Blood flow measurement in the in vivo mouse model by the combination of Doppler OCT and the signal power decrease in spectral domain OCT

This study aimed to evaluate normal blood flow in the vertebral arteries and the basilar artery of preterm and term neonates by Doppler sonography. Blood flow in both vertebral arteries and the basilar artery was examined in 102 neonates between the biological ages of 28 and 41 weeks. Fifty-one boys and 51 girls underwent Doppler sonography. Measurements were usually undertaken at 6 days old. Systolic and diastolic flow velocities, including the resistive index, were measured and analyzed, taking into consideration biological age, weight, and sex. Anatomic aberrations of the vertebral arteries were recorded. Mean blood flow values ± SD in the basilar artery were 35.2 ± 7.4 cm/s (systolic velocity) and 10.9 ± 3.5 cm/s (diastolic velocity). Mean blood flow values in the right vertebral artery were 26.8 ± 9.3 cm/s (systolic velocity) and 8.0 ± 3.7 cm/s (diastolic velocity). Mean blood flow values in the left vertebral artery were 28.6 ± 8.3 cm/s (systolic velocity) and 8.7 ± 3.3 cm/s (diastolic velocity). Systolic and diastolic blood flow in both vertebral arteries was significantly higher from 38 to 41 weeks compared with 28 to 32 and 33 to 37 weeks (P < .05). Regression analysis of systolic and diastolic blood flow velocities in the vertebral arteries versus biological age yielded significant results (P < .05). Sonography is an excellent tool for examining blood flow in the basilar and vertebral arteries of premature and term neonates. Mean systolic and diastolic blood flow velocities in the vertebral arteries increase significantly with age.

Blood flow measurement with spectrometer-based Fourier domain optical coherence tomography (FD-OCT) is limited by the motion-induced signal fading and the resulting reduction of flow sensitivity. Therefore, we have numerically simulated the signal power decrease of an obliquely moved scattering layer as a function of the absolute sample velocity composed of an axial and transverse component. In contrast to the prevalent expectance, the resulting signal damping is not only the sum of axial and transverse effect. In this study, we take advantage of the signal decay and present the feasibility to quantify high flow velocities at which the standard Doppler OCT does not work any longer. For the validation of our approach, a flow phantom model consisting of a 1%-Intralipid solution and a 320 &mu;m glass capillary was used. With this phantom study, depth-resolved flow was visualized and the quantitative velocities were extracted from the OCT images without phase information.

Fourier domain optical coherence tomography (FD OCT) enables imaging of long coronary artery segments within few seconds, employing high data acquisitions, speed and fast automated catheter pullback. However, the reproducibility of these high-speed pullbacks in the clinical situation is unknown. We tested the reproducibility of in vivo, intracoronary FD OCT and assessed the influence of different computer-assisted algorithms on quantitative analysis. In patients undergoing elective coronary stenting, two repeated FD OCT pullbacks (20 mm/sec), were acquired. Lumen area (LA) and stent area (SA) were measured at 1 mm longitudinal intervals (n=18 pullbacks, n=326 frames). Inter-study variability in terms of absolute difference of mean LA, mean SA and minimum LA was very low (-0.06±0.28 mm2, -0.05±0.29 mm2 and -0.11±0.33 mm2 in software 1) Sources of variability were incomplete visualisation of the vessel circumference, ambiguous luminal borders and drift of internal catheter calibration (Z-offset). Inter-software variability for LA and SA was low (R2=0.98 ~ 1.00, p<0.01, respectively). FD OCT shows excellent reproducibility for consecutive pullbacks and represents a reliable tool for the in vivo assessment of stented coronaries. Computer-assisted quantitative analysis of FD OCT may be a valuable tool for future studies.

In vivo measurement of blood flow in the retina has been made possible with the advent of Fourier domain optical coherence tomography (OCT). Doppler OCT has seen many advances in recent years in algorithms used for quantifying blood flow. We compare the relative retinal blood flow estimates as measured by the standard phase-resolved (PR) algorithm and the more recent moving-scatterer-sensitive (MSS) algorithm as a function of vessel size. We find that the PR-to-MSS flow ratio significantly decreases with decreasing vessel diameter. We also develop a simulation to approximate the scattering from blood cells in tissue and compare the relative blood flow estimates. The flow ratio measured with simulation closely matches that found in vivo. Our simulation predicts that whereas PR underestimates the flow, MSS overestimates it. Our simulation may help to correct for algorithm bias in in vivo retinal flow estimates.

AimTo compare detection rates of drusen and subretinal fluid by Fourier domain optical coherence tomography (FD OCT) and orange pigment by fundus autofluorescence (FAF) with ophthalmoscopy in indeterminate choroidal melanocytic...

