Measurement Of Blood Oxygenation Research Articles

Estimating sparse functional brain networks with spatial constraints for MCI identification.

Functional brain network (FBN), estimated with functional magnetic resonance imaging (fMRI), has become a potentially useful way of diagnosing neurological disorders in their early stages by comparing the connectivity patterns between different brain regions across subjects. However, this depends, to a great extent, on the quality of the estimated FBNs, indicating that FBN estimation is a key step for the subsequent task of disorder identification. In the past decades, researchers have developed many methods to estimate FBNs, including Pearson’s correlation and (regularized) partial correlation, etc. Despite their widespread applications in current studies, most of the existing methods estimate FBNs only based on the dependency between the measured blood oxygen level dependent (BOLD) signals, which ignores spatial relationship of signals associated with different brain regions. Due to the space and material parsimony principle of our brain, we believe that the spatial distance between brain regions has an important influence on FBN topology. Therefore, in this paper, we assume that spatially neighboring brain regions tend to have stronger connections and/or share similar connections with others; based on this assumption, we propose two novel methods to estimate FBNs by incorporating the information of brain region distance into the estimation model. To validate the effectiveness of the proposed methods, we use the estimated FBNs to identify subjects with mild cognitive impairment (MCI) from normal controls (NCs). Experimental results show that the proposed methods are better than the baseline methods in the sense of MCI identification accuracy.

A Review of Photoplethysmography-based Physiological Measurement and Estimation, Part 1: Single Input Methods.

Photoplethysmography is a non-invasive and easy to administer optical method used primarily to mea-sure blood oxygen saturation, but also used widely to estimate and measure various other physiological parameters. ⁄is paper reviews several physiological parameter estimations that have been done with just this waveform signal, i.e. heart rate, lipid profiling by morphological PPG analysis, blood glucose, ankle brachial pressure, and respiratory rate. Additional physiological estimations which use additional input measurements are reviewed in Part 2 of this paper. The different methods and signal processing techniques based on the principle of operation are discussed in this review. ⁄e validity of each of these optical measurement techniques are reviewed where the results were compared with the results obtained using the gold reference standards. Future research considerations for non-invasive wearable devices for physiological parameter measurements are also highlighted in this review which could be helpful for future research.

Comparison of Closed Kinetic Chain Exercises and Conventional Therapy on Cardiac Parameters in Post CABG Subjects

Introduction: Cardiovascular disorders are public health problems worldwide. In industrialized world they are the leading cause of morbidity and mortality. Coronary artery bypass grafting (CABG) has proved to be a major life saving operative method in cardiovascular disease. Physiotherapy interventions play major role in rehabilitation post CABG so the study was conducted with the aim to find the effect of closed kinetic chain exercises and conventional therapy on cardiac parameters in post CABG subjects. Method: In this comparative study 20 subjects were treated for post CABG subjects between the age group of 40-50 years. Group A were given conventional treatment and Group B were given Closed Kinetic Chain exercise. The pre and post -test was measure blood pressure, respiratory rate, heart rate, oxygen saturation and borg scale. Results: The statistical analysis for conventional therapy pre and post week1 day 1-systolic blood pressure(p=<0.0001), diastolic blood pressure(p=0.005), respiratory rate(p=0.001), heart rate(p=0.011), oxygen saturation(p=0.081) and borg scale(p=0.003). pre and post week6 day 3- diastolic blood pressure(p=0.018), respiratory rate(p=<0.0001), heart rate(p=0.005), systolic blood pressure(p=0.186), oxygen saturation(p=0.343) and borg scale(p=0). The statistical analysis for experimental group pre and post week1 day 1-heart rate (p=0.01) diastolic blood pressure(p=0.002), systolic blood pressure(p=<0.0001), respiratory rate(p=<0.0001),borg scale(p=0.0007), oxygen saturation (p=0.508). pre and post week6 day 3-borg scale(p=0), diastolic blood pressure(p=0.051),heart rate (p=<0.0001), respiratory rate(p=<0.0001), systolic blood pressure(p=0.26) and oxygen saturation(p=0.34).The study had found that conventional therapy is more effective than experimental group. Conclusion: The study concluded that conventional treatment is more effective than closed kinetic chain exercises. However, it cannot be stated that CKC has no effect because of its additional benefits on functional capacity (improve joint integrity). Therefore, it can be concluded that further studies can evaluate the improvement noted with a right combination of both and obtain greater benefit

Reduced Dynamic Complexity of BOLD Signals Differentiates Mild Cognitive Impairment From Normal Aging.

