Imaging Of Oxygen Saturation Research Articles

Enhancing eMSOT with nonlinear mixed model approaches for precise blood oxygenation imaging in tissues

Multispectral optoacoustic tomography (MSOT) utilizes multiple wavelengths to illuminate tissue, producing a series of optoacoustic images rich in spectral information. This approach offers a more comprehensive spectral profile compared to conventional optoacoustic techniques. Contrasted with single-wavelength optoacoustic images, the spectral information can be amalgamated with endogenous chromophores or exogenous dyes within biological organisms, thereby unveiling physiological, cellular, and subcellular functions. The development of eigenspectral optoacoustic tomography (eMSOT), grounded in the linear mixture model (LMM), along with its various derivative methods, facilitates label-free imaging of tissue oxygen saturation in deep-seated structures. However, the effectiveness of the LMM may diminish in the presence of multiple scattering effects or inter-substance interactions, thereby impairing the performance of the eMSOT method in heterogeneous tissues. To address this issue, we propose incorporating a nonlinear model to enhance the eMSOT technique, which we refer to as NL-eMSOT (non-linear eMSOT). This model employs the Hadamard product as a nonlinear component of the LMM, effectively characterizing the interactions between photons and both oxygenated and deoxygenated hemoglobin within the near-infrared spectral window. This innovation resolves the nonlinear unmixing problem inherent in optoacoustic imaging. Our approach, validated through numerical simulations, phantom experiments, and in vivo studies, improves the accuracy of quantitative oxygen saturation estimation in heterogeneous tissues by accounting for inter-substance interactions. Consequently, it necessitates the consideration of more complex mixing models to adequately address nonlinear interactions.

Imaging technology to assess tissue oxygen saturation of the gastric conduit in thoracic esophagectomy

ObjectiveThe objective of the study was to evaluate a novel imaging technology for assessing tissue oxygen saturation (StO2) in the gastric conduit during thoracic esophagectomy, comparing it to the traditional method of indocyanine green (ICG) fluorescence angiography, which has several limitations. MethodsThis prospective study included 60 patients with thoracic esophageal cancer undergoing thoracic esophagectomy, approved by the National Cancer Center Hospital’s institutional review board. A new videoscope system with oxygen saturation imaging (OXEI) mode was tested. Intraoperative StO2 and ICG measurements were taken at the tip of the gastric conduit, the demarcation line of visible perfusion, and the end of the right gastroepiploic artery. The study aimed to compare the correlation between StO2 and ICG values and evaluate the incidence of postoperative anastomotic leakage. ResultsOut of 60 patients, 57 were analyzed after excluding three for oncological reasons. Anastomotic leakage occurred in three patients. StO2 values decreased towards the tip of the conduit and were significantly lower at the tip compared to the demarcation line (P = 0.001). The mean StO2 at the anastomosis site was significantly lower in patients with leakage (P = 0.04). There was a negative correlation between StO2 and ICG values at the end of the right gastroepiploic artery (r = -0.361; P = 0.03). Two of the three patients with leakage had normal ICG values but low StO2 values and marked congestion. ConclusionStO2 imaging proved useful in determining the anastomotic site and addressed the limitations of the ICG method, which is contraindicated in patients with iodine allergy and subject to measurement biases. The OXEI method, being non-invasive and capable of real-time assessment, shows promise in predicting anastomotic leakage. Further prospective studies in larger, multi-center trials are planned to confirm these findings and evaluate the efficacy of OXEI compared to ICG.

Artificial neural networks trained on simulated multispectral data for real-time imaging of skin microcirculatory blood oxygen saturation.

Imaging blood oxygen saturation ( ) in the skin can be of clinical value when studying ischemic tissue. Emerging multispectral snapshot cameras enable real-time imaging but are limited by slow analysis when using inverse Monte Carlo (MC), the gold standard for analyzing multispectral data. Using artificial neural networks (ANNs) facilitates a significantly faster analysis but requires a large amount of high-quality training data from a wide range of tissue types for a precise estimation of . We aim to develop a framework for training ANNs that estimates in real time from multispectral data with a precision comparable to inverse MC. ANNs are trained using synthetic data from a model that includes MC simulations of light propagation in tissue and hardware characteristics. The model includes physiologically relevant variations in optical properties, unique sensor characteristics, variations in illumination spectrum, and detector noise. This approach enables a rapid way of generating high-quality training data that covers different tissue types and skin pigmentation. The ANN implementation analyzes an image in 0.11s, which is at least 10,000 times faster than inverse MC. The hardware modeling is significantly improved by an in-house calibration of the sensor spectral response. An in-vivo example shows that inverse MC and ANN give almost identical values with a mean absolute deviation of 1.3%-units. ANN can replace inverse MC and enable real-time imaging of microcirculatory in the skin if detailed and precise modeling of both tissue and hardware is used when generating training data.

