Echocardiographic assessment of left ventricular diastolic function.

PubMed

Pirat, Bahar; Zoghbi, William A

2007-09-01

Assessment of diastolic function and left ventricular filling pressures in the setting of both normal and reduced systolic function is of major importance particularly in patients with dyspnea. Since multiple echocardiography parameters are used to assess diastolic function each with some limitations, a comprehensive approach should be applied. Transmitral Doppler flow should be evaluated in combination with newer, less load dependent Doppler techniques. Tissue Doppler imaging provides accurate, well validated data regarding diastolic properties and filling pressures of the left ventricle. Tissue Doppler imaging should be the part of a routine echocardiography study due to its ease of use and high reproducibility. Pulmonary vein Doppler and flow propagation velocity should be incorporated into the evaluation when needed.

Standardised imaging technique for guided M-mode and Doppler echocardiography in the horse.

PubMed

Long, K J; Bonagura, J D; Darke, P G

1992-05-01

Eighteen echocardiographic images useful for diagnostic imaging, M-mode echocardiography, and Doppler echocardiography of the equine heart were standardised by relating the position of the axial beam to various intracardiac landmarks. The transducer orientation required for each image was recorded in 14 adult horses by describing the degree of sector rotation and the orientation of the axial beam relative to the thorax. Repeatable images could be obtained within narrow limits of angulation and rotation for 14 of the 18 standardised images evaluated. Twenty-seven National Hunt horses were subsequently examined using this standardised technique. Selected cardiac dimensions were measured from two-dimensional and guided M-mode studies. Satisfactory results were achieved in 26 of the 27 horses. There was no linear correlation between any of the measured cardiac values and bodyweight. There was no significant difference between measurements taken from the left and the right hemithorax. Six horses were imaged on three consecutive days to assess the repeatability of the measurements. No significant difference was found between measurements obtained on different days. This study demonstrates a method for standardised echocardiographic evaluation of the equine heart that is repeatable, valuable for teaching techniques of equine echocardiography, applicable for diagnostic imaging and quantification of cardiac size, and useful for the evaluation of blood-flow patterns by Doppler ultrasound.

Application of the multiple PRF technique to resolve Doppler centroid estimation ambiguity for spaceborne SAR

NASA Technical Reports Server (NTRS)

Chang, C. Y.; Curlander, J. C.

1992-01-01

Estimation of the Doppler centroid ambiguity is a necessary element of the signal processing for SAR systems with large antenna pointing errors. Without proper resolution of the Doppler centroid estimation (DCE) ambiguity, the image quality will be degraded in the system impulse response function and the geometric fidelity. Two techniques for resolution of DCE ambiguity for the spaceborne SAR are presented; they include a brief review of the range cross-correlation technique and presentation of a new technique using multiple pulse repetition frequencies (PRFs). For SAR systems, where other performance factors control selection of the PRF's, an algorithm is devised to resolve the ambiguity that uses PRF's of arbitrary numerical values. The performance of this multiple PRF technique is analyzed based on a statistical error model. An example is presented that demonstrates for the Shuttle Imaging Radar-C (SIR-C) C-band SAR, the probability of correct ambiguity resolution is higher than 95 percent for antenna attitude errors as large as 3 deg.

Staggered Multiple-PRF Ultrafast Color Doppler.

PubMed

Posada, Daniel; Poree, Jonathan; Pellissier, Arnaud; Chayer, Boris; Tournoux, Francois; Cloutier, Guy; Garcia, Damien

2016-06-01

Color Doppler imaging is an established pulsed ultrasound technique to visualize blood flow non-invasively. High-frame-rate (ultrafast) color Doppler, by emissions of plane or circular wavefronts, allows severalfold increase in frame rates. Conventional and ultrafast color Doppler are both limited by the range-velocity dilemma, which may result in velocity folding (aliasing) for large depths and/or large velocities. We investigated multiple pulse-repetition-frequency (PRF) emissions arranged in a series of staggered intervals to remove aliasing in ultrafast color Doppler. Staggered PRF is an emission process where time delays between successive pulse transmissions change in an alternating way. We tested staggered dual- and triple-PRF ultrafast color Doppler, 1) in vitro in a spinning disc and a free jet flow, and 2) in vivo in a human left ventricle. The in vitro results showed that the Nyquist velocity could be extended to up to 6 times the conventional limit. We found coefficients of determination r(2) ≥ 0.98 between the de-aliased and ground-truth velocities. Consistent de-aliased Doppler images were also obtained in the human left heart. Our results demonstrate that staggered multiple-PRF ultrafast color Doppler is efficient for high-velocity high-frame-rate blood flow imaging. This is particularly relevant for new developments in ultrasound imaging relying on accurate velocity measurements.

Doppler-Only Synthetic Aperture Radar

DTIC Science & Technology

2006-12-01

5 B. TARGET RECOGNITION TECHNIQUES .................................................6 1. Cooperative Targets...6 3. Techniques ............................................................................................6 C. TARGET RECOGNITION...3. Implementation of High Range Resolution Techniques .................12 F. TWO-DIMENSIONAL IMAGING

Vibration amplitude sonoelastography lesion imaging using low-frequency audible vibration

NASA Astrophysics Data System (ADS)

Taylor, Lawrence; Parker, Kevin

2003-04-01

Sonoelastography or vibration amplitude imaging is an ultrasound imaging technique in which low-amplitude, low-frequency shear waves, less than 0.1-mm displacement and 1-kHz frequency, are propagated deep into tissue, while real time Doppler techniques are used to image the resulting vibration pattern. Finite-element studies and experiments on tissue-mimicking phantoms verify that a discrete hard inhomogeneity present within a larger region of soft tissue will cause a decrease in the vibration field at its location. This forms the basis for tumor detection using sonoelastography. Real time relative imaging of the vibration field is possible because a vibrating particle will phase modulate an ultrasound signal. The particle's amplitude is directly proportional to the spectral spread of the reflected Doppler echo. Real time estimation of the variance of the Doppler power spectrum at each pixel allows the vibration field to be imaged. Results are shown for phantom lesions, thermal lesions, and 3-D in vitro and 2-D in vivo prostate cancer. MRI and whole mount histology is used to validate the system accuracy.

Transthoracic Ultrafast Doppler Imaging of Human Left Ventricular Hemodynamic Function

PubMed Central

Osmanski, Bruno-Félix; Maresca, David; Messas, Emmanuel; Tanter, Mickael; Pernot, Mathieu

2016-01-01

Heart diseases can affect intraventricular blood flow patterns. Real-time imaging of blood flow patterns is challenging because it requires both a high frame rate and a large field of view. To date, standard Doppler techniques can only perform blood flow estimation with high temporal resolution within small regions of interest. In this work, we used ultrafast imaging to map in 2D human left ventricular blood flow patterns during the whole cardiac cycle. Cylindrical waves were transmitted at 4800 Hz with a transthoracic phased array probe to achieve ultrafast Doppler imaging of the left ventricle. The high spatio-temporal sampling of ultrafast imaging permits to rely on a much more effective wall filtering and to increase sensitivity when mapping blood flow patterns during the pre-ejection, ejection, early diastole, diastasis and late diastole phases of the heart cycle. The superior sensitivity and temporal resolution of ultrafast Doppler imaging makes it a promising tool for the noninvasive study of intraventricular hemodynamic function. PMID:25073134

New Approaches For Asteroid Spin State and Shape Modeling From Delay-Doppler Radar Images

NASA Astrophysics Data System (ADS)

Raissi, Chedy; Lamee, Mehdi; Mosiane, Olorato; Vassallo, Corinne; Busch, Michael W.; Greenberg, Adam; Benner, Lance A. M.; Naidu, Shantanu P.; Duong, Nicholas

2016-10-01

Delay-Doppler radar imaging is a powerful technique to characterize the trajectories, shapes, and spin states of near-Earth asteroids; and has yielded detailed models of dozens of objects. Reconstructing objects' shapes and spins from delay-Doppler data is a computationally intensive inversion problem. Since the 1990s, delay-Doppler data has been analyzed using the SHAPE software. SHAPE performs sequential single-parameter fitting, and requires considerable computer runtime and human intervention (Hudson 1993, Magri et al. 2007). Recently, multiple-parameter fitting algorithms have been shown to more efficiently invert delay-Doppler datasets (Greenberg & Margot 2015) - decreasing runtime while improving accuracy. However, extensive human oversight of the shape modeling process is still required. We have explored two new techniques to better automate delay-Doppler shape modeling: Bayesian optimization and a machine-learning neural network.One of the most time-intensive steps of the shape modeling process is to perform a grid search to constrain the target's spin state. We have implemented a Bayesian optimization routine that uses SHAPE to autonomously search the space of spin-state parameters. To test the efficacy of this technique, we compared it to results with human-guided SHAPE for asteroids 1992 UY4, 2000 RS11, and 2008 EV5. Bayesian optimization yielded similar spin state constraints within a factor of 3 less computer runtime.The shape modeling process could be further accelerated using a deep neural network to replace iterative fitting. We have implemented a neural network with a variational autoencoder (VAE), using a subset of known asteroid shapes and a large set of synthetic radar images as inputs to train the network. Conditioning the VAE in this manner allows the user to give the network a set of radar images and get a 3D shape model as an output. Additional development will be required to train a network to reliably render shapes from delay-Doppler images.This work was supported by NASA Ames, NVIDIA, Autodesk and the SETI Institute as part of the NASA Frontier Development Lab program.

A multimodal imaging platform with integrated simultaneous photoacoustic microscopy, optical coherence tomography, optical Doppler tomography and fluorescence microscopy

NASA Astrophysics Data System (ADS)

Dadkhah, Arash; Zhou, Jun; Yeasmin, Nusrat; Jiao, Shuliang

2018-02-01

Various optical imaging modalities with different optical contrast mechanisms have been developed over the past years. Although most of these imaging techniques are being used in many biomedical applications and researches, integration of these techniques will allow researchers to reach the full potential of these technologies. Nevertheless, combining different imaging techniques is always challenging due to the difference in optical and hardware requirements for different imaging systems. Here, we developed a multimodal optical imaging system with the capability of providing comprehensive structural, functional and molecular information of living tissue in micrometer scale. This imaging system integrates photoacoustic microscopy (PAM), optical coherence tomography (OCT), optical Doppler tomography (ODT) and fluorescence microscopy in one platform. Optical-resolution PAM (OR-PAM) provides absorption-based imaging of biological tissues. Spectral domain OCT is able to provide structural information based on the scattering property of biological sample with no need for exogenous contrast agents. In addition, ODT is a functional extension of OCT with the capability of measurement and visualization of blood flow based on the Doppler effect. Fluorescence microscopy allows to reveal molecular information of biological tissue using autofluoresce or exogenous fluorophores. In-vivo as well as ex-vivo imaging studies demonstrated the capability of our multimodal imaging system to provide comprehensive microscopic information on biological tissues. Integrating all the aforementioned imaging modalities for simultaneous multimodal imaging has promising potential for preclinical research and clinical practice in the near future.

Quantification of gastric emptying and duodenogastric reflux stroke volumes using three-dimensional guided digital color Doppler imaging.

PubMed

Hausken, T; Li, X N; Goldman, B; Leotta, D; Ødegaard, S; Martin, R W

2001-07-01

To develop a non-invasive method for evaluating gastric emptying and duodenogastric reflux stroke volumes using three-dimensional (3D) guided digital color Doppler imaging. The technique involved color Doppler digital images of transpyloric flow in which the 3D position and orientation of the images were known by using a magnetic location system. In vitro, the system was found to slightly underestimate the reference flow (by average 8.8%). In vivo (five volunteers), stroke volume of gastric emptying episodes lasted on average only 0.69 s with a volume on average of 4.3 ml (range 1.1-7.4 ml), and duodenogastric reflux episodes on average 1.4 s with a volume of 8.3 ml (range 1.3-14.1 ml). With the appropriate instrument settings, orientation determined color Doppler can be used for stroke volume quantification of gastric emptying and duodenogastric reflux episodes.

Development of Rayleigh Doppler lidar for measuring middle atmosphere winds

NASA Astrophysics Data System (ADS)

Raghunath, K.; Patra, A. K.; Narayana Rao, D.

Interpretation of most of the middle and upper atmospheric dynamical and chemical data relies on the climatological description of the wind field Rayleigh Doppler lidar is one instrument which monitors wind profiles continuously though continuity is limited to clear meteorological conditions in the middle atmosphere A Doppler wind lidar operating in incoherent mode gives excellent wind and temperature information at these altitudes with necessary spectral sensitivity It observes atmospheric winds by measuring the spectral shift of the scattered light due to the motions of atmospheric molecules with background winds and temperature by spectral broadening The presentation is about the design and development of Incoherent Doppler lidar to obtain wind information in the height regions of 30-65 km The paper analyses and describes various types of techniques that can be adopted viz Edge technique and Fringe Imaging technique The paper brings out the scientific objectives configuration simulations error sources and technical challenges involved in the development of Rayleigh Doppler lidar The presentation also gives a novel technique for calibrating the lidar

Detection of cavernous transformation of the portal vein by contrast-enhanced ultrasound.

