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Methods of Recording Tumor Blood Flow
Published in Hans-Inge Peterson, Tumor Blood Circulation: Angiogenesis, Vascular Morphology and Blood Flow of Experimental and Human Tumors, 2020
More work seem necessary to validate the Sapirstein method against direct volumeflow methods. Validation of 86Rb for determination of intratumoral blood-flow distribution has to be done, e.g., against serial microangiography.2
General Radiation Histopathology
Published in George W. Casarett, Radiation Histopathology, 2019
At early times after irradiation the radiation-induced changes in small blood vessels and interstitial connective tissue are subtle and inconspicuous upon casual examination, especially after moderate doses of radiation. Furthermore, these changes are spotty in their distribution along the course of the vessels rather than uniform and continuous. Consequently, in any one thin histological tissue section, thorough and competent examination of the fine vessels may reveal relatively few sites of prominent change even when many of the small blood vessels may be affected at one or another point along their course. Serial sectioning or microangiography reveals the extent of such vascular changes more fully. It is obvious that a focal narrowing or occlusion of an arteriole supplying a capillary network, especially if the occlusion is distal to the last effective collateral channel of blood supply, may be all that is necessary to disrupt the blood supply to a considerable amount of tissue dependent on the portion of the capillary bed in question. With progression of the vascular damage and the cicatrization process with passing time, more and more points along the course of the affected small vessels may show degenerative and fibrotic changes, so that more and more sections of small blood vessels per unit area of tissue section may reveal changes, and the changes may become more obvious.
Application of Microcirculation Research to Clinical Disease
Published in John H. Barker, Gary L. Anderson, Michael D. Menger, Clinically Applied Microcirculation Research, 2019
Bengt Fagrell, Alfred Bollinger
One of the most striking findings in the skin of the ankle region in patients with deep venous insufficiency and/or insufficient ankle perforators is the appearance of a “halo” formation around the nutritional skin capillaries.3,34,35 This halo is caused by a specific microedema that can be easily demonstrated by ordinary capillaroscopy. In some patients, it has been possible to puncture the halo with an injection needle, and marked leakage of fluid can be seen concomitantly with a decrease in the halo size.3,34 Recently, this microedema has been nicely demonstrated by fluorescence microangiography and microlymphography.3,32 The edema fluid seems to contain high concentrations of fibrin,36 other proteins, and neutral polysaccharides.37 The development of the halo formation is most probably due not only to incompetence of the venous, but also of the lymphatic system of the affected leg.38
Recent advances in wide field and ultrawide field optical coherence tomography angiography in retinochoroidal pathologies
Published in Expert Review of Medical Devices, 2021
Gagan Kalra, Francesco Pichi, Nitin Kumar Menia, Daraius Shroff, Nopasak Phasukkijwatana, Kanika Aggarwal, Aniruddha Agarwal
With the widespread acceptance and use of optical coherence tomography (OCT) and OCT angiography (OCTA), several methods have now been described to noninvasively visualize the retinal and choroidal vasculature using OCT signal. Traditionally described techniques implemented Doppler techniques, phase variance, speckle variance, amplitude decorrelation (Split-Spectrum Amplitude-Decorrelation Angiography – SSADA) for imaging the vasculature. A newer, more advanced technique (i.e. optical microangiography; OMAG) [4] has been described that utilizes both amplitude and phase variance techniques and has promising results. In comparison with FA, the major limitation of conventional OCTA is the limited FOV that allows incomplete assessment of vitreoretinal pathologies. The restricted FOV has also limited its widespread diagnostic and screening applications. More work in this area has resulted in newer techniques with wider FOV and a need for standardizing nomenclature of these newer modalities. A consensus formed by the International Widefield Imaging Study Group recommended definitions for wide field and UWF imaging were 60–100 degrees and 110–120 degrees respectively [5].
Optical coherence tomography angiography in primary eye care
Published in Clinical and Experimental Optometry, 2021
Alexandra M Coffey, Emily K Hutton, Louise Combe, Pooja Bhindi, Demi Gertig, Paul A Constable
OCT‐A is an extension of OCT which was developed in 1991 with the first reports of OCT‐A imaging retinal vasculature published in 2006.1,4 OCT‐A captures a three‐dimensional image of the vasculature through motion contrast of moving erythrocytes.2,4 The only motion over a period of time is blood flow within the vasculature.4 Repeated B‐scans at the same retinal cross‐section with a specified interscan time are required to detect blood flow.2,4 Commercial OCT‐A instruments acquire two to eight consecutive B‐scans within approximately six seconds.2,4 Decorrelation data is generated from the change in backscattered OCT signal intensity and the phase between sequential B‐scans, and is then displayed as a motion contrast image using manufacture‐specific algorithms. Various algorithms exist including optical microangiography which uses variances between consecutive B‐scans requiring the correction of motion artefacts to map the microvasculature and split spectrum amplitude decorrelation that does not require removal of motion artefacts and uses decorrelation between scans.1,4
Using miniature brain implants in rodents for novel drug discovery
Published in Expert Opinion on Drug Discovery, 2019
The first goal of generating an artificial human blood-brain barrier in a rodent is achieving vascularization of the brain organoid. We have developed iPSCs from the fibroblasts of a patient [49] and subsequently differentiated the patient’s iPSCs into endothelial cells and brain organoids [1]. We were able to show vascularization of human brain organoids with human endothelial cells in vitro and in vivo. The next step is to show the perfusion of human endothelial cells with murine blood. Brain organoid perfusion can be qualitatively analyzed by intra-cardiac injection of DilC12, DilC18 or fluorescein-labeled Dextrans. DilC18 is a hydrophobic carbocyanin that can be used for vessel painting since it labels the endothelial plasma membrane through insertion into the lipid bilayer [50–52]. DilC12 has subsequently been shown to have superior vessel painting qualities [53,54]. The mouse vasculature can be easily visualized with intracardiac DilC12 with liposomes perfusion (Figure 1(a)). Another method of mapping cerebrovascular blood perfusion non-invasively is optical microangiography [55]. We would expect perfusion of human endothelial cells in an organoid within 2 weeks since Mansour et al. were able to achieve perfusion of murine endothelial cells in such a time frame [2].