A novel imaging technology to assess tissue oxygen saturation and its correlation with indocyanine green in the gastric conduit during thoracic esophagectomy

BackgroundAnastomotic leakage in esophagectomy is a serious complication, and assessing blood perfusion in the conduit can help minimize this risk. Indocyanine green is the most widely used method to assess tissue blood flow; however, this technique has disadvantages. Evaluating tissue oxygen saturation in the gastric conduit during thoracic esophagectomy compared with indocyanine green blood perfusion assessment addresses these disadvantages and can be performed easily and repeatedly. MethodsThis was a prospective study of patients with esophageal cancer who underwent thoracic esophagectomy. Intraoperative tissue oxygen saturation and indocyanine green measurements were obtained to determine the anastomotic site and to compare the correlation between the 2 methods. Tissue oxygen saturation and indocyanine green values were obtained at the tip of the gastric conduit, the demarcation line indicating visible perfusion, and the end of the right gastroepiploic artery. ResultsFifty-seven patients were enrolled in this study; 3 developed anastomotic leakage, and all 3 underwent robotic thoracic surgery. The tissue oxygen saturation value decreased gradually toward the tip of the conduit, as did congestion, and was significantly decreased at the tip compared with the value at the demarcation line (P = .001). Mean tissue oxygen saturation differed significantly between the leakage and no-leakage groups at the anastomosis site (P = .04). We found a negative correlation between tissue oxygen saturation and indocyanine green values at the end of the right gastroepiploic artery (r = −0.361; P = .03). ConclusionTissue oxygen saturation imaging was useful in determining the anastomotic site and addressed the disadvantages associated with indocyanine green.

Quantitative Analysis of the Concentration of Trifluridine in Tumor Hypoxic Regions Using a Novel Platform Combining Functional Endoscopy and Mass Spectrometry.

Hypoxic regions in solid tumors are highly resistant to drugs and thus represents an obstacle in drug discovery. Currently, however, there are technical barriers in sampling human hypoxic tumors and examining drug delivery with high sensitivity and accuracy. Herein, we present a new platform combining functional endoscopy and highly sensitive liquid chromatography-mass spectrometry (LC-MS) to assess drug delivery to hypoxic regions. Because oxygen saturation endoscopic imaging (OXEI), a functional endoscopy, can evaluate lesions and hypoxia in real-time by simultaneously acquiring a pseudocolor map of oxygen saturation and conventional endoscopic images, this platform can be used to evaluate drug delivery with human samples from hypoxic regions. As the first clinical application of this platform, the relationship between hypoxic regions and the concentration of trifluridine (FTD) incorporated into DNA was evaluated in patients with advanced gastric cancer treated with FTD/tipiracil (FTD/TPI; n = 13) by obtaining and analysis of tissue samples by OXEI and LC-MS and vascular maturity index by CD31/α-SMA staining ex vivo. The results showed that the concentration of FTD was significantly higher in the normoxic region than in the hypoxic region (P < 0.05) and there were significantly more immature vessels in hypoxic regions than in normoxic regions (P < 0.05). These results indicate that the platform was sufficiently sensitive to evaluate differences in drug anabolism in different oxygenic regions of human tumor tissue. This new platform allows quantitative drug analysis in hypoxic regions and is expected to initiate a new era of drug discovery and development.

Oxygen Saturation or Tissue Oxygen Determinations on Skin Whose Viability is at Risk.

