Comparison of OPS imaging and conventional capillary microscopy to study the human microcirculation.

Orthogonal polarization spectral (OPS) imaging is a new clinical technique for observation of the microcirculation of organ surfaces. For validation purposes, we compared OPS images of the nailfold skin with those obtained from conventional capillary microscopy at rest and during venous occlusion in 10 male volunteers. These images were computer analyzed to provide red blood cell velocity and capillary diameters of the same nailfold capillaries at rest and during venous occlusion. Results showed that OPS images provided similar values for red blood cell velocity and capillary diameter as those obtained from capillary microscopy images. OPS imaging, however, provided significantly better image quality, as shown by comparison of image contrast between OPS imaging and capillary microscopy. This made image analysis better and easier to perform. It is anticipated, therefore, that OPS imaging will become a new and powerful technique in the study of the human microcirculation in vivo because it can be used on human internal organs.     

Validation of OPS imaging for microvascular measurements during isovolumic hemodilution and low hematocrits

Orthogonal polarization spectral (OPS) imaging is a new technique that can be used to visualize the microcirculation with reflected light. It uses hemoglobin absorption to visualize the red blood cells (RBCs). Thus the method could fail at low hematocrit (Hct). The aim of this study was to validate OPS imaging for quantitative measurements of diameter and functional capillary density (FCD) under conditions of hemodilution of varying degrees to achieve a wide range of Hcts. The validation was performed in the dorsal skinfold chamber of nine awake Syrian golden hamsters. Measurements of vessel diameter and FCD were performed off-line using Cap-Image on video sequences captured using OPS imaging and standard intravital fluorescence microscopy at baseline, 85, 70, 55, and 40% of the initial Hct. For hemodilution, isovolumic exchange of blood for 6% Dextran 60 was performed. Bland-Altman plots for the vessel diameter and FCD show good agreement between the two methods for both parameters at all studied Hcts. As expected, there was a systematic bias of approximately 4 microm in the diameter measurements since the RBC column was measured and not the intravascular diameter. In conclusion, OPS imaging can be used to measure diameter and FCD at a wide range of Hcts.     

Noninvasive in vivo assessment of the skeletal muscle and small intestine serous surface microcirculation in rat: sidestream dark-field (SDF) imaging

The pathophysiology of microcirculation is intensively investigated to understand disease development at the microscopic level. Orthogonal polarization spectral (OPS) imaging and its successor sidestream dark-field (SDF) imaging are relatively new noninvasive optical techniques allowing direct visualization of microcirculation in both clinical and experimental studies. The goal of this experimental study was to describe basic microcirculatory parameters of skeletal muscle and ileal serous surface microcirculation in the rat using SDF imaging and to standardize the technical aspects of the protocol. Interindividual variability in functional capillary density (FCD) and small vessels (<25 microm in diameter) proportion was determined in anesthetized rats on the surface of quadriceps femoris (m. rectus femoris and m. vastus medialis) and serous surface of ileum. Special custom made flexible arm was used to fix the SDF probe minimizing the pressure movement artifacts. Clear high contrast images were analyzed off-line. The mean FCD obtained from the surface of skeletal muscle and ileal serous surface was 219 (213-225 cm/cm(2)) and 290 (282-298 cm/cm(2)) respectively. There was no statistically significant difference between rats in mean values of FCD obtained from the muscle (P = 0.273) in contrast to ileal serous surface, where such difference was statistically significant (P = 0.036). No statistically significant differences in small vessels percentage was detected on either the muscle surface (P = 0.739) or on ileal serous surface (P = 0.659). Our study has shown that interindividual variability of basic microcirculatory parameters in rat skeletal muscle and ileum is acceptable when using SDF imaging technique according to a highly standardized protocol and with appropriate fixation device. SDF imaging represents promising technology for experimental and clinical studies.     

