31 research outputs found
Blood flow rate estimation in optic disc capillaries and vessels using Doppler optical coherence tomography with 3D fast phase unwrapping
The retinal volumetric flow rate contains useful information not only for ophthalmology but also for the diagnosis of common civilization diseases such as diabetes, Alzheimer's disease, or cerebrovascular diseases. Non-invasive optical methods for quantitative flow assessment, such as Doppler optical coherence tomography (OCT), have certain limitations. One is the phase wrapping that makes simultaneous calculations of the flow in all human retinal vessels impossible due to a very large span of flow velocities. We demonstrate that three-dimensional Doppler OCT combined with three-dimensional four Fourier transform fast phase unwrapping (3D 4FT FPU) allows for the calculation of the volumetric blood flow rate in real-time by the implementation of the algorithms in a graphics processing unit (GPU). The additive character of the flow at the furcations is proven using a microfluidic device with controlled flow rates as well as in the retinal veins bifurcations imaged in the optic disc area of five healthy volunteers. We show values of blood flow rates calculated for retinal capillaries and vessels with diameters in the range of 12-150 µm. The potential of quantitative measurement of retinal blood flow volume includes noninvasive detection of carotid artery stenosis or occlusion, measuring vascular reactivity and evaluation of vessel wall stiffness
Year in review in Intensive Care Medicine 2010: III. ARDS and ALI, mechanical ventilation, noninvasive ventilation, weaning, endotracheal intubation, lung ultrasound and paediatrics
SCOPUS: re.jinfo:eu-repo/semantics/publishe
Improved measurement of vibration amplitude in dynamic optical coherence elastography
Optical coherence elastography employs optical coherence tomography (OCT) to measure the displacement of tissues under load and, thus, maps the resulting strain into an image, known as an elastogram. We present a new improved method to measure vibration amplitude in dynamic optical coherence elastography. The tissue vibration amplitude caused by sinusoidal loading is measured from the spread of the Doppler spectrum, which is extracted using joint spectral and time domain signal processing. At low OCT signal-to-noise ratio (SNR), the method provides more accurate vibration amplitude measurements than the currently used phasesensitive method. For measurements performed on a mirror at OCT SNR = 5 dB, our method introduces 20% using the phasesensitive method. We present elastograms of a tissue-mimicking phantom and excised porcine tissue that demonstrate improvements, including a 50% increase in the depth range of reliable vibration amplitude measurement
Improved measurement of vibration amplitude in dynamic optical coherence elastography
Optical coherence elastography employs optical coherence tomography (OCT) to measure the displacement of tissues under load and, thus, maps the resulting strain into an image, known as an elastogram. We present a new improved method to measure vibration amplitude in dynamic optical coherence elastography. The tissue vibration amplitude caused by sinusoidal loading is measured from the spread of the Doppler spectrum, which is extracted using joint spectral and time domain signal processing. At low OCT signal-to-noise ratio (SNR), the method provides more accurate vibration amplitude measurements than the currently used phasesensitive method. For measurements performed on a mirror at OCT SNR = 5 dB, our method introduces 20% using the phasesensitive method. We present elastograms of a tissue-mimicking phantom and excised porcine tissue that demonstrate improvements, including a 50% increase in the depth range of reliable vibration amplitude measurement
Blood flow measurement and slow flow detection in retinal vessels with Joint Spectral and Time domain method in ultrahigh speed OCT
We present an application of the Joint Spectral and Time domain OCT (STdOCT) method for detection of wide range of flows in the retinal vessels. We utilized spectral/Fourier domain OCT (SOCT) technique for development of scan protocols for Doppler signal analysis. We performed retinal imaging in normal eyes using ultrahigh speed (200 000 axial scans/s) SOCT instrument with a CMOS camera. Various raster scan protocols were implemented for investigation of blood flow in the retina. Data analysis was performed using the method of joint Spectral and Time domain OCT (STdOCT). Detection of blood flow velocities ranging from several tens of mm/s to a fraction of mm/s was possible with scanning methods allowing for appropriate selection of time intervals between data taken for Doppler OCT analysis. Axial blood flow velocity measurement was possible in retinal vessels. Doppler OCT signal can be utilized as a contrast mechanism for visualization of retinal capillaries.Poland. Ministry of Science and Higher Education (Grant Number 2076/B/H03/2009/37