and a flexible silicone inserter. The inserter is designed to maximize comfort and usability for the patient. The PPRIM shows high-resolution imaging capabilities at the 20 mm working distance and 25 mm circular field of view. The PPRIM demonstrates the ability to resolve birefringent sample orientation and full field capture of a healthy, non-pregnant cervix.ConclusionThe development of the PPRIM aims to improve access to the standard of care for women’s reproductive health using polarized Mueller-matrix imaging of the cervix and reduce infant and maternal mortality rates and better quality of life.
Preterm birth accounts for 35% of annual infant deaths and is defined as any birth before 37 weeks of gestation. We have developed the Portable PReterm IMaging system capable of a 4x3 MMI, designed for comfort and ease of use to help fill the need for a diagnostic tool to monitor and detect preterm birth risks. Critical design components have been developed to be comfortable for the user and have a robust core structure. Imaging tests and evaluations are performed on volunteer human subjects with clinician assistance at the Florida International University Health Clinic.
The uterine cervix is composed mainly of fibrous connective tissues where collagen and glycosaminoglycans are the main components. Recent work has shown that elastic fibers also contribute to the cervix's change in mechanical function during pregnancy. While cervical collagen can be visualized with non-linear optical techniques, elastic fibers cannot be uniquely identified without an extensive staining protocol. Here we propose the development of a compound Mueller Matrix microscope to image Mice cervices at different gestation points and visualize collagen and elastic fibers using a convolutional neural network (CNN) and K-nearest neighbor (K-NN) classifiers. The study demonstrates a new methodology for classifying collagen and elastic fibers in the uterine cervix that can be applied to any Mueller Matrix polarimeter once initial calibration is conducted.
Optical devices for monitoring individuals’ physiology are becoming omnipresent with the advent of wearable and point-of-care (POC) devices capable of photoplethysmography and pulse oximetry. These devices can also provide unique opportunities for managing obesity. We have conducted a pilot human study to characterize the obese optical properties and their connection to body mass index (BMI – a metric of obesity). We have shown computationally and experimentally that obesity is an important biological variable that cannot be ignored when developing optics-based instrumentation. We will report on our recent findings and propose strategies to improve wearable functionality.
Significance: Obesity is a worldwide epidemic contributing directly to several cardiovascular risk factors including hypertension and type 2 diabetes. Wearable devices are becoming better at quantifying biomarkers relevant for the management of health and fitness. Unfortunately, both anecdotal evidence and recent studies indicate that some wearables have higher levels of error when utilized by populations with darker skin tones and high body mass index (BMI). There is an urgent need for a better evaluation of the limits of wearable health technologies when used by obese individuals.
Aims: (1) To review the current know-how on changes due to obesity in the skin epidermis, dermis, and subcutis that could affect the skin optical properties; (2) for the green wavelength range, to evaluate the difference in absorption and scattering coefficients from the abdominal skin between individuals with and without elevated BMI. The changes include alterations in layer thickness and cell size, as well as significant differences in chromophores and scatterer content, e.g., water, hemoglobin, collagen, and lipids.
Approach: We have summarized literature pertaining to changes in skin and its components in obesity and report the results of our search using articles published between years 1971 and 2020. A linear model was used to demonstrate the absorption and reduced scattering coefficient of the abdominal skin of individuals with and without elevated BMI in the green wavelength range (530 to 550 nm) that is typically found in most wearables.
Results: The general trends indicate a decrease in absorption for both dermis and subcutis and an increase in reduced scattering for both epidermis and dermis. At 544-nm wavelength, a typical wavelength used for photoplethysmography (PPG), the absorption coefficient’s relative percentage difference between high and low BMI skin, was 49% in the subcutis, 19% in the dermis, and negligible in the epidermis, whereas the reduced scattering coefficient relative difference was 21%, 29%, and 165% respectively.
Conclusions: These findings suggest that there could be significant errors in the output of optical devices used for monitoring health and fitness if changes due to obesity are not accounted for in their design.