The triad of ischaemia, neuropathy, and infection are among the principal causes of lower extremity wounds that are commonly prevalent in patients with diabetic foot (DF) a condition in which peripheral arterial disease commonly co-exists. The prevalence of this condition is increasing globally and with it, the mounting costs of its management. One aspect of management is saving limbs and or digits, a crucial part of this process is assessing tissue viability of skin which is a focus of this review: there are other aspects which are well described in the literature. Amputations are offered to limit the damage resulting from acute/chronic ischaemia. Holstein measured skin perfusion pressure using a radioisotope clearance technique to describe critically ischaemic skin; he found 30 mm Hg as the threshold above which healing may reliably be expected. Recent advances in vascular surgery and related technology have informed evidence-based advice to revascularize and save limbs; in practice, this may leave a wound in the distal skin unhealed; managing these raises questions of tissue viability. Much effort has been made to manage, prevent and to better understand these lower extremity wounds using measurements of tissue oxygen, oxygen saturation and skin imaging. The measurement techniques and their relevant merits are examined in this article. Advances in wound management systems and protocols can also facilitate the repair processes, and those which can have a particular impact on restoring or maintaining tissue perfusion are also discussed in the article.

Association of vitamin D with the severity of disease and mortality in COVID-19: Prospective study in central India.

Many factors have been proposed to be associated with the severity of disease and mortality in COVID-19. Vitamin D had recently been reviewed as one of these factors. To evaluate the association between Vitamin D and the disease severity and mortality in COVID-19. After approval from Institutional Ethics Committee, this prospective cohort study was carried out in selected tertiary care teaching medical institutes of Central India. Participants were COVID-19 patients of the age group of 18 years and above admitted during the study period. They were categorized into four groups as asymptomatic (Group A), mild (Group B), moderate (Group C), and severe (Group D) based on clinical symptoms, respiratory rate, oxygen saturation, and chest imaging. Serum level of Vitamin 25(OH) D was measured using chemiluminescent immunoassay. The outcome of the disease was classified as recovery and death during hospitalization. The association of sociodemographic and medical characteristics with treatment outcome was studied using an appropriate statistical test. A full logistic regression model was built for the assessment of the relationship between treatment outcomes with Vitamin D level. Further, one receiver operating characteristic curve was developed to examine the prognostic significance of Vitamin D levels in COVID-19 patients. Out of 748 enrolled patients, 44 (5.88%), had severe disease (Group D). A total of 721 cases (96.39%) recovered and were discharged, whereas 27 (3.61%) died during hospitalization. Mean Vitamin D level was found to be significantly different in discharged patients compared to those who were deceased. Increasing age-adjusted odds ratio (AOR) (95% confidence interval [CI]=1.07 [1.02-1.12]), known hypertension AOR (95%CI) = 3.38 (1.13-10.08), and diabetes mellitus AOR (95%CI) =28.5 (6.04-134.13) were found to be significant predictors of death among COVID-19 patients. Increasing Vitamin D level was found to be protective against COVID-19-related death (AOR (95% CI = 0.87 [0.80-0.94]). Vitamin D was significantly associated with the disease severity and mortality in COVID-19.

Magnetic resonance imaging of hypoxia in acute stroke compared with fluorine-18 fluoromisonidazole-positronemissiontomography:Across-validationstudy?

Acute ischemic stroke results in an ischemic core surrounded by a tissue at risk, named the penumbra, which is potentially salvageable. One way to differentiate the tissues is to measure the hypoxia status. The purpose of the current study is to correlate the abnormal brain tissue volume derived from magnetic resonance-based imaging of brain oxygen saturation (St O2 -MRI) to the fluorine-18 fluoromisonidazole ([18 F]FMISO) positron emission tomography (PET) volume for hypoxia imaging validation, and to analyze the ability of St O2 -MRI to depict the different hypoxic tissue types in the acute phase of stroke. In a pertinent model of stroke in the rat, the volume of tissue with decreased St O2 -MRI signal and that with increased uptake of [18 F]FMISO were equivalent and correlated (r = 0.706; p = 0.015). The values of St O2 in the tissue at risk were significantly greater than those quantified in the core of the lesion, and were less than those for healthy tissue (52.3% ± 2.0%; 43.3% ± 1.9%, and 67.9 ± 1.4%, respectively). A threshold value for St O2 of ≈60% as the cut-off for the identification of the tissue at risk was calculated. Tissue volumes with reduced St O2 -MRI correlated with the final lesion (r = 0.964, p < 0.0001). The findings show that the St O2 -MRI approach is sensitive for the detection of hypoxia and for the prediction of the final lesion after stroke. Once validated in acute clinical settings, this approach might be used to enhance the stratification of patients for potential therapeutic interventions.