PubMed

Hwang, Misun; Thimm, Matthew A; Guerrerio, Anthony L

2018-06-01

Cavernous transformation of the portal vein can be missed on color Doppler exam or arterial phase cross-sectional imaging due to their slow flow and delayed enhancement. Contrast-enhanced ultrasound (CEUS) offers many advantages over other imaging techniques and can be used to successfully detect cavernous transformations of the portal vein. A 10-month-old female was followed for repeat episodes of hematemesis. Computed tomography angiography (CTA) and magnetic resonance arteriogram (MRA) and portal venography were performed. Color Doppler exam of the portal vein was performed followed by administration of Lumason, a microbubble US contrast agent. Magnetic resonance arteriogram, CTA, and color Doppler exam at the time of initial presentation was unremarkable without obvious vascular malformation within the limits of motion degraded exam. At 8-month follow-up, esophagogastroduodenoscopy revealed a vascular malformation in the distal esophagus which was sclerosed. At 6 month after sclerosis of the lesion, portal venography revealed occlusion of the portal vein with extensive collateralization. Color Doppler revealed subtle hyperarterialization and periportal collaterals. CEUS following color Doppler exam demonstrated extensive enhancement of periportal collaterals. Repeat color Doppler after contrast administration demonstrated extensive Doppler signal in the collateral vessels, suggestive of cavernous transformation. We describe a case of cavernous transformation of the portal vein missed on initial color Doppler, CTA and MRA, but detected with contrast-enhanced ultrasound technique.

Evaluation of contrast-enhanced power Doppler imaging for measuring blood flow

NASA Astrophysics Data System (ADS)

Ansaloni, Sara; Arger, Peter H.; Cary, Ted W.; Sehgal, Chandra M.

2005-04-01

Power Doppler ultrasound enhanced by microbubble contrast agent has been used to image tissue vascularity and blood flow for the assessment of antivascular therapies. We have proposed a multigating technique that measures bubble concentration as a function of ultrasound exposure for deriving tumor blood flow and vascularity.1 Techniques using ultrasound contrast agent are known to be sensitive to the choice of imaging parameters like mechanical index and tissue attenuation. In this paper, the roles of mechanical index (MI) and tissue attenuation were evaluated experimentally in a rubber tubing flow phantom connected to a mixing chamber and a variable speed pump. The contrast was injected in the mixing chamber and the flow rate was measured using power Doppler imaging. The measurements were repeated at different MIs (0.1 to 1.3), and at different levels of attenuation, obtained with solutions of glycerol-water (10-20%). True flow was measured by collecting liquid flowing out of the phantom over a fixed duration. At low MI (<0.5), the grayscale and Doppler signal were weak, making these images unsuitable for analysis. At higher MI (> 0.8), there was a well-defined enhancement by contrast agent resulting in reproducible flow measurements at variable MIs. A balance between the number of bubbles destroyed and the echo they generate must be achieved for optimal imaging. The increased attenuation of ultrasound by the overlying medium did not influence the flow measurements.

High-definition flow Doppler ultrasonographic technique to assess hepatic vasculature compared with color or power Doppler ultrasonography: preliminary experience.

PubMed

Kim, Se Hyung; Lee, Jeong Min; Kim, Young Jun; Lee, Jae Young; Han, Joon Koo; Choi, Byung Ihn

2008-10-01

The purpose of this study was to introduce a new high-definition flow (HDF) Doppler technique and to compare its performance with those of color Doppler ultrasonography (CDU) and power Doppler ultrasonography (PDU) for assessment of hepatic vasculature in native and transplanted livers. High-definition flow was invented as a high-resolution bidirectional PDU technique. We obtained CDU, PDU, and HDF images of the hepatic artery (HA), portal vein (PV), and hepatic vein from 60 patients. They were divided into 2 groups: a liver transplantation group (group 1, n = 10) and a native liver group (group 2, n = 50). Two radiologists independently reviewed the cine images and graded them using a 4-point scale in terms of the clarity of the vessel margin and degree of depiction of the HA, flow filling, and flash artifacts. The degree of differentiation between the HA and PV was also evaluated. Flow directionality was recorded, and interobserver agreement was finally analyzed. Moderate to almost perfect agreement was achieved between radiologists for all parameters of each ultrasonographic technique. High-definition flow was significantly superior to both CDU and PDU with respect to all analyzed items except the degree of flash artifacts (P < .05). With regard to flash artifacts, CDU was significantly better than either PDU or HDF. High-definition flow provided directional information, as did CDU. The HDF technique provides better resolution for depicting hepatic vessels as well as their margins with less blooming compared with conventional Doppler ultrasonography in both native and transplanted liver. It also provides solid directional flow information. One point of concern, however, is the frequency of flash artifacts compared with that on CDU.

A new fringeline-tracking approach for color Doppler ultrasound imaging phase unwrapping

NASA Astrophysics Data System (ADS)

Saad, Ashraf A.; Shapiro, Linda G.

2008-03-01

Color Doppler ultrasound imaging is a powerful non-invasive diagnostic tool for many clinical applications that involve examining the anatomy and hemodynamics of human blood vessels. These clinical applications include cardio-vascular diseases, obstetrics, and abdominal diseases. Since its commercial introduction in the early eighties, color Doppler ultrasound imaging has been used mainly as a qualitative tool with very little attempts to quantify its images. Many imaging artifacts hinder the quantification of the color Doppler images, the most important of which is the aliasing artifact that distorts the blood flow velocities measured by the color Doppler technique. In this work we will address the color Doppler aliasing problem and present a recovery methodology for the true flow velocities from the aliased ones. The problem is formulated as a 2D phase-unwrapping problem, which is a well-defined problem with solid theoretical foundations for other imaging domains, including synthetic aperture radar and magnetic resonance imaging. This paper documents the need for a phase unwrapping algorithm for use in color Doppler ultrasound image analysis. It describes a new phase-unwrapping algorithm that relies on the recently developed cutline detection approaches. The algorithm is novel in its use of heuristic information provided by the ultrasound imaging modality to guide the phase unwrapping process. Experiments have been performed on both in-vitro flow-phantom data and in-vivo human blood flow data. Both data types were acquired under a controlled acquisition protocol developed to minimize the distortion of the color Doppler data and hence to simplify the phase-unwrapping task. In addition to the qualitative assessment of the results, a quantitative assessment approach was developed to measure the success of the results. The results of our new algorithm have been compared on ultrasound data to those from other well-known algorithms, and it outperforms all of them.

Echocardiographic Evaluation of Left Atrial Mechanics: Function, History, Novel Techniques, Advantages, and Pitfalls.

PubMed

Leischik, Roman; Littwitz, Henning; Dworrak, Birgit; Garg, Pankaj; Zhu, Meihua; Sahn, David J; Horlitz, Marc

2015-01-01

Left atrial (LA) functional analysis has an established role in assessing left ventricular diastolic function. The current standard echocardiographic parameters used to study left ventricular diastolic function include pulsed-wave Doppler mitral inflow analysis, tissue Doppler imaging measurements, and LA dimension estimation. However, the above-mentioned parameters do not directly quantify LA performance. Deformation studies using strain and strain-rate imaging to assess LA function were validated in previous research, but this technique is not currently used in routine clinical practice. This review discusses the history, importance, and pitfalls of strain technology for the analysis of LA mechanics.

Proceedings of Workshop on Laser Diagnostics in Fluid Mechanics and Combustion

NASA Astrophysics Data System (ADS)

1993-10-01

Proceedings of the Workshop on Laser Diagnostics in Fluid Mechanics and Combustion are presented. Topics included are: Accuracy of Laser Doppler Anemometry; Applications of Raman-Rayleigh-LIF Diagnostics in Combustion Research; Phase Doppler Anemometer Technique Concepts and Applications; CARS; Particle Image Velocimetry; Practical Consideration in the Use and Design of Laser Velocimetry Systems in Turbomachinery Applications; Phase Doppler Measurements of Gas-Particle Flow Through a Tube Bank; Degenerate Four Wave Mixing for Shock Tunnel Studies of Supersonic Combustion; Laser Induced Photodissociation and Fluorescence (LIPF) of Sodium Species Present in Coal Combustion; 3D Holographic Measurements Inside a Spark Ignition Engine; Laser Doppler Velocimeter Measurements in Compressible Flow; Bursting in a Tornado Vortex; Quantitative Imaging of OH and Temperature Using a Single Laser Source and Single Intensified Camera; and Laser Doppler Measurements Inside an Artificial Heart Valve.

Doppler centroid estimation ambiguity for synthetic aperture radars

NASA Technical Reports Server (NTRS)

Chang, C. Y.; Curlander, J. C.

1989-01-01

A technique for estimation of the Doppler centroid of an SAR in the presence of large uncertainty in antenna boresight pointing is described. Also investigated is the image degradation resulting from data processing that uses an ambiguous centroid. Two approaches for resolving ambiguities in Doppler centroid estimation (DCE) are presented: the range cross-correlation technique and the multiple-PRF (pulse repetition frequency) technique. Because other design factors control the PRF selection for SAR, a generalized algorithm is derived for PRFs not containing a common divisor. An example using the SIR-C parameters illustrates that this algorithm is capable of resolving the C-band DCE ambiguities for antenna pointing uncertainties of about 2-3 deg.

Proceedings of the XXII A.I.VE.LA. National Meeting

NASA Astrophysics Data System (ADS)

Primo Tomasini, Enrico

2015-11-01

A.I.VE.LA. - the Italian Association of Laser Velocimetry and non-invasive diagnostics - is a non-profit cultural association whose objective is to promote and support research in the field of non-contact or minimally invasive measurement techniques, particularly electromagnetic-based techniques and optical techniques. Through its Annual Meeting, AIVELA aims to create an active and stimulating forum where current research results and technical advances can be exchanged and the development of new systems for laboratory use, field testing and industrial application can be promoted. The techniques covered include Laser Doppler Anemometry - LDA, Phase Doppler Anemometry - PDA, Image Velocimetry - PIV, Flow visualization techniques, Spectroscopic measurement techniques (LIF, Raman, etc.), Laser Doppler Vibrometry - LDV, Speckle Pattern Interferometry - ESPI, Holographic techniques, Shearography, Digital Image Correlation - DIC, Moiré techniques, Structured light techniques, Infrared imaging, Photoelasticity, Image based measurement techniques, Ultrasonic sensing, Acoustic and Aeroacoustic measurements, etc. The first Annual Meeting was held back in October 1992 and since then there has been a large consensus among the research and scientific communities that the papers presented at the event are of a high scientific interest. The XXII AIVELA Annual Meeting was held at the Faculty of Engineering of University of Rome Tor Vergata on 15-16 December 2014 and was organised in collaboration with the International Master Courses in "Protection Against CBRNe Events". This volume contains a selection of the papers presented at the event. The detailed Programme of the Meeting can be found at: http://www.aivela.org/XXII_Convegno/index.html Trusting our Association and its initiatives will meet your interest, I wish to thank you in advance for your kind attention and hope to meet you soon at one of our events.

Computerized Doppler Tomography and Spectrum Analysis of Carotid Artery Flow

PubMed Central

Morton, Paul; Goldman, Dave; Nichols, W. Kirt

1981-01-01

Contrast angiography remains the definitive study in the evaluation of atherosclerotic occlusive vascular disease. However, a safer technique for serial screening of symptomatic patients and for routine follow up is necessary. Computerized pulsed Doppler ultrasonic arteriography is a noninvasive technique developed by Miles6 for imaging lateral, antero-posterior and transverse sections of the carotid artery. We [ill] this system with new software and hardware to analyze the three-dimensional blood flow data. The system now provides information about the location of the occlusive process in the artery and a semi-quantitative evaluation of the degree of obstruction. In addition, we interfaced a digital signal analyzer to the system which permits spectrum analysis of the pulsed Doppler signal. This addition has allowed us to identify lesions which are not yet hemodynamically significant. ImagesFig. 2bFig. 2c

Translation compensation and micro-Doppler extraction for precession ballistic targets with a wideband terahertz radar

NASA Astrophysics Data System (ADS)

Yang, Qi; Deng, Bin; Wang, Hongqiang; Zhang, Ye; Qin, Yuliang

2018-01-01

Imaging, classification, and recognition techniques of ballistic targets in midcourse have always been the focus of research in the radar field for military applications. However, the high velocity translation of ballistic targets will subject range profile and Doppler to translation, slope, and fold, which are especially severe in the terahertz region. Therefore, a two-step translation compensation method based on envelope alignment is presented. The rough compensation is based on the traditional envelope alignment algorithm in inverse synthetic aperture radar imaging, and the fine compensation is supported by distance fitting. Then, a wideband imaging radar system with a carrier frequency of 0.32 THz is introduced, and an experiment on a precession missile model is carried out. After translation compensation with the method proposed in this paper, the range profile and the micro-Doppler distributions unaffected by translation are obtained, providing an important foundation for the high-resolution imaging and micro-Doppler extraction of the terahertz radar.