A variety of promising approaches for quantitative flow velocity measurement in OCT have been proposed in recent years. The question is: Which method gets the most precise flow velocity out of the interference signals detected. We have compared the promising joint spectral and time domain optical coherence tomography (jSTdOCT) and the commonly used phase-resolved Doppler OCT (DOCT) and describe the link between these two proven methods for OCT in the Fourier domain (FD OCT). First, we show that jSTdOCT can be significantly improved by calculating the center of gravity via an unbiased complex algorithm instead of detecting the maximum intensity signal of the broadened Doppler frequency spectrum. Secondly, we introduce a unified mathematical description for DOCT and jSTdOCT that differs only in one exponent and call it enhjSTdOCT. Third, we present that enhjSTdOCT has the potential to significantly reduce the noise of the velocity measurement by choosing an exponent depending on the transverse sample velocity component and the signal-to-noise ratio. EnhjSTdOCT is verified numerically and experimentally to find the optimal parameters for maximal velocity noise reduction.

Barely Visible 10-Millisecond Pascal Laser Photocoagulation for Diabetic Macular Edema: Observations of Clinical Effect and Burn Localization

In this paper we present, for the first time to our knowledge, the experimental results for determining suspension viscosity in a capillary type viscometer from flow velocity profiles measured by Doppler Optical Coherence Tomography. The suspension of 0.3?m polystyrene microspheres in a glycerol-water solution was used as a model fluid. The viscosity of the suspension was controlled by glycerol concentration. The shear rate and the shear stress at the capillary wall were measured at six flow rates. The corresponding viscosities were calculated. The comparison of the measured shear rates with the values calculated according to the flow rate of the syringe precision pump was performed. Additionally, the viscosities of the studied suspensions were measured by a rotational viscometer. Full Text: PDFReferences K.A. Hayes, M.R. buckley, I. Cohen, L.A. Archer, "High Resolution Shear Profile Measurements in Entangled Polymers", Phys. Rev. Lett. 101, 218301 (2008)[CrossRef] N. Willenbacher, H. Hanciogullari, H.G. Wagner, "High shear rheology of paper coating colors ? more than just viscosity", Chem. Eng. Technol. 20, 557 (1997)[CrossRef] M. Iotti, O.W. Gregersen, S. Moe, M. Lenes, "Rheological Studies of Microfibrillar Cellulose Water Dispersions", J. Polym. Environ. 19, 137 (2011)[CrossRef] M.T. Roberts, A. Mohraz, K.T. Christensen, J.A. Lewis, "Direct Flow Visualization of Colloidal Gels in Microfluidic Channels", Langmuir 23, 8726 (2007)[CrossRef] M. Schmidt, E. Wassner, H. Münstedt, "Setup and Test of a Laser Doppler Velocimeter for Investigations of Flow Behaviour of Polymer Melts", Mech. Time-Depend. Mater. 3, 371, (1999)[CrossRef] S. Schuberth, H. Münstedt, "Simultaneous measurements of velocity and stress distributions in polyisobutylenes using laser-Doppler velocimetry and flow induced birefringence", Rheol. Acta 47, 111 (2008)[CrossRef] Th. Wunderlich, P.O. Brunn, "A wall layer correction for ultrasound measurement in tube flow: comparison between theory and experiment", Flow Meas. Instrum. 11, 63 (2000)[CrossRef] J. Wiklund, I. Shahram, M. Stading, "Methodology for in-line rheology by ultrasound Doppler velocity profiling and pressure difference techniques", Chem. Eng. Sci. 62, 4277 (2007)[CrossRef] S. Yazdanfar, M.D. Kulkarni, J.A. Izatt, "High resolution imaging of in vivo cardiac dynamics using color Doppler optical coherence tomography", Opt. Express 1(13), 424 (1997)[CrossRef] Y. Zhao et al., "Phase-resolved optical coherence tomography and optical Doppler tomography for imaging blood flow in human skin with fast scanning speed and high velocity sensitivity", Opt. Lett. 25(2), 114 (2000)[CrossRef] J. Moger, S.J. Matcher C.P. Winlove, A. Shore, "Measuring red blood cell flow dynamics in a glass capillary using Doppler optical coherence tomography and Doppler amplitude optical coherence tomography", J. Biomed. Opt. 9(5), 982 (2004)[CrossRef] S. Tamborski et al., "Simultaneous analysis of flow velocity and spectroscopic properties of scattering media with the use of joint Spectral and Time domain OCT", Phot. Lett. Poland 1(2), 49 (2009) B. Povazay et al., "Submicrometer axial resolution optical coherence tomography", Opt. Lett. 27(20), 1800 (2002)[CrossRef] M. Harvey, T.A. Waigh, "Optical coherence tomography velocimetry in controlled shear flow", Phys. Rev. E 83, 031502 (2011)[CrossRef] J. Lauri, M. Wang, M. Kinnunen, R. Myllylä, "Measurement of microfluidic flow velocity profile with two Doppler optical coherence tomography systems", Proc. SPIE 6863, 68630F (2008)[CrossRef]