Preterm birth (PTB) is defined as any birth prior to 37 weeks of gestation. Preterm birth contributes to 35% of 3.1 million neonatal deaths annually. There is a critical absence of clinical tools for diagnosis of preterm birth risk. We have proposed the use of Mueller Matrix Imaging (MMI) as a sensitive tool to monitor the atypical remodeling of collagen occurring in PTB. Here we expand our previous work to demonstrate that a Portable PReterm IMaging System capable of 3x4 MMI can be used at the point of care. It consists of a sheath insertable in the vaginal canal combined with a polarized imaging system. The main PPRIM body consists of a camera with integrated polarizers combined with a custom-made LED ring illuminator. The optical layout consists of a reverse telephoto lens suitable for imaging at long front working distance. Angle of incidence of the optical elements are minimized to reduce the sensitivity to misalignment and polarization aberrations. The system has a field of view of approximately 25 x 25 mm2 at 20 mm working distance. PPRIM is controlled by a laptop computer and custom software. To demonstrate the feasibility of the device, imaging tests were performed on a Gynecologic Skills Trainer as well as healthy volunteers.
Obesity is a widespread chronic illness which affects over 40% of the US adult population and its world-wide prevalence has increased over the years impacting both low and high-income countries. Obesity has been linked to higher risk of non-communicable diseases such as cardiovascular disease, type-2 diabetes, dyslipidemia, hypertension, among others. Currently the mostly prescribed regimes to combat chronic illness associated with obesity are efforts to change diet, behavior, and physical activity. Wearable devices have the potential of helping users reduce their obesity levels as these devices can easily acquire and communicate biometric data with users and clinicians. However, these technologies depend on optical sensors that are sensitive to molecular skin composition. We hypothesize that individuals with high BMI levels will present changes in skin optical properties when compared to their non-obese counterparts. Our objective is to capture skin optical properties at the wrist among a diverse cohort using a commercial optical system for research use. To meet an appropriate power, the human study, composed of males and females, is conducted with 100 adult participants. Statistical methods, including linear regression and t-tests, are used to determine interactions between measured data and participant demographics. We believe these results can improve design of optical wearables for the obese.
KEYWORDS: Arteries, Photoplethysmography, Blood pressure, Tissue optics, Signal attenuation, Monte Carlo methods, Instrument modeling, Geometrical optics, Finite element methods, Blood
Obesity is a significant risk factor for development and management of cardiovascular disease, one of the leading causes of death in the United States. Blood pressure (BP) is a key factor for monitoring cardiac health. In support of design and development of wearable health devices, we have developed a model to generate synthetic photoplethysmographic waveforms captured by a commercial device for the radial artery at the volar surface of the wrist. We focus on impacts to the PPG signal as a result of various changes attributed to obesity, epidermal melanin, and vascular layers.
Wearable devices, with Photoplethysmography (PPG)-based sensors, are helping patients to monitor chronic health conditions outside the clinic. The prime source of PPG signals is the blood volume change in the dermal vasculature. Here, we present a novel approach of using a skin model, containing double vascular layer within the dermis to investigate the pulsatile contribution from the region. Finite Element Method (FEM) is used to design vessels and PPG signals from the wrist are extracted by studying light transport through Monte Carlo simulations. By assessing PPG sensors in common wearables, the influence of obesity on the PPG signals are also investigated.
Obesity leads to a higher risk of diabetes and cardiovascular diseases. Wearable devices can be used to manage and promote the healthy lifestyle among the obese by measuring heart rate, heart rate variability, perfusion, and pressure pulse-wave velocities. While operational challenges are common in wearable devices using electrical or thermal sensors, those with optical sensors are more robust. Current optical sensors rely on fluctuations in light intensity due to spatio-temporal variations in tissue absorption. The thick layer of adipose tissue in high body mass index (BMI) individuals strongly scatters light, reducing the optical contrast and signal to noise ratio. Moreover, higher BMI alters chemical concentrations— like water, oxygenation, and blood volume in the dermal layer— and thus the optical properties (OP). Although OP of the skin exists in literature, no study has strictly recorded the effect and magnitude of a higher BMI on them. In this study, we combine the spatial frequency domain spectroscopy (SFDS) with a multi-sensor blood flow imaging device (PulseCam) to characterize the OPs and monitor the vascularization in the obese. The effects of skin morphology and physiology on the performance of optical sensor are preliminarily investigated.