Pathophysiological Changes in Rhesus Monkeys with Paraquat-Induced Pulmonary Fibrosis.

PurposePulmonary fibrosis is a life-threatening lung disorder. A comprehensive understanding of the pathophysiological changes in the development of pulmonary fibrosis will lead to new insights into its treatment.MethodsWe used a paraquat (PQ)-induced rhesus monkey model of pulmonary fibrosis to comprehensively investigate the process of pulmonary fibrosis development. Rhesus monkeys were orally administered PQ at concentrations of 25 mg/kg, 40 mg/kg, and 80 mg/kg. The dose was given once. Behavior and clinical data, such as PQ concentration, arterial oxygen saturation, biochemical evaluation, lung histopathology, and medical imaging, were continuously observed.ResultsParaquat-exposed monkeys developed pulmonary fibrosis following an expected time course, especially at 25 mg/kg. CT images showed ground-glass lesions in the lung after 4 weeks, and pulmonary fibrosis persisted until the end of follow-up. Using pathological examination, the lung sustained collagen deposition and slight inflammatory cell infiltration. All rhesus monkeys had obvious inflammatory infiltration within 1 week according to the immunohistochemical results and the number of leukocytes in the blood. The CT results showed that pulmonary fibrosis had not formed, indicating that drugs with powerful anti-inflammatory ability are potential candidates for early pulmonary fibrosis treatment.ConclusionOur study describes the dynamic process of paraquat-induced pulmonary fibrosis in rhesus monkeys and provided a pathophysiological basis for the treatment of pulmonary fibrosis.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00408-022-00572-9.

Metabolic reprogramming under hypoxic storage preserves faster oxygen unloading from stored red blood cells

AbstractStored red blood cells (RBCs) incur biochemical and morphological changes, collectively termed the storage lesion. Functionally, the storage lesion manifests as slower oxygen unloading from RBCs, which may compromise the efficacy of transfusions where the clinical imperative is to rapidly boost oxygen delivery to tissues. Recent analysis of large real-world data linked longer storage with increased recipient mortality. Biochemical rejuvenation with a formulation of adenosine, inosine, and pyruvate can restore gas-handling properties, but its implementation is impractical for most clinical scenarios. We tested whether storage under hypoxia, previously shown to slow biochemical degradation, also preserves gas-handling properties of RBCs. A microfluidic chamber, designed to rapidly switch between oxygenated and anoxic superfusates, was used for single-cell oxygen saturation imaging on samples stored for up to 49 days. Aliquots were also analyzed flow cytometrically for side-scatter (a proposed proxy of O2 unloading kinetics), metabolomics, lipidomics, and redox proteomics. For benchmarking, units were biochemically rejuvenated at 4 weeks of standard storage. Hypoxic storage hastened O2 unloading in units stored to 35 days, an effect that correlated with side-scatter but was not linked to posttranslational modifications of hemoglobin. Although hypoxic storage and rejuvenation produced distinct biochemical changes, a subset of metabolites including pyruvate, sedoheptulose 1-phosphate, and 2/3 phospho-d-glycerate, was a common signature that correlated with changes in O2 unloading. Correlations between gas handling and lipidomic changes were modest. Thus, hypoxic storage of RBCs preserves key metabolic pathways and O2 exchange properties, thereby improving the functional quality of blood products and potentially influencing transfusion outcomes.

Two-step proximal gradient descent algorithm for photoacoustic signal unmixing

Photoacoustic microscopy uses multiple wavelengths to measure concentrations of different absorbers. The speed of sound limits the shortest wavelength switching time to sub-microseconds, which is a bottleneck for high-speed broad-spectrum imaging. Via computational separation of overlapped signals, we can break the sound-speed limit on the wavelength switching time. This paper presents a new signal unmixing algorithm named two-step proximal gradient descent. It is advantageous in separating multiple wavelengths with long overlapping and high noise. In the simulation, we can unmix up to nine overlapped signals and successfully separate three overlapped signals with 12-ns delay and 15.9-dB signal-to-noise ratio. We apply this technique to separate three-wavelength photoacoustic images in microvessels. In vivo results show that the algorithm can successfully unmix overlapped multi-wavelength photoacoustic signals, and the unmixed data can improve accuracy in oxygen saturation imaging.