Bone surface enhancement in ultrasound images using a new Doppler-based acquisition/processing method.

PubMed

Yang, Xu; Tang, Songyuan; Tasciotti, Ennio; Righetti, Raffaella

2018-01-17

Ultrasound (US) imaging has long been considered as a potential aid in orthopedic surgeries. US technologies are safe, portable and do not use radiations. This would make them a desirable tool for real-time assessment of fractures and to monitor fracture healing. However, image quality of US imaging methods in bone applications is limited by speckle, attenuation, shadow, multiple reflections and other imaging artifacts. While bone surfaces typically appear in US images as somewhat 'brighter' than soft tissue, they are often not easily distinguishable from the surrounding tissue. Therefore, US imaging methods aimed at segmenting bone surfaces need enhancement in image contrast prior to segmentation to improve the quality of the detected bone surface. In this paper, we present a novel acquisition/processing technique for bone surface enhancement in US images. Inspired by elastography and Doppler imaging methods, this technique takes advantage of the difference between the mechanical and acoustic properties of bones and those of soft tissues to make the bone surface more easily distinguishable in US images. The objective of this technique is to facilitate US-based bone segmentation methods and improve the accuracy of their outcomes. The newly proposed technique is tested both in in vitro and in vivo experiments. The results of these preliminary experiments suggest that the use of the proposed technique has the potential to significantly enhance the detectability of bone surfaces in noisy ultrasound images.

Bone surface enhancement in ultrasound images using a new Doppler-based acquisition/processing method

NASA Astrophysics Data System (ADS)

Yang, Xu; Tang, Songyuan; Tasciotti, Ennio; Righetti, Raffaella

2018-01-01

Ultrasound (US) imaging has long been considered as a potential aid in orthopedic surgeries. US technologies are safe, portable and do not use radiations. This would make them a desirable tool for real-time assessment of fractures and to monitor fracture healing. However, image quality of US imaging methods in bone applications is limited by speckle, attenuation, shadow, multiple reflections and other imaging artifacts. While bone surfaces typically appear in US images as somewhat ‘brighter’ than soft tissue, they are often not easily distinguishable from the surrounding tissue. Therefore, US imaging methods aimed at segmenting bone surfaces need enhancement in image contrast prior to segmentation to improve the quality of the detected bone surface. In this paper, we present a novel acquisition/processing technique for bone surface enhancement in US images. Inspired by elastography and Doppler imaging methods, this technique takes advantage of the difference between the mechanical and acoustic properties of bones and those of soft tissues to make the bone surface more easily distinguishable in US images. The objective of this technique is to facilitate US-based bone segmentation methods and improve the accuracy of their outcomes. The newly proposed technique is tested both in in vitro and in vivo experiments. The results of these preliminary experiments suggest that the use of the proposed technique has the potential to significantly enhance the detectability of bone surfaces in noisy ultrasound images.

4-D OCT in Developmental Cardiology

NASA Astrophysics Data System (ADS)

Jenkins, Michael W.; Rollins, Andrew M.

Although strong evidence exists to suggest that altered cardiac function can lead to CHDs, few studies have investigated the influential role of cardiac function and biophysical forces on the development of the cardiovascular system due to a lack of proper in vivo imaging tools. 4-D imaging is needed to decipher the complex spatial and temporal patterns of biomechanical forces acting upon the heart. Numerous solutions over the past several years have demonstrated 4-D OCT imaging of the developing cardiovascular system. This chapter will focus on these solutions and explain their context in the evolution of 4-D OCT imaging. The first sections describe the relevant techniques (prospective gating, direct 4-D imaging, retrospective gating), while later sections focus on 4-D Doppler imaging and measurements of force implementing 4-D OCT Doppler. Finally, the techniques are summarized, and some possible future directions are discussed.

Imaging and characterizing shear wave and shear modulus under orthogonal acoustic radiation force excitation using OCT Doppler variance method.

PubMed

Zhu, Jiang; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K Kirk; Zhou, Qifa; Chen, Zhongping

2015-05-01

We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan.

Vector Doppler: spatial sampling analysis and presentation techniques for real-time systems

NASA Astrophysics Data System (ADS)

Capineri, Lorenzo; Scabia, Marco; Masotti, Leonardo F.

2001-05-01

The aim of the vector Doppler (VD) technique is the quantitative reconstruction of a velocity field independently of the ultrasonic probe axis to flow angle. In particular vector Doppler is interesting for studying vascular pathologies related to complex blood flow conditions. Clinical applications require a real-time operating mode and the capability to perform Doppler measurements over a defined volume. The combination of these two characteristics produces a real-time vector velocity map. In previous works the authors investigated the theory of pulsed wave (PW) vector Doppler and developed an experimental system capable of producing off-line 3D vector velocity maps. Afterwards, for producing dynamic velocity vector maps, we realized a new 2D vector Doppler system based on a modified commercial echograph. The measurement and presentation of a vector velocity field requires a correct spatial sampling that must satisfy the Shannon criterion. In this work we tackled this problem, establishing a relationship between sampling steps and scanning system characteristics. Another problem posed by the vector Doppler technique is the data representation in real-time that should be easy to interpret for the physician. With this in mine we attempted a multimedia solution that uses both interpolated images and sound to represent the information of the measured vector velocity map. These presentation techniques were experimented for real-time scanning on flow phantoms and preliminary measurements in vivo on a human carotid artery.

Applying Zeeman Doppler imaging to solar spectra

NASA Astrophysics Data System (ADS)

Hussain, G. A. J.; Saar, S. H.; Collier Cameron, A.

2004-03-01

A new generation of spectro-polarimeters with high throughput (e.g. CFHT/ESPADONS and LBT/PEPSI) is becoming available. This opportunity can be exploited using Zeeman Doppler imaging (ZDI), a technique that inverts time-series of Stokes V spectra to map stellar surface magnetic fields (Semel 1989). ZDI is assisted by ``Least squares deconvolution'' (LSD), which sums up the signal from 1000's of photospheric lines to produce a mean deconvolved profile with higher S:N (Donati & Collier Cameron 1997).

Spotlight-Mode Synthetic Aperture Radar Processing for High-Resolution Lunar Mapping

NASA Technical Reports Server (NTRS)

Harcke, Leif; Weintraub, Lawrence; Yun, Sang-Ho; Dickinson, Richard; Gurrola, Eric; Hensley, Scott; Marechal, Nicholas

2010-01-01

During the 2008-2009 year, the Goldstone Solar System Radar was upgraded to support radar mapping of the lunar poles at 4 m resolution. The finer resolution of the new system and the accompanying migration through resolution cells called for spotlight, rather than delay-Doppler, imaging techniques. A new pre-processing system supports fast-time Doppler removal and motion compensation to a point. Two spotlight imaging techniques which compensate for phase errors due to i) out of focus-plane motion of the radar and ii) local topography, have been implemented and tested. One is based on the polar format algorithm followed by a unique autofocus technique, the other is a full bistatic time-domain backprojection technique. The processing system yields imagery of the specified resolution. Products enabled by this new system include topographic mapping through radar interferometry, and change detection techniques (amplitude and coherent change) for geolocation of the NASA LCROSS mission impact site.

Imaging of the human choroid with a 1.7 MHz A-scan rate FDML swept source OCT system

NASA Astrophysics Data System (ADS)

Gorczynska, I.; Migacz, J. V.; Jonnal, R.; Zawadzki, R. J.; Poddar, R.; Werner, J. S.

2017-02-01

We demonstrate OCT angiography (OCTA) and Doppler OCT imaging of the choroid in the eyes of two healthy volunteers and in a geographic atrophy case. We show that visualization of specific choroidal layers requires selection of appropriate OCTA methods. We investigate how imaging speed, B-scan averaging and scanning density influence visualization of various choroidal vessels. We introduce spatial power spectrum analysis of OCT en face angiographic projections as a method of quantitative analysis of choroicapillaris morphology. We explore the possibility of Doppler OCT imaging to provide information about directionality of blood flow in choroidal vessels. To achieve these goals, we have developed OCT systems utilizing an FDML laser operating at 1.7 MHz sweep rate, at 1060 nm center wavelength, and with 7.5 μm axial imaging resolution. A correlation mapping OCA method was implemented for visualization of the vessels. Joint Spectral and Time domain OCT (STdOCT) technique was used for Doppler OCT imaging.

MicroV Technology to Improve Transcranial Color Coded Doppler Examinations.

PubMed

Malferrari, Giovanni; Pulito, Giuseppe; Pizzini, Attilia Maria; Carraro, Nicola; Meneghetti, Giorgio; Sanzaro, Enzo; Prati, Patrizio; Siniscalchi, Antonio; Monaco, Daniela

2018-05-04

The purpose of this review is to provide an update on technology related to Transcranial Color Coded Doppler Examinations. Microvascularization (MicroV) is an emerging Power Doppler technology which can allow visualization of low and weak blood flows even at high depths, thus providing a suitable technique for transcranial ultrasound analysis. With MicroV, reconstruction of the vessel shape can be improved, without any overestimation. Furthermore, by analyzing the Doppler signal, MicroV allows a global image of the Circle of Willis. Transcranial Doppler was originally developed for the velocimetric analysis of intracranial vessels, in particular to detect stenoses and the assessment of collateral circulation. Doppler velocimetric analysis was then compared to other neuroimaging techniques, thus providing a cut-off threshold. Transcranial Color Coded Doppler sonography allowed the characterization of vessel morphology. In both Color Doppler and Power Doppler, the signal overestimated the shape of the intracranial vessels, mostly in the presence of thin vessels and high depths of study. In further neurosonology technology development efforts, attempts have been made to address morphology issues and overcome technical limitations. The use of contrast agents has helped in this regard by introducing harmonics and subtraction software, which allowed better morphological studies of vessels, due to their increased signal-to-noise ratio. Having no limitations in the learning curve, in time and contrast agent techniques, and due to its high signal-to-noise ratio, MicroV has shown great potential to obtain the best morphological definition. Copyright © 2018 by the American Society of Neuroimaging.

Modern Diagnostic Techniques for the Assessment of Ocular Blood Flow in Myopia: Current State of Knowledge.

PubMed

Grudzińska, Ewa; Modrzejewska, Monika

2018-01-01

Myopia is the most common refractive error and the subject of interest of various studies assessing ocular blood flow. Increasing refractive error and axial elongation of the eye result in the stretching and thinning of the scleral, choroid, and retinal tissues and the decrease in retinal vessel diameter, disturbing ocular blood flow. Local and systemic factors known to change ocular blood flow include glaucoma, medications and fluctuations in intraocular pressure, and metabolic parameters. Techniques and tools assessing ocular blood flow include, among others, laser Doppler flowmetry (LDF), retinal function imager (RFI), laser speckle contrast imaging (LSCI), magnetic resonance imaging (MRI), optical coherence tomography angiography (OCTA), pulsatile ocular blood flowmeter (POBF), fundus pulsation amplitude (FPA), colour Doppler imaging (CDI), and Doppler optical coherence tomography (DOCT). Many researchers consistently reported lower blood flow parameters in myopic eyes regardless of the used diagnostic method. It is unclear whether this is a primary change that causes secondary thinning of ocular tissues or quite the opposite; that is, the mechanical stretching of the eye wall reduces its thickness and causes a secondary lower demand of tissues for oxygen. This paper presents a review of studies assessing ocular blood flow in myopes.

High-speed optical coherence tomography using fiberoptic acousto-optic phase modulation

NASA Astrophysics Data System (ADS)

Xie, Tuqiang; Wang, Zhenguo; Pan, Yingtian

2003-12-01

We report a new rapid-scanning optical delay device suitable for high-speed optical coherence tomography (OCT) in which an acousto-optic modulator (AOM) is used to independently modulate the Doppler frequency shift of the reference light beam for optical heterodyne detection. Experimental results show that the fluctuation of the measured Doppler frequency shift is less than +/-0.2% over 95% duty cycle of OCT imaging, thus allowing for enhanced signal-to-noise ratio of optical heterodyne detection. The increased Doppler frequency shift by AOM also permits complete envelop demodulation without the compromise of reducing axial resolution; if used with a resonant rapid-scanning optical delay, it will permit high-performance real-time OCT imaging. Potentially, this new rapid-scanning optical delay device will improve the performance of high-speed Doppler OCT techniques.

Automated flow quantification in valvular heart disease based on backscattered Doppler power analysis: implementation on matrix-array ultrasound imaging systems.

