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1.

Validation of diffuse correlation spectroscopy measures of critical closing pressure against transcranial Doppler ultrasound in stroke patients

Kuan-Cheng Wu John Sunwoo Faheem Sheriff Parisa Farzam Parya Y. Farzam Felipe Orihuela-Espina Sarah L. LaRose Andrew D. Monk Mohammad A. Aziz-Sultan Nirav Patel Henrikas Vaitkevicius Maria Angela Franceschini 《Journal of biomedical optics》2021,26(3)

Significance: Intracranial pressure (ICP), variability in perfusion, and resulting ischemia are leading causes of secondary brain injury in patients treated in the neurointensive care unit. Continuous, accurate monitoring of cerebral blood flow (CBF) and ICP guide intervention and ultimately reduce morbidity and mortality. Currently, only invasive tools are used to monitor patients at high risk for intracranial hypertension.Aim: Diffuse correlation spectroscopy (DCS), a noninvasive near-infrared optical technique, is emerging as a possible method for continuous monitoring of CBF and critical closing pressure (CrCP or zero-flow pressure), a parameter directly related to ICP.Approach: We optimized DCS hardware and algorithms for the quantification of CrCP. Toward its clinical translation, we validated the DCS estimates of cerebral blood flow index (

{CBF}_{i}

) and CrCP in ischemic stroke patients with respect to simultaneously acquired transcranial Doppler ultrasound (TCD) cerebral blood flow velocity (CBFV) and CrCP.Results: We found CrCP derived from DCS and TCD were highly linearly correlated (ipsilateral

R^{2} = 0.77

,

p = 9 \times 10^{- 7}

; contralateral

R^{2} = 0.83

,

p = 7 \times 10^{- 8}

). We found weaker correlations between

{CBF}_{i}

and CBFV (ipsilateral

R^{2} = 0.25

,

p = 0.03

; contralateral

R^{2} = 0.48

,

p = 1 \times 10^{- 3}

) probably due to the different vasculature measured.Conclusion: Our results suggest DCS is a valid alternative to TCD for continuous monitoring of CrCP. 相似文献

2.

Globally deployed COVID-19 fever screening devices using infrared thermographs consistently normalize high readings to afebrile range

Conor Healy Zachary Segal Chris Hinnerichs Ethan Ace Derek Ward John Honovich 《Journal of biomedical optics》2021,26(4)

Significance: The need for regulatory review of infrared thermographs (IRTs) used on humans was removed in response to the unique circumstances of the SARS-CoV-2 pandemic (a.k.a., COVID-19). The market for these devices has since expanded considerably. This evaluation of IRT performance may have significant implications for febrility screening worldwide.Aim: Perform controlled nonhuman trials of IRT devices to identify and quantify deviations in the human temperature range.Approach: We compared IRT readings of a temperature-controlled non-human subject with one FDA-cleared IRT and one FDA-cleared handheld NCIT. In individual trials for each device, the subject was measured between 35°C and 40°C at 0.25°C increments.Results: The IRT device measurements were consistently normalized around the human mean (

\sim 37 ° C

). Temperatures were decremented as they approached the febrile range, and systematically reported as normal across all seven devices. This effect does not appear to be explained by a fixed offset or any known approach to estimating body temperature, or by random error.Conclusion: The IRTs in this study generated human temperature measurements that were systematically biased to the mean human temperature. Given that these devices are utilized for sentinel detection of possible infectious disease transmission, and are now globally employed, the implications for reduced detection of febrility are a widespread false sense of security. This vulnerability must be considered with respect to facility access control, clinical applications, and travel screening in the context of the ongoing COVID-19 pandemic response. 相似文献

3.

Melanoma Detection Using Spatial and Spectral Analysis on Superpixel Graphs

Mahmoud H. Annaby Asmaa M. Elwer Muhammad A. Rushdi Mohamed E. M. Rasmy 《Journal of digital imaging》2021,34(1):162

相似文献

4.

