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The Sidestream Dark Field (SDF) Handheld Imaging Device


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     Now medical studies have shown that there is a very clear and good correlation between sublingual microcirculation and human visceral microcirculation. Therefore observation of sublingual microcirculation can infer the status of visceral microcirculation (microvascular)

     The sidestream dark field (sidestream dark visual field) detection system  can detect microcirculation (microvascular) blood flow status of large animals such as sheep, pigs, or even rat skulls (rat skull microvascular,rat head microvascular,rat microvascular,rat microcirculation), (rat skull microvascular,rat head microvascular,rat microvascular,rat microcirculation) . Because existing standard test samples are mostly made based on rat blood vessels, it is very convenient for researchers to compare microcirculation status detected in rat skulls by our device to standard test models of rats.

The Sidestream Dark Field (SDF) Handheld Imaging Device

(Microvascular (blood) image observation instrument,Sidestream Dark Field (SDF) microscopy,sidestream dark field imaging (SDF))

       Microvascular (blood) image observation instrument

       

      The microvessel (blood) image observation instrument(Sidestream Dark Field (SDF) Handheld Imaging Device ) use SDF technology, observe the special parts of the animal or human blood flow changes.
The condition of the blood vessels and blood of experimental animals can provide for the animal experiments, in order to cardiovascular disease in experimental animals blood poisoning、sepsis and failure early noninvasive monitoring and scientific data, and provide scientific data for the human disease.
Its technical characteristics are as follows:
(1) Use SDF technology, can observe animal or person special parts such as the tongue, kidney and other parts of the blood flow changes.
(2)can provide the number of capillaries, vascular caliber and velocity, TVD / PVD, PPV, / MFI of experimental animals of data , and so on .
(3) equipment with convenience, can be carried out directly noninvasive observed in the laboratory experiments bedside characteristics, operation is simple.

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Sublingual microcirculation
Vladimir Cerny1,2
1 Department of Anesthesiology and Intensive Care Medicine, University Hospital
Hradec Kralove, Czech Republic 2 Department of Anesthesia, Dalhousie University, Halifax, Canada