Magnetic Resonance Assessment of Response to Therapy: Tumor Change Measurement,Truth Data and Error Sources

This article describes methods and issues that are specific to the assessment of change in tumor characteristics as measured using quantitative magnetic resonance (MR) techniques and how this relates to the establishment of quantitative MR imaging (MRI) biomarkers of patient response to therapy. The initial focus is on the various sources of bias and variance in the measurement of microvascular parameters and diffusion parameters as such parameters are being used relatively commonly as secondary or exploratory end points in current phase 1/2 clinical trails of conventional and targeted therapies. Several ongoing initiatives that seek to identify the magnitude of some of the sources of measurement variations are then discussed. Finally, resources being made available through the National Cancer Institute Reference Image Database to Evaluate Response (RIDER) project that might be of use in investigations of quantitative MRI biomarker change analysis are described. These resources include 1) data from phantom-based assessment of system response, including short-term (1 hour) and moderate-term (1 week) contrast response and relaxation time measurement, 2) data obtained from repeated dynamic contrast agent-enhanced MRI studies in intracranial tumors, and 3) data obtained from repeated diffusion MRI studies in both breast and brain. A concluding section briefly discusses issues that must be addressed to allow the transition of MR-based imaging biomarker measures from their current role as secondary/exploratory end points in clinical trials to primary/surrogate markers of response and, ultimately, in clinical application.     

Vascularized acellular dermal matrix island flaps for the repair of abdominal muscle defects

The potential widespread use of tissue-engineered matrices in soft-tissue reconstruction has been limited by the difficulty in fabricating and confirming a functional microcirculation. Acellular dermal matrix placed in a soft-tissue pocket acts as a scaffold to be incorporated by the host's fibrovascular tissue. A new method for noninvasive real-time observation of functional microvascular networks using orthogonal polarization spectral (OPS) imaging has recently been reported. Arterioles, venules, and capillaries can be directly visualized, and the movement of individual blood cells through them can be observed. The present study was performed to investigate the use of prefabricated acellular dermal matrix with an arteriovenous unit for the repair of abdominal muscle defects. OPS imaging was used to determine the presence of a functional microcirculation in the neovascularized matrix. In Sprague-Dawley rats, vascularized matrix was prefabricated by placing the superficial epigastric artery and vein on a 2-cm x 2-cm implant-type acellular dermal matrix in the thigh. Three weeks after implantation, the matrix-arteriovenous unit was elevated as an axial-type flap and a 2-cm x 2-cm full-thickness block of abdominal muscle immediately superior to the inguinal ligament was resected. Additional procedures were performed according to group: no repair (group 1, n = 20); repair with nonvascularized acellular dermal matrix (group 2, n = 20); repair with devascularized acellular dermal matrix (group 3, = 20); and repair with vascularized acellular dermal matrix (group 4, n = 20). OPS imaging (field of view, 1 mm in diameter; scan depth range, 0.2 mm) was performed on both sides of each flap on a total of 10 random distal regions before and after pedicle transection in group 3 and with the pedicle preserved in group 4. Hernia rate and duration of survival were compared for 21 days. OPS imaging showed directional blood cell movement through the capillary network in all areas scanned in group 4. No microvascular perfusion was observed after pedicle transection in group 3. Hernia rates of 100, 80, 90, and 0 percent were seen in groups 1, 2, 3, and 4, respectively. Median survival times of 9, 11.5, 9, and 21 postoperative days were noted in groups 1, 2, 3, and 4, respectively. Histopathologic analysis with factor VIII revealed full-thickness infiltration of the matrix by endothelial cells, signifying newly formed blood vessels. Repair of abdominal muscle defects using vascularized acellular dermal matrix resulted in no hernia and survival of all animals for the duration of study. However, repairs using avascular or devascularized matrix resulted in significant rates of hernia and decreased survival. Acellular dermal matrix can be prefabricated into vascularized tissue using an arteriovenous unit and used successfully to repair abdominal muscle defects. OPS imaging allowed for high-contrast direct visualization of microcirculation in previously acellular tissue following prefabrication with an arteriovenous unit.     