Symmorphosis and skeletal muscle V˙O2 max : in vivo and in vitro measures reveal differing constraints in the exercise‐trained and untrained human

Jayson R. Gifford Ryan S. Garten Ashley D. Nelson Joel D. Trinity Gwenael Layec Melissa A. H. Witman Joshua C. Weavil Tyler Mangum Corey Hart Cory Etheredge Jake Jessop Amber Bledsoe David E. Morgan D. Walter Wray Matthew J. Rossman Russell S. Richardson 《The Journal of physiology》2016,594(6):1741-1751

Key points

The concept of symmorphosis predicts that the capacity of each step of the oxygen cascade is attuned to the task demanded of it during aerobic exercise at maximal rates of oxygen consumption ( ${\dot{V}}_{O_{2} \max}$ ) such that no single process is limiting or in excess at ${\dot{V}}_{O_{2} \max}$ .
The present study challenges the applicability of this concept to humans by revealing clear, albeit very different, limitations and excesses in oxygen supply and consumption among untrained and endurance‐trained humans.
Among untrained individuals, ${\dot{V}}_{O_{2} \max}$ is limited by the capacity of the mitochondria to consume oxygen, despite an excess of oxygen supply, whereas, among trained individuals, ${\dot{V}}_{O_{2} \max}$ is limited by the supply of oxygen to the mitochondria, despite an excess of mitochondrial respiratory capacity.

Abstract

The concept of symmorphosis postulates a matching of structural capacity to functional demand within a defined physiological system, regardless of endurance exercise training status. Whether this concept applies to oxygen (O₂) supply and demand during maximal skeletal muscle O₂ consumption (

{\dot{V}}_{O_{2} \max}

) in humans is unclear. Therefore, in vitro skeletal muscle mitochondrial

{\dot{V}}_{O_{2} \max}

(_Mito

{\dot{V}}_{O_{2} \max}

, mitochondrial respiration of fibres biopsied from vastus lateralis) was compared with in vivo skeletal muscle

{\dot{V}}_{O_{2} \max}

during single leg knee extensor exercise (_KE

{\dot{V}}_{O_{2} \max}

, direct Fick by femoral arterial and venous blood samples and Doppler ultrasound blood flow measurements) and whole‐body

{\dot{V}}_{O_{2} \max}

during cycling (_Body

{\dot{V}}_{O_{2} \max}

, indirect calorimetry) in 10 endurance exercise‐trained and 10 untrained young males. In untrained subjects, during KE exercise, maximal O₂ supply (_KE

\dot{Q}

O_2max) exceeded (462 ± 37 ml kg⁻¹ min⁻¹, P < 0.05) and _KE

{\dot{V}}_{O_{2} \max}

matched (340 ± 22 ml kg⁻¹ min⁻¹, P > 0.05) _Mito

{\dot{V}}_{O_{2} \max}

(364 ± 16 ml kg⁻¹ min⁻¹). Conversely, in trained subjects, both _KE

\dot{Q}

O_2max (557 ± 35 ml kg⁻¹ min⁻¹) and _KE

{\dot{V}}_{O_{2} \max}

(458 ± 24 ml kg⁻¹ min⁻¹) fell far short of _Mito

{\dot{V}}_{O_{2} \max}

(743 ± 35 ml kg⁻¹ min⁻¹, P < 0.05). Although _Mito

{\dot{V}}_{O_{2} \max}

was related to _KE

{\dot{V}}_{O_{2} \max}

(r = 0.69, P < 0.05) and _Body

{\dot{V}}_{O_{2} \max}

(r = 0.91, P < 0.05) in untrained subjects, these variables were entirely unrelated in trained subjects. Therefore, in untrained subjects,

{\dot{V}}_{O_{2} \max}

is limited by mitochondrial O₂ demand, with evidence of adequate O₂ supply, whereas, in trained subjects, an exercise training‐induced mitochondrial reserve results in skeletal muscle

{\dot{V}}_{O_{2} \max}

being markedly limited by O₂ supply. Taken together, these in vivo and in vitro measures reveal clearly differing limitations and excesses at

{\dot{V}}_{O_{2} \max}

in untrained and trained humans and challenge the concept of symmorphosis as it applies to O₂ supply and demand in humans. 相似文献

5.