Abstract
Microcirculation plays a crucial role in the interaction between blood and tissue both in physiolog¬ical and pathophysiological states. Orthogonal polarization spectral (OPS) and Side stream dark field (SDF) imaging sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrumentare relatively new noninvasive methods that allow the investigation of mucos¬al sites, especially sublingual area, particularly in critically ill patients. OPS imaging has been val¬idated against conventional capillary microscopy, results demonstrated that OPS images provided similar values for RBC-velocity and capillary diameter as those measured by conventional capillary microscopy. Despite some limitations, sublingual microcirculation has been considered as a possi¬ble surrogate measure for splanchnic blood flow. There are several areas in human medicine, where observation of sublingual microcirculatory bed has been carried out C different kinds of shock, cardiac arrest, effect of various treatments, drugs and extreme physiological conditions as well. Early detection of microvascular abnormality seems to be a key factor to start early therapeu¬tic intervention in order to reverse microvascular dysfunction, to maintain efficient microvascular flow and to contribute to better clinical outcome. In experimental setting, observing sublingual microcirculation is an important part of any research focused on the role of microcirculation dur¬ing various diseases models and to assess effect of different treatment modalities on microcircula¬tion.
Key words: Microcirculation, sublingual, Orthogonal polarization spectral imaging (OPS), Side stream dark field (SDF) imaging sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument
Introduction standing of microcirculatory pathology in its
molecular level, especially in critically ill pa-Microcirculation plays a crucial role in the tients (5, 8, 9). The gold standard for assess¬interaction between blood and tissue both in ment of microcirculation is intravital mi¬physiological and pathophysiological states. croscopy (IVM). However, this technique Analysis of microvascular blood flow alter-cannot be performed in humans because ations gives a unique perspective to study there is a need for fluorescent dyes and tran¬processes at the microscopic level in clinical sillumination. The size of instrumentation for medicine (1). Despite the critical role of mi-IVM can be also a limiting factor for its use crocirculation in numerous diseases includ-in clinical medicine. For many years, capil¬ing diabetes, hypertension, sepsis or multiple lary microscopy (capillaroscopy, nailfold organ failure (2-5), methods for direct visual-videomicroscopy) has been the only method ization and quantitative assessment of the for assessment of the human microcircula¬human microcirculation at the bedside are tion at the microscopic level in vivo. The use limited (6). The interest in microhemody-of this technique in humans is limited to eas¬namic monitoring (7) grows with the under-ily accessible surfaces like the skin, nailfold,
lip or the bulbar conjunctiva (10). The nail¬fold microcirculation is extremely sensitive to external temperature and vasoconstrictive agents (11) and the nailfold videomicroscopy may not be a reliable indicator of microcircu¬lation in other parts of the body, particularly in critically ill patients. Orthogonal polariza¬tion spectral (OPS) and Side stream dark field (SDF) imaging sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument represent relatively new non¬invasive methods that allow the investigation of mucosal sites, especially sublingual area. There is growing evidence that relationship between microcirculatory dysfunction and clinical outcome exists (12, 13). Neverthe¬less, this technique may be used in experi¬mental settings as well. Access to sublingual area seems to be very easy, however the key question is whether this area represents mi¬crocirculation status of other body tissues or organs; nevertheless, sublingual area repre¬sents one of the best accessible mucosa sur¬faces in humans.
Figure 1: Anatomy of sublin¬gual area (adapted from Klijn, 2008)
Anatomy
The sublingual area is one of the easiest to access areas in human mucosal surfaces. The major arteries supplying this area are the ex¬ternal carotid artery, the lingual artery and the sublingual artery (9, 14-16) (Figure 1). Only limited number of sublingual arterioles are present, whereas numerous capillaries (less than 20 um) and venules (20-100 um) are present in this area (9, 17, 18). External carotid artery contributes to the perfusion of sublingual mucosa and therefore sublingual perfusion may reflect cerebral blood flow as well (9). Despite this fact, only few studies focus on this relationship (19, 20). Sublin¬gual microcirculation has been considered as a surrogate measure for splanchnic blood flow, mainly because 1) the tongue and relat¬ed areas share a common embryogenic ori¬gin with the gut and 2) the close correlation between sublingual capnometry and gastric tonometry (21-24).
sidestream dark field (SDF) handheld imaging device
Imaging techniques
Orthogonal Polarization Spectral Imaging and Side Stream Dark Field (SDF) Imaging (sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)