PubMed

Buck, Thomas; Hwang, Shawn M; Plicht, Björn; Mucci, Ronald A; Hunold, Peter; Erbel, Raimund; Levine, Robert A

2008-06-01

Cardiac ultrasound imaging systems are limited in the noninvasive quantification of valvular regurgitation due to indirect measurements and inaccurate hemodynamic assumptions. We recently demonstrated that the principle of integration of backscattered acoustic Doppler power times velocity can be used for flow quantification in valvular regurgitation directly at the vena contracta of a regurgitant flow jet. We now aimed to accomplish implementation of automated Doppler power flow analysis software on a standard cardiac ultrasound system utilizing novel matrix-array transducer technology with detailed description of system requirements, components and software contributing to the system. This system based on a 3.5 MHz, matrix-array cardiac ultrasound scanner (Sonos 5500, Philips Medical Systems) was validated by means of comprehensive experimental signal generator trials, in vitro flow phantom trials and in vivo testing in 48 patients with mitral regurgitation of different severity and etiology using magnetic resonance imaging (MRI) for reference. All measurements displayed good correlation to the reference values, indicating successful implementation of automated Doppler power flow analysis on a matrix-array ultrasound imaging system. Systematic underestimation of effective regurgitant orifice areas >0.65 cm(2) and volumes >40 ml was found due to currently limited Doppler beam width that could be readily overcome by the use of new generation 2D matrix-array technology. Automated flow quantification in valvular heart disease based on backscattered Doppler power can be fully implemented on board a routinely used matrix-array ultrasound imaging systems. Such automated Doppler power flow analysis of valvular regurgitant flow directly, noninvasively, and user independent overcomes the practical limitations of current techniques.

An Adaptive Moving Target Imaging Method for Bistatic Forward-Looking SAR Using Keystone Transform and Optimization NLCS.

PubMed

Li, Zhongyu; Wu, Junjie; Huang, Yulin; Yang, Haiguang; Yang, Jianyu

2017-01-23

Bistatic forward-looking SAR (BFSAR) is a kind of bistatic synthetic aperture radar (SAR) system that can image forward-looking terrain in the flight direction of an aircraft. Until now, BFSAR imaging theories and methods for a stationary scene have been researched thoroughly. However, for moving-target imaging with BFSAR, the non-cooperative movement of the moving target induces some new issues: (I) large and unknown range cell migration (RCM) (including range walk and high-order RCM); (II) the spatial-variances of the Doppler parameters (including the Doppler centroid and high-order Doppler) are not only unknown, but also nonlinear for different point-scatterers. In this paper, we put forward an adaptive moving-target imaging method for BFSAR. First, the large and unknown range walk is corrected by applying keystone transform over the whole received echo, and then, the relationships among the unknown high-order RCM, the nonlinear spatial-variances of the Doppler parameters, and the speed of the mover, are established. After that, using an optimization nonlinear chirp scaling (NLCS) technique, not only can the unknown high-order RCM be accurately corrected, but also the nonlinear spatial-variances of the Doppler parameters can be balanced. At last, a high-order polynomial filter is applied to compress the whole azimuth data of the moving target. Numerical simulations verify the effectiveness of the proposed method.

MEMS-Based Handheld Fourier Domain Doppler Optical Coherence Tomography for Intraoperative Microvascular Anastomosis Imaging

PubMed Central

Huang, Yong; Furtmüller, Georg J.; Tong, Dedi; Zhu, Shan; Lee, W. P. Andrew; Brandacher, Gerald; Kang, Jin U.

2014-01-01

Purpose To demonstrate the feasibility of a miniature handheld optical coherence tomography (OCT) imager for real time intraoperative vascular patency evaluation in the setting of super-microsurgical vessel anastomosis. Methods A novel handheld imager Fourier domain Doppler optical coherence tomography based on a 1.3-µm central wavelength swept source for extravascular imaging was developed. The imager was minimized through the adoption of a 2.4-mm diameter microelectromechanical systems (MEMS) scanning mirror, additionally a 12.7-mm diameter lens system was designed and combined with the MEMS mirror to achieve a small form factor that optimize functionality as a handheld extravascular OCT imager. To evaluate in-vivo applicability, super-microsurgical vessel anastomosis was performed in a mouse femoral vessel cut and repair model employing conventional interrupted suture technique as well as a novel non-suture cuff technique. Vascular anastomosis patency after clinically successful repair was evaluated using the novel handheld OCT imager. Results With an adjustable lateral image field of view up to 1.5 mm by 1.5 mm, high-resolution simultaneous structural and flow imaging of the blood vessels were successfully acquired for BALB/C mouse after orthotopic hind limb transplantation using a non-suture cuff technique and BALB/C mouse after femoral artery anastomosis using a suture technique. We experimentally quantify the axial and lateral resolution of the OCT to be 12.6 µm in air and 17.5 µm respectively. The OCT has a sensitivity of 84 dB and sensitivity roll-off of 5.7 dB/mm over an imaging range of 5 mm. Imaging with a frame rate of 36 Hz for an image size of 1000(lateral)×512(axial) pixels using a 50,000 A-lines per second swept source was achieved. Quantitative vessel lumen patency, lumen narrowing and thrombosis analysis were performed based on acquired structure and Doppler images. Conclusions A miniature handheld OCT imager that can be used for intraoperative evaluation of microvascular anastomosis was successfully demonstrated. PMID:25474742

Depth-encoded dual beam phase-resolved Doppler OCT for Doppler-angle-independent flow velocity measurement

NASA Astrophysics Data System (ADS)

Qian, Jie; Cheng, Wei; Cao, Zhaoyuan; Chen, Xinjian; Mo, Jianhua

2017-02-01

Phase-resolved Doppler optical coherence tomography (PR-D-OCT) is a functional OCT imaging technique that can provide high-speed and high-resolution depth-resolved measurement on flow in biological materials. However, a common problem with conventional PR-D-OCT is that this technique often measures the flow motion projected onto the OCT beam path. In other words, it needs the projection angle to extract the absolute velocity from PR-D-OCT measurement. In this paper, we proposed a novel dual-beam PR-D-OCT method to measure absolute flow velocity without separate measurement on the projection angle. Two parallel light beams are created in sample arm and focused into the sample at two different incident angles. The images produced by these two beams are encoded to different depths in single B-scan. Then the Doppler signals picked up by the two beams together with the incident angle difference can be used to calculate the absolute velocity. We validated our approach in vitro on an artificial flow phantom with our home-built 1060 nm swept source OCT. Experimental results demonstrated that our method can provide an accurate measurement of absolute flow velocity with independency on the projection angle.

ICIASF '85 - International Congress on Instrumentation in Aerospace Simulation Facilities, 11th, Stanford University, CA, August 26-28, 1985, Record

NASA Technical Reports Server (NTRS)

1985-01-01

Developments related to laser Doppler velocimetry are discussed, taking into account a three-component dual beam laser-Doppler-anemometer to be operated in large wind tunnels, a new optical system for three-dimensional laser-Doppler-anemometry using an argon-ion and a dye laser, and a two-component laser Doppler velocimeter by switching fringe orientation. Other topics studied are concerned with facilities, instrumentation, control, hot wire/thin film measurements, optical diagnostic techniques, signal and data processing, facilities and adaptive wall test sections, data acquisition and processing, ballistic instrument systems, dynamic testing and material deformation measurements, optical flow measurements, test techniques, force measurement systems, and holography. Attention is given to nonlinear calibration of integral wind tunnel balances, a microcomputer system for real time digitized image compression, and two phase flow diagnostics in propulsion systems.

Experimental Study and Numerical Modeling of Gas Flow in Microchannels and Micronozzles

DTIC Science & Technology

2005-12-01

built and used to study gas flows in microscale. Gas velocity measurements in microscale were conducted using both Laser Induced Fluorescence...velocity measurements in microscale were conducted using both Laser Induced Fluorescence technique (LIF) in conjunction with Image Correlation...micronozzles, several velocity measurement techniques have been used, such as laser doppler anemometry (LDA), particle image velocimetry (PIV), molecular

Noninvasive clinical assessment of port-wine stain birthmarks using current and future optical imaging technology: A review

PubMed Central

Sharif, S.A.; Taydas, E.; Mazhar, A.; Rahimian, R.; Kelly, K.M.; Choi, B.; Durkin, A.J.

2012-01-01

Port wine stain (PWS) birthmarks are one class of benign congenital vascular malformation. Laser therapy is the most successful treatment modality of PWS. Unfortunately, this approach has limited efficacy, with only 10% of patients experiencing complete blanching of the PWS. To address this problem, several research groups have developed technologies and methods designed to study treatment outcome and improve treatment efficacy. This paper reviews seven optical imaging techniques currently in use or under development to assess treatment efficacy, focusing on: Reflectance spectrophotometers/tristimulus colorimeters, Laser Doppler flowmetry (LDF) and Laser Doppler imaging (LDI), Cross-polarized diffuse reflectance color imaging system (CDR), Reflectance Confocal Microscopy (RCM), Optical Coherence Tomography (OCT), Spatial Frequency Domain Imaging (SFDI), and Laser Speckle Imaging (LSI). PMID:22804872

Microwave imaging of spinning object using orbital angular momentum

NASA Astrophysics Data System (ADS)

Liu, Kang; Li, Xiang; Gao, Yue; Wang, Hongqiang; Cheng, Yongqiang

2017-09-01

The linear Doppler shift used for the detection of a spinning object becomes significantly weakened when the line of sight (LOS) is perpendicular to the object, which will result in the failure of detection. In this paper, a new detection and imaging technique for spinning objects is developed. The rotational Doppler phenomenon is observed by using the microwave carrying orbital angular momentum (OAM). To converge the radiation energy on the area where objects might exist, the generation method of OAM beams is proposed based on the frequency diversity principle, and the imaging model is derived accordingly. The detection method of the rotational Doppler shift and the imaging approach of the azimuthal profiles are proposed, which are verified by proof-of-concept experiments. Simulation and experimental results demonstrate that OAM beams can still be used to obtain the azimuthal profiles of spinning objects even when the LOS is perpendicular to the object. This work remedies the insufficiency in existing microwave sensing technology and offers a new solution to the object identification problem.

Evaluation of hemodynamics changes during interventional stent placement using Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Vuong, Barry; Genis, Helen; Wong, Ronnie; Ramjist, Joel; Jivraj, Jamil; Farooq, Hamza; Sun, Cuiru; Yang, Victor X. D.

2015-03-01

Carotid atherosclerosis is a critical medical concern that can lead to ischemic stroke. Local hemodynamic patterns have also been associated with the development of atherosclerosis, particularly in regions with disturbed flow patterns such as bifurcations. Traditionally, this disease was treated using carotid endarterectomy, however recently there is an increasing trend of carotid artery stenting due to its minimally invasive nature. It is well known that this interventional technique creates changes in vasculature geometry and hemodynamic patterns due to the interaction of stent struts with arterial lumen, and is associated with complications such as distal emboli and restenosis. Currently, there is no standard imaging technique to evaluate regional hemodynamic patterns found in stented vessels. Doppler optical coherence tomography (DOCT) provides an opportunity to identify in vivo hemodynamic changes in vasculature using high-resolution imaging. In this study, blood flow profiles were examined at the bifurcation junction in the internal carotid artery (ICA) in a porcine model following stent deployment. Doppler imaging was further conducted using pulsatile flow in a phantom model, and then compared to computational fluid dynamics (CFD) simulation of a virtual bifurcation to assist with the interpretation of emphin vivo results.

High-sensitivity detection and monitoring of microcirculation using cutaneous and catheter probes for Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Yang, Victor X.; Gordon, M. L.; Qi, B.; Yue, E. Seng; Tang, S.; Bisland, Stuart K.; Pekar, J.; Lo, S.; Marcon, Norman E.; Wilson, B.; Vitkin, Alex

2003-07-01

Background: Currently clinical Doppler ultrasound cannot detect microvascular blood flow and it is difficult to provide depth discrimination using laser Doppler flowmetry. Doppler optical coherence tomography (DOCT) is a novel technique for noninvasive subsurface imaging of microcirculation and tissue structure. Aims: To design handheld and catheter-based DOCT probes for clinical cutaneous and endoscopic imaging. To develop signal processing techniques for real-time detection and quantification of microvascular blood flow. Methods: A DOCT system, with interchangeable cutaneous and catheter probes, was developed. The axial spatial resolution was 10 μm, and the velocity resolution was 20 μm/s, using a 1300 nm broadband infrared light. The system achieved real-time imaging with frame rates up to 32 Hz at 512 x 256 pixels per frame. We used the system to detect microcirculation in human skin and rat esophagus, and to monitor microvascular responses to photodynamic therapy (PDT) in a rat tumor model. Results: We present experimental results from in vivo DOCT imaging of microcirculation in human skin arterio-venous malformations (AVM), normal rat esophagus, and a rat gliosarcoma PDT model. In the PDT model, we followed microvascular responses to PDT and observed differences in the microcirculation during and after therapy, which can have important implications for PDT dosimetry and treatment optimization. Conclusions: To our knowledge, this is the first demonstration of endoscopic catheter-based DOCT detection of microcirculation in vivo. In addition, AVM can be detected using handheld cutaneous DOCT probes under clinical settings. DOCT may serve as a real-time monitoring tool for PDT dosimetry, especially for vascular targeting photosensitizers.