Real-time whole-brain imaging of hemodynamics and oxygenation at micro-vessel resolution with ultrafast wide-field photoacoustic microscopy

High-speed high-resolution imaging of the whole-brain hemodynamics is critically important to facilitating neurovascular research. High imaging speed and image quality are crucial to visualizing real-time hemodynamics in complex brain vascular networks, and tracking fast pathophysiological activities at the microvessel level, which will enable advances in current queries in neurovascular and brain metabolism research, including stroke, dementia, and acute brain injury. Further, real-time imaging of oxygen saturation of hemoglobin (sO2) can capture fast-paced oxygen delivery dynamics, which is needed to solve pertinent questions in these fields and beyond. Here, we present a novel ultrafast functional photoacoustic microscopy (UFF-PAM) to image the whole-brain hemodynamics and oxygenation. UFF-PAM takes advantage of several key engineering innovations, including stimulated Raman scattering (SRS) based dual-wavelength laser excitation, water-immersible 12-facet-polygon scanner, high-sensitivity ultrasound transducer, and deep-learning-based image upsampling. A volumetric imaging rate of 2 Hz has been achieved over a field of view (FOV) of 11 × 7.5 × 1.5 mm3 with a high spatial resolution of ~10 μm. Using the UFF-PAM system, we have demonstrated proof-of-concept studies on the mouse brains in response to systemic hypoxia, sodium nitroprusside, and stroke. We observed the mouse brain’s fast morphological and functional changes over the entire cortex, including vasoconstriction, vasodilation, and deoxygenation. More interestingly, for the first time, with the whole-brain FOV and micro-vessel resolution, we captured the vasoconstriction and hypoxia simultaneously in the spreading depolarization (SD) wave. We expect the new imaging technology will provide a great potential for fundamental brain research under various pathological and physiological conditions.

MnCO3@BSA-ICG nanoparticles as a magnetic resonance/photoacoustic dual-modal contrast agent for functional imaging of acute ischemic stroke

Timely and accurate diagnosis of acute ischemic stroke (AIS) and simultaneous functional imaging of cerebral oxygen saturation (sO2) are essential to improve the survival rate of stroke patients but remains challenging. Herein, we developed a pH-responsive manganese (Mn)-based nanoplatform as a magnetic resonance/photoacoustic (MR/PA) dual-modal contrast agent for AIS diagnosis. The Mn-based nanoplatform was prepared via a simple and green biomimetic method using bovine serum albumin (BSA) as a scaffold for fabrication of MnCO3 NPs as the T1 MR contrast agent and accommodation of indocyanine green (ICG) as the PA probe. The obtained MnCO3@BSA-ICG NPs were biocompatible and exhibited a pH-responsive longitudinal relaxation rate and a concentration-dependent PA signal. In vivo MR/PA dual-modal imaging demonstrated that MnCO3@BSA-ICG NPs quickly and efficiently led to the MR/PA contrast enhancements in the infarcted area while not in the normal region, allowing a timely and accurate diagnosis of AIS. Moreover, PA imaging could directly monitor the sO2 level, enabling a functional imaging of AIS. Therefore, MnCO3@BSA-ICG NPs could be applied as a potential MR/PA contrast agent for timely and functional imaging of AIS.

Comprehensive imaging of microcirculatory changes in the foot during endovascular intervention - A technical feasibility study.

Chronic limb-threatening ischemia (CLTI) has a major impact on patients' lives and is associated with a heavy health care burden with high morbidity and mortality. Treatment by endovascular intervention is mostly based on macrocirculatory information from angiography and does not consider the microcirculation. Despite successful endovascular intervention according to angiographic criteria, a proportion of patients fail to heal ischemic lesions. This might be due to impaired microvascular perfusion and variations in the supply to different angiosomes. Non-invasive optical techniques for microcirculatory perfusion and oxygen saturation imaging have the potential to provide the interventionist with additional information in real-time, supporting clinical decisions during the intervention. This study presents a novel multimodal imaging system, based on multi-exposure laser speckle contrast imaging and multi-spectral imaging, for continuous use during endovascular intervention. The results during intervention display spatiotemporal changes in the microcirculation compatible with expected physiological reactions during balloon dilation, with initially induced ischemia followed by a restored perfusion, and local administration of a vasodilator inducing hyperemia. We also present perioperative and postoperative follow-up measurements with a pulsatile microcirculation perfusion. Finally, cases of spatial heterogeneity in the oxygen saturation and perfusion are discussed. In conclusion, this technical feasibility study shows the potential of the methodology to characterize changes in microcirculation before, during, and after endovascular intervention.