Mild cognitive impairment (MCI) is characterized as a transitional phase between cognitive decline associated with normal aging and Alzheimer’s disease (AD). Resting-state functional magnetic resonance imaging (fMRI) measuring blood oxygenation level-dependent (BOLD) signals provides complementary information considered essential for understanding disease progression. Previous studies suggested that multi-scale entropy (MSE) analysis quantifying the complexity of BOLD signals is a novel and promising method for investigating neurodegeneration associated with cognitive decline in different stages of MCI. Therefore, the current study used MSE to explore the changes in the complexity of resting-state brain BOLD signals in patients with early MCI (EMCI) and late MCI (LMCI). We recruited 345 participants’ data from the Alzheimer’s Disease Neuroimaging Initiative database, including 176 normal control (NC) subjects, 87 patients with EMCI and 82 patients with LMCI. We observed a significant reduction of brain signal complexity toward regularity in the left fusiform gyrus region in the EMCI group and in the rostral anterior cingulate cortex in the LMCI group. Our results extend prior work by revealing that significant reductions of brain BOLD signal complexity can be detected in different stages of MCI independent of age, sex and regional atrophy. Notably, the reduction of BOLD signal complexity in the rostral anterior cingulate cortex was significantly associated with greater risk of progression to AD. The present study thus identified MSE as a potential imaging biomarker for the early diagnosis of pre-clinical Alzheimer’s disease and provides further insights into the neuropathology of cognitive decline in prodromal AD.

Cortical oxygenation during exposure therapy - in situ fNIRS measurements in arachnophobia.

Exposure therapy is a well-studied and highly efficacious treatment for phobic disorders. Although the neurobiological model of fear is well underpinned by various studies, the mechanisms of exposure therapy are still under discussion. Partly, this is due to the fact that most neurophysiological methods like fMRI are not able to be used in the natural therapeutic settings. The current study used in situ measurements of cortical blood oxygenation (O2Hb) during exposure therapy by means of functional near-infrared spectroscopy. 37 subjects (N=30 completers) underwent exposure therapy during 5 adapted sessions in which subjects were exposed to Tegenaria Domestica (domestic house spider - experimental condition) and Dendrobaena Veneta/ Eisenaia hortensis (red earthworm - control condition). Compared to the control condition, patients showed higher O2Hb levels in the anticipation and exposure phase of spider exposure in areas of the cognitive control network (CCN). Further, significant decreases in O2Hb were observed during the session accompanied by reductions in fear related symptoms. However, while symptoms decreased in a linear quadratic manner, with higher reductions in the beginning of the session, CCN activity decreased linearly. Further, higher anxiety at the beginning of session one was associated with increased O2Hb in the CCN. This association decreased within the following sessions. The current study sheds light on the neuronal mechanisms of exposure therapy. The results are discussed in light of a phase model of exposure therapy that posits a role of cognitive control in the beginning and routine learning at the end of the therapy session.

Functional Brain Network Learning Based on Spatial Similarity for Brain Disorders Identification

Functional brain network (FBN) measures based on functional magnetic resonance imaging (fMRI) data, has become important biomarkers for early diagnosis and prediction of clinical outcomes in neurological diseases, such as Alzheimer’s diseases (AD) and its prodromal state (i.e., Mild cognitive impairment, MCI). In the past decades, researchers have developed numbers of approaches for FBN estimation, including Pearson’s correction (PC), sparse representation (SR), and so on. Despite their popularity and wide applications in current studies, most of the approaches for FBN estimation only consider the dependency between the measured blood oxygen level dependent (BOLD) time series, but ignore the spatial relationships between pairs of brain regions. In practice, the strength of functional connection between brain regions will decrease as their distance increases. Inspired by this, we proposed a new approach for FBN estimation based on the assumption that the closer brain regions tend to share stronger relationships or similarities. To verify the effectiveness of the proposed method, we conduct experiments on a public dataset to identify the patients with MCIs from health controls (HCs) using the estimated FBNs. Experimental results demonstrate that the proposed approach yields statistically significant improvement in seven performance metrics over using the baseline methods.