In vivo imaging of apoptosis in oncology: an update

In this review, data on noninvasive imaging of apoptosis in oncology are reviewed. Imaging data available are presented in order of occurrence in time of enzymatic and morphologic events occurring during apoptosis. Available studies suggest that various radiopharmaceutical probes bear great potential for apoptosis imaging by means of positron emission tomography and single-photon emission computed tomography (SPECT). However, for several of these probes, thorough toxicologic studies are required before they can be applied in clinical studies. Both preclinical and clinical studies support the notion that 99mTc-hydrazinonicotinamide-annexin A5 and SPECT allow for noninvasive, repetitive, quantitative apoptosis imaging and for assessing tumor response as early as 24 hours following treatment instigation. Bioluminescence imaging and near-infrared fluorescence imaging have shown great potential in small-animal imaging, but their usefulness for in vivo imaging in humans is limited to structures superficially located in the human body. Although preclinical tumor-based data using high-frequency-ultrasonography (US) are promising, whether or not US will become a routinely clinically useful tool in the assessment of therapy response in oncology remains to be proven. The potential of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) for imaging late apoptotic processes is currently unclear. Neither 31P MRS nor 1H MRS signals seems to be a unique identifier for apoptosis. Although MRI-measured apparent diffusion coefficients are altered in response to therapies that induce apoptosis, they are also altered by nonapoptotic cell death, including necrosis and mitotic catastrophe. In the future, rapid progress in the field of apoptosis imaging in oncology is expected.     

In situ assessment of the liver microcirculation in mechanically ventilated rats using sidestream dark-field imaging

Assessment of hepatic microcirculation by on-line visualization has been impossible for a long time. Sidestream dark-field (SDF) imaging is a relatively new method allowing direct visualization of both mucosal microcirculation and surface layers microcirculation of solid organs using hand-held probe for direct contact with target tissue. The aim of this study was to evaluate the feasibility of studying the rat hepatic microcirculation in situ by SDF imaging. The liver lobes were left in situ, and images were obtained using SDF imaging on the surface of the liver via upper midline laparotomy. Images were captured intermittently during 10-sec apnoea and recorded. The microvascular parameters were compared with previous validation studies. Clear high contrast SDF images were successfully obtained. Quantitative analysis revealed a mean FSD (functional sinusoidal density) of 402+/-15 cm/cm(2), a sinusoidal diameter of 10.2+/-0.5 microm and postsinusoidal venular diameter of 33.9+/-13 microm. SDF imaging is a suitable noninvasive method for accurate quantification of the basic microcirculatory parameters of the liver in situ without a need to exteriorize the liver lobes. This method seems to be applicable in animal studies with possibility to use SDF imaging also intraoperatively, providing unique opportunity to study liver microcirculation during various experimental and clinical settings.     

In situ assessment of the brain microcirculation in mechanically-ventilated rabbits using sidestream dark-field (SDF) imaging

Assessment of the cerebral microcirculation by on-line visualization has been impossible for a long time. Sidestream dark-field (SDF) imaging is a relatively new method allowing direct visualization of cerebral surface layer microcirculation using hand-held probe for direct contact with target tissue. The aim of this study was to elucidate the feasibility of studying the cerebral microcirculation in situ by SDF imaging and to assess the basic cerebral microcirculatory parameters in mechanically ventilated rabbits. Images were obtained using SDF imaging from the surface of the brain via craniotomy. Clear high contrast SDF images were successfully obtained. Total small-vessel density was 14.6+/-1.8 mm/mm(2), total all-vessel density was 17.9+/-1.7 mm/mm(2), DeBacker score was 12.0+/-1.6 mm(-1) and microvascular flow index was 3.0+/-0.0. This method seems to be applicable in animal studies with possibility to use SDF imaging also intraoperatively, providing unique opportunity to study cerebral microcirculation during various experimental and clinical settings.     