Orthogonal Polarization Spectral Imaging (OPS) technology was invented by Cytomet¬rics, Inc. (Philadelphia, PA, USA) during the process of developing a videomicroscope able to create high contrast images of blood in the microcirculation using reflected light. The original purpose was to develop an in¬strument for analyzing images of the micro¬circulation using spectrophotometry in order to compute a complete blood count (CBC) without removing blood from the body (25,26).
In conventional reflectance imaging (CRI), high-quality image contrast and detail are limited by multiple surface scattering and turbidity of the surrounding tissue (25). In OPS imaging, the main difference from CRI consists in the phenomenon of cross-polar¬ization that reduces these effects. As shown in schematic figure (Figure 2), incident light is linearly polarized in one plane and pro¬jected through a beam splitter onto the sub¬ject. Most of the reflected light keeps its po¬larization and cannot pass through the or¬thogonal polarizer (analyzer) to form the im¬age. The light that penetrates the tissue more deeply and undergoes multiple scattering events becomes depolarized. There is evi¬dence that more than ten scattering events are necessary to depolarize the light effec¬tively (27, 28). Hence, only this depolarized scattered light passing through orthogonal polarizer (analyzer) effectively back-illumi¬nates absorbing material in the foreground. A wavelength of the emitted light (548 nm) was chosen to achieve optimal imaging of the microcirculation because at this wave¬length oxy- and deoxy-hemoglobin absorb the light equally. Thus, the blood vessels of the microcirculation can be visualized by OPS imaging. A detailed description of OPS imaging technology and further technical im¬provement has been published previously (26,29). A new device based on OPS tech¬nology has been developed C Side stream dark field (SDF) imaging sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument. In this modality a
Side stream dark field (SDF) imaging
light guide imaging the microcirculation is surrounded by light-emitting diodes of a wavelength (530 nm) absorbed by the hemo¬globin of erythrocytes so that they can be clearly observed as flowing cells. Covered by a disposable cap the probe is placed on tissue surfaces. This way of observing the mi¬crocirculation provides clear images of the capillaries without blurring (Figure 3) (30, 31). Recent clinical studies of the human mi¬crocirculation using OPS imaging (Side stream dark field (SDF) imagingsidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)in various pathological states have shown a wide spec¬ trum of different clinical applications with evident impact on diagnosis, treatment or prognosis assessment. Thus, there is a great effort to validate OPS imaging for various clinical purposes. The validation experimen¬tal studies are mostly based on comparison of IVM and OPS imaging where IVM is sup¬posed to be a gold standard for main micro¬circulation parameters assessment (32-34). OPS imaging has been validated especially in animals (32,35,36) and partly in humans (37). Current knowledge on the microcircu-
sidestream dark field (SDF) handheld imaging device
Figure 3: SDF imaging(Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument), optical scheme. (1) Green light is emitted by (2) peripheral 540 \ 50 nm light¬emitting diodes (LEDs) toward tissue arranged in a circle at the end of the light guide. The microcir¬culation is directly penetrated and illuminated from the side by green light absorbed by hemoglobin of erythrocytes which are observed as (3) dark moving cells. Imaging central part of light guide (4) is optically isolated from LEDs. A magnifying lens (5) projects the image onto a camera (6) (adapted from Cerny et al, 2006)
lation is mainly derived from animal studies. Measurements of the microcirculation in hu¬mans were limited to easily accessible sur¬faces such as skin and nailfold capillaries. The basic validation studies in animals have been performed both on peripheral tissues and solid organs. OPS imaging techniques (Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)has been validated using a highly standard¬ized model of the hamster dorsal skinfold chambre (38). Four main parameters were measured to validate CYTOSCANTM A/R against standard fluorescent videomi¬croscopy under normal conditions and in is¬chemia/reperfusion injury: functional capil¬lary density (FCD), arteriolar and venular di¬ameter and venular red blood cell (RBC) ve¬locity. There were not significant differences between the two techniques for any of the parameters using Bland-Altman analysis. Similar validation study in ischemia/reperfu¬sion injury realized using the CYTOSCAN E-II has confirmed the comparability of OPS imaging and IVM (38). Functional capillary density is defined as the length of perfused capillaries per unit area and is given in cm/cm2. The FCD is a parameter of the tissue perfusion and an indirect indicator of the oxygen delivery. It is widely used in clinical studies as semiquantitative method to deter¬mine capillary density and the proportion of perfused capillaries. OPS imaging (Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)was also validated against IVM in mouse skin flaps and cremaster muscle preparations. The ve¬locities in straight vessels were comparable in both methods (39). The dorsal skinfold chamber model in hamsters was also used to validate OPS imaging under conditions of hemodilution with a wide range of hemat¬ocrit (Hct) (38). Bland-Altman analysis of the vessel diameter and FCD showed good agreement between OPS imaging technique and IVM at a wide range of Hct. OPS imag¬ing has been validated against IVM on solid organs in rats, the model of ischemia/reper¬fusion injury of the rat liver has been used for the assessment of hepatic microcirculation applying both techniques (40). There was significant agreement for data obtained from both methods; correlation parameters for si¬