Systolic and diastolic blood pressure values can be used as an indicator of an individual’s risk for cardiovascular disease. The common practice of blood pressure (BP) measurement using a cuff-based system provides a snapshot of blood pressure at a single instance in time and can be inconvenient and intrusive. The development of optical methods to determine blood pressure could provide continuous monitoring of blood pressure through techniques such as pulse transit time (PTT) or pulse arrival time (PAT) when used with echocardiogram. Cuff based BP devices are known to have variation and inaccuracies when applied to larger arm sizes as seen in individuals with obesity but little is known of the influence of obesity in the PPG/PTT and PAT signals. We propose that accurate waveform replication is required for the derivation of blood pressure applied to individuals with obesity. Here we use the Monte Carlo framework to develop the PPG waveform as a means to derive blood pressure through cuff less techniques. The development of a simulated waveform incorporates realistic changes in the artery related to its biomechanical properties as a pressure wave is propagated through the vessel. It is shown that a change in vessel pressure and geometry directly affects the captured optical signal. The system can account for variations in body-mass index to compensate for geometrical changes in adipose tissue layer and changes in optical properties.
Blood pressure is a primary candidate to be remotely characterized by continuous monitoring devices, as high blood pressure is frequently a symptom of chronic conditions such as diabetes, obesity, and cardiovascular disease while also leading to morbidity itself. Much work has been done to characterize an electrocardiogram (EKG)-photoplethysmogram (PPG) continuous monitor, however a dual PPG continuous monitor may yield more accurate results due to the lack of the inherent pre-ejection period. To predict the anticipated signal of a remote dual-photoplethysmogram (PPG) blood pressure monitor, we utilized parallelized multi-layer Monte Carlo modelling to estimate light transport through the index finger at the proximal phalange. Monte Carlo models of the digital artery and surrounding tissue were created that represent various skin tones as well as the presence of arterioles. Additionally, the signal contribution by arteriole and artery was also determined. By varying incident wavelength, source-detector separation, skin tone, and arterial diameter as a function of pulse propagation; the feasibility of a proximal phalange PPG can be estimated and further optimized to aid development of a dual-PPG blood pressure monitor. The modelling results indicate that at a separation of 3.0mm, 700nm wavelength provides signal resolution that is indicative of contribution from the artery and not the arterioles, which could be beneficial for estimating pulse transit time toward calculating blood pressure. Further work should be completed to optimize sourcedetector separation for arterial contribution to signal and explore various locations on the body, as much optical property variation exists within literature.
Obesity is a pandemic affecting more than 93 million adults in the U.S. Obese are defined as individuals with a Body Mass Index (BMI) of 30 or more. Several studies are demonstrating that this weight-to-height ratio does not fully characterize the patient’s pathophysiology. Monitoring muscle metabolism, the synthesis and breakdown of muscle protein, may be a more useful metric in the characterization of pathologies associated to weight gain. Long term imbalances of energy intake to energy expenditures lead to obesity. Total expenditure is the summation of energies related to the thermic effect of food, activity, and resting expenditure. While at rest, muscle metabolism is the primary component of resting energy expenditure.Daily energy release in muscle mass could significantly lead a net-loss of fat in the long-run, and thus potentially contribute to the prevention of obesity. Near Infrared Spectroscopy (NIRS) measurement of muscle oxygenation can be used to study muscle metabolism. NIRS has the advantage of being a non-invasive, reproducible, and inexpensive methodology. Unfortunately, commercial NIRS system fail to produce accurate results in the obese population due to excess adipose thicknesses (AT) that alter the optical signal. We have used Monte Carlo models of light transfer to probe the optimal source-detector separation necessary to use NIRS in the obese. We have also developed a low-cost wearable muscle oximeter targeted to individuals with high BMI. We will demonstrate our system validation in optical phantoms and volunteers.
Patients with spinal cord injuries (SCI) are often subject to continues stationary pressure on prominent bony areas which, over and extended period of time, become high risk regions for pressure ulcers. Pressure ulcers are as prevalent as 30% in those with SCI and are one of the leading causes of re-hospitalization. In order to develop a better understanding of the methods of treating and preventing these pressure ulcers, we have developed a voxilization based model of the ischial tuberosity based on a Monte Carlo framework. The 3D model of the underside of the pelvis, the ischial tuberosity, allows for variation of the layers of the skin, fat, and muscle created in Solidworks. From the 3D model, the simulation was done with Monte Carlo eXtreme, a GPU-based Monte Carlo model. Tissue layer changes due to movement of the muscle and compression when sitting which results in a significant reduction of the muscle thickness have been accounted for in our model. Skin and muscle profusion of SCI patients is not well known and limited experimental work has been conducted in this environment. This model can aid in the study of methods of improving and maintaining skin health and help with rehabilitation and prevention of pressure ulcers.
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