超声心动图评价冠状动脉慢血流现象的应用进展

摘要：冠状动脉慢血流现象(coronary slow flow phenomenon, CSFP)是通过冠状动脉血管造影(coronary angiography, CAG)发现的以冠状动脉内径正常或接近正常的血管远端造影剂显像延迟为特征的冠状动脉血管病变。多数患者心脏无器质性病变,但反复出现各种不同形式的心肌缺血症状,CSFP也可能引发如恶性心律失常、急性心肌梗死等严重的心脏不良事件,因此早期评估CSFP尤为重要。既往多种影像学检查手段价格昂贵、检查时间过长,并且后期随访及疗效评估困难,限制了这类检查在临床上的应用。传统的超声心动图指标难以反映早期心肌损伤,近年来各种超声心动图新技术检查在CSFP的定性、定量研究中都发挥了重要作用,其中斑点追踪成像技术(speckle tracking imaging,STI)更是在安全无创的基础上具有更高的准确性和敏感性。     

Application of metabolic PET imaging in radiation oncology

Positron emission tomography (PET) is a noninvasive imaging technique that provides functional or metabolic assessment of normal tissue or disease conditions and is playing an increasing role in cancer radiotherapy planning. (18)F-Fluorodeoxyglucose PET imaging (FDG-PET) is widely used in the clinic for tumor imaging due to increased glucose metabolism in most types of tumors; its role in radiotherapy management of various cancers is reviewed. In addition, other metabolic PET imaging agents at various stages of preclinical and clinical development are reviewed. These agents include radiolabeled amino acids such as methionine for detecting increased protein synthesis, radiolabeled choline for detecting increased membrane lipid synthesis, and radiolabeled acetate for detecting increased cytoplasmic lipid synthesis. The amino acid analogs choline and acetate are often more specific to tumor cells than FDG, so they may play an important role in differentiating cancers from benign conditions and in the diagnosis of cancers with either low FDG uptake or high background FDG uptake. PET imaging with FDG and other metabolic PET imaging agents is playing an increasing role in complementary radiotherapy planning.     

Automated Tracking of Quantitative Assessments of Tumor Burden in Clinical Trials

There are two key challenges hindering effective use of quantitative assessment of imaging in cancer response assessment: 1) Radiologists usually describe the cancer lesions in imaging studies subjectively and sometimes ambiguously, and 2) it is difficult to repurpose imaging data, because lesion measurements are not recorded in a format that permits machine interpretation and interoperability. We have developed a freely available software platform on the basis of open standards, the electronic Physician Annotation Device (ePAD), to tackle these challenges in two ways. First, ePAD facilitates the radiologist in carrying out cancer lesion measurements as part of routine clinical trial image interpretation workflow. Second, ePAD records all image measurements and annotations in a data format that permits repurposing image data for analyses of alternative imaging biomarkers of treatment response. To determine the impact of ePAD on radiologist efficiency in quantitative assessment of imaging studies, a radiologist evaluated computed tomography (CT) imaging studies from 20 subjects having one baseline and three consecutive follow-up imaging studies with and without ePAD. The radiologist made measurements of target lesions in each imaging study using Response Evaluation Criteria in Solid Tumors 1.1 criteria, initially with the aid of ePAD, and then after a 30-day washout period, the exams were reread without ePAD. The mean total time required to review the images and summarize measurements of target lesions was 15% (P < .039) shorter using ePAD than without using this tool. In addition, it was possible to rapidly reanalyze the images to explore lesion cross-sectional area as an alternative imaging biomarker to linear measure.We conclude that ePAD appears promising to potentially improve reader efficiency for quantitative assessment of CT examinations, and it may enable discovery of future novel image-based biomarkers of cancer treatment response.     