Discontinuing vs continuing ACEIs and ARBs in hospitalized patients with COVID-19 according to disease severity: Insights from the BRACE CORONA trial

BackgroundWe explored the effect of discontinuing versus continuing angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) on clinical outcomes in patients with COVID-19 according to baseline disease severity.MethodsWe randomized 659 patients with a confirmed diagnosis of COVID-19 and classified them as having mild or moderate COVID-19 disease severity at hospital presentation using blood oxygen saturation and lung imaging. The primary outcome was the mean ratio of number of days alive and out of the hospital at 30 days according to disease severity.ResultsAt presentation, 376 patients (57.1%) had mild and 283 (42.9%) had moderate COVID-19. In patients with mild disease, there was no significant difference in the number of days alive and out of the hospital between ACEI/ARB discontinuation (mean 23.5 [SD 6.3] days) and continuation (mean 23.8 [SD 6.5] days), with a mean ratio of 0.98 (95% CI 0.92-1.04). However, in patients with moderate disease, there were fewer days alive and out of the hospital with ACEI/ARB discontinuation (mean 19.6 [SD 9.5] days) than continuation (mean 21.6 [SD 7.6] days), with a mean ratio of 0.90 (95% CI 0.81-1.00; P-interaction = .01). The impact of discontinuing versus continuing ACEIs/ARBs on days alive and out of hospital through 30 days differed according to baseline COVID-19 disease severity.ConclusionsUnlike patients with mild disease, patients with moderate disease who continued ACEIs/ARBs had more days alive and out of hospital through 30 days than those who discontinued ACEIs/ARBs. This suggests that ACEIs/ARBs should be continued for patients with moderate COVID-19 disease severity.Clinical Trial RegistrationClinicalTrials.gov (NCT04364893).

A novel imaging technology to assess oxygen saturation of the gastric conduit in thoracic esophagectomy.

Real-time evaluation of blood perfusion is important when selecting the site of anastomosis during thoracic esophagectomy. This study investigated a novel imaging technology that assesses tissue oxygen saturation (StO2) in the gastric conduit and examined its efficacy. Fifty-one patients undergoing thoracic esophagectomy for esophageal cancer who underwent intraoperative StO2 endoscopic imaging to assess the gastric conduit for the optimal site of anastomosis were examined. Efficacy of oxygen saturation imaging and patient outcomes were analyzed. All 51 patients underwent esophagectomy without intraoperative problems. Mean StO2 in the gastric tube was highest at the pre-pylorus area and then gradually decreased proceeding toward the tip. StO2 was well preserved in areas supplied by the right gastroepiploic artery but low in other areas. Anastomotic sites were selected based on StO2 imaging and tension considerations; most were located within 3cm of the end of the right gastroepiploic artery. Three patients developed postoperative anastomotic leakage (5.8%). Mean StO2 at the point of anastomosis was significantly lower in the patients who experienced leakage than in those who did not (P = 0.04). Intraoperative endoscopic StO2 imaging is useful in esophageal cancer patients undergoing thoracic esophagectomy to determine the optimal site for anastomosis to minimize the risk of anastomotic leakage.

Neutrophil-to-Lymphocyte Ratio as a Predictor of Disease Severity and Mortality in Coronavirus Disease 2019: Prospective Study From Central India.

Background: Clinical presentation of coronavirus disease 2019 (COVID-19) varies from an asymptomatic state to severe disease characterized by acute respiratory distress syndrome, respiratory failure, thrombosis, and multi-organ dysfunction syndrome. The neutrophil-to-lymphocyte ratio (NLR) has been reviewed as one of the laboratory factors that have been proposed to predict the severity of disease and mortality in COVID-19 pandemic.Aim and objectives: To evaluate the association between NLR and the disease severity and mortality in COVID-19.Materials and methods: After approval from Institutional Ethics Committee, this prospective cohort study was carried out in a tertiary-care teaching medical institute of Central India. COVID-19 patients of the age group 18 years and above admitted during the study period were included. Cases were categorized into four groups as asymptomatic (Group A), mild (Group B), moderate (Group C), and severe (Group D) based on clinical symptoms, respiratory rate, oxygen saturation, and chest imaging. NLR was calculated by doing a complete blood count at the time of hospitalization by the Mindray BC-6000 auto hematology analyzer. The outcome of the disease was classified as recovery and death during hospitalization. Receiver operating characteristic (ROC) curve analysis was used to assess the ability of NLR at admission to predict severe COVID-19 or mortality. Ordinal regression analysis was used to assess the impact of NLR on disease severity and mortality.Results: Mean NLR was significantly higher in the severe COVID-19 group as compared to the mild/moderate group and in deceased as compared to discharged cases. ROC curve analysis revealed NLR to be an excellent predictor of disease severity as well as a prognostic parameter for risk of death. NLR was found to be a significant independent positive predictor for contracting the severe disease (Odd’s ratio 1.396, 95% CI=1.112-1.753, p=0.004) and mortality (Odd’s ratio 1.276, 95% CI=1.085-1.499, p=0.003).Conclusion: High NLR was significantly associated with the disease severity and mortality in COVID-19.