Doppler flow imaging of cytoplasmic streaming using spectral domain phase microscopy

NASA Astrophysics Data System (ADS)

Choma, Michael A.; Ellerbee, Audrey K.; Yazdanfar, Siavash; Izatt, Joseph A.

2006-03-01

Spectral domain phase microscopy (SDPM) is a function extension of spectral domain optical coherence tomography. SDPM achieves exquisite levels of phase stability by employing common-path interferometry. We discuss the theory and limitations of Doppler flow imaging using SDPM, demonstrate monitoring the thermal contraction of a glass sample with nanometer per second velocity sensitivity, and apply this technique to measurement of cytoplasmic streaming in an Amoeba proteus pseudopod. We observe reversal of cytoplasmic flow induced by extracellular CaCl2, and report results that suggest parabolic flow of cytoplasm in the A. proteus pseudopod.

Microvascular anastomosis in rodent model evaluated by Fourier domain Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Huang, Yong; Tong, Dedi; Zhu, Shan; Wu, Lehao; Ibrahim, Zuhaib; Lee, WP Andrew; Brandacher, Gerald; Kang, Jin U.

2014-03-01

Vascular and microvascular anastomosis are critical components of reconstructive microsurgery, vascular surgery and transplant surgery. Imaging modality that provides immediate, real-time in-depth view and 3D structure and flow information of the surgical site can be a great valuable tool for the surgeon to evaluate surgical outcome following both conventional and innovative anastomosis techniques, thus potentially increase the surgical success rate. Microvascular anastomosis for vessels with outer diameter smaller than 1.0 mm is extremely challenging and effective evaluation of the outcome is very difficult if not impossible using computed tomography (CT) angiograms, magnetic resonance (MR) angiograms and ultrasound Doppler. Optical coherence tomography (OCT) is a non-invasive high-resolution (micron level), high-speed, 3D imaging modality that has been adopted widely in biomedical and clinical applications. Phaseresolved Doppler OCT that explores the phase information of OCT signals has been shown to be capable of characterizing dynamic blood flow clinically. In this work, we explore the capability of Fourier domain Doppler OCT as an evaluation tool to detect commonly encountered post-operative complications that will cause surgical failure and to confirm positive result with surgeon's observation. Both suture and cuff based techniques were evaluated on the femoral artery and vein in the rodent model.

4D microvascular imaging based on ultrafast Doppler tomography.

PubMed

Demené, Charlie; Tiran, Elodie; Sieu, Lim-Anna; Bergel, Antoine; Gennisson, Jean Luc; Pernot, Mathieu; Deffieux, Thomas; Cohen, Ivan; Tanter, Mickael

2016-02-15

4D ultrasound microvascular imaging was demonstrated by applying ultrafast Doppler tomography (UFD-T) to the imaging of brain hemodynamics in rodents. In vivo real-time imaging of the rat brain was performed using ultrasonic plane wave transmissions at very high frame rates (18,000 frames per second). Such ultrafast frame rates allow for highly sensitive and wide-field-of-view 2D Doppler imaging of blood vessels far beyond conventional ultrasonography. Voxel anisotropy (100 μm × 100 μm × 500 μm) was corrected for by using a tomographic approach, which consisted of ultrafast acquisitions repeated for different imaging plane orientations over multiple cardiac cycles. UFT-D allows for 4D dynamic microvascular imaging of deep-seated vasculature (up to 20 mm) with a very high 4D resolution (respectively 100 μm × 100 μm × 100 μm and 10 ms) and high sensitivity to flow in small vessels (>1 mm/s) for a whole-brain imaging technique without requiring any contrast agent. 4D ultrasound microvascular imaging in vivo could become a valuable tool for the study of brain hemodynamics, such as cerebral flow autoregulation or vascular remodeling after ischemic stroke recovery, and, more generally, tumor vasculature response to therapeutic treatment. Copyright © 2015 Elsevier Inc. All rights reserved.

Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

NASA Astrophysics Data System (ADS)

Werkmeister, René M.; Vietauer, Martin; Knopf, Corinna; Fürnsinn, Clemens; Leitgeb, Rainer A.; Reitsamer, Herbert; Gröschl, Martin; Garhöfer, Gerhard; Vilser, Walthard; Schmetterer, Leopold

2014-10-01

A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%;. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats.

Semi-automation of Doppler Spectrum Image Analysis for Grading Aortic Valve Stenosis Severity.

PubMed

Niakšu, O; Balčiunaitė, G; Kizlaitis, R J; Treigys, P

2016-01-01

Doppler echocardiography analysis has become a golden standard in the modern diagnosis of heart diseases. In this paper, we propose a set of techniques for semi-automated parameter extraction for aortic valve stenosis severity grading. The main objectives of the study is to create echocardiography image processing techniques, which minimize manual image processing work of clinicians and leads to reduced human error rates. Aortic valve and left ventricle output tract spectrogram images have been processed and analyzed. A novel method was developed to trace systoles and to extract diagnostic relevant features. The results of the introduced method have been compared to the findings of the participating cardiologists. The experimental results showed the accuracy of the proposed method is comparable to the manual measurement performed by medical professionals. Linear regression analysis of the calculated parameters and the measurements manually obtained by the cardiologists resulted in the strongly correlated values: peak systolic velocity's and mean pressure gradient's R2 both equal to 0.99, their means' differences equal to 0.02 m/s and 4.09 mmHg, respectively, and aortic valve area's R2 of 0.89 with the two methods means' difference of 0.19 mm. The introduced Doppler echocardiography images processing method can be used as a computer-aided assistance in the aortic valve stenosis diagnostics. In our future work, we intend to improve precision of left ventricular outflow tract spectrogram measurements and apply data mining methods to propose a clinical decision support system for diagnosing aortic valve stenosis.

SDOCT Doppler velocimetry for investigating the morphological influences on blood flow in the developing chick embryo heart

NASA Astrophysics Data System (ADS)

Davis, Anjul M.; Rothenberg, Florence G.; Law, Tzuo H.; Taber, Larry A.; Izatt, Joseph A.

2007-02-01

The onset of congenital heart disease (CHD) is believed to occur at very early stages of development. Investigations in the initiation and development of CHD has been hampered by the inability to image early stage heart structure and function, in vivo. Imaging small animals using optical coherence tomography (OCT) has filled a niche between the limited penetration depth of confocal microscopy and insufficient resolution from ultrasound. Previous demonstrations of chick heart imaging using OCT have entailed excision of, or arresting the heart to prevent motion artifacts. In this summary, we introduce SDOCT Doppler velocimetry as an enhancement of Doppler OCT for in vivo measurement of localized temporal blood flow dynamics. With this technique, dynamic velocity waveforms were measured in the outflow tract of the heart tube. These flow dynamics correlate to a finite element model of pulsatile flow and may lead to a further understanding of morphological influences on early heart development.

Imaging Active Giants and Comparisons to Doppler Imaging

NASA Astrophysics Data System (ADS)

Roettenbacher, Rachael

2018-04-01

In the outer layers of cool, giant stars, stellar magnetism stifles convection creating localized starspots, analogous to sunspots. Because they frequently cover much larger regions of the stellar surface than sunspots, starspots of giant stars have been imaged using a variety of techniques to understand, for example, stellar magnetism, differential rotation, and spot evolution. Active giants have been imaged using photometric, spectroscopic, and, only recently, interferometric observations. Interferometry has provided a way to unambiguously see stellar surfaces without the degeneracies experienced by other methods. The only facility presently capable of obtaining the sub-milliarcsecond resolution necessary to not only resolve some giant stars, but also features on their surfaces is the Center for High-Angular Resolution Astronomy (CHARA) Array. Here, an overview will be given of the results of imaging active giants and details on the recent comparisons of simultaneous interferometric and Doppler images.

Spatially Resolved MR-Compatible Doppler Ultrasound: Proof of Concept for Triggering of Diagnostic Quality Cardiovascular MRI for Function and Flow Quantification at 3T.

PubMed

Crowe, Lindsey Alexandra; Manasseh, Gibran; Chmielewski, Aneta; Hachulla, Anne-Lise; Speicher, Daniel; Greiser, Andreas; Muller, Hajo; de Perrot, Thomas; Vallee, Jean-Paul; Salomir, Rares

2018-02-01

We demonstrate the use of a magnetic-resonance (MR)-compatible ultrasound (US) imaging probe using spatially resolved Doppler for diagnostic quality cardiovascular MR imaging (MRI) as an initial step toward hybrid US/MR fetal imaging. A newly developed technology for a dedicated MR-compatible phased array ultrasound-imaging probe acquired pulsed color Doppler carotid images, which were converted in near-real time to a trigger signal for cardiac cine and flow quantification MRI. Ultrasound and MR data acquired simultaneously were interference free. Conventional electrocardiogram (ECG) and the proposed spatially resolved Doppler triggering were compared in 10 healthy volunteers. A synthetic "false-triggered" image was retrospectively processed using metric optimized gating (MOG). Images were scored by expert readers, and sharpness, cardiac function and aortic flow were quantified. Four-dimensional (4-D) flow (two volunteers) showed feasibility of Doppler triggering over a long acquisition time. Imaging modalities were compatible. US probe positioning was stable and comfortable. Image quality scores and quantified sharpness were statistically equal for Doppler- and ECG-triggering (p ). ECG-, Doppler-triggered, and MOG ejection fractions were equivalent (p ), with false-triggered values significantly lower (p < 0.0005). Aortic flow showed no difference between ECG- and Doppler-triggered and MOG (p > 0.05). 4-D flow quantification gave consistent results between ECG and Doppler triggering. We report interference-free pulsed color Doppler ultrasound during MR data acquisition. Cardiovascular MRI of diagnostic quality was successfully obtained with pulsed color Doppler triggering. The hardware platform could further enable advanced free-breathing cardiac imaging. Doppler ultrasound triggering is applicable where ECG is compromised due to pathology or interference at higher magnetic fields, and where direct ECG is impossible, i.e., fetal imaging.

The application of coded excitation technology in medical ultrasonic Doppler imaging

NASA Astrophysics Data System (ADS)

Li, Weifeng; Chen, Xiaodong; Bao, Jing; Yu, Daoyin

2008-03-01

Medical ultrasonic Doppler imaging is one of the most important domains of modern medical imaging technology. The application of coded excitation technology in medical ultrasonic Doppler imaging system has the potential of higher SNR and deeper penetration depth than conventional pulse-echo imaging system, it also improves the image quality, and enhances the sensitivity of feeble signal, furthermore, proper coded excitation is beneficial to received spectrum of Doppler signal. Firstly, this paper analyzes the application of coded excitation technology in medical ultrasonic Doppler imaging system abstractly, showing the advantage and bright future of coded excitation technology, then introduces the principle and the theory of coded excitation. Secondly, we compare some coded serials (including Chirp and fake Chirp signal, Barker codes, Golay's complementary serial, M-sequence, etc). Considering Mainlobe Width, Range Sidelobe Level, Signal-to-Noise Ratio and sensitivity of Doppler signal, we choose Barker codes as coded serial. At last, we design the coded excitation circuit. The result in B-mode imaging and Doppler flow measurement coincided with our expectation, which incarnated the advantage of application of coded excitation technology in Digital Medical Ultrasonic Doppler Endoscope Imaging System.

Optimized doppler optical coherence tomography for choroidal capillary vasculature imaging

NASA Astrophysics Data System (ADS)

Liu, Gangjun; Qi, Wenjuan; Yu, Lingfeng; Chen, Zhongping

2011-03-01

In this paper, we analyzed the retinal and choroidal blood vasculature in the posterior segment of the human eye with optimized color Doppler and Doppler variance optical coherence tomography. Depth-resolved structure, color Doppler and Doppler variance images were compared. Blood vessels down to capillary level were able to be obtained with the optimized optical coherence color Doppler and Doppler variance method. For in-vivo imaging of human eyes, bulkmotion induced bulk phase must be identified and removed before using color Doppler method. It was found that the Doppler variance method is not sensitive to bulk motion and the method can be used without removing the bulk phase. A novel, simple and fast segmentation algorithm to indentify retinal pigment epithelium (RPE) was proposed and used to segment the retinal and choroidal layer. The algorithm was based on the detected OCT signal intensity difference between different layers. A spectrometer-based Fourier domain OCT system with a central wavelength of 890 nm and bandwidth of 150nm was used in this study. The 3-dimensional imaging volume contained 120 sequential two dimensional images with 2048 A-lines per image. The total imaging time was 12 seconds and the imaging area was 5x5 mm2.

Closed loop tracked Doppler optical coherence tomography based heart monitor for the Drosophila melanogaster larvae.