Evaluation of the Microcirculation in a Rabbit Hemorrhagic Shock Model Using Laser Doppler Imaging

The aim of this study is to evaluate the feasibility of Laser Doppler imaging (LDI) for noninvasive and dynamic assessment of hemorrhagic shock in a rabbit model. A rabbit model of hemorrhagic shock was generated and LDI of the microcirculation in the rabbit ears was performed before and at 0, 30, 60, and 90 min after hemorrhage. The CCD (Charge Coupled Device) image of the ears, the mean arterial pressure (MAP) and the heart rate (HR) were monitored. The mean LDI flux was calculated. The HR of rabbits was significantly (p < 0.05) elevated and the MAP was decreased after hemorrhage, compared to the pre-hemorrhage level. Within the initial 30 min after hemorrhage, the perfusion flux lineally dropped down. In contrast, the MAP values did not differ significantly between the time points of 0 and 30 after hemorrhage (p > 0.05). Both the flux numbers and the red-to-blue color changes on LDI imaging showed the reduction of the microcirculation. LDI imaging is a noninvasive and non-contact approach to evaluate the microcirculation and may offer benefits in the diagnosis and treatment of hemorrhage shock. Further studies are needed to confirm its effectiveness in clinical practice.     

The role of histamine release in shock.

More than 80 years after its discovery and nearly 70 years after its first being implicated in the mechanism of shock, the precise role of histamine (H) in the pathophysiology of the condition remains to be determined. The prevailing view over the decades has been that H is a noxious mediator contributing to the fatal outcome of shock. An adequate assessment of its role has long been hampered by the lack of a sufficiently sensitive and specific method for the measurement of H and by deficiencies of design in many studies. We now know that H is released in all types of shock. In low-output, high-resistance states, as in hypovolemic and cardiogenic shock, its effect (contrary to previous notions) appears to be beneficial, probably through the inhibition of excessive vasoconstriction and through a positive inotropic effect. In endotoxin shock the results are conflicting, but seem to indicate that H is not a lethal factor. In human septic shock, patients who died had higher H levels. The role of H release in the various forms of shock, both experimental and human, clearly needs an adequate, critical reevaluation, in carefully designed and executed studies using satisfactory methodology.     

Advanced imaging of the macrostructure and microstructure of bone

Noninvasive and/or nondestructive techniques are capable of providing more macro- or microstructural information about bone than standard bone densitometry. Although the latter provides important information about osteoporotic fracture risk, numerous studies indicate that bone strength is only partially explained by bone mineral density. Quantitative assessment of macro- and microstructural features may improve our ability to estimate bone strength. The methods available for quantitatively assessing macrostructure include (besides conventional radiographs) quantitative computed tomography (QCT) and volumetric quantitative computed tomography (vQCT). Methods for assessing microstructure of trabecular bone noninvasively and/or nondestructively include high-resolution computed tomography (hrCT), micro-computed tomography (muCT), high-resolution magnetic resonance (hrMR), and micromagnetic resonance (muMR). vQCT, hrCT and hrMR are generally applicable in vivo; muCT and muMR are principally applicable in vitro. Although considerable progress has been made in the noninvasive and/or nondestructive imaging of the macro- and microstructure of bone, considerable challenges and dilemmas remain. From a technical perspective, the balance between spatial resolution versus sampling size, or between signal-to-noise versus radiation dose or acquisition time, needs further consideration, as do the trade-offs between the complexity and expense of equipment and the availability and accessibility of the methods. The relative merits of in vitro imaging and its ultrahigh resolution but invasiveness versus those of in vivo imaging and its modest resolution but noninvasiveness also deserve careful attention. From a clinical perspective, the challenges for bone imaging include balancing the relative advantages of simple bone densitometry against the more complex architectural features of bone or, similarly, the deeper research requirements against the broader clinical needs. The considerable potential biological differences between the peripheral appendicular skeleton and the central axial skeleton have to be addressed further. Finally, the relative merits of these sophisticated imaging techniques have to be weighed with respect to their applications as diagnostic procedures requiring high accuracy or reliability on one hand and their monitoring applications requiring high precision or reproducibility on the other.     

脑微血管形态参数和细胞化学定量参数测量法

本文介绍采用图象分析仪测量脑微血管一些形态定量参数和细胞化学定量参数的方法。脑毛细血管的一些三维形态参数根据数学形态学和体视学原理进行测量和计算。这些定量参数对于微血管和微循环的定量研究和临床诊断有一定的实用价值。     

Computer-assisted measurement of vessel shape from 3T magnetic resonance angiography of mouse brain

Blood vessel morphology (vessel radius, branching pattern, and tortuosity) is altered by a multitude of diseases. Although murine models of human pathology are important to the investigation of many diseases, there are few publications that address quantitative measurements of murine vascular morphology. This report outlines methods of imaging mice in vivo using magnetic resonance angiograms obtained on a clinical 3T unit, of defining mouse vasculature from these images, and of quantifying measures of vessel shape. We provide examples of both healthy and diseased vasculature and illustrate how the approach can be used to assess pathology both visually and quantitatively. The method is amenable to the assessment of many diseases in both human beings and mice.     

Characterization and biological role of the O-polysaccharide gene cluster of Yersinia enterocolitica serotype O:9

Yersinia enterocolitica serotype O:9 is a gram-negative enteropathogen that infects animals and humans. The role of lipopolysaccharide (LPS) in Y. enterocolitica O:9 pathogenesis, however, remains unclear. The O:9 LPS consists of lipid A to which is linked the inner core oligosaccharide, serving as an attachment site for both the outer core (OC) hexasaccharide and the O-polysaccharide (OPS; a homopolymer of N-formylperosamine). In this work, we cloned the OPS gene cluster of O:9 and identified 12 genes organized into four operons upstream of the gnd gene. Ten genes were predicted to encode glycosyltransferases, the ATP-binding cassette polysaccharide translocators, or enzymes required for the biosynthesis of GDP-N-formylperosamine. The two remaining genes within the OPS gene cluster, galF and galU, were not ascribed a clear function in OPS biosynthesis; however, the latter gene appeared to be essential for O:9. The biological functions of O:9 OPS and OC were studied using isogenic mutants lacking one or both of these LPS parts. We showed that OPS and OC confer resistance to human complement and polymyxin B; the OPS effect on polymyxin B resistance could be observed only in the absence of OC.     

Assessing hemorrhagic shock: Feasibility of using an ultracompact photoacoustic microscope

Hemorrhagic shock, as an important clinical issue, is regarding as a critical disease with a high mortality rate. Unfortunately, existing clinical technologies are inaccessible to assess the hemorrhagic shock via hemodynamics in microcirculation. Here, we propose an ultracompact photoacoustic microscope to assess hemorrhagic shock using a rat model and demonstrate its clinical feasibility by visualizing buccal microcirculation of healthy volunteers. Both functional and morphological features of the microvascular network including concentration of total hemoglobin (C_HbT), number of blood vessels (VN), small vascular density (SVD) and vascular diameter (VD) were derived to assess the microvascular hemodynamics of different organs. Animal studies show the feasibility of the proposed tool to assess and stage the hemorrhagic shock via microcirculation. in vivo oral imaging of healthy volunteers indicates the translational possibility of this technique for clinical evaluation of hemorrhagic shock.      

Imaging of angiogenesis: from microscope to clinic

Advances in imaging are transforming our understanding of angiogenesis and the evaluation of drugs that stimulate or inhibit angiogenesis in preclinical models and human disease. Vascular imaging makes it possible to quantify the number and spacing of blood vessels, measure blood flow and vascular permeability, and analyze cellular and molecular abnormalities in blood vessel walls. Microscopic methods ranging from fluorescence, confocal and multiphoton microscopy to electron microscopic imaging are particularly useful for elucidating structural and functional abnormalities of angiogenic blood vessels. Magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), ultrasonography and optical imaging provide noninvasive, functionally relevant images of angiogenesis in animals and humans. An ongoing dilemma is, however, that microscopic methods provide their highest resolution on preserved tissue specimens, whereas clinical methods give images of living tissues deep within the body but at much lower resolution and specificity and generally cannot resolve vessels of the microcirculation. Future challenges include developing new imaging methods that can bridge this resolution gap and specifically identify angiogenic vessels. Another goal is to determine which microscopic techniques are the best benchmarks for interpreting clinical images. The importance of angiogenesis in cancer, chronic inflammatory diseases, age-related macular degeneration and reversal of ischemic heart and limb disease provides incentive for meeting these challenges.