nusoidal perfusion rate, vessel diameter and venular RBC velocity were significant. The pancreatic microcirculation has also been under investigation using OPS imaging (Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument,)and IVM (41). Absolute values of the pancreatic functional capillary density were not signifi¬cantly different between the two methods. Bland-Altman analyses confirmed good agreement between OPS imaging and IVM. Thus, OPS imaging is a suitable tool for quantitative assessment of pancreatic capil¬lary perfusion during baseline conditions. A murine model of inflammatory bowel dis¬ease was applied to validate OPS imaging against IVM for the visualization of colon mi¬crocirculation (42). Postcapillary venular di¬ameter, venular RBC velocity and FCD were analyzed. All parameters correlated signifi¬cantly between the both methods. The as¬sessment of antivascular tumour treatment using OPS imaging and IVM showed excel¬lent correlation in FCD, diameter of mi¬crovessels and RBC velocity between both techniques (35). Validation studies in hu¬mans are limited to easily accessible sur¬faces; fluorescent intravital microscopy is excluded because of need to use fluorescent dye. Thus, OPS imaging has been validated against conventional capillary microscopy in nailfold skin at rest and after venous occlu¬sion in healthy volunteers (37). Results demonstrated that OPS images provided sim¬ilar values for RBC-velocity and capillary di¬ameter as those measured by conventional capillary microscopy.
Technical limitations
Despite further development and technical improvement in OPS and SDF imaging (Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)de¬vices (CYTOSCANTM, MicroScanTM www.mi¬crovisionmedical.com) several limitations re¬main. There are two main conditions for suc¬cessful OPS/SDF imaging. 1. to create an im¬age of high quality 2. to evaluate the images as quantitatively as possible. Three basic technical limitations have been defined pre¬viously (Lindert et al., n d): undesirable pres¬sure of the probe affects blood flow, lateral
movement of tissue precludes continuous in¬vestigation of selected microvascular region, and blood flow velocities above 1 mm/s are difficult to measure, thus information on ar¬teriolar flow remains hidden. Stabilizing de¬vice which maintains a fixed distance be¬tween probe and tissue has been developed to eliminate movement and pressure artefact as much as possible (43). Image analysis ac¬cording to the principle of spatial correlation allows extending the range of detectable blood flow velocities to over 20 mm/s.
The methods for image analysis and quan¬tification in clinical practise has been report¬ed previously (44), further analysis improve¬ment using flow scoring system has been published recently (33). The technology of OPS-SDF imaging (Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)has been incorporated into a small hand-held video-microscope, which can be used in clinical setting. OPS imaging can assess tissue perfusion using FCD param¬eter, which is a sensitive parameter for deter¬mining the status of perfusion to the tissue
and also an indirect measure of oxygen deliv¬ery. The most easily accessible site in humans is the mouth, where OPS/SDF technology produces excellent images of the sublingual microcirculation (Figure 4). However, several limitations should be acknowledged. Secre¬tions and movement artefacts may impair im¬age quality. In addition, movement artefacts can spuriously interrupt flow in some mi¬crovessels. To limit movement artefacts and to decrease the risk of pressure artefacts, use of stabilization devices has been proposed (43). Moreover, current OPS/SDF technology (Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)can investigate only tissues covered by a thin epithelial layer and therefore internal organs are not accessible, except for perioperative use. Another major problem with OPS/SDF imaging is the great variability of the vessels measured. Identical site of interest cannot be examined over time in contrast to intravital microscopy in animal experiments (e.g. skin¬fold chamber). Movement artefacts, uncon¬trolled application pressure, semi quantitative
sidestream dark field (SDF) handheld imaging device
Figure 4: Image of human sublingual microcirculation. SDF imaging (Side stream dark field (SDF) imaging ,sidestream dark field (SDF) handheld imaging device ,Sidestream Dark Field (SDF) microscopy,Microvascular (blood) image observation instrument)of sublingual area in a healthy volunteer (male, 48 years), captured by MicroScan Video Microscope System
......and so on

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