Multispectral snapshot imaging of skin microcirculatory hemoglobin oxygen saturation using artificial neural networks trained on in vivo data.

.SignificanceDeveloping algorithms for estimating blood oxygenation from snapshot multispectral imaging (MSI) data is challenging due to the complexity of sensor characteristics and photon transport modeling in tissue. We circumvent this using a method where artificial neural networks (ANNs) are trained on in vivo MSI data with target values from a point-measuring reference method.AimTo develop and evaluate a methodology where a snapshot filter mosaic camera is utilized for imaging skin hemoglobin oxygen saturation (), using ANNs.ApproachMSI data were acquired during occlusion provocations. ANNs were trained to estimate with MSI data as input, targeting data from a validated probe-based reference system. Performance of ANNs with different properties and training data sets was compared.ResultsThe method enables spatially resolved estimation of skin tissue . Results are comparable to those acquired using a Monte-Carlo-based approach when relevant training data are used.ConclusionsTraining an ANN on in vivo MSI data covering a wide range of target values acquired during an occlusion protocol enable real-time estimation of maps. Data from the probe-based reference system can be used as target despite differences in sampling depth and measurement position.

Optical oxygen saturation imaging in cellular ex vivo lung perfusion to assess lobular pulmonary function.

Ex vivo lung perfusion (EVLP) is an emerging tool to evaluate marginal lungs in lung transplantation. However, there is no objective metric to monitor lobular regional oxygenation during EVLP. In this study, we developed oxygen saturation (SaO2) imaging to quantitatively assess the regional gas exchange potential of the lower lobes. Ten porcine lungs were randomly divided into control and donation after circulatory death (DCD) groups (n = 5, each). Lungs were perfused in cellular EVLP for 2 h, and multispectral images were continuously collected from the dorsal sides of the lower lobes. We examined whether lower lobe SaO2 correlated with PaO2/FiO2 (P/F) ratios in lower pulmonary veins (PV). The wet/dry ratio in lower lobes was measured and Monte Carlo simulations were performed to investigate the method's feasibility. There was a significant correlation between lower lobe SaO2 and the P/F ratio in lower PV (r = 0.855, P < 0.001). The DCD group was associated with lower SaO2 and higher wet/dry ratio than the control group (P < 0.001). The error of estimated SaO2 was limited according to Monte Carlo simulations. The developed technology provides a noninvasive and regional evaluative tool of quantitative lobular function in EVLP.

Dual-foci fast-scanning photoacoustic microscopy with 3.2-MHz A-line rate

We report fiber-based dual-foci fast-scanning OR-PAM that can double the scanning rate without compromising the imaging resolution, the field of view, and the detection sensitivity. To achieve fast scanning speed, the OR-PAM system uses a single-axis water-immersible resonant scanning mirror that can confocally scan the optical and acoustic beams at 1018 Hz with a 3-mm range. Pulse energies of 45∼100-nJ are sufficient for acquiring vascular and oxygen-saturation images. The dual-foci method can double the B-scan rate to 2036 Hz. Using two lasers and stimulated Raman scattering, we achieve dual-wavelength excitation on both foci, and the total A-line rate is 3.2-MHz. In in vivo experiments, we inject epinephrine and monitor the hemodynamic and oxygen saturation response in the peripheral vessels at 1.7 Hz over 2.5 × 6.7 mm2. Dual-foci OR-PAM offers a new imaging tool for the study of fast physiological and pathological changes.