Papers by Danuta Bukowska
Journal of Medical Imaging, 2016
Ophthalmology, 2011
To investigate whether confluent drusen may be accompanied by fluid accumulation underneath the s... more To investigate whether confluent drusen may be accompanied by fluid accumulation underneath the sensory retina and to determine if the detection of subretinal fluid on spectral-domain optical coherence tomography (OCT) in patients with coalescent drusen is indicative of choroidal neovascularization (CNV).
Proceedings of Spie the International Society For Optical Engineering, 2009
In this submission we demonstrate a new application of the joint Spectral and Time domain Optical... more In this submission we demonstrate a new application of the joint Spectral and Time domain Optical Coherence Tomography (STdOCT) technique for segmenting and measuring the retinal blood flow velocity in three dimensions. The method is based on direct detection of Doppler shift that arises in time during the measurement. New scanning protocols and analysis tools are proposed to create velocity distribution maps of the retina and to segment and visualize 3D vasculature of human eye in-vivo. STdOCT segmentation is more sensitive than methods based on phase measurements and calculations are more straightforward than other techniques, which require more complex experimental setup and more sophisticated numerical tools. The usage of ultra-fast line scan camera allows to broaden the axial velocity range up to +/-24mm/s, thus all high flows in human retina can be registered.
Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XX, 2016
Clinical & experimental ophthalmology, Jan 19, 2015
To evaluate and classify image artefacts in optical coherence tomography (OCT) angiography (OCTA)... more To evaluate and classify image artefacts in optical coherence tomography (OCT) angiography (OCTA) of the choroid in a group of patients with macular diseases. Retrospective observational study. 5 patients with age-related macular degeneration, 3 with central serous retinopathy, 1 with polypoidal choroidal vasculopathy and 1 with multiple evanescent white dot syndrome. OCTA and OCT reflectivity (OCTR) maps were reviewed along with their fluorescein angiography and indocyanine green angiography. 60 OCTA images (20 outer retina, 20 Sattler and 20 Haller layers) were graded for image artefacts by 2 examiners independently. OCTA artefacts and their correlation with OCTR maps, angiography and OCT B-scans. Artefacts (frequency) were classified into (1) motion (70-100%), (2) fringe washout (100%), (3) decorrelation projection (0-20%), (4) masking and unmasking (50-65%), and (5) stromal decorrelation signal (100%). Motion artefact in OCTA is characterised by horizontal dark lines or bands no...
Biomedical Optics Express, 2015
A large number of human retinal diseases are characterized by a progressive loss of cones, the ph... more A large number of human retinal diseases are characterized by a progressive loss of cones, the photoreceptors critical for visual acuity and color perception. Adaptive Optics (AO) imaging presents a potential method to study these cells in vivo. However, AO imaging in ophthalmology is a relatively new phenomenon and quantitative analysis of these images remains difficult and tedious using manual methods. This paper illustrates a novel semi-automated quantitative technique enabling registration of AO images to macular landmarks, cone counting and its radius quantification at specified distances from the foveal center. The new cone counting approach employs the circle Hough transform (cHT) and is compared to automated counting methods, as well as arbitrated manual cone identification. We explore the impact of varying the circle detection parameter on the validity of cHT cone counting and discuss the potential role of using this algorithm in detecting both cones and rods separately.
Clinical & experimental ophthalmology, Jan 11, 2015
Optics Express, 2015
We demonstrate a novel optical method for the detection and differentiation between erythrocytes ... more We demonstrate a novel optical method for the detection and differentiation between erythrocytes and leukocytes that uses amplitude and phase information provided by optical coherence tomography (OCT). Biological cells can introduce significant phase modulation with substantial scattering anisotropy and dominant forward-scattered light. Such physical properties may favor the use of a trans-illumination imaging technique. However, an epi-illumination mode may be more practical and robust in many applications. This study describes a new way of measuring the phase modulation introduced by flowing microobjects. The novel part of this invention is that it uses the backscattered signal from the substrate located below the flowing/moving objects. The identification of cells is based on phase-sensitive OCT signals. To differentiate single cells, a custom-designed microfluidic device with a highly scattering substrate is introduced. The microchannels are molded in polydimethylsiloxane (PDMS) mixed with titanium dioxide (TiO2) to ensure high scattering properties. The statistical parameters of the measured signal depend on the cells' features, such as their size, shape, and internal structure.
Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVI, 2012
ABSTRACT We propose two independent OCT data processing methods allowing visualization and analys... more ABSTRACT We propose two independent OCT data processing methods allowing visualization and analysis of the blood flow. These methods utilize variations in the OCT intensity images caused by flowing blood. The first method calculates standard deviation of intensity to generate retinal OCT angiograms. We present algorithm of this method and results of application for visualization of the microvasculature in the macular area of the human eye in vivo. The second method calculates cross power spectra of the volumetric intensity images to assess blood flow velocity in three dimensions. Validation of this method for OCT imaging was performed in a flow phantom.
Case Reports in Ophthalmological Medicine, 2015
An 80-year-old female with reading difficulty presented with progressive arcuate field defect des... more An 80-year-old female with reading difficulty presented with progressive arcuate field defect despite low intraocular pressure. Over a 5-year period, the field defect evolved into an incongruous homonymous hemianopia and the repeated neuroimaging revealed progressive posterior cortical atrophy. Further neuropsychiatric assessment demonstrated symptoms and signs consistent with Benson's syndrome.
Biomedical Optics Express, 2015
We compare four optical coherence tomography techniques for noninvasive visualization of microcap... more We compare four optical coherence tomography techniques for noninvasive visualization of microcapillary network in the human retina and murine cortex. We perform phantom studies to investigate contrast-tonoise ratio for angiographic images obtained with each of the algorithm. We show that the computationally simplest absolute intensity difference angiographic OCT algorithm that bases only on two cross-sectional intensity images may be successfully used in clinical study of healthy eyes and eyes with diabetic maculopathy and branch retinal vein occlusion.
Optics Express, 2013
Although Doppler optical coherence tomography techniques have enabled the imaging of blood flow i... more Although Doppler optical coherence tomography techniques have enabled the imaging of blood flow in mid-sized vessels in biological tissues, the generation of velocity maps of capillary networks remains a challenge. To better understand the origin and information content of the Doppler signal from small vessels and limitations of such measurements, we used joint spectral and time domain optical coherence tomography to monitor the flow in a model, semitransparent microchannel device. The results obtained for Intralipid, whole blood, as well as separated red blood cells indicate that the technique is suitable to record velocity profiles in vitro, in a range of microchannel configurations.
Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVII, 2013
ABSTRACT In this report the application of graphics processing unit (GPU) programming for real-ti... more ABSTRACT In this report the application of graphics processing unit (GPU) programming for real-time 3D Fourier domain Optical Coherence Tomography (FdOCT) imaging with implementation of Doppler algorithms for visualization of the flows in capillary vessels is presented. Generally, the time of the data processing of the FdOCT data on the main processor of the computer (CPU) constitute a main limitation for real-time imaging. Employing additional algorithms, such as Doppler OCT analysis, makes this processing even more time consuming. Lately developed GPUs, which offers a very high computational power, give a solution to this problem. Taking advantages of them for massively parallel data processing, allow for real-time imaging in FdOCT. The presented software for structural and Doppler OCT allow for the whole processing with visualization of 2D data consisting of 2000 A-scans generated from 2048 pixels spectra with frame rate about 120 fps. The 3D imaging in the same mode of the volume data build of 220 × 100 A-scans is performed at a rate of about 8 frames per second. In this paper a software architecture, organization of the threads and optimization applied is shown. For illustration the screen shots recorded during real time imaging of the phantom (homogeneous water solution of Intralipid in glass capillary) and the human eye in-vivo is presented.