Mirau-based line-field confocal optical coherence tomography for three-dimensional high-resolution skin imaging

Weikai Xue Jonas Ogien Pavel Bulkin Anne-Lise Coutrot Arnaud Dubois 《Journal of biomedical optics》2022,27(8)

SignificanceLine-field confocal optical coherence tomography (LC-OCT) is a recently introduced high-resolution imaging modality based on a combination of low-coherence optical interferometry and reflectance confocal optical microscopy with line illumination and line detection. Capable of producing three-dimensional (3D) images of the skin with cellular resolution, in vivo, LC-OCT has been mainly applied in dermatology and dermo-cosmetology. The LC-OCT devices capable of acquiring 3D images reported so far are based on a Linnik interferometer using two identical microscope objectives. In this configuration, LC-OCT cannot be designed to be a very compact and light device, and the image acquisition speed is limited.AimThe objective of this work was to develop a more compact and lighter LC-OCT device that is capable of acquiring images faster without significant degradation of the resolution and with optimized detection sensitivity.ApproachWe developed an LC-OCT device based on a Mirau interferometer using a single objective. Dynamic adjustment of the camera frequency during the depth scan is implemented, using a faster camera and a more powerful light source. The reflectivity of the beam-splitter in the Mirau interferometer was optimized to maximize the detection sensitivity. A galvanometer scanner was incorporated into the device for scanning the illumination line laterally. A stack of adjacent B-scans, constituting a 3D image, can thus be acquired.ResultsThe device is able to acquire and display B-scans at 17 fps. 3D images with a quasi-isotropic resolution of

\sim 1.5 μ m

(1.3, 1.9, and

1.1 μ m

in the

x, y

, and

z

directions, respectively) over a field of

940 μ m \times 600 μ m \times 350 μ m

(

x \times y \times z

) can be obtained. 3D imaging of human skin at cellular resolution, in vivo, is reported.ConclusionsThe acquisition rate of the B-scans, at 17 fps, is unprecedented in LC-OCT. Compared with the conventional LC-OCT devices based on a Linnik interferometer, the reported Mirau-based LC-OCT device can acquire B-scans

\sim 2

times faster. With potential advantages in terms of compactness and weight, a Mirau-based device could easily be integrated into a smaller and lighter handheld probe for use by dermatologists in their daily medical practice. 相似文献

6.

Haematological rather than skeletal muscle adaptations contribute to the increase in peak oxygen uptake induced by moderate endurance training

David Montero Adrian Cathomen Robert A. Jacobs Daniela Flück Jeroen de Leur Stefanie Keiser Thomas Bonne Niels Kirk Anne‐Kristine Lundby Carsten Lundby 《The Journal of physiology》2015,593(20):4677-4688

Key points

This study assessed the respective contributions of haematological and skeletal muscle adaptations to any observed improvement in peak oxygen uptake ( ${\dot{V}}_{O_{2} peak}$ ) induced by endurance training (ET).
${\dot{V}}_{O_{2} peak}$ , peak cardiac output ( ${\dot{Q}}_{peak}$ ), blood volumes and skeletal muscle biopsies were assessed prior (pre) to and after (post) 6 weeks of ET. Following the post‐ET assessment, red blood cell volume (RBCV) reverted to the pre‐ET level following phlebotomy and ${\dot{V}}_{O_{2} peak}$ and ${\dot{Q}}_{peak}$ were determined again.
We speculated that the contribution of skeletal muscle adaptations to an ET‐induced increase in ${\dot{V}}_{O_{2} peak}$ could be identified when offsetting the ET‐induced increase in RBCV.
${\dot{V}}_{O_{2} peak}$ , ${\dot{Q}}_{peak}$ , blood volumes, skeletal muscle mitochondrial volume density and capillarization were increased after ET. Following RBCV normalization, ${\dot{V}}_{O_{2} peak}$ and ${\dot{Q}}_{peak}$ reverted to pre‐ET levels.
These results demonstrate the predominant contribution of haematological adaptations to any increase in ${\dot{V}}_{O_{2} peak}$ induced by ET.