PubMed

Zurauskas, Mantas; Bradu, Adrian; Ferguson, Daniel R; Hammer, Daniel X; Podoleanu, Adrian

2016-03-01

This paper presents a novel instrument for biosciences, useful for studies of moving embryos. A dual sequential imaging/measurement channel is assembled via a closed-loop tracking architecture. The dual channel system can operate in two regimes: (i) single-point Doppler signal monitoring or (ii) fast 3-D swept source OCT imaging. The system is demonstrated for characterizing cardiac dynamics in Drosophila melanogaster larva. Closed loop tracking enables long term in vivo monitoring of the larvae heart without anesthetic or physical restraint. Such an instrument can be used to measure subtle variations in the cardiac behavior otherwise obscured by the larvae movements. A fruit fly larva (top) was continuously tracked for continuous remote monitoring. A heartbeat trace of freely moving larva (bottom) was obtained by a low coherence interferometry based doppler sensing technique. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Internet (WWW) based system of ultrasonic image processing tools for remote image analysis.

PubMed

Zeng, Hong; Fei, Ding-Yu; Fu, Cai-Ting; Kraft, Kenneth A

2003-07-01

Ultrasonic Doppler color imaging can provide anatomic information and simultaneously render flow information within blood vessels for diagnostic purpose. Many researchers are currently developing ultrasound image processing algorithms in order to provide physicians with accurate clinical parameters from the images. Because researchers use a variety of computer languages and work on different computer platforms to implement their algorithms, it is difficult for other researchers and physicians to access those programs. A system has been developed using World Wide Web (WWW) technologies and HTTP communication protocols to publish our ultrasonic Angle Independent Doppler Color Image (AIDCI) processing algorithm and several general measurement tools on the Internet, where authorized researchers and physicians can easily access the program using web browsers to carry out remote analysis of their local ultrasonic images or images provided from the database. In order to overcome potential incompatibility between programs and users' computer platforms, ActiveX technology was used in this project. The technique developed may also be used for other research fields.

Choroidal imaging by one-micrometer dual-beam Doppler optical coherence angiography with adjustable velocity range

NASA Astrophysics Data System (ADS)

Jaillon, Franck; Makita, Shuichi; Yasuno, Yoshiaki

2012-03-01

Ability of a new version of one-micrometer dual-beam optical coherence angiography (OCA) based on Doppler optical coherence tomography (OCT), is demonstrated for choroidal vasculature imaging. A particular feature of this system is the adjustable time delay between two probe beams. This allows changing the measurable velocity range of moving constituents such as blood without alteration of the scanning protocol. Since choroidal vasculature is made of vessels having blood flows with different velocities, this technique provides a way of discriminating vessels according to the velocity range of their inner flow. An example of choroid imaging of a normal emmetropic eye is here given. It is shown that combining images acquired with different velocity ranges provides an enhanced vasculature representation. This method may be then useful for pathological choroid characterization.

The Surface Brightness Contribution of II Peg: A Comparison of TiO Band Analysis and Doppler Imaging

NASA Astrophysics Data System (ADS)

Senavci, H. V.; O'Neal, D.; Hussain, G. A. J.; Barnes, J. R.

2015-01-01

We investigate the surface brightness contribution of the very well known active SB1 binary II Pegasi , to determine the star spot filling factor and the spot temperature parameters. In this context, we analyze 54 spectra of the system taken over 6 nights in September - October of 1996, using the 2.1m Otto Struve Telescope equipped with SES at the McDonald Observatory. We measure the spot temperatures and spot filling factors by fitting TiO molecular bands in this spectroscopic dataset, with model atmosphere approximation using ATLAS9 and with proxy stars obtained with the same instrument. The same dataset is then used to also produce surface spot maps using the Doppler imaging technique. We compare the spot filling factors obtained with the two independent techniques in order to better characterise the spot properties of the system and to better assess the limitations inherent to both techniques. The results obtained from both techniques show that the variation of spot filling factor as a function of phase agree well with each other, while the amount of TiO and DI spot

Comparison of phase-contrast MR imaging and endovascular sonography for intracranial blood flow velocity measurements.

PubMed

Schneiders, J J; Ferns, S P; van Ooij, P; Siebes, M; Nederveen, A J; van den Berg, R; van Lieshout, J; Jansen, G; vanBavel, E; Majoie, C B

2012-10-01

Local hemodynamic information may help to stratify rupture risk of cerebral aneurysms. Patient-specific modeling of cerebral hemodynamics requires accurate data on BFV in perianeurysmal arteries as boundary conditions for CFD. The aim was to compare the BFV measured with PC-MR imaging with that obtained by using intra-arterial Doppler sonography and to determine interpatient variation in intracranial BFV. In 10 patients with unruptured intracranial aneurysms, BFV was measured in the cavernous ICA with PC-MR imaging in conscious patients before treatment, and measured by using an intra-arterial Doppler sonography wire when the patient was anesthetized with either propofol (6 patients) or sevoflurane (4 patients). Both techniques identified a pulsatile blood flow pattern in cerebral arteries. PSV differed >50 cm/s between patients. A mean velocity of 41.3 cm/s (95% CI, 39.3-43.3) was measured with PC-MR imaging. With intra-arterial Doppler sonography, a mean velocity of 29.3 cm/s (95% CI, 25.8-32.8) was measured with the patient under propofol-based intravenous anesthesia. In patients under sevoflurane-based inhaled anesthesia, a mean velocity of 44.9 cm/s (95% CI, 40.6-49.3) was measured. We showed large differences in BFV between patients, emphasizing the importance of using patient-specific hemodynamic boundary conditions in CFD. PC-MR imaging measurements of BFV in conscious patients were comparable with those obtained with the intra-arterial Doppler sonography when the patient was anesthetized with a sevoflurane-based inhaled anesthetic.

Developments in laser Doppler blood perfusion monitoring

NASA Astrophysics Data System (ADS)

Leahy, Martin J.; de Mul, Frits F. M.; Nilsson, Gert E.; Maniewski, Roman; Liebert, Adam

2003-03-01

This paper reviews the development and use of laser Doppler perfusion monitors and imagers. Despite their great success and almost universal applicability in microcirculation research, they have had great difficulty in converting to widespread clinical application. The enormous interest in microvascular blood perfusion coupled with the 'ease of use' of the technique has led to 2000+ publications citing its use. However, useful results can only be achieved with an understanding of the basic principles of the instrumentation and its application in the various clinical disciplines. The basic technical background is explored and definitions of blood perfusion and laser Doppler perfusion are established. The calibration method is then described together with potential routes to standardisation. A guide to the limitations in application of the technique gives the user a clear indication of what can be achieved in new studies as well as possible inadequacy in some published investigations. Finally some clinical applications have found acceptability and these will be explored.

Expanding applications, accuracy, and interpretation of laser speckle contrast imaging of cerebral blood flow

PubMed Central

Kazmi, S M Shams; Richards, Lisa M; Schrandt, Christian J; Davis, Mitchell A; Dunn, Andrew K

2015-01-01

Laser speckle contrast imaging (LSCI) provides a rapid characterization of cortical flow dynamics for functional monitoring of the microcirculation. The technique stems from interactions of laser light with moving particles. These interactions encode the encountered Doppler phenomena within a random interference pattern imaged in widefield, known as laser speckle. Studies of neurovascular function and coupling with LSCI have benefited from the real-time characterization of functional dynamics in the laboratory setting through quantification of perfusion dynamics. While the technique has largely been relegated to acute small animal imaging, its scalability is being assessed and characterized for both chronic and clinical neurovascular imaging. PMID:25944593

Diagnostic Accuracy of B-mode USG and Doppler Scan for Ovarian Lesions

PubMed Central

Agarwal, Vinish Kumar

2016-01-01

Introduction Ultrasonography (USG) is considered as the primary imaging modality for confirmation of ovarian mass and to differentiate them in to benign or malignant. Aim The present study was conducted with the aim to evaluate accuracy of B- mode USG and Doppler scan (Colour Doppler + Spectral Doppler) for ovarian lesions. Materials and Methods The patients included in the study were from those referred with either palpable adnexal mass or incidentally detected adnexal masses. Total 250 women were evaluated by USG, Doppler scan. Only fifty patients who had true ovarian mass intraoperatively and on histopathology were included in study, rest masses were excluded. Study parameters were morphological indexing on B- Mode USG, flow study, vessel arrangement, and vessel morphology and vessel location in Colour Doppler and resistive index and pulsatility index in spectral Doppler. Results Total 50 women were included in present study. Out of these 46% were pre-menopausal while 54% were menopaused women, 66.7% of post-menopausal women had malignant ovarian masses compared to 8.7% of premenopausal. Sensitivity, specificity, positive predictive value and negative predictive value of B-Mode USG for ovarian masses were 94.44%, 48.15%, 54.84% and 92.86% respectively, with p-value = 0.007, while sensitivity, specificity, positive predictive value and negative predictive value of Doppler scan were 85%, 90%, 85% and 90% respectively, with p-value = 0.0001. Conclusion USG and its different techniques are accepted as the primary imaging modality for early stage diagnosis of an ovarian malignancy. Statistical analysis suggests that Doppler Scan (Colour + Spectral) was more accurate (88%) than B-Mode USG (67%), but author is in view that both of these modalities should be used in conjunction to screen the ovarian lesions. PMID:27790544

Application of Thinned-Skull Cranial Window to Mouse Cerebral Blood Flow Imaging Using Optical Microangiography

PubMed Central

Wang, Ruikang K.

2014-01-01

In vivo imaging of mouse brain vasculature typically requires applying skull window opening techniques: open-skull cranial window or thinned-skull cranial window. We report non-invasive 3D in vivo cerebral blood flow imaging of C57/BL mouse by the use of ultra-high sensitive optical microangiography (UHS-OMAG) and Doppler optical microangiography (DOMAG) techniques to evaluate two cranial window types based on their procedures and ability to visualize surface pial vessel dynamics. Application of the thinned-skull technique is found to be effective in achieving high quality images for pial vessels for short-term imaging, and has advantages over the open-skull technique in available imaging area, surgical efficiency, and cerebral environment preservation. In summary, thinned-skull cranial window serves as a promising tool in studying hemodynamics in pial microvasculature using OMAG or other OCT blood flow imaging modalities. PMID:25426632

A new Doppler-echo method to quantify regurgitant volume.

PubMed

Wang, S S; Rubenstein, J J; Goldman, M; Sidd, J J

1992-01-01

An in vitro technique using color flow imaging and continuous wave Doppler was developed to measure the initial regurgitant flow jet diameter and velocity integral to yield the parameters for a volume calculation. Jets were produced by volume-controlled injection through tubes of various diameters (1.3, 1.9, 2.8, and 3.5 mm) to deliver volumes from 1 to 7 ml over 100 to 300 msec at pressures from 40 to 200 mm Hg. One hundred forty-five samples were obtained. Flow jet diameter consistently overestimated tube diameter by 2 mm when injected volume was 1.5 to 7 ml and by 1.5 mm when injected volume was less than 1.5 ml. This offset was stable with various transducers (2.5, 3.5, 5.0 MHz) at normal gain setting (just under noise). Therefore, corrected flow jet diameter (FJD) = FJD - 2 mm, and Doppler volume = corrected flow jet area x velocity integral. A range of injectates from 1.1 to 7 ml generated Doppler volume of 1.0 to 8.2 ml. The relation between Doppler volume (DV) and injected volume (IV) was DV = 1.079 IV - 0.22, r2 = 0.945, p less than 0.01. This relation was not altered by tube diameter. Thus a method combining color flow imaging and continuous wave Doppler provides a reliable and accurate measure of in vitro flow volume.

Evaluation of joint effusion in rabbits by color Doppler, power Doppler, and contrast-enhanced power Doppler ultrasonography.

PubMed

Lim, Gye-Yeon; Im, Soo Ah; Jung, Won Sang; Lee, Jae Mun; Lee, Ah Won

2005-09-01

The aim of this prospective study was to evaluate the diagnostic value of power Doppler ultrasonography (PDUS) and contrast-enhanced PDUS (CEPDUS) in the depiction and characterization of experimentally induced arthritis in the rabbit. Thirty rabbits were divided into three groups consisting of one control group (saline injection group) and two experimental groups: a suppurative arthritis group and a chemically induced synovitis group. The same amount (1 ml) of each agent was directly injected into the right hip joint. Serial color Doppler ultrasound (CDUS), PDUS, and CEPDUS images were obtained before and after injection. We observed that all of the infected knees in the suppurative arthritis group with Staphylococcus aureus demonstrated an increased signal on PDUS after inoculation. A minimal power Doppler signal was presented in the chemically induced synovitis group with talc injection, but none of the control knees demonstrated any increased signals. CEPDUS was the most sensitive imaging modality for evaluating the increase of blood flows in suppurative arthritis and was subsequently followed by PDUS and CDUS. The increased signals obtained with PDUS represent increased local blood flows; therefore, this technique can be used for evaluating the degree of inflammation. Furthermore, using the contrast agent enhances the sensitivity of PDUS, and it can even be useful for differentiating borderline cases. Copyright 2005 Wiley Periodicals, Inc

Coronal Structures in Cool Stars

NASA Technical Reports Server (NTRS)

Oliversen, Ronald (Technical Monitor); Dupree, Andrea K.

