In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography

We present in vivo volumetric images of human retinal micro-circulation using Fourier-domain optical coherence tomography (Fd-OCT) with the phase-variance based motion contrast method. Currently fundus fluorescein angiography (FA) is the standard technique in clinical settings for visualizing blood circulation of the retina. High contrast imaging of retinal vasculature is achieved by injection of a fluorescein dye into the systemic circulation. We previously reported phase-variance optical coherence tomography (pvOCT) as an alternative and non-invasive technique to image human retinal capillaries. In contrast to FA, pvOCT allows not only noninvasive visualization of a two-dimensional retinal perfusion map but also volumetric morphology of retinal microvasculature with high sensitivity. In this paper we report high-speed acquisition at 125 kHz A-scans with pvOCT to reduce motion artifacts and increase the scanning area when compared with previous reports. Two scanning schemes with different sampling densities and scanning areas are evaluated to find optimal parameters for high acquisition speed in vivo imaging. In order to evaluate this technique, we compare pvOCT capillary imaging at 3x3 mm^2 and 1.5x1.5 mm^2 with fundus FA for a normal human subject. Additionally, a volumetric view of retinal capillaries and a stitched image acquired with ten 3x3 mm^2 pvOCT sub-volumes are presented. Visualization of retinal vasculature with pvOCT has potential for diagnosis of retinal vascular diseases

Mobility and transverse flow visualization using phase variance contrast with spectral domain optical coherence tomography

Phase variance-based motion contrast is demonstrated using two phase analysis methods in a spectral domain optical coherence tomography system. Mobility contrast is demonstrated for an intensity matched Intralipid solution placed without flow within agarose wells. Vasculature oriented transversely to the imaging direction has been imaged for 3-4 dpf in vivo zebrafish using the phase variance contrast methods. 2D phase variance contrast images are demonstrated with imaging times only 25% higher than a Doppler flow image with comparable statistics. En face images created by integrating depth regions of 3D zebrafish intensity and phase variance contrast data demonstrate vasculature consistent with expected images

Pump-probe scheme for optical coherence tomography using indocyanine green mixed with albumin or human plasma

Use of indocyanine green (ICG) in a pump-probe scheme for OCT is proposed. The study illustrates that ICG in protein solution shows unusual pump-probe imaging potential, indicating its usefulness as a contrast agent for OCT

Volumetric microvascular imaging of human retina using optical coherence tomography with a novel motion contrast technique

Phase variance-based motion contrast imaging is demonstrated using a spectral domain optical coherence tomography system for the in vivo human retina. This contrast technique spatially identifies locations of motion within the retina primarily associated with vasculature. Histogram-based noise analysis of the motion contrast images was used to reduce the motion noise created by transverse eye motion. En face summation images created from the 3D motion contrast data are presented with segmentation of selected retinal layers to provide non-invasive vascular visualization comparable to currently used invasive angiographic imaging. This motion contrast technique has demonstrated the ability to visualize resolution-limited vasculature independent of vessel orientation and flow velocity

Utjecaj organskih i mineralnih sastojaka tla na sorpcijsko ponašanje klorfenolnih i triazinskih mikrozagađivala

This article compares the sorption behaviour of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol, chlorotriazine atrazine, methylthiotriazine ametryn, methoxytriazine atratone, hydroxyatrazine, and didelakylated atrazine in a topsoil and an aquifer sediment before and after removal of sorbent organic matter and in humic acid. Freundlich isotherm coeffi cients Kf and 1/n and free energy change (∆G°) were calculated for all compounds in all sorbents. According to sorbent pH values, chlorophenolate anions and uncharged triazine species dominated in all sorption experiments with topsoil and aquifer sediment. In experiments with humic acid, chlorophenols, atrazine, and didealkylated atrazine existed almost completely as neutral species, whereas protonated species dominated for hydroxyatrazine, atratone, and ametryn. In addition to a hydrophobic partition, sorption of all compounds in native soil and sediment sorbents includes specifi c, more polar interactions, which greatly depend on sorbate acidity/ basicity, specifi c properties of the sorbent organic matter and of mineral surface, as well as on the system pH. A signifi cantly greater sorption intensity of all compounds in “organic-free” than in the native aquifer sediment confi rmed the importance and possible dominance of mineral surface in the sorption process. Sorption intensity of chlorophenol and triazine compounds in humic acid was closely related to compound hydrophobicity. Greater sorption of almost completely protonated hydroxyatrazine than of the more hydropohobic but uncharged atrazine indicated different humic acid reaction sites for two compounds and consequently different sorption mechanisms.Uspoređena je sorpcija 2,4,6-triklorfenola, 2,3,4,6-tetraklorfenola i pentaklorfenola te različito supstituiranih triazinskih spojeva - klortriazina atrazina, metiltiotriazina ametrina, metoksitriazina atratona i razgradnih produkata atrazina hidroksiatrazina i didealkiliranog atrazina – u površinskom tlu i sedimentu vodonosnika prije i nakon uklanjanja organske tvari te u huminskoj kiselini. Izračunani su koefi cijenti Freundlichove izoterme Kf i 1/n te izmjena slobodne energije (∆G°) za sve spojeve i sorbense. U skladu s pH-vrijednostima sorbensa u svim su sorpcijskim pokusima s nativnim tlom i sedimentom prevladavali klorfenolatni anioni i neutralni triazinski spojevi. U pokusima s huminskom kiselinom klorfenoli, atrazin i didealkilirani atrazin postojali su kao neutralne vrste, dok su hidroksiatrazin, atraton i ametrin bili većim dijelom protonirani. Sorpcija svih spojeva u prirodnom tlu i sedimentu uključuje uz hidrofobnu particiju i specifi čne polarnije interakcije ovisne o kiselosti/bazičnosti sorbata, specifi čnim svojstvima organske tvari i mineralne površine sorbensa te o pH-vrijednosti sustava. Intenzitet sorpcije svih spojeva u sedimentu iz kojeg je uklonjena organska tvar bio je značajno veći od sorpcije u prirodnom sedimentu, što potvrđuje važnost i moguću dominantnu ulogu mineralne površine u sorpcijskom procesu. Intenzitet sorpcije klorfenola te klortriazina, metiltiotriazina i metoksitriazina u huminskoj kiselini korelirao je s hidrofobnosti spojeva. Veća sorpcija gotovo potpuno protoniranog hidroksiatrazina od hidrofobnijeg, ali neutralnog atrazina upućuje na različita reakcijska mjesta za ova dva spoja, a time i na različite mehanizme sorpcije u huminskoj kiselini