Troglitazone improves blood flow by inhibiting neointimal formation after balloon injury in Otsuka Long-Evans Tokushima Fatty rats

Doppler optical coherence tomography (DOCT) is an emerging imaging modality demonstrated in 1991 for the first time and is a functional extension of optical coherence tomography (OCT) to including flow measurement. DOCT allows not only high-resolution, non-invasive, cross-sectional imaging but also simultaneous real-time visualization of sample structure and flow. DOCT is often compared to clinical Doppler ultrasound. However, the spatial resolution of clinical Doppler ultrasound is limited to approximately 100 μm due to the relatively long wavelength of acoustic waves. DOCT takes advantage of the short coherence length of broadband light sources in order to achieve cross-sectional images with micrometer (2–10 μm) scale resolution. DOCT is also superior to ultrasound in that DOCT is operated in non-contact-mode. The last four years have witnessed an era of technology revolution in DOCT, introduced by the Fourier-domain technology that shows tremendous advantage over time-domain DOCT. Fourier-domain Doppler optical coherence tomography (FDDOCT) instruments have higher imaging speed and higher system sensitivity which are able to overcome motion artifacts and enhance minimum measurable velocity, respectively. Because of the aforementioned merits, FDDOCT has a broad range of clinical applications including ophthalmology, cardiology, urology, etc with information of tissue microstructure and blood flow. However, FDDOCT has seldom been applied to diagnose microfluidic devices. In this keynote paper, system configuration, principle behind, and applications of FDDOCT for microfluidics will be covered.

Doppler OCT is a functional extension of OCT that provides information on flow in biological tissues. We present a novel approach for total retinal blood flow assessment using ultrahigh speed Doppler OCT. A swept source / Fourier domain OCT system at 1050 nm was used for 3D imaging of the human retina. The high axial scan rate of 200 kHz allowed measuring the high flow velocities in the central retinal vessels. By analyzing en-face images extracted from 3D Doppler data sets, absolute flow for single vessels as well as total retinal blood flow can be measured using a simple and robust protocol.

Optical coherence tomography (OCT) techniques have been applied to develop a new generation of the technology, called spectral domain (SD) or Fourier domain (FD) OCT. The commercially available SD-OCT technology...

Speckle contrast based optical coherence angiography (OCA) and optical coherence Doppler tomography (ODT) have been applied to image cerebral blood flow previously. However, the contrast mechanisms of these two methods are not fully studied. Here, we present both flow phantom and in vivo animal experiments using ultrahigh-resolution OCA (μOCA) and ODT (μODT) to investigate the flow sensitivity differences between these two methods. Our results show that the high sensitivity of μOCA for visualizing minute vasculature (e.g., slow capillary beds) is due to the enhancement by random Brownian motion of scatterers (e.g., red and white blood cells) within the vessels; whereas, μODT permits detection of directional flow below the Brownian motion regime (e.g., laser-induced microischemia) and is, therefore, more suitable for brain functional imaging.

Purpose: To define and measure macular thickness and volume using Fourier domain OCT (FD OCT) and compare the values with Stratus OCT in normal eyes and eyes with macular disease. Methods: On the same day, macular thicknesses of the ETDRS 9 subfield and total macular volumes were measured in 35 eyes of 23 normal subjects and 19 diseased eyes of 24 patients with FD OCT and Stratus OCT. The macular cube scan protocol for FD OCT and the fast macular thickness map protocol for Stratus OCT were used to measure macular thicknesses. Results: Foveal thickness of the central subfield in FD OCT (251.49) was thicker than the value of Stratus OCT (210.26 ) (p and 7.040.96 for FD OCT and Stratus OCT, respectively (p

The conventional Fourier domain optical coherence tomography system requires single scanner for two dimensional cross-sectional image and two scanners for volumetric image. Parallel spectral domain optical coherence tomography has advantage of single scanner for volumetric image, while two dimensional cross-sectional images are obtained by parallel acquisition of illuminated line on sample using area camera. In this study, the industrial inspection of optical thin film on touch screen panels was demonstrated using parallel spectral domain optical coherence tomography. The cross-sectional and volumetric images were acquired to detect the internal sub layer defects in optical thin film which are difficult to observe using visual or machine vision based inspection methods. The results indicate the possible application of the proposed system in touch screen panels inspection for quality assurance of product at consumer end.