2004-01-01

Many papers have been published that further elucidate the structure of coronas in cool stars as determined from EUVE, HST, FUSE, Chandra, and XMM-Newton observations. In addition we are exploring the effects of coronas on the He I 1083081 transition that is observed in the infrared. Highlights of these are summarized below including publications during this reporting period and presentations. Ground-based magnetic Doppler imaging of cool stars suggests that active stars have active regions located at high latitudes on their surface. We have performed similar imaging in X-ray to locate the sites of enhanced activity using Chandra spectra. Chandra HETG observations of the bright eclipsing contact binary 44i Boo and Chandra LETG observations for the eclipsing binary VW Cep show X-ray line profiles that are Doppler-shifted by orbital motion. After careful analysis of the spectrum of each binary, a composite line-profile is constructed by adding the individual spectral lines. This high signal-to-noise ratio composite line-profile yields orbital velocities for these binaries that are accurate to 30 km/sec and allows their orbital motion to be studied at higher time resolutions. In conjunction with X-ray lightcurves, the phase-binned composite line-profiles constrain coronal structures to be small and located at high latitudes. These observations and techniques show the power of the Doppler Imaging Technique applied to X-ray line emission.

SHEAR WAVE DISPERSION MEASURES LIVER STEATOSIS

PubMed Central

Barry, Christopher T.; Mills, Bradley; Hah, Zaegyoo; Mooney, Robert A.; Ryan, Charlotte K.; Rubens, Deborah J.; Parker, Kevin J.

2012-01-01

Crawling waves, which are interfering shear wave patterns, can be generated in liver tissue over a range of frequencies. Some important biomechanical properties of the liver can be determined by imaging the crawling waves using Doppler techniques and analyzing the patterns. We report that the dispersion of shear wave velocity and attenuation, that is, the frequency dependence of these parameters, are strongly correlated with the degree of steatosis in a mouse liver model, ex vivo. The results demonstrate the possibility of assessing liver steatosis using noninvasive imaging methods that are compatible with color Doppler scanners and, furthermore, suggest that liver steatosis can be separated from fibrosis by assessing the dispersion or frequency dependence of shear wave propagations. PMID:22178165

Tissue Doppler and strain imaging: anything left in the echo-lab?

PubMed Central

Citro, Rodolfo; Bossone, Eduardo; Kuersten, Bettina; Gregorio, Giovanni; Salustri, Alessandro

2008-01-01

Medline research indicates that an increasing number of manuscripts have been published in the last decade claiming, the feasibility and the potential clinical role of tissue Doppler and strain/strain rate imaging. However, despite this amount of scientific evidence, these technologies are still confined to dedicated, high-tech, research-oriented echocardiography laboratories. In this review we have critically evaluated these techniques, analysing their physical principles, the technical problems related to their current clinical application, and the future perspectives. Finally, this review explores the reasons why these technologies are still defined "new technologies" and the impact of their implementation on the current clinical activity of an echocardiography laboratory. PMID:18973677

Transesophageal Doppler measurement of renal arterial blood flow velocities and indices in children.

PubMed

Zabala, Luis; Ullah, Sana; Pierce, Carol D'Ann; Gautam, Nischal K; Schmitz, Michael L; Sachdeva, Ritu; Craychee, Judith A; Harrison, Dale; Killebrew, Pamela; Bornemeier, Renee A; Prodhan, Parthak

2012-06-01

Doppler-derived renal blood flow indices have been used to assess renal pathologies. However, transesophageal ultrasonography (TEE) has not been previously used to assess these renal variables in pediatric patients. In this study, we (a) assessed whether TEE allows adequate visualization of the renal parenchyma and renal artery, and (b) evaluated the concordance of TEE Doppler-derived renal blood flow measurements/indices compared with a standard transabdominal renal ultrasound (TAU) in children. This prospective cohort study enrolled 28 healthy children between the ages of 1 and 17 years without known renal dysfunction who were undergoing atrial septal defect device closure in the cardiac catheterization laboratory. TEE was used to obtain Doppler renal artery blood velocities (peak systolic velocity, end-diastolic velocity, mean diastolic velocity, resistive index, and pulsatility index), and these values were compared with measurements obtained by TAU. Concordance correlation coefficient (CCC) was used to determine clinically significant agreement between the 2 methods. The Bland-Altman plots were used to determine whether these 2 methods agree sufficiently to be used interchangeably. Statistical significance was accepted at P ≤ 0.05. Obtaining 2-dimensional images of kidney parenchyma and Doppler-derived measurements using TEE in children is feasible. There was statistically significant agreement between the 2 methods for all measurements. The CCC between the 2 imaging techniques was 0.91 for the pulsatility index and 0.66 for the resistive index. These coefficients were sensitive to outliers. When the highest and lowest data points were removed from the analysis, the CCC between the 2 imaging techniques was 0.62 for the pulsatility index and 0.50 for the resistive index. The 95% confidence interval (CI) for pulsatility index was 0.35 to 0.98 and for resistive index was 0.21 to 0.89. The Bland-Altman plots indicate good agreement between the 2 methods; for the pulsatility index, the limits of agreement were -0.80 to 0.53. The correlation of the size of the measurement and the mean difference in methods (-0.14; 95% CI = -0.28, 0.01) was not statistically significant (r = 0.31, P = 0.17). For the resistive index, the limits of agreement were -0.22 to 0.12. The correlation of the size of the measurement and the mean difference in methods (-0.05; 95% CI = -0.09, -0.01) was not statistically significant (r = 0.10, P = 0.65). This study confirms the feasibility of obtaining 2-dimensional images of kidney parenchyma and Doppler-derived measurements using TEE in children. Angle-independent TEE Doppler-derived indices show significant concordance with those derived by TAU. Further studies are required to assess whether this correlation holds true in the presence of renal pathology. This technique has the potential to help modulate intraoperative interventions based on their impact on renal variables and may prove helpful in the perioperative period for children at risk of acute kidney injury.

The first Doppler images of the eclipsing binary SZ Piscium

NASA Astrophysics Data System (ADS)

Xiang, Yue; Gu, Shenghong; Cameron, A. Collier; Barnes, J. R.; Zhang, Liyun

2016-02-01

We present the first Doppler images of the active eclipsing binary system SZ Psc, based on the high-resolution spectral data sets obtained in 2004 November and 2006 September-December. The least-squares deconvolution technique was applied to derive high signal-to-noise profiles from the observed spectra of SZ Psc. Absorption features contributed by a third component of the system were detected in the LSD profiles at all observed phases. We estimated the mass and period of the third component to be about 0.9 M⊙ and 1283 ± 10 d, respectively. After removing the contribution of the third body from the least-squares deconvolved profiles, we derived the surface maps of SZ Psc. The resulting Doppler images indicate significant star-spot activities on the surface of the K subgiant component. The distributions of star-spots are more complex than that revealed by previous photometric studies. The cooler K component exhibited pronounced high-latitude spots as well as numerous low- and intermediate-latitude spot groups during the entire observing seasons, but did not show any large, stable polar cap, different from many other active RS CVn-type binaries.

High-intensity focused ultrasound ablation assisted using color Doppler imaging for the treatment of hepatocellular carcinomas.

PubMed

Fukuda, Hiroyuki; Numata, Kazushi; Nozaki, Akito; Kondo, Masaaki; Morimoto, Manabu; Maeda, Shin; Tanaka, Katsuaki; Ohto, Masao; Ito, Ryu; Ishibashi, Yoshiharu; Oshima, Noriyoshi; Ito, Ayao; Zhu, Hui; Wang, Zhi-Biao

2013-12-01

We evaluated the usefulness of color Doppler flow imaging to compensate for the inadequate resolution of the ultrasound (US) monitoring during high-intensity focused ultrasound (HIFU) for the treatment of hepatocellular carcinoma (HCC). US-guided HIFU ablation assisted using color Doppler flow imaging was performed in 11 patients with small HCC (<3 lesions, <3 cm in diameter). The HIFU system (Chongqing Haifu Tech) was used under US guidance. Color Doppler sonographic studies were performed using an HIFU 6150S US imaging unit system and a 2.7-MHz electronic convex probe. The color Doppler images were used because of the influence of multi-reflections and the emergence of hyperecho. In 1 of the 11 patients, multi-reflections were responsible for the poor visualization of the tumor. In 10 cases, the tumor was poorly visualized because of the emergence of a hyperecho. In these cases, the ability to identify the original tumor location on the monitor by referencing the color Doppler images of the portal vein and the hepatic vein was very useful. HIFU treatments were successfully performed in all 11 patients with the assistance of color Doppler imaging. Color Doppler imaging is useful for the treatment of HCC using HIFU, compensating for the occasionally poor visualization provided by B-mode conventional US imaging.

Swept-source based, single-shot, multi-detectable velocity range Doppler optical coherence tomography

PubMed Central

Meemon, Panomsak; Rolland, Jannick P.

2010-01-01

Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) allows visualization and characterization of the location, direction, velocity, and profile of flow activity embedded in a static sample structure. The detectable Velocity Dynamic Range (VDR) of each particular PR-DOCT system is governed by a detectable Doppler phase shift, a flow angle, and an acquisition time interval used to determine the Doppler phase shift. In general, the lower boundary of the detectable Doppler phase shift is limited by the phase stability of the system, while the upper boundary is limited by the π phase ambiguity. For a given range of detectable Doppler phase shift, shortening the acquisition duration will increase not only the maximum detectable velocity but unfortunately also the minimum detectable velocity, which may lead to the invisibility of a slow flow. In this paper, we present an alternative acquisition scheme for PR-DOCT that extends the lower limit of the velocity dynamic range, while maintaining the maximum detectable velocity, hence increasing the overall VDR of PR-DOCT system. The essence of the approach is to implement a technique of multi-scale measurement to simultaneously acquire multiple VDRs in a single measurement. We demonstrate an example of implementation of the technique in a dual VDR DOCT, where two Doppler maps having different detectable VDRs were simultaneously detected, processed, and displayed in real time. One was a fixed VDR DOCT capable of measuring axial velocity of up to 10.9 mm/s without phase unwrapping. The other was a variable VDR DOCT capable of adjusting its detectable VDR to reveal slow flow information down to 11.3 μm/s. The technique is shown to effectively extend the overall detectable VDR of the PR-DOCT system. Examples of real time Doppler imaging of an African frog tadpole are demonstrated using the dual-VDR DOCT system. PMID:21258521

Command Wire Sensor Measurements

DTIC Science & Technology

2012-09-01

coupled with the extreme harsh terrain has meant that few of these techniques have proved robust enough when moved from the laboratory to the field...to image stationary objects and does not accurately image moving targets. Moving targets can be seriously distorted and displaced from their true...battlefield and for imaging of fixed targets. Moving targets can be detected with a SAR if they have a Doppler frequency shift greater than the

Three-Dimensional Wind Profiling of Offshore Wind Energy Areas With Airborne Doppler Lidar

NASA Technical Reports Server (NTRS)

Koch, Grady J.; Beyon, Jeffrey Y.; Cowen, Larry J.; Kavaya, Michael J.; Grant, Michael S.

2014-01-01

A technique has been developed for imaging the wind field over offshore areas being considered for wind farming. This is accomplished with an eye-safe 2-micrometer wavelength coherent Doppler lidar installed in an aircraft. By raster scanning the aircraft over the wind energy area (WEA), a three-dimensional map of the wind vector can be made. This technique was evaluated in 11 flights over the Virginia and Maryland offshore WEAs. Heights above the ocean surface planned for wind turbines are shown to be within the marine boundary layer, and the wind vector is seen to show variation across the geographical area of interest at turbine heights.

Does ketogenic diet have any negative effect on cardiac systolic and diastolic functions in children with intractable epilepsy?: One-year follow-up results.

