Pressure stimulus study on acupuncture points with multi-channel multimode-fiber diffuse speckle contrast analysis (MMF-DSCA).

A multi-channel multimode-fiber deep tissue flowmetry system has been constructed based on diffuse speckle contrast analysis (DSCA) for simultaneous blood flow measurements at different locations on the human body. This system has been utilized in an acupuncture study within the field of traditional Chinese medicine (TCM), primarily focusing on acupuncture points along the large intestine meridian. Deep tissue blood flow was monitored at four different acupuncture points (LI1, LI5, LI10, and ST25) with a sampling rate of 60 Hz while applying pressure stimulus on LI4 (hegu or hapgok). Although the blood flow index (BFI) and blood volume (BV) did not exhibit significant changes after the pressure stimulus, an increase in the amplitude and complexity of low-frequency oscillations (LFOs) in microcirculation was observed.

A Review on Progress, Challenges, and Prospects of Material Jetting of Copper and Tungsten.

Copper (Cu) and tungsten (W) possess exceptional electrical and thermal conductivity properties, making them suitable candidates for applications such as interconnects and thermal conductivity enhancements. Solution-based additive manufacturing (SBAM) offers unique advantages, including patterning capabilities, cost-effectiveness, and scalability among the various methods for manufacturing Cu and W-based films and structures. In particular, SBAM material jetting techniques, such as inkjet printing (IJP), direct ink writing (DIW), and aerosol jet printing (AJP), present a promising approach for design freedom, low material wastes, and versatility as either stand-alone printers or integrated with powder bed-based metal additive manufacturing (MAM). Thus, this review summarizes recent advancements in solution-processed Cu and W, focusing on IJP, DIW, and AJP techniques. The discussion encompasses general aspects, current status, challenges, and recent research highlights. Furthermore, this paper addresses integrating material jetting techniques with powder bed-based MAM to fabricate functional alloys and multi-material structures. Finally, the factors influencing large-scale fabrication and potential prospects in this area are explored.

Dataset on transcriptome signature of skeletal muscle of young, adult and aged mice.

This data article reports the level of expression of messenger RNA (mRNA) obtained from a set of 18 skeletal muscle samples using Affymetrix Genechips Exon arrays. Data were obtained from Gastrocnemius muscle of C57BL6 male mice at 3 distinct age groups, 2, 11 and 25 months old representing young, mature adult and aged groups. The data submitted to GEO constitute a large dataset of 15,300 mRNA levels. The data include eighteen .CEL files obtained after scanning mouse exon arrays and one .xls file obtained after processing with Genespring GX 14.9. Three distinct files containing affymetrix data processed using Genespring and analyzed for differences between stages 2 per 2 are provided as supplementary data.

Blood flow estimation via numerical integration of temporal autocorrelation function in diffuse correlation spectroscopy.

BACKGROUND AND OBJECTIVE: Diffuse correlation spectroscopy (DCS) is an optical technique widely used to monitor blood flow. Recently, efforts have been made to derive new signal processing methods to minimize the systems used and shorten the signal processing time. Herein, we propose alternative approaches to obtain blood flow information via DCS by numerically integrating the temporal autocorrelation curves. METHODS: We use the following methods: the inverse of K2 (IK2)-based on the framework of diffuse speckle contrast analysis-and the inverse of the numerical integration of squared g1 (INISg1) which, based on the normalized electric field autocorrelation curve, is more simplified than IK2. In addition, g1 thresholding is introduced to further reduce computational time and make the suggested methods comparable to the conventional nonlinear fitting approach. To validate the feasibility of the suggested methods, studies using simulation, liquid phantom, and in vivo settings were performed. In the meantime, the suggested methods were implemented and tested on three types of Arduino (Arduino Due, Arduino Nano 33 BLE Sense, and Portenta H7) to demonstrate the possibility of miniaturizing the DCS systems using microcotrollers for signal processing. RESULTS: The simulation and experimental results confirm that both IK2 and INISg1 are sufficiently relevant to capture the changes in blood flow information. More interestingly, when g1 thresholding was applied, our results showed that INISg1 outperformed IK2. It was further confirmed that INISg1 with g1 thresholding implemented on a PC and Portenta H7, an advanced Arduino board, performed faster than did the deep learning-based, state-of-the-art processing method. CONCLUSION: Our findings strongly indicate that INISg1 with g1 thresholding could be an alternative approach to derive relative blood flow information via DCS, which may contribute to the simplification of DCS methodologies.

A Scalable Solution Route to Porous Networks of Nanostructured Black Tungsten.

This paper studied the feasibility of a new solution-processed method to manufacture black tungsten nanostructures by laser conversion of tungsten hexacarbonyl precursor on the Inconel 625 substrate under argon atmosphere at ambient pressure. The results show that sublimation of the precursor can be prevented if the decomposition temperature (>170 °C) is achieved using the laser heating method. Three different laser powers from 60-400 W were used to investigate the role of laser parameters on the conversion. It was found that lower laser power of 60 W resulted in a mixture of unconverted precursor and converted tungsten. Higher laser powers >200 W resulted in α-W (BCC) in one step without further heat treatment. Different oxygen concentrations from 0.5 ppm to 21 vol% were used in the laser canister to investigate the effect of oxygen concentration on the conversion. It was found that the hard vacuum (>10-4 torr) or hydrogen is not necessary to obtain α-W (BCC). The solar absorptance varied from 63-97%, depending on the amount of precursor deposited on the substrate and oxygen content in the laser canister. This solution-based laser conversion of tungsten precursor is a scalable method to manufacture tungsten coatings for high-temperature applications.

Low frequency oscillations assessed by diffuse speckle contrast analysis for foot angiosome concept.

An angiosome refers to a 3D tissue volume that is vascularized by a single artery and is a relatively new concept that is useful in vascular surgery; however, the direct relationship between arterial blood flow and micro-perfusion is still controversial. Here, we propose a diffuse speckle contrast analysis (DSCA), which is an emerging tissue perfusion monitoring modality, to investigate the correlations among low frequency oscillations (LFOs) measured from different areas on the feet of healthy subjects. We obtained reproducible results from the correlation analyses of LFOs, and their physiological implications were discussed. In order to confirm the changes in the frequency oscillations, we analyzed and compared the power spectral density changes due to heart rate variability in the electrocardiographic signal during reactive hyperemia and head-up tilt protocols.

Correction: Early assessment of tumor response to photodynamic therapy using combined diffuse optical and diffuse correlation spectroscopy to predict treatment outcome.

[This corrects the article DOI: 10.18632/oncotarget.15720.].

Muscular blood flow responses as an early predictor of the severity of diabetic neuropathy at a later stage in streptozotocin-induced type I diabetic rats: a diffuse correlation spectroscopy study.

We propose a novel application of diffuse correlation spectroscopy to evaluate microvascular malfunctions of muscle tissue affected by hyperglycemia and determine their correlation with the severity of diabetic neuropathy at a later stage. Microvascular responses of the thigh muscle and the mechanical pain threshold of the hind paw of streptozotocin-induced type I diabetic rats were continuously monitored once per week for 70 days. Significantly decreased baseline blood flow and reactive hyperemia responses were observed as early as 1 week after hyperglycemia induction. The reactive hyperemia response at 2 weeks of hyperglycemia was highly correlated with the mechanical pain threshold at 8 weeks, at which time a decreased pain threshold was statistically confirmed in hyperglycemic rats relative to controls.

Early assessment of tumor response to photodynamic therapy using combined diffuse optical and diffuse correlation spectroscopy to predict treatment outcome.

Photodynamic therapy (PDT) of cancer involves the use of a photosensitizer that can be light-activated to eradicate tumors via direct cytotoxicity, damage to tumor vasculature and stimulating the body's immune system. Treatment outcome may vary between individuals even under the same regime; therefore a non-invasive tumor response monitoring system will be useful for personalization of the treatment protocol. We present the combined use of diffuse optical spectroscopy (DOS) and diffuse correlation spectroscopy (DCS) to provide early assessment of tumor response. The relative tissue oxygen saturation (rStO2) and relative blood flow (rBF) in tumors were measured using DOS and DCS respectively before and after PDT with reference to baseline values in a mouse model. In complete responders, PDT-induced decreases in both rStO2 and rBF levels were observed at 3 h post-PDT and the rBF remained low until 48 h post-PDT. Recovery of these parameters to baseline values was observed around 2 weeks after PDT. In partial responders, the rStO2 and rBF levels also decreased at 3 h post PDT, however the rBF values returned toward baseline values earlier at 24 h post-PDT. In contrast, the rStO2 and rBF readings in control tumors showed fluctuations above the baseline values within the first 48 h. Therefore tumor response can be predicted at 3 to 48 h post-PDT. Recovery or sustained decreases in the rBF at 48 h post-PDT corresponded to long-term tumor control. Diffuse optical measurements can thus facilitate early assessment of tumor response. This approach can enable physicians to personalize PDT treatment regimens for best outcomes.

Simultaneous blood flow and blood oxygenation measurements using a combination of diffuse speckle contrast analysis and near-infrared spectroscopy.

A combined diffuse speckle contrast analysis (DSCA)-near-infrared spectroscopy (NIRS) system is proposed to simultaneously measure qualitative blood flow and blood oxygenation changes in human tissue. The system employs an optical switch to alternate two laser sources at two different wavelengths and a CCD camera to capture the speckle image. Therefore, an optical density can be measured from two wavelengths for NIRS measurements and a speckle contrast can be calculated for DSCA measurements. In order to validate the system, a flow phantom test and an arm occlusion protocol for arterial and venous occlusion were performed. Shorter exposure times (<1 ms ) show a higher drop (between 50% and 66%) and recovery of 1/K²S values after occlusion (approximately 150%), but longer exposure time (3 ms) shows more consistent hemodynamic changes. For four subjects, the 1/K²S values dropped to an average of 82.1±4.0% during the occlusion period and the average recovery of 1/K²S values after occlusion was 109.1±0.8% . There was also an approximately equivalent amplitude change in oxyhemoglobin (OHb) and deoxyhemoglobin (RHb) during arterial occlusion (max RHb=0.0085±0.0024 mM/DPF, min OHb=-0.0057±0.0044 mM/DPF). The sensitivity of the system makes it a suitable modality to observe qualitative hemodynamic trends during induced physiological changes.

Avian embryo monitoring during incubation using multi-channel diffuse speckle contrast analysis.

Determining the survival rate of avian embryos during incubation is essential for cost-saving in the poultry industry. A multi-channel diffuse speckle contrast analysis (DSCA) system, comprising four optical fiber channels, is proposed to achieve noninvasive in vivo measurements of deep tissue flow. The system was able to monitor chick embryo vital signs over the entire incubation period. Moreover, it proved useful in distinguishing between chick embryos in healthy and weakened conditions.

Optical methods for blood perfusion measurement--theoretical comparison among four different modalities.

Blood perfusion in human tissue can be measured in vivo by means of various optical methods, which seem to be very different from one another. The most prominent examples of them are laser Doppler flowmetry, laser speckle contrast imaging, diffuse correlation spectroscopy, and the most recently developed diffuse speckle contrast analysis. In this paper, we claim that these four seemingly different modalities are examining different aspects of the same entity-the temporal autocorrelation function of scattered photons. We will show how the observables in each modality can be theoretically derived from the temporal autocorrelation function, and will discuss the merits and drawbacks of each modality in its practical use.

Hemodynamic monitoring of Chlorin e6-mediated photodynamic therapy using diffuse optical measurements.