Abstract

It remains unclear whether improvements in peak oxygen uptake (

{\dot{V}}_{O_{2} peak}

) following endurance training (ET) are primarily determined by central and/or peripheral adaptations. Herein, we tested the hypothesis that the improvement in

{\dot{V}}_{O_{2} peak}

following 6 weeks of ET is mainly determined by haematological rather than skeletal muscle adaptations. Sixteen untrained healthy male volunteers (age = 25 ± 4 years,

{\dot{V}}_{O_{2} peak}

= 3.5 ± 0.5 l min⁻¹) underwent supervised ET (6 weeks, 3–4 sessions per week).

{\dot{V}}_{O_{2} peak}

, peak cardiac output (

{\dot{Q}}_{peak}

), haemoglobin mass (Hb_mass) and blood volumes were assessed prior to and following ET. Skeletal muscle biopsies were analysed for mitochondrial volume density (Mito_VD), capillarity, fibre types and respiratory capacity (OXPHOS). After the post‐ET assessment, red blood cell volume (RBCV) was re‐established at the pre‐ET level by phlebotomy and

{\dot{V}}_{O_{2} peak}

and

{\dot{Q}}_{peak}

were measured again. We speculated that the contribution of skeletal muscle adaptations to the ET‐induced increase in

{\dot{V}}_{O_{2} peak}

would be revealed when controlling for haematological adaptations.

{\dot{V}}_{O_{2} peak}

and

{\dot{Q}}_{peak}

were increased (P < 0.05) following ET (9 ± 8 and 7 ± 6%, respectively) and decreased (P < 0.05) after phlebotomy (−7 ± 7 and −10 ± 7%). RBCV, plasma volume and Hb_mass all increased (P < 0.05) after ET (8 ± 4, 4 ± 6 and 6 ± 5%). As for skeletal muscle adaptations, capillary‐to‐fibre ratio and total Mito_VD increased (P < 0.05) following ET (18 ± 16 and 43 ± 30%), but OXPHOS remained unaltered. Through stepwise multiple regression analysis,

{\dot{Q}}_{peak}

, RBCV and Hb_mass were found to be independent predictors of

{\dot{V}}_{O_{2} peak}

. In conclusion, the improvement in

{\dot{V}}_{O_{2} peak}

following 6 weeks of ET is primarily attributed to increases in

{\dot{Q}}_{peak}

and oxygen‐carrying capacity of blood in untrained healthy young subjects.

Abbreviations

a–vO_2diff: arteriovenous oxygen difference
BV: blood volume
CO: carbon monoxide
ET: endurance training
ETS: electron transfer system capacity
FTa: fast twitch type IIa muscle fibre
FTx: fast twitch type IIx muscle fibre
[Hb]: haemoglobin concentration
%HbCO: percentage carboxyhaemoglobin
Hb_mass: haemoglobin mass
Hct: haematocrit
IMF: intermyofibrillar
Mito_VD: mitochondrial volume density
N₂O: nitrous oxide
OXPHOS: maximal oxidative phosphorylation capacity
PV: plasma volume
${\dot{Q}}_{peak}$: peak cardiac output
RBCV: red blood cell volume
SS: subsarcolemmal
ST: slow twitch type I muscle fibre
VIF: variance inflation factor
${\dot{V}}_{O_{2} peak}$: peak oxygen uptake
${\dot{W}}_{p e a k}$: peak power output

相似文献

7.

Melting,Solidification, and Crystallization of a Thermoplastic Polyurethane as a Function of Hard Segment Content

Almut Stribeck Berend Eling Elmar Pselt Marc Malfois Edgar Schander 《Macromolecular chemistry and physics.》2019,220(11)

Thermoplastic polyurethanes (TPU) with varying hard segment contents (HSC) are monitored during melting and solidifying (

| \dot{T} | = 20 K/min

, T_max = 220 ° C) by small‐angle and wide‐angle X‐ray scattering (WAXS and SAXS). Hard segments: MDI/BD. Soft segments: PTHF1000. The neat materials are injection‐molded, having small amorphous hard domains (chord length

{\bar{d}}_{h} < 6 nm

). Results indicate complexity of morphology changes. For example, crystals are predominantly produced in freshly segregated, sufficiently large hard domains, while the temperature decreases slowly enough. After the thermal treatment, only the materials with HSC >～ 35% show sharp Bragg peaks and larger hard domains (

{\bar{d}}_{h} > 7 nm

). When heated, small domains melt, but crystallization in the remaining large domains is not detected. Upon cooling, large agglomerates segregate first, which crystallize immediately. Segregation starts for HSC = 42% at 160 °C and for HSC = 75% at 210 °C. When HSC ≤ 30%, the morphologies before and after are similar, but afterward, many hard blocks are dissolved in the soft phase at the expense of the hard domain fraction. In heating and cooling the melts, multiple homogenization and segregation processes are observed, which are explained by the agglomeration of hard blocks of different lengths in the colloidal fluid. 相似文献

8.

Color Rendering in Medical Extended-Reality Applications

Andrea Seung Kim Wei-Chung Cheng Ryan Beams Aldo Badano 《Journal of digital imaging》2021,34(1):16

Cross-platform development of medical applications in extended-reality (XR) head-mounted displays (HMDs) often relies on game engines with rendering capabilities currently not standardized in the context of medical visualizations. Many aspects of the visualization pipeline including the characterization of color have yet to be consistently defined across rendering models and platforms. We examined the transfer of color properties from digital objects, through the rendering and image processing steps, to the RGB values sent to the display device. Five rendering pipeline configurations within the Unity engine were evaluated using 24 digital color patches. In the second experiment, the same configurations were evaluated with a tissue slide sample image. Measurements of the change in color associated with each configuration were characterized using the CIE 1976 color difference (

Δ E

). We found that the distribution of

Δ E

for the first experiment ranges from zero, as in the case using an Unlit Shader, to 25.97, as in the case using default configurations. The default Unity configuration consistently returned the highest

Δ E

across all 24 colors and also the largest range of color differences. In the second experiment,

Δ E

E ranged from 7.49 to 34.18. The Unlit configuration resulted in the highest

Δ E

in three of four selected pixels in the tissue sample image. Changes in color image properties associated with texture import settings were then evaluated in a third experiment using the TG18-QC test pattern. Differences in pixel values were found in all nine of the investigated texture import settings. The findings provide an initial characterization of color transfer and a basis for future work on standardization, consistency, and optimization of color in medical XR applications. 相似文献

9.

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

F.A. Cunha R.A. Montenegro A.W. Midgley F. Vasconcellos P.P. Soares P. Farinatti 《Brazilian journal of medical and biological research》2014,47(8):706-714

The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve (

% {\dot{V} O}_{2} R

) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and

{\dot{V} O}_{2}

at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL·kg^-1·min^-1 (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R² ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and

{% \dot{V} O}_{2} R

was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and

{% \dot{V} O}_{2} R

at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise. 相似文献

10.