Theta Burst Transcranial Magnetic Stimulation of Fronto-Parietal Networks: Modulation by Mental State.

Transcranial magnetic stimulation (TMS) treats neuropsychiatric disorders, but effects of stimulation are highly state-dependent and in most therapeutic applications, mental state is not controlled. This exploratory proposal will test the broad hypothesis that when TMS, specifically intermittent theta burst stimulation (iTBS), is applied during a controlled mental state, network changes will be facilitated, compared to stimulation when mental state is uncontrolled. We will focus on the dorsolateral prefrontal cortex (dlPFC) and the associated fronto-parietal network (FPN), which subserves cognitive control, an important neural and behavioral target of therapeutic TMS. After a baseline functional magnetic resonance imaging (fMRI) session, iTBS will be administered to 40 healthy subjects in three sessions over three days in a within-subjects, cross-over design: (1) dlPFC stimulation by iTBS alone, (2) dlPFC stimulation by iTBS while simultaneously performing a cognitive task, and (3) vertex (control) iTBS stimulation. Immediately after each iTBS session, we will measure blood oxygenation level-dependent (BOLD) activation during a cognitive control task (“n-back” task) and during the resting state, using BOLD connectivity and arterial spin labeling (ASL). We will test hypotheses that persisting neural changes and performance enhancement induced by iTBS to the dlPFC, compared to iTBS to the vertex, will affect the FPN, and these effects will be modulated by whether or not subjects receive iTBS when they are engaged in a cognitive control task. Demonstrating this interaction between iTBS and mental state will lay critical groundwork for future studies to show how controlling mental state during TMS can improve therapeutic effects.Trial RegistrationClinicaltrials.gov NCT04010461.

Hexokinase 2 couples glycolysis with the profibrotic actions of TGF-β.

Metabolic dysregulation in fibroblasts is implicated in the profibrotic actions of transforming growth factor-β (TGF-β). Here, we present evidence that hexokinase 2 (HK2) is important for mediating the fibroproliferative activity of TGF-β both in vitro and in vivo. Both Smad-dependent and Smad-independent TGF-β signaling induced HK2 accumulation in murine and human lung fibroblasts through induction of the transcription factor c-Myc. Knockdown of HK2 or pharmacological inhibition of HK2 activity with Lonidamine decreased TGF-β-stimulated fibrogenic processes, including profibrotic gene expression, cell migration, colony formation, and activation of the transcription factors YAP and TAZ, with no apparent effect on cellular viability. Fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) exhibited an increased abundance of HK2. In a mouse model of bleomycin-induced lung fibrosis, Lonidamine reduced the expression of genes encoding profibrotic markers (collagenΙα1, EDA-fibronectin, α smooth muscle actin, and connective tissue growth factor) and stabilized or improved lung function as assessed by measurement of peripheral blood oxygenation. These findings provide evidence of how metabolic dysregulation through HK2 can be integrated within the context of profibrotic TGF-β signaling.

Measurement device for detecting oxygen saturation in blood, heart rate, and temperature of human body

The progress of science and technology must be able to help resolve human medical problems for human survival. In this study, integrated measurement of oxygen saturation in the blood, heart rate and temperature of the human body have been made into one tool whose measurement results are displayed directly on the LCD display on a measuring instrument and an Android Smartphone. This tool uses Arduino Nano as its Microcontroller, Bluetooth as wireless serial communication with Android smartphone, Android Application Made with MIT App Inventor, MAX30100 sensor is used to measure blood oxygen saturation and heart rate, and MLX90614 sensor to measure body temperature. Testing Measurements that have been made are calibrated with Industrial standard measuring instruments (Oximeters) and digital thermometers. The result is that the accuracy of the tool reaches 99.62% for blood oxygen saturation measurements, 97.55% for heart rate, and 99.62% for body temperature when compared with industry standard devices. Android applications have been successfully installed on 5 types of smartphones with different brands and specifications. The Bluetooth range of a measuring device for a smartphone in maximum data transfer is 29 meters without a hitch and a maximum of 21.5 meters with obstacles.