PubMed

Ozdemir, Rahmi; Kucuk, Mehmet; Guzel, Orkide; Karadeniz, Cem; Yilmaz, Unsal; Mese, Timur

2016-10-01

The ketogenic diet (KD) has been referred to as an "effective therapy with side effects" for children with intractable epilepsy. Among the most recognized adverse effects, there are cardiac conduction abnormalities, vascular and myocardial dysfunction. However, very limited and controversial data are available regarding the effects of the KD on cardiac functions. We sought to analyze the mid-term effect of ketogenic diet on cardiac functions in patients with intractable epilepsy who received a ketogenic diet for at least 12months using conventional and relatively new imaging techniques. This prospective study included 61 patients with intractable epilepsy who received ketogenic diet for at least 12months. Clinical examinations, serum carnitine and selenium levels as well as electrocardiographic and echocardiographic examinations were scheduled prior to the procedure and at 1, 3, 6 and 12months. We utilized two-dimensional, M-mode, colored Doppler, spectral Doppler and pulsed wave tissue Doppler imaging techniques to investigate ventricular systolic and diastolic functions of this subgroup of patients. In our study, there was no significant difference after 1year of KD therapy compared to baseline values-except a significantly decreased A wave velocity-in terms of pulse wave Doppler echocardiographic measurements of the diastolic function. The tissue Doppler measurements obtained from the lateral wall of tricuspide and mitral annuli were not different at baseline and at month 12 of the treatment, as well. The ketogenic diet appears to have no disturbing effect on ventricular functions in epileptic children in the midterm. Copyright © 2016 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Cardiovascular Imaging and Image Processing: Theory and Practice - 1975

NASA Technical Reports Server (NTRS)

Harrison, Donald C. (Editor); Sandler, Harold (Editor); Miller, Harry A. (Editor); Hood, Manley J. (Editor); Purser, Paul E. (Editor); Schmidt, Gene (Editor)

1975-01-01

Ultrasonography was examined in regard to the developmental highlights and present applicatons of cardiac ultrasound. Doppler ultrasonic techniques and the technology of miniature acoustic element arrays were reported. X-ray angiography was discussed with special considerations on quantitative three dimensional dynamic imaging of structure and function of the cardiopulmonary and circulatory systems in all regions of the body. Nuclear cardiography and scintigraphy, three--dimensional imaging of the myocardium with isotopes, and the commercialization of the echocardioscope were studied.

Three-dimensional ultrasound imaging of the prostate

NASA Astrophysics Data System (ADS)

Fenster, Aaron; Downey, Donal B.

1999-05-01

Ultrasonography, a widely used imaging modality for the diagnosis and staging of many diseases, is an important cost- effective technique, however, technical improvements are necessary to realize its full potential. Two-dimensional viewing of 3D anatomy, using conventional ultrasonography, limits our ability to quantify and visualize most diseases, causing, in part, the reported variability in diagnosis and ultrasound guided therapy and surgery. This occurs because conventional ultrasound images are 2D, yet the anatomy is 3D; hence the diagnostician must integrate multiple images in his mind. This practice is inefficient, and may lead to operator variability and incorrect diagnoses. In addition, the 2D ultrasound image represents a single thin plane at some arbitrary angle in the body. It is difficult to localize and reproduce the image plane subsequently, making conventional ultrasonography unsatisfactory for follow-up studies and for monitoring therapy. Our efforts have focused on overcoming these deficiencies by developing 3D ultrasound imaging techniques that can acquire B-mode, color Doppler and power Doppler images. An inexpensive desktop computer is used to reconstruct the information in 3D, and then is also used for interactive viewing of the 3D images. We have used 3D ultrasound images for the diagnosis of prostate cancer, carotid disease, breast cancer and liver disease and for applications in obstetrics and gynecology. In addition, we have also used 3D ultrasonography for image-guided minimally invasive therapeutic applications of the prostate such as cryotherapy and brachytherapy.

A systematic review on the quality of measurement techniques for the assessment of burn wound depth or healing potential.

PubMed

Jaspers, Mariëlle E H; van Haasterecht, Ludo; van Zuijlen, Paul P M; Mokkink, Lidwine B

2018-06-22

Reliable and valid assessment of burn wound depth or healing potential is essential to treatment decision-making, to provide a prognosis, and to compare studies evaluating different treatment modalities. The aim of this review was to critically appraise, compare and summarize the quality of relevant measurement properties of techniques that aim to assess burn wound depth or healing potential. A systematic literature search was performed using PubMed, EMBASE and Cochrane Library. Two reviewers independently evaluated the methodological quality of included articles using an adapted version of the Consensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist. A synthesis of evidence was performed to rate the measurement properties for each technique and to draw an overall conclusion on quality of the techniques. Thirty-six articles were included, evaluating various techniques, classified as (1) laser Doppler techniques; (2) thermography or thermal imaging; (3) other measurement techniques. Strong evidence was found for adequate construct validity of laser Doppler imaging (LDI). Moderate evidence was found for adequate construct validity of thermography, videomicroscopy, and spatial frequency domain imaging (SFDI). Only two studies reported on the measurement property reliability. Furthermore, considerable variation was observed among comparator instruments. Considering the evidence available, it appears that LDI is currently the most favorable technique; thereby assessing burn wound healing potential. Additional research is needed into thermography, videomicroscopy, and SFDI to evaluate their full potential. Future studies should focus on reliability and measurement error, and provide a precise description of which construct is aimed to measure. Copyright © 2018 Elsevier Ltd and ISBI. All rights reserved.

Investigation of Antiangiogenic Mechanisms Using Novel Imaging Techniques

DTIC Science & Technology

2010-02-01

of the tumor environment can sensitize the tumor to conventional cytotoxic therapies. To this end, we employ the window chamber model to optically ...facilitate longitudinal, in vivo investigation into the parameters of interest. These include Doppler Optical Coherence Tomography for the measurement of... Optical Techniques, Tumor Pathophysiology, Treatment Response, Vascular Normalization 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18

The use of the color Doppler ultrasonography in the diagnosis and monitoring of an atypical case of giant-cell arteritis.

PubMed

Martins, N; Polido-Pereira, J; Rodrigues, A M; Soares, F; Batista, P; Pereira da Silva, J A

2016-01-01

Giant Cell Arteritis (GCA) is a large vessels vasculitis that is typically characterised by headache, scalp tenderness, jaw claudication and visual disturbances. Temporal arteries color Doppler ultrasonography (CDUS) is a sensitive and non-invasive image technique used in the diagnosis of this disease. This work highlights the importance of CDUS in the diagnostic workup of GCA and also demonstrates it´s usefullness in the evaluation and documentation of the response to corticosteroids therapy in an atypical case of ACG.

Spread-Spectrum Beamforming and Clutter Filtering for Plane-Wave Color Doppler Imaging.

PubMed

Mansour, Omar; Poepping, Tamie L; Lacefield, James C

2016-07-21

Plane-wave imaging is desirable for its ability to achieve high frame rates, allowing the capture of fast dynamic events and continuous Doppler data. In most implementations of plane-wave imaging, multiple low-resolution images from different plane wave tilt angles are compounded to form a single high-resolution image, thereby reducing the frame rate. Compounding improves the lateral beam profile in the high-resolution image, but it also acts as a low-pass filter in slow time that causes attenuation and aliasing of signals with high Doppler shifts. This paper introduces a spread-spectrum color Doppler imaging method that produces high-resolution images without the use of compounding, thereby eliminating the tradeoff between beam quality, maximum unaliased Doppler frequency, and frame rate. The method uses a long, random sequence of transmit angles rather than a linear sweep of plane wave directions. The random angle sequence randomizes the phase of off-focus (clutter) signals, thereby spreading the clutter power in the Doppler spectrum, while keeping the spectrum of the in-focus signal intact. The ensemble of randomly tilted low-resolution frames also acts as the Doppler ensemble, so it can be much longer than a conventional linear sweep, thereby improving beam formation while also making the slow-time Doppler sampling frequency equal to the pulse repetition frequency. Experiments performed using a carotid artery phantom with constant flow demonstrate that the spread-spectrum method more accurately measures the parabolic flow profile of the vessel and outperforms conventional plane-wave Doppler in both contrast resolution and estimation of high flow velocities. The spread-spectrum method is expected to be valuable for Doppler applications that require measurement of high velocities at high frame rates.

Velocity visualization in gaseous flows

NASA Technical Reports Server (NTRS)

Hanson, R. K.

1985-01-01

Techniques are established for visualizing velocity in gaseous flows. Two approaches are considered, both of which are capable of yielding velocity simultaneously at a large number of flowfield locations, thereby providing images of velocity. The first technique employs a laser to mark specific fluid elements and a camera to track their subsequent motion. Marking is done by laser-induced phosphorescence of biacetyl, added as a tracer species in a flow of N2, or by laser-induced formation of sulfur particulates in SF6-H2-N2 mixtures. The second technique is based on the Doppler effect, and uses an intensified photodiode array camera and a planar form of laser-induced fluorescence to detect 2-d velocities of I2 (in I2-N2 mixtures) via Doppler-shifted absorption of narrow-linewidth laser radiation at 514.5 nm.

Corrected tetralogy of Fallot: comparison of tissue doppler imaging and velocity-encoded MR for assessment of performance and temporal activation of right ventricle.

PubMed

van der Hulst, Annelies E; Roest, Arno A W; Delgado, Victoria; Kroft, Lucia J M; Holman, Eduard R; Blom, Nico A; Bax, Jeroen J; de Roos, Albert; Westenberg, Jos J M

2011-07-01

To compare velocity-encoded (VE) magnetic resonance (MR) imaging with tissue Doppler imaging to assess right ventricular (RV) peak systolic velocities and timing of velocities in patients with corrected tetralogy of Fallot and healthy subjects. Local institutional review board approval was obtained; patients or their parents gave informed consent. Thirty-three patients (20 male, 13 female; median age, 12 years; interquartile range [IQR], 11-15 years; age range, 8-18 years) and 19 control subjects (12 male, seven female; median age, 14 years; IQR, 12-16 years; age range, 8-18 years) underwent VE MR imaging and tissue Doppler imaging. Peak systolic velocity and time to peak systolic velocity (percentage of cardiac cycle) were assessed at the RV free wall (RVFW) and RV outflow tract (RVOT). Data were analyzed by using linear regression, paired and unpaired tests, and Bland-Altman plots. Good correlation and agreement between the two techniques were observed. For peak systolic velocity at RVFW, r = 0.95 (mean difference, -0.4 cm/sec, P < .01), and at RVOT, r = 0.95 (mean difference, -0.4 cm/sec, P = .02). For timing at RVFW, r = 0.94 (mean difference, -0.2%, P = .44), and at RVOT, r = 0.89 (mean difference, -0.5%, P = .01). Peak systolic velocity was reduced in patients with corrected tetralogy of Fallot (at RVFW, median was 8.2 cm/sec [IQR, 6.4-9.7 cm/sec] vs 12.4 cm/sec [IQR, 10.8-13.8 cm/sec], P < .01; at RVOT, 4.7 cm/sec [IQR, 4.1-7.2 cm/sec] vs 10.2 cm/sec [IQR, 8.7-11.2 cm/sec], P < .01). The time delay between RVFW and RVOT was observed, which was significantly shorter in patients with corrected tetralogy of Fallot (median, 5.9% [IQR, 4.9%-7.4%] vs 8.4% [IQR, 6.6%-12.4%], P < .01). VE MR imaging and tissue Doppler imaging enable assessment of RV systolic performance and timing of velocities at the RVFW and RVOT in patients with corrected tetralogy of Fallot. Both techniques can be used interchangeably to clinically assess velocities and timing of velocities of the RV.

Doppler Optical Coherence Tomography

NASA Astrophysics Data System (ADS)

Chen, Zhongping; Zhang, Jun

Noninvasive techniques for imaging in vivo blood flow are of great value to biomedical research and clinical diagnostics where many diseases have a vascular etiology or component. In ophthalmology, many diseases involve disturbances in ocular blood flow, including diabetic retinopathy, low tension glaucoma, anterior ischemic optic neuritis, and macular degeneration. Simultaneous imaging of tissue structure and blood flow could provide critical information for early diagnosis of ocular diseases.

COMPARISON OF SEISMIC SIGNATURES OF FLARES OBTAINED BY SOHO/MICHELSON DOPPLER IMAGER AND GONG INSTRUMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zharkov, S.; Matthews, S. A.; Zharkova, V. V.

2011-10-01

The first observations of seismic responses to solar flares were carried out using time-distance (TD) and holography techniques applied to SOHO/Michelson Doppler Imager (MDI) Dopplergrams obtained from space and unaffected by terrestrial atmospheric disturbances. However, the ground-based network GONG is potentially a very valuable source of sunquake observations, especially in cases where space observations are unavailable. In this paper, we present an updated technique for pre-processing of GONG observations for the application of subjacent vantage holography. Using this method and TD diagrams, we investigate several sunquakes observed in association with M- and X-class solar flares and compare the outcomes withmore » those reported earlier using MDI data. In both GONG and MDI data sets, for the first time, we also detect the TD ridge associated with the 2001 September 9 flare. Our results show reassuringly positive identification of sunquakes from GONG data that can provide further information about the physics of seismic processes associated with solar flares.« less

Role of four-dimensional echocardiography with high-definition flow imaging and spatiotemporal image correlation in detecting fetal pulmonary veins.

PubMed

Sun, Xue; Zhang, Ying; Fan, Miao; Wang, Yu; Wang, Meilian; Siddiqui, Faiza Amber; Sun, Wei; Sun, Feifei; Zhang, Dongyu; Lei, Wenