Time-sequential Images Research Articles

Dynamic imaging of a small artery underneath skin surface of a human finger by optical coherence tomography

OCT is a powerful tool for detection of physiological functions of micro organs underneath the human skin surface, besides the clinical application to ophthalmology, as recently demonstrated by the authors’ group. In particular, dynamics of peripheral vessels can be observed clearly in the time-sequential OCT images. Among the vascular system, only the small artery has two physiological functions both for the elastic artery and for muscle-controlled one. It, therefore, is important for dynamic analysis of blood flow and circulation. In the time-sequential OCT images obtained with 25 frames/sec, it is found that the small artery makes a sharp response to sound stress for contraction and expansion while it continues pulsation in synchronization with the heartbeats. This result indicates that the small artery exhibits clearly the two physiological functions for blood flow and circulation. In response to sound stress, blood flow is controlled effectively by thickness change of the tunica media which consists of five to six layers of smooth muscles. It is thus found that the thickness of the tunica media changes remarkably in response to external stress, which shows the activity of the sympathetic nerve. The dynamic analysis of the small artery presented here will allow us not only to understand the mechanism of blood flow control and also to detect abnormal physiological functions in the whole vascular system.

Dynamic Analysis of Mental Sweating by the Time-Sequential Piled-Up En-Face OCT Images

In this paper, the dynamic analysis of mental sweating for sound stimulus of a few tens of eccrine sweat glands is performed by the time-sequential piled-up en-face optical coherence tomography (OCT) images with the frame spacing of 3.3 sec. In the experiment, the amount of excess sweat can be evaluated simultaneously for a few tens of sweat glands by piling up of all the en-face OCT images. Strong non-uniformity is observed in mental sweating where the amount of sweat in response to sound stimulus is different for each sweat gland. Furthermore, the amount of sweat is significantly increased in proportion to the strength of the stimulus.

Observation of fundus using a novel high‐speed and high resolution optical coherent tomography: a preliminary report

AbstractPurpose to evaluate capability of femto‐second white laser in observing the fundus when applying it to optical coherent tomography (OCT) as a light source.Methods We have successfully developed 8 fs cw mode0locked Titanium Sapphire (TiS) laser which had broad band with ranging from 650 nm down to 950 nm. Using this laser, over 200 nm bandwidth portion ranging from 750 nm down to 950 nm pulse was created.. Acquistion time of one OCT image is o.o2 second and vertical resolution in the air is 2 μm in the air. Horizontal resolution is less than1 μm. High‐speed acquisition time allows us to observe time sequential OCT images like an OCT movie for one second using a computer soft ware. Fundus examination using this OCT system was performed in eyes of healthy volunteers and patients with age‐related macular degeneration (AMD) under approval of IRB. Effect of indocyanine green (ICG) in OCT images was also evaluated in the AMD patients when who has a routine ICG examination at clinic.Results Pulsative movement of choroidal vasculature and retinal vessels at the optic disc head could be observed in motion OCT images. Single scan OCT image of healthy macula delineated four distinctive lines in stead of three when observed with a conventional SD‐OCT, particularly in images scanned through extra fovea. Furthermore, as structure of the optic nerve head was clearly illustrated, so a manner of optic nerve how getting through the lamina cribrosa was well appreciated.Conclusion Femto‐second laser OCT is a promising tool to explore a new dimension of clinical ophthalmology particularly in examining AMD as well as glaucoma patients. Commercial interest

Extending Microscopic Resolution with Single-Molecule Imaging and Active Control

Superresolution imaging of biological structures provides information beyond the optical diffraction limit. One class of superresolution techniques uses the power of single fluorescent molecules as nanoscale emitters of light combined with emission control, variously described by the acronyms PALM/FPALM/STORM and many others. Even though the acronyms differ and refer mainly to different active-control mechanisms, the underlying fundamental principles behind these "pointillist" superresolution imaging techniques are the same. Circumventing the diffraction limit requires two key steps. The first step (superlocalization) is the detection and localization of spatially separated single molecules. The second step actively controls the emitting molecules to ensure a very low concentration of single emitters such that they do not overlap in any one imaging frame. The final image is reconstructed from time-sequential imaging and superlocalization of the single emitting labels decorating the structure of interest. The statistical, imaging, and active-control strategies for achieving superresolution imaging with single molecules are reviewed.

A Depth Video-based Facial Expression Recognition System

Video cameras are being actively used with a lot of functions in many applications nowadays. In this paper, a depth camera-based new method is proposed to recognize several facial expressions from time-sequential depth images. At first, Independent Component (IC) features are extracted from the time-sequential depth faces that are further improved by Generalized Discriminant Analysis (GDA) to generate more robust features. Finally, Hidden Markov Models (HMMs) are utilized to train and recognize different facial expressions successfully. Performance of the proposed facial expression recognition system is compared against conventional RGB camera-based approaches and obtained superior recognition rate over them.

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Stereoscopic multi-user systems provide multiple users with individual views of a virtual environment. We developed a new projection-based stereoscopic display for six users, which employs six customized DLP projectors for fast time-sequential image display in combination with polarization. Our intelligent high-speed shutter glasses can be programmed from the application to adapt to the situation. For instance, it does this by staying open if users do not look at the projection screen or switch to a VIP high brightness mode if less than six users use the system. Each user is tracked and can move freely in front of the display while perceiving perspectively correct views of the virtual environment. Navigating a group of six users through a virtual world leads to situations in which the group will not fit through spatial constrictions. Our augmented group navigation techniques ameliorate this situation by fading out obstacles or by slightly redirecting individual users along a collision-free path. While redirection goes mostly unnoticed, both techniques temporarily give up the notion of a consistent shared space. Our user study confirms that users generally prefer this trade-off over naïve approaches.

Dynamic analysis for mental sweating of a group of eccrine sweat glands on a human fingertip by optical coherence tomography

An important function of skin physiology is mental sweating, where sweating is accelerated via the sympathetic nerve by mental or physical stress externally applied to a volunteer. Activity of the sympathetic nerve (ASN) is evaluated by quantitative measurement of mental sweating. Optical coherence tomography (OCT) is highly potential for in vivo observation of human sweating dynamics which affects ASN. We demonstrate dynamic OCT analysis of mental sweating of a group of eccrine sweat glands. The sweating dynamics is tracked simultaneously for 19 sweat glands by time-sequential piled-up en-face OCT images with the frame spacing of 3.3 s. The en-face OCT images of the spiral lumen of the eccrine sweat gland are constructed by data acquisition of the 128 B-mode OCT images. It is thus found that the response to mental stress is different for each sweat gland even though the sweat glands are adjacent to each other. Such strong non-uniformity is observed in mental sweating where the amount of excess sweat is different for each sweat gland although the sweat glands are adjacent to each other. The non-uniformity should be necessary to adjust as precisely the total amount of excess sweat as possible through the sympathetic nerve in response to strength of the stress.

Lifetime-based phosphor thermometry of an optical engine using a high-speed CMOS camera

The surface temperature inside an optical engine was measured both with and without heating the intake gas. The temperature distribution was measured by lifetime-based phosphor thermometry using 10 time-sequential images during a single decay recorded by a non-intensified high-speed complementary metal oxide semiconductor camera and by accounting for the pixel-to-pixel variation in the nonlinearity of the sensor. Consequently, the system was simple and compact. One goal of this research is to use a single camera to measure the temperature field because it is easy to use such a system in practical experiments. The shot-to-shot standard deviation of the decay constant for uniform temperature conditions was 0.17–0.33% at 80–160 °C and it varied ±0.15% with position, indicating that the pixel nonlinearity is highly nonuniform. The present measurement method had a measurement error of −2.25 to 1.15 °C and it exhibited a similar level of shot-to-shot fluctuations (±0.42–2.34 °C). This technique was used to measure the temperature in an optical engine and it gave reasonable temperature maps.

Viscoelastic characterization of the retracting cytoskeleton using subcellular detachment

Characterization of the cytoskeleton’s viscoelastic properties is essential for understanding cellular dynamics in many biological functions of the cell, especially cell migration. The viscoelastic properties of the retracting NIH 3T3 fibroblasts are investigated here to shed light on the mechanics and dynamics of cell migration. A part of the cell is detached by electrochemically desorbing a gold-thiol self-assembled monolayer. The viscoelastic properties of the detached and retracting cytoskeleton are then estimated using time-sequential imaging combined with atomic force microscopy. The retracting cytoskeleton exhibits a threefold decrease in stiffness and a 30-fold increase in viscous damping capacity as compared to those in the adhered (stationary) cytoskeleton.

A Novel Human Action Recognition Algorithm Based on Edit Distance

A novel human action recognition algorithm based on edit distance is proposed in this paper. In the method, the mesh feature of each image in human action sequence is firstly calculated; then the feature vectors are quantized through a rival penalized competitive neural network; and through this processing, the time-sequential image sequences are converted into symbolic sequences. For human action recognition, the observed action is firstly vector quantized with the former competitive neural network; then the normalized edit distances to the training samples are calculated and the action which best matches the observed sequence is chosen as the final category. The experiments on Weizmann dataset demonstrate that our method is effective for human action recognition. The average recognition accuracy can reach above 94%.

Visualizing supersonic inlet duct unstart using planar laser Rayleigh scattering

Planar laser Rayleigh scattering (PLRS) from condensed CO2 particles is used to visualize flow structure in a Mach 5 wind tunnel undergoing unstart. Detailed flow features such as laminar/turbulent boundary layers and shockwaves are readily illustrated by the technique. A downstream transverse air jet, inducing flow unchoking downstream of the jet, is injected into the free stream flow of the tunnel, resulting in tunnel unstart. Time sequential PLRS images reveal that the boundary layer growth/separation on a surface with a thick turbulent boundary layer, initiated by the jet injection, propagates upstream and produces an oblique unstart shock. The tunnel unstarts upon the arrival of the shock at the inlet. In contrast, earlier flow separation on the opposite surface, initially supporting a thin laminar boundary layer, is observed when a jet induced bow shock strikes that surface. The resulting disturbance to this boundary layer also propagates upstream and precedes the formation of an unstart shock.

Regional-scale boreal forest cover and change mapping using Landsat data composites for European Russia

Boreal forests are a critical component of the global carbon cycle, and timely monitoring allows for assessing forest cover change and its impacts on carbon dynamics. Earth observation data sets are an important source of information that allow for systematic monitoring of the entire biome. Landsat imagery, provided free of charge by the USGS Center for Earth Resources Observation and Science (EROS) enable consistent and timely forest cover updates. However, irregular image acquisition within parts of the boreal biome coupled with an absence of atmospherically corrected data hamper regional-scale monitoring efforts using Landsat imagery. A method of boreal forest cover and change mapping using Landsat imagery has been developed and tested within European Russia between circa year 2000 and 2005. The approach employs a multi-year compositing methodology adapted for incomplete annual data availability, within-region variation in growing season length and frequent cloud cover. Relative radiometric normalization and cloud/shadow data screening algorithms were employed to create seamless image composites with remaining cloud/shadow contamination of less than 0.5% of the total composite area. Supervised classification tree algorithms were applied to the time-sequential image composites to characterize forest cover and gross forest loss over the study period. Forest cover results when compared to independently-derived samples of Landsat data have high agreement (overall accuracy of 89%, Kappa of 0.78), and conform with official forest cover statistics of the Russian government. Gross forest cover loss regional-scale mapping results are comparable with individual Landsat image pair change detection (overall accuracy of 98%, Kappa of 0.71). The gross forest cover loss within European Russia 2000–2005 is estimated to be 2210 thousand hectares, and constitutes a 1.5% reduction of year 2000 forest cover. At the regional scale, the highest proportional forest cover loss is estimated for the most populated regions (Leningradskaya and Moskovskaya Oblast). Our results highlight the forest cover depletion around large industrial cities as the hotspot of forest cover change in European Russia.

In Vivo Microscopic Approaches for Facial Melanocytic Lesions after Quality-Switched Ruby Laser Therapy: Time-Sequential Imaging of Melanin and Melanocytes of Solar Lentigo in Asian Skin

The quality-switched ruby laser (QSRL) has been widely used for the treatment of pigmented lesions, but clinical evaluations in most studies have been conducted on macroscopic skin color observation comparing the laser-treated skin with its nontreated surrounding area. A few investigations examined skin changes after laser therapy at a cellular level, but almost none did so noninvasively. To elucidate the dynamic changes after QSRL irradiation of facial solar lentigo using noninvasive optical techniques. Time-sequential imaging of Japanese female patients with a clinical diagnosis of solar lentigo was performed using ultraviolet photography, high-magnification videomicroscopy, and reflectance-mode confocal microscopy to examine pigmentary change after QSRL irradiation. The present study showed that remaining melanocytes were visible in the solar lentigo of all subjects when crusts peeled off, despite hardly observable skin pigmentation to the naked eye. Moreover, noninvasive confocal imaging revealed that pigmented melanocytes varied in each solar lentigo after QSRL treatment, as indicated by melanin reflection level. Optical techniques facilitate the evaluation of the in vivo dynamics of epidermal-melanocytic changes in solar lentigo after QSRL therapy and may be useful for monitoring outcomes after laser irradiation.

Dissolution kinetics of calcite at 50–70 °C: An atomic force microscopic study under near-equilibrium conditions

Direct measurements of calcite ( 10 1 ¯ 4 ) faces were performed using in situ atomic force microscopy (AFM) to reveal the dissolution processes as a function of solution saturation state and temperature. Time-sequential AFM images demonstrated that step velocities at constant temperature increased with increasing undersaturation. The anisotropy of obtuse and acute step velocities appeared to become more significant as solutions approached equilibrium and temperature increased. At saturation state Ω > 0.02, a curvilinear boundary was formed at the intersection of two acute steps and the initially rhombohedral etch pit exhibited a nearly triangular shape. This suggests that the [ 4 ¯ 41 ] a and [ 48 1 ¯ ] a steps may not belong to the calcite-aqueous solution equilibrium system. Further increase in the saturation state ( Ω ⩾ 0.3) led to a lack of etch pit formation and dissolution primarily occurred at existing steps, in accordance with Teng (2004). Analysis of step kinetics at different temperatures yielded activation energies of 25 ± 6 kJ/mol and 14 ± 13 kJ/mol for obtuse and acute steps, respectively. The inconsistencies in etch pit morphology, step anisotropy, and step activation energies from the present study with those of studies far-from-equilibrium can be explained by increased influence of the backward reaction, or growth, near-equilibrium. We propose that the backward reaction occurs preferentially at the acute–acute kink sites. The kinetics and effective activation energies of near-equilibrium calcite dissolution presented in this work provide accurate experimental data under likely CO 2 sequestration conditions, and thus are crucial to the development of robust geochemical models that predict the long-term performance of mineral-trapped CO 2.

Choriocapillary blood propagation in normal volunteers and in patients with central serous chorioretinopathy

Background/aimsTo evaluate early choroidal vascular dye-filling and dye propagation patterns in normal subjects and in patients with central serous chorioretinopathy (CSC) using indocyanine green (ICG) angiography.MethodsSeventeen healthy volunteers (21–81 years...

An enhanced independent component-based human facial expression recognition from video

Facial expression recognition (FER) from video is an essential research area in the field of human computer interfaces (HCI). In this work, we present a new method to recognize several facial expressions from time sequential facial expression images. To produce robust facial expression features, enhanced independent component analysis (EICA) is utilized to extract locally independent component (IC) features which are further classified by Fisher linear discriminant analysis (FLDA). Using these features, discrete hidden Markov models (HMMs) are utilized to model different facial expressions such as joy, anger, and sad. Performance of our proposed FER system is compared against four other conventional feature extraction approaches (i.e., PCA, PCA-FLDA, ICA, and EICA) in conjunction with the same HMM scheme. The experimental results using the Cohn-Kanade database of facial expression videos show that our proposed system yields much improved recognition rate reaching the mean recognition rate of 93.23% whereas the conventional methods yield 82.92% at best.

Using conventional fluorescent markers for far‐field fluorescence localization nanoscopy allows resolution in the 10‐nm range

We present a novel technique of far-field localization nanoscopy combining spectral precision distance microscopy with widely used fluorochromes like the Green Fluorescent Protein (GFP) derivatives eGFP, EmGFP, Yellow Fluorescent Protein (YFP) and eYFP, synthetic dyes like Alexa 488 and Alexa 568, as well as fluoresceine derivates. Spectral precision distance microscopy allows the surpassing of conventional resolution limits in fluorescence far-field microscopy by precise object localization after the optical isolation of single signals in time. Based on the principles of this technique, our novel nanoscopic method was realized for laser optical precision localization and image reconstruction with highly enhanced optical resolution in intact cells. This allows for spatial assignment of individual fluorescent molecules with nanometre precision. The technique is based on excitation intensity dependent reversible photobleaching of the molecules used combined with fast time sequential imaging under appropriate focusing conditions. A meaningful advantage of the technique is the simple applicability as a universal tool for imaging and investigations to the major part of already available preparations according to standard protocols. Using the above mentioned fluorophores, the positions of single molecules within cellular structures were determined by visible light with an estimated localization precision down to 3 nm; hence distances in the range of 10-30 nm were resolved between individual fluorescent molecules allowing to apply different quantitative structure analysis tools.

Classifying pretended and evoked facial expressions of positive and negative affective states using infrared measurement of skin temperature

Earlier researchers were able to extract the transient facial thermal features from thermal infrared images (TIRIs) to make binary distinctions between the expressions of affective states. However, effective human-computer interaction would require machines to distinguish between the subtle facial expressions of affective states. This work, for the first time, attempts to use the transient facial thermal features for recognizing a much wider range of facial expressions. A database of 324 time-sequential, visible-spectrum, and thermal facial images was developed representing different facial expressions from 23 participants in different situations. A novel facial thermal feature extraction, selection, and classification approach was developed and invoked on various Gaussian mixture models constructed using: neutral and pretended happy and sad faces, faces with multiple positive and negative facial expressions, faces with neutral and six (pretended) basic facial expressions, and faces with evoked happiness, sadness, disgust, and anger. This work demonstrates that (1) infrared imaging can be used to observe the affective-state-specific facial thermal variations, (2) pixel-grey level analysis of TIRIs can help localise significant facial thermal feature points along the major facial muscles, and (3) cluster-analytic classification of transient thermal features can help distinguish between the facial expressions of affective states in an optimized eigenspace of input thermal feature vectors. The observed classification results exhibited influence of a Gaussian mixture model's structure on classifier-performance. The work also unveiled some pertinent aspects of future research on the use of facial thermal features in automated facial expression classification and affect recognition.

Dynamic analysis of internal and external mental sweating by optical coherence tomography

Mental sweating is human sweating that is accelerated via the sympathetic nerve by application of mental or physical stress. In the neurosciences, there is keen interest in this type of sweating, because the amount of sweat in response to a stress applied to a volunteer directly reflects activity of the sympathetic nerve. It is therefore of particular value that optical coherence tomography (OCT) can provide clear in vivo imaging of the spiral lumen of an eccrin sweat gland in the epidermis with a spatial resolution around 10 mum. We demonstrate dynamic OCT of mental sweating of an eccrin sweat gland on a human fingertip, where the sweating dynamics can be tracked by time-sequential OCT images with a frame spacing of one second. An instantaneous amount of sweat stored in the spiral lumen is evaluated quantitatively in each OCT image, resulting in time variation measurements of excess sweat in response to mental or physical stress. In the dynamic OCT of mental sweating, as demonstrated here, we note for the first time internal sweating without ejection of excess sweat from the spiral lumen to the skin surface. Internal sweating has not been previously detected without the availability of our dynamic OCT technique. Until now, it has been commonly accepted that sweating is always accompanied with ejection of excess sweat to the skin surface. On the basis of our findings reported here, this type of sweating should now be referred to as external sweating. In this study, we demonstrate that internal sweating occurs more often in the case where mental stress is applied to a volunteer, and that it is more useful for evaluation of activity of the sympathetic nerve. The dynamic OCT for both external and internal sweating is demonstrated.

Tomographic imaging of airglow from airborne spectroscopic measurements

A description is given of the methodology based on a single, aircraft-mounted spectroscopic imager to tomographically reconstruct airglow perturbations induced by atmospheric gravity waves. In this configuration, the imager passes under the airglow structure to gather multiple-angle views of the wave structure in a relatively short amount of time. Under the assumption that the airglow structure does not change significantly during the acquisition interval, the data can be tomographically inverted to estimate the 2D (horizontal-vertical) airglow structure. We develop an inversion strategy for this image formation task and illustrate its applicability by inverting time-sequential imaging data taken from different vantage points during the ALOHA-93 campaign to reconstruct atmospheric gravity wave structures.