Tumor response during photodynamic therapy (PDT) is heavily dependent on treatment parameters such as light dose, photosensitizer concentration, and tissue oxygenation. Therefore, it is desirable to have a real-time hemodynamic monitoring device in order to fine-tune the parameters and improve PDT efficacy. In this paper, such a tumor response monitoring system was built incorporating both frequency domain diffuse optical spectroscopy (FD-DOS) and diffuse correlation spectroscopy (DCS), which enables concurrent monitoring of tissue oxygenation (StO2), total hemoglobin concentration (THC) and relative blood flow (rBF). The tumor metabolic rate of oxygen (TMRO2) was calculated by using the hemodynamic parameters. Mouse models bearing xenograft tumors were subjected to chlorin e6 (Ce6)-mediated PDT, and the four parameters were monitored with varying treatment conditions. The results show (1) At 3 h post-PDT, rStO2, rBF and rTMRO2 exhibited sharp PDT-induced decreases in responders (>40% reduction in tumor volume). Statistically significant difference between responders and non-responders were observed in rStO2 and rBF, but not in rTMRO2. (2) Non-responders show gradual recovery of rStO2, rBF and rTMRO2 from ∼24 h post-PDT, while responder group did not show recovery up until 48 h post-PDT. Long-term study results up to 2 weeks are also shown. It suggests the hybrid diffuse optical system is not only capable of real-time treatment monitoring, but also able to extract tumor metabolic rate of oxygen to provide more insights about therapy mechanism. Translation of this technique to the clinic will make a quick prognosis feasible and help with treatment optimization.

Apoptosis in capillary endothelial cells in ageing skeletal muscle.

The age-related loss of skeletal muscle mass and function (sarcopenia) is a consistent hallmark of ageing. Apoptosis plays an important role in muscle atrophy, and the intent of this study was to specify whether apoptosis is restricted to myofibre nuclei (myonuclei) or occurs in satellite cells or stromal cells of extracellular matrix (ECM). Sarcopenia in mouse gastrocnemius muscle was characterized by myofibre atrophy, oxidative type grouping, delocalization of myonuclei and ECM fibrosis. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) indicated a sharp rise in apoptosis during ageing. TUNEL coupled with immunostaining for dystrophin, paired box protein-7 (Pax7) or laminin-2α, respectively, was used to identify apoptosis in myonuclei, satellite cells and stromal cells. In adult muscle, apoptosis was not detected in myofibres, but was restricted to stromal cells. Moreover, the age-related rise in apoptotic nuclei was essentially due to stromal cells. Myofibre-associated apoptosis nevertheless occurred in old muscle, but represented < 20% of the total muscle apoptosis. Specifically, apoptosis in old muscle affected a small proportion (0.8%) of the myonuclei, but a large part (46%) of the Pax7(+) satellite cells. TUNEL coupled with CD31 immunostaining further attributed stromal apoptosis to capillary endothelial cells. Age-dependent rise in apoptotic capillary endothelial cells was concomitant with altered levels of key angiogenic regulators, perlecan and a perlecan domain V (endorepellin) proteolytic product. Collectively, our results indicate that sarcopenia is associated with apoptosis of satellite cells and impairment of capillary functions, which is likely to contribute to the decline in muscle mass and functionality during ageing.

Multi-channel deep tissue flowmetry based on temporal diffuse speckle contrast analysis.

Recently, diffuse speckle contrast analysis (DSCA) was introduced as a competent modality for deep tissue blood flow measurement, where the speckle contrast is calculated over spatial domain on the CCD image of diffuse reflectance. In this paper, we introduce time-domain DSCA where temporal statistics are used for speckle contrast calculation and results in the same deep tissue flow measurement. This new modality is especially suitable for multi-channel real-time flowmetry, and we demonstrate its performance on human arm during cuff occlusion test. Independent component analysis (ICA) study on multi-channel data shows promising results about underlying physiology.

Deep tissue flowmetry based on diffuse speckle contrast analysis.

Diffuse correlation spectroscopy (DCS) is an emerging modality for noninvasive deep tissue blood flow monitoring that is becoming increasingly popular; it conducts an autocorrelation analysis of fast fluctuating photon count signals from a single speckle. In this Letter, we show that the same level of deep tissue flow information can be obtained from a much simpler analysis on the spatial distribution of the speckles that is obtained by a CCD camera, which we named diffuse speckle contrast analysis (DSCA). Both the flow phantom experiment and in vivo cuff occlusion data are presented. DSCA can be considered a new optical modality that combines DCS and laser speckle contrast imaging (LSCI), which exploits simple instrumentation and analysis and yet is sensitive to deep tissue flow.

Diffuse correlation spectroscopy with a fast Fourier transform-based software autocorrelator.

Diffuse correlation spectroscopy (DCS) is an emerging noninvasive technique that probes the deep tissue blood flow, by using the time-averaged intensity autocorrelation function of the fluctuating diffuse reflectance signal. We present a fast Fourier transform (FFT)-based software autocorrelator that utilizes the graphical programming language LabVIEW (National Instruments) to complete data acquisition, recording, and processing tasks. The validation and evaluation experiments were conducted on an in-house flow phantom, human forearm, and photodynamic therapy (PDT) on mouse tumors under the acquisition rate of ∼400 kHz. The software autocorrelator in general has certain advantages, such as flexibility in raw photon count data preprocessing and low cost. In addition to that, our FFT-based software autocorrelator offers smoother starting and ending plateaus when compared to a hardware correlator, which could directly benefit the fitting results without too much sacrifice in speed. We show that the blood flow index (BFI) obtained by using a software autocorrelator exhibits better linear behavior in a phantom control experiment when compared to a hardware one. The results indicate that an FFT-based software autocorrelator can be an alternative solution to the conventional hardware ones in DCS systems with considerable benefits.

Coherent backscattering cone shape depends on the beam size.

Coherent backscattering (CBS) is a beautiful physical phenomenon that takes place in a highly scattering medium, which has potential application in noninvasive optical property measurement. The current model that explains the CBS cone shape, however, assumes the incoming beam diameter is infinitely large compared to the transport length. In this paper, we evaluate the effect of a finite scalar light illumination area on the CBS cone, both theoretically and experimentally. The quantitative relationship between laser beam size and the CBS cone shape is established by using two different finite beam models (uniform top hat and Gaussian distribution). A series of experimental data with varying beam diameters is obtained for comparison with the theory. Our study shows the CBS cone shape begins to show distortion when beam size becomes submillimeter, and this effect should not be ignored in general. In biological tissue where a normal large beam CBS cone is too narrow for detection, this small beam CBS may be more advantageous for more accurate and higher resolution tissue characterization.

Optical mammography: Diffuse optical imaging of breast cancer.

Existing imaging modalities for breast cancer screening, diagnosis and therapy monitoring, namely X-ray mammography and magnetic resonance imaging, have been proven to have limitations. Diffuse optical imaging is a set of non-invasive imaging modalities that use near-infrared light, which can be an alternative, if not replacement, to those existing modalities. This review covers the background knowledge, recent clinical outcome, and future outlook of this newly emerging medical imaging modality.

Nanoarray-based biomolecular detection using individual Au nanoparticles with minimized localized surface plasmon resonance variations.

Here, we present a mean to expand the use of individual metallic nanoparticles to two-dimensional plasmonic nanoarrays. An optical detection platform to track down localized surface plasmon resonance (LSPR) signals of individual nanoparticles on substrates was built for the application of plasmonic nanoarrays. A pseudoimage of nanoparticles on a substrate was reconstructed from their scattering spectra obtained by scanning a user-defined area. The spectral and spatial resolutions of the system were also discussed in detail. Most importantly, we present a method to normalize the localized surface plasmon resonance from geometrically different nanoparticles. After normalization, plasmonic responses from different particles become highly consistent, creating well-fitted dose-response curves of both surrounding refractive index changes and receptor-analyte binding to the surface of individual nanoparticles. Finally, the proof-of-concept system for plasmonic nanoarray detection is demonstrated by the measurement of the aptamer-thrombin binding event.