Energy system contribution in a maximal incremental test: correlations with pacing and overall performance in a 10-km running trial

M.V. Damasceno L.A. Pasqua A.E. Lima-Silva R. Bertuzzi 《Brazilian journal of medical and biological research》2015,48(11):1048-1054

This study aimed to verify the association between the contribution of energy systems during an incremental exercise test (IET), pacing, and performance during a 10-km running time trial. Thirteen male recreational runners completed an incremental exercise test on a treadmill to determine the respiratory compensation point (RCP), maximal oxygen uptake (

{\dot{V} O}_{2 \max}

), peak treadmill speed (PTS), and energy systems contribution; and a 10-km running time trial (T10-km) to determine endurance performance. The fractions of the aerobic (W_AER) and glycolytic (W_GLYCOL) contributions were calculated for each stage based on the oxygen uptake and the oxygen energy equivalents derived by blood lactate accumulation, respectively. Total metabolic demand (W_TOTAL) was the sum of these two energy systems. Endurance performance during the T10-km was moderately correlated with RCP,

{\dot{V} O}_{2 \max}

and PTS (P<@0.05), and moderate-to-highly correlated with W_AER, W_GLYCOL, and W_TOTAL (P<0.05). In addition, W_AER, W_GLYCOL, and W_TOTAL were also significantly correlated with running speed in the middle (P<0.01) and final (P<0.01) sections of the T10-km. These findings suggest that the assessment of energy contribution during IET is potentially useful as an alternative variable in the evaluation of endurance runners, especially because of its relationship with specific parts of a long-distance race. 相似文献

11.

Simultaneous Wide-Field Planar Strain–Fiber Orientation Distribution Measurement Using Polarized Spatial Domain Imaging

Dover Coinneach Mackenzie Goth Will Goodbrake Christian Tunnell James W. Sacks Michael S. 《Annals of biomedical engineering》2022,50(3):253-277

相似文献

12.

Inpatient outcomes comparing White and Black patients with obesity hospitalized for COVID-19 infection

《Journal of the National Medical Association》2023,115(2):157-163

相似文献

13.

Impact of 8 weeks of repeated ischemic preconditioning on running performance

Slysz Joshua T. Burr Jamie F. 《European journal of applied physiology》2019,119(6):1431-1437

相似文献

14.

Modified electrode placements for measurement of hemodynamic parameters using impedance cardiography

Vu Duy Hai Phan Dang Hung Chu Quang Dan 《Journal of medical engineering & technology》2020,44(7):357-367

相似文献

15.

Influence of developmental nicotine exposure on the ventilatory and metabolic response to hyperthermia

Jonathan Ferng Ralph F. Fregosi 《The Journal of physiology》2015,593(23):5201-5213

AbstractTo determine whether developmental nicotine exposure (DNE) alters the ventilatory and metabolic response to hyperthermia in neonatal rats (postnatal age 2–4 days), pregnant dams were exposed to nicotine (6 mg kg⁻¹ of nicotine tartrate daily) or saline with an osmotic mini‐pump implanted subdermally on day 5 of gestation. Rat pups (a total of 72 controls and 72 DNE pups) were studied under thermoneutral conditions (chamber temperature 33°C) and during moderate thermal stress (37.5°C). In all pups, core temperature was similar to chamber temperature, with no treatment effects. The rates of pulmonary ventilation (

{\dot{V}}_{I}

), O₂ consumption (

{\dot{V}}_{O_{2}}

) and CO₂ production (

{\dot{V}}_{C O_{2}}

) did not change with hyperthermia in either control or DNE pups. However,

{\dot{V}}_{I}

was lower in DNE pups at both chamber temperatures, whereas the duration of spontaneous apnoeas was longer in DNE pups than in controls at 33°C. The

{\dot{V}}_{I}

/

{\dot{V}}_{O_{2}}

ratio increased at 37.5°C in control pups, although it did not change in DNE pups. To simulate severe thermal stress, additional pups were studied at 33°C and 43°C.

{\dot{V}}_{I}

increased with heating in control pups but not in DNE pups. As heat stress continued, gasping was evoked in both groups, with no effect of DNE on the gasping pattern. Over a 20 min recovery period at 33°C,