A CMOS NMR needle for probing brain physiology with high spatial and temporal resolution.

Magnetic resonance imaging and spectroscopy are versatile methods for probing brain physiology, but their intrinsically low sensitivity limits the achievable spatial and temporal resolution. Here, we introduce a monolithically integrated NMR-on-a-chip needle that combines an ultra-sensitive 300 µm NMR coil with a complete NMR transceiver, enabling in vivo measurements of blood oxygenation and flow in nanoliter volumes at a sampling rate of 200 Hz.

Lower Oxygen Saturation in the Internal Cerebral Vein of Patients with Sickle Cell Disease Revealed By Qsm-MRI

Introduction: Imaging of brain oxygenation can be a powerful tool to assess the risk of stroke in patients with sickle cell disease (SCD), and may potentially aid in stroke prevention. Currently, there is disagreement in oxygen extraction fraction estimated by techniques that measure tissue oxygenation from deep brain structures, and techniques that measure blood oxygenation in the sagittal sinus. Quantitative susceptibility mapping (QSM) is an MRI technique that can noninvasively measure venous blood oxygen saturation (SvO2) in deep cerebral structures based on the magnetic susceptibility shift of venous blood caused by deoxyhemoglobin. In this study, our goal was to compare venous oxygen saturation measured by QSM in the internal cerebral vein (ICV) to venous oxygenation in the sagittal sinus (SS) in SCD patients, anemia subjects with normal hemoglobin and healthy controls. Methods: 16 SCD patients, 7 non-sickle anemia patients and 11 healthy controls participated in the study(Table 1). All subjects provided written consent to a protocol approved by the Committee on Clinical Investigation (CCI#11-00083). Images were acquired on a clinical 3 T Philips system with a 32-channel RF coil. The 3D gradient echo sequence had parameters: TR = 30 ms, α = 25°, 2 echoes: TE1 = 4.94 ms, ΔTE = 5.2 ms, FOV = 210 x 190 x 120 mm, spatial resolution: 0.6 x 0.6 x 1.3 mm, SENSE acceleration rate = 2 in the phase-encoding direction, BW = 289 Hz/pix and total acquisition time = 6 mins 50 seconds. Flow-compensation was added in the readout direction only, which was the anterior-posterior (AP) direction. For each subject, phase images were fitted to generate a B0 field map. Brain extraction and phase unwrapping was performed using FSL. Background field was removed using PDF. Unreliable phase voxels were identified and removed from the brain mask for subsequent processing. L1-regularized field-to-susceptibility inversion was performed to derive the susceptibility map (lambda = 4*10-4). Venous oxygen saturation was computed based on: χ = (1 - SvO2)χd-oHct + χo-wHct [1] where χ is the susceptibility measurement of the ICV, χd-o is the susceptibility shift per unit hematocrit between fully oxygenated and fully deoxygenated erythrocytes, and χo-w is the susceptibility shift between oxygenated blood cells and water. Values of 0.27 ppm (c.g.s unit) and -0.03 ppm were used for χd-o and χo-w. The ROI mask of the ICV was manually selected based on the susceptibility map that was threshold at 0.1 ppm to avoid partial-volume effect. Only the segment that had an angle below 30 degree with respect to the AP axis was included. The purpose was to exclude regions that were susceptible to flow artifact. Intra-ROI average venous oxygen saturation were computed. Group difference of venous oxygen saturation was tested using Student t-test. Results: Figure 2a shows ICV magnetic susceptibility increases linearly with hematocrit as predicted by Eq [1]. Mean ICV venous oxygen saturation in the three groups was 73.9% in CTL, 73.6% in ACTL, compared with SCD 69.3%, p<0.05 by analysis of variance. Figure 3 compares the ICV and SS oxygen saturation as a function of hemoglobin concentration. At normal hemoglobin values, SS saturation was lower than in the ICV, but this difference disappeared with increasing anemia severity. After controlling for hemoglobin value, there were no patient group differences in oxygen saturation in either location. Discussion: In non-anemic subjects, SS oxygen saturation was lower than in the ICV, potentially reflecting increased oxygen demand of the cerebral cortex compared with deep brain structures. ICV is one of the major deep cortical veins, and oxygen saturation of this vein can indicate the oxygenation of deep structures of the cerebral hemispheres, including the basal ganglia, corpus callosum and thalamus. With progressive anemia, brain blood flow increases to preserve cerebral oxygen delivery (not shown), but favors grey matter perfusion at the expense of deep white matter structures. This could explain the decline in venous saturation with hemoglobin seen in the ICV compared with the rise in venous saturation observed in the SS. Alternatively, global increases in flow may homogenize and shorten microvascular transit times, equalizing the oxygen extraction across brain vascular territories. Disclosures Coates: celgene: Consultancy, Honoraria, Other: steering committee of clinical study; agios pharma: Consultancy, Honoraria; vifor: Consultancy, Honoraria; apo pharma: Consultancy, Honoraria, Speakers Bureau. Wood:Apopharma: Consultancy; BiomedInformatics: Consultancy; National Institutes of Health: Research Funding; Imago Biosciences: Consultancy; WorldcareClinical: Consultancy; Philips Healthcare: Research Funding; BluebirdBio: Consultancy; Celgene: Consultancy.