Ophthalmic Technologies XIX, 2009
In this submission we demonstrate a new application of the joint Spectral and Time domain Optical... more In this submission we demonstrate a new application of the joint Spectral and Time domain Optical Coherence Tomography (STdOCT) technique for segmenting and measuring the retinal blood flow velocity in three dimensions. The method is based on direct detection of Doppler shift that arises in time during the measurement. New scanning protocols and analysis tools are proposed to create velocity distribution maps of the retina and to segment and visualize 3D vasculature of human eye in-vivo. STdOCT segmentation is more sensitive than methods based on phase measurements and calculations are more straightforward than other techniques, which require more complex experimental setup and more sophisticated numerical tools. The usage of ultra-fast line scan camera allows to broaden the axial velocity range up to ±24mm/s, thus all high flows in human retina can be registered.
Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVI, 2012
ABSTRACT Although the Doppler Optical Coherence Tomography techniques have already enabled imagin... more ABSTRACT Although the Doppler Optical Coherence Tomography techniques have already enabled imaging of blood flow in large vessels in biological tissues, the generation of velocity maps of the capillary network is still a challenge. Since several important physiological and pathological phenomena occur in the microcirculation, the possibility of flow imaging and velocity assessment in microcapillaries may be important for medical diagnostics. Understanding of the origin of the Doppler signal in capillary vessels and limitations of such measurements is essential for further development of Doppler OCT methods. In the OCT flow maps of a microcapillary network randomly varying Doppler signals are observed. To answer the question how accurate is the Doppler OCT flow measurement for blood motion in small vessels, we have investigated the possibility to obtain velocity profiles of blood in vitro in well controlled experimental configuration. We have used a rectangular microchannel (100 μm wide, 40 μm deep) as a microcapillary phantom. Imaging was performed with a Fourier domain OCT setup with a CMOS camera. Data analysis was performed using joint Spectral and Time Domain OCT method (STdOCT).
Ophthalmic Technologies XX, 2010
ABSTRACT We present both axial and transverse components estimation using joint Spectral and Time... more ABSTRACT We present both axial and transverse components estimation using joint Spectral and Time domain Optical Coherence Tomography (STdOCT) method. Whereas axial component of velocity vector can be determined from the time-dependent Doppler beating frequency, the transverse component can be assessed by the analysis of the broadening of flow velocity profiles (Doppler bandwidth). This enables us to quantitatively determine the absolute value of the velocity vector. The accurate analyses are performed using well-defined flow of Intralipid solution in the glass capillary. This enables performing in vivo imaging and allows to calculate velocity maps of the retinal vasculature.
Frontiers in Optics 2011/Laser Science XXVII, 2011
Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVII, 2013
ABSTRACT We show results of a project which focuses on detection of activity in neural tissue wit... more ABSTRACT We show results of a project which focuses on detection of activity in neural tissue with Optical Coherence Tomography (OCT) methods. Experiments were performed in neural cords dissected from the American cockroach (Periplaneta americana L.). Functional OCT imaging was performed with ultrahigh resolution spectral / Fourier domain OCT system (axial resolution 2.5 μm). Electrical stimulation (voltage pulses) was applied to the sensory cercal nerve of the neural cord. Optical detection of functional activation of the sample was performed in the connective between the terminal abdominal ganglion and the fifth abdominal ganglion. Functional OCT data were collected over time with the OCT beam illuminating selected single point in the connectives (i.e. OCT M-scans were acquired). Phase changes of the OCT signal were analyzed to visualize occurrence of activation in the neural cord. Electrophysiology recordings (microelectrode method) were also performed as a reference method to demonstrate electrical response of the sample to stimulation.
ABSTRACT In this paper we report that optical inhomogeneity of flowing fluid has influence on Dop... more ABSTRACT In this paper we report that optical inhomogeneity of flowing fluid has influence on Doppler OCT measurement. Additional Doppler signal from scattering steady medium below blood vessels is visible. To investigate this phenomenon, the experiments with different scattering mediums and different well controlled experimental configurations were carried out. Imaging was performed using SOCT instrument with CCD camera, and joint Spectral and Time domain OCT method was used during data analysis.
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Papers by Danuta Bukowska