A Low-Power Dynamic-Range Relaxed Analog Front End for Wearable Heart Rate and Blood Oximetry Sensor

Photoplethysmogram (PPG) is widely implemented to monitor heart rate and oxygen saturation in wearable body sensor networks for healthcare management. This paper presents a low-power analog front end that enables PPG signal acquisition. By implementing a high-pass function, the ac and dc components of PPG signal are separately extracted to calculate heart rate and oxygen saturation, and the dynamic range requirement of the readout channel is relaxed. In addition, the chopping modulation is implemented to ensure the low-noise operation. The analog front-end circuit is designed and fabricated in the CMOS 0.18- $\mu \text{m}$ standard technology. The measurements show that the consuming power is approximately $180~\mu \text{W}$ at a supply of 2.5 V. The circuit achieves an input noise of 6.45 pArms. The calibrated algorithm is implemented using a Cortex-M3 MCU, and the demonstration, which is compared with the FLUKE Simulator as the reference, shows that the heart rate is accurately detected, and the error of the measured blood oxygen saturation is less than 1.5%.

The effect of acute cocoa flavanol intake on the BOLD response and cognitive function in type 1 diabetes: a randomized, placebo-controlled, double-blinded cross-over pilot study

Type 1 diabetes (T1D), a chronic autoimmune disease, can result in cognitive dysfunction and is associated with vascular dysfunction. Cocoa flavanols (CFs) can stimulate nitric oxide-dependent vasodilation, resulting in enhanced hemodynamic responses and better cognitive function. To investigate whether acute CF supplementation can improve cognitive function and hemodynamic responses in T1D. In this randomized, double-blinded, cross-over pilot study, 11 patients with T1D and their healthy matched controls consumed CF (900mg CF) and placebo (15mg CF) 2h before a flanker test. fMRI was used to measure blood oxygen level-dependent (BOLD) response during the cognitive test. Repeated measure ANOVAs were used to test the effects of CF and T1D on BOLD response and cognitive performance. CF improved reaction time on the flanker test and increased the BOLD response in the supramarginal gyrus parietal lobe and inferior frontal gyrus, compared to placebo, in both groups. In patients with T1D, cognitive performance was not deteriorated while the BOLD response was smaller in T1D compared to healthy controls in the subgyral temporal lobe and the cerebellum. Acute CF intake improved reaction time on the flanker test and increased the BOLD response in the activated brain areas in patients with T1D and their matched controls.

Abstract TP156: A Novel and Logical Strategy for Prevention of Hyperperfusion Syndrome; Intentional Residual Stenosis After Carotid Artery Stenting of an Extremely High-Grade Stenosis

Introduction: Hyperperfusion syndrome ( HPS ) probably occurs after carotid artery stenting ( CAS ) of an extremely high-grade carotid artery stenosis (ex-CS). However, it has not been established how to prevent HPS. Hypothesis: Intentional residual stenosis (iRS ) after CAS not followed by balloon dilatation (bD) can prevent HPS in patients with an ex-CS and spontaneously dilates thereafter. Methods: We included in our study patients with an ex-CS who underwent elective CAS not followed by bD for iRS from 2015 to 2018. We defined an ex-CS as a stenosis of more than NASCET 70% which caused delayed filling of contrast material in an internal carotid angiogram and reduced signal intensity (ratio of less than 0.9) of the ipsilateral middle cerebral artery (MCA) compared to the contralateral MCA on magnetic resonance angiograms (MRA), and defined a residual stenosis (rS) as angiographic stenosis of more than NASCET 30% or peak systolic velocity (PSV) of more than 80 cm/s by Doppler ultrasonography. We defined hyperperfusion phenomenon (HPP) as increase of cerebral blood flow in single photon emission computed tomography scans or cerebral metabolic rate of oxygen by measuring blood oxygen content. We evaluated patients’ baseline characteristics, rS just after CAS, incidence of HPS and HPP. Three months after CAS, they underwent conventional angiographic investigation. Results: During the study period, 26 CAS met our inclusive criteria. Their median carotid stenosis was NASCET 81.8%. Signal intensity ratio of MRA was 0.75. Median PSV before and just after CAS was 311.5 and 76.1 cm/s (p<0.0001). Just after CAS, median stent diameter stenosis was 33.3%. Seventeen patients (65.4%) had angiographic rS. Twelve patients (46.2%) had PSV of more than 80 cm/s. Ten patients had both. Comprehensively nineteen (73.1%) patients had significant rS. Among 26 patients with an ex-CS, no one experienced HPS, although comprehensively 15 patients (57.7%) presented asymptomatic HPP. Among 26 patients, 23 patients finished 3-month angiography and their stents significantly spontaneously dilated (p<0.0001). Conclusion: Intentional residual stenosis after CAS of an ex-CS probably prevented hyperperfusion syndrome and spontaneously dilated at 3 months after CAS.

Signal quality measure for pulsatile physiological signals using morphological features: Applications in reliability measure for pulse oximetry.

Pulse oximetry is a noninvasive and low-cost physiological monitor that measures blood oxygen levels. While the noninvasive nature of pulse oximetry is advantageous, the estimates of oxygen saturation generated by these devices are prone to motion artifacts and ambient noise, reducing the reliability of such estimations. Clinicians combat this by assessing the quality of oxygen saturation estimation by visual inspection of the photoplethysmograph (PPG), which represents changes in pulsatile blood volume and is also generated by the pulse oximeter. In this paper, we propose six morphological features that can be used to determine the quality of the PPG signal and generate a signal quality index. Unlike many similar studies, this approach uses machine learning and does not require a separate signal, such as ECG, for reference. Multiple algorithms were tested against 46 30-min PPG segments of patients with cardiovascular and respiratory conditions, including atrial fibrillation, hypoxia, acute heart failure, pneumonia, ARDS, and pulmonary embolism. These signals were independently annotated for signal quality by two clinicians, with the union of their annotations used as the ground-truth. Similar to any physiological signal recorded in a clinical setting, the utilized dataset is also unbalanced in favor of good quality segments. The experiments showed that a cost-sensitive Support Vector Machine (SVM) outperformed other tested methods and was robust to the unbalanced nature of the data. Though the proposed algorithm was tested on PPG signals, the methodology remains agnostic to the dataset used, and may be applied to any type of pulsatile physiological signal.

Feasibility of Commercially Marketed Health Devices for Potential Clinical Application.

Concerns have been raised regarding the lack of validation on consumer-marketed health-monitoring devices. An investigation to characterize current health monitoring devices was carried out in the laboratory using widely accepted clinical and industry criteria. In total, 16 unique devices were examined. These devices were assessed according to their sensing modalities: step count, blood pressure, body temperature, electrocardiogram, blood oxygen saturation, and respiratory rate. Devices were tested at rest and immediately following exercise. Our results revealed that only four devices meet target requirements for accuracy. The AliveCor, a portable ECG monitor, accurately detected the heart rate for 87% of all recordings. To meet the target criterion for accuracy, the heart rate must be within ± 5 beats/minute or 10% of the standard measurement, whichever is lower. The Withings Pulse Ox, the Tinké, and the Santamedical SM-110 measured blood oxygen saturation with 2.1, 2.6, and 1.4 root-mean-square (rms) error, respectively. For blood oxygen saturation, the device should demonstrate rms error of < 3%. However, the Withings Pulse Ox and the Tinké failed to meet the accuracy criteria for their alternative biosensing capabilities: step count and respiratory rate, respectively. We conclude that the use of consumer-marketed health-monitoring devices for clinical or medical purposes should be undertaken with caution, especially in the absence of FDA or comparable clearance.

Imaging functional motor connectivity in hemiparetic children with perinatal stroke.

Perinatal stroke causes lifelong disability, particularly hemiparetic cerebral palsy. Arterial ischemic strokes (AIS) are large, cortical, and subcortical injuries acquired near birth due to acute occlusion of the middle cerebral artery. Periventricular venous infarctions (PVI) are smaller, subcortical strokes acquired prior to 34 weeks gestation involving injury to the periventricular white matter. Both stroke types can damage motor pathways, thus, we investigated resulting alterations in functional motor networks and probed function. We measured blood oxygen level dependent (BOLD) fluctuations at rest in 38 participants [10 arterial patients (age = 14.7 ± 4.1 years), 10 venous patients (age = 13.5 ± 3.7 years), and 18 typically developing controls (TDCs) (age = 15.3 ± 5.1 years)] and explored strength and laterality of functional connectivity in the motor network. Inclusion criteria included MRI-confirmed, unilateral perinatal stroke, symptomatic hemiparetic cerebral palsy, and 6-19 years old at time of imaging. Seed-based functional connectivity analyses measured temporal correlations in BOLD response over the whole brain using primary motor cortices as seeds. Laterality indices based on mean z-scores in lesioned and nonlesioned hemispheres explored laterality. In AIS patients, significant differences in both strength and laterality of motor network connections were observed compared with TDCs. In PVI patients, motor networks largely resembled those of healthy controls, albeit slightly weaker and asymmetric, despite subcortical damage and hemiparesis. Functional connectivity strengths were not related to motor outcome scores for either stroke group. This study serves as a foundation to better understand how resting-state fMRI can assess motor functional connectivity and potentially be applied to explore mechanisms of interventional therapies after perinatal stroke.

A Wearable Pulse Oximeter With Wireless Communication and Motion Artifact Tailoring for Continuous Use.

Advances in several engineering fields have led to a trend toward miniaturization and portability of wearable biosensing devices, which used to be confined to large tools and clinical settings. Various systems to continuously measure electrophysiological activity through electrical and optical methods are one category of such devices. Being wearable and intended for prolonged use, the amount of noise introduced on sensors by movement remains a challenge and requires further optimization. User movement causes motion artifacts that alter the overall quality of the signals obtained, hence corrupting the resulting measurements. This paper introduces a fully wearable optical biosensing system to continuously measure pulse oximetry and heart rate, utilizing a reflectance-based probe. Furthermore, a novel data-dependent motion artifact tailoring algorithm is implemented to eliminate noisy data due to the motion artifact and measure oxygenation level with high accuracy in real time. By taking advantages of current wireless transmission and signal processing technologies, the developed wearable photoplethysmography device successfully captures the measured signals and sends them wirelessly to a mobile device for signal processing in real time. After applying motion artifact tailoring, evaluating accuracy with a continuous clinical device, the blood oxygenation measurements obtained from our system yielded an accuracy of at least 98%, when compared to a range of 93.6%-96.7% observed before from the same initial data. Additionally, heart rate accuracy above 97% was achieved. Motion artifact tailoring and removal in real time, continuous systems will allow wearable devices to be truly wearable and a reliable electrophysiological monitoring and diagnostics tool for everyday use.

Quantitative susceptibility mapping in the human fetus to measure blood oxygenation in the superior sagittal sinus.

To present the feasibility of performing quantitative susceptibility mapping (QSM) in the human fetus to evaluate the oxygenation (SvO2) of cerebral venous blood in vivo. Susceptibility weighted imaging (SWI) data were acquired from healthy pregnant subjects (n = 21, median = 31.3 weeks, interquartile range = 8.8 weeks). The susceptibility maps were generated from the SWI-phase images using a modified QSM processing pipeline, optimised for fetal applications. The processing pipeline is as follows: (1) mild high-pass filtering followed by quadratic fitting of the phase images to eliminate background phase variations; (2) manual creation of a fetal brain mask that includes the superior sagittal sinus (SSS); (3) inverse filtering of the resultant masked phase images using a truncated k-space approach with geometric constraint. Further, the magnetic susceptibility, ∆χv and corresponding putative SvO2 of the SSS were quantified from the generated susceptibility maps. Systematic error in the measured SvO2 due to the modified pipeline was also studied through simulations. Simulations showed that the systematic error in SvO2 when using a mask that includes a minimum of 5 voxels around the SSS and five slices remains < 3% for different orientations of the vessel relative to the main magnetic field. The average ∆χv in the SSS quantified across all gestations was 0.42 ± 0.03 ppm. Based on ∆χv, the average putative SvO2 in the SSS across all fetuses was 67% ± 7%, which is in good agreement with published studies. This in vivo study demonstrates the feasibility of using QSM in the human fetal brain to estimate ∆χv and SvO2. • A modified quantitative susceptibility mapping (QSM) processing pipeline is tested and presented for the human fetus. • QSM is feasible in the human fetus for measuring magnetic susceptibility and oxygenation of venous blood in vivo. • Blood magnetic susceptibility values from MR susceptometry and QSM agree with each other in the human fetus.

Movement artefact removal from NIRS signal using multi-channel IMU data

BackgroundThe non-invasive nature of near-infrared spectroscopy (NIRS) makes it a widely accepted method for blood oxygenation measurement in various parts of the human body. One of the main challenges in this method lies in the successful removal of movement artefacts in the detected signal. In this respect, multi-channel inertia measurement unit (IMU) containing accelerometer, gyroscope and magnetometer can be used for better modelling of movement artefact than using accelerometer only, which as a result, movement artefact can be more accurately removed.MethodsA wearable two-channel continuous wave NIRS system, incorporating an IMU sensor which contain accelerometer, gyroscope and magnetometer in it, was developed to record NIRS signal along with the simultaneous recording of movement artefacts related signal using the IMU. Four healthy subjects volunteered in the recording of the NIRS signals. During the recording from the first two subject, movement artefacts were simulated in one of the NIRS channels by tapping the photodiode sensor nearby. The corresponding IMU data for the simulated movement artefacts were used to estimate the artefacts in the corrupted signal by autoregressive with exogenous input method and subtracted from the corrupted signal to remove the artefacts in the NIRS signal. Signal-to-noise ratio (SNR) improvement was used to evaluate the performance of the movement artefacts removal process. The performance of the movement artefacts estimation and removal were compared using accelerometer only, accelerometer and gyroscope, and accelerometer, gyroscope and magnetometer data from IMU sensor to estimate the artefact in NIRS reading. For the remaining two subjects the NIRS signal was recorded by natural movement artefacts impact and the results of artefacts removal was compared using accelerometer only, accelerometer and gyroscope, and accelerometer, gyroscope and magnetometer data from IMU sensor to estimate the artefact in NIRS reading.ResultsThe quantitative and qualitative results revealed that the SNR improvement increases with the number of IMU channels used in the artefacts estimation, and there were approximately 5–11 dB increase in SNR when nine channel IMU data were used rather than using only three channel accelerometer data only. The artefact removal from natural movements also demonstrated that the combination of gyroscope and magnetometer sensors with accelerometer provided better estimation and removal of the movement artefacts, which was revealed by the minimal change of the HbO2 and Hb level before, during and after movement artefacts occurred in the NIRS signal.ConclusionThe movement artefacts in NIRS can be more accurately estimated and removed by using accelerometer, gyroscope and magnetograph signals from an integrated IMU sensor than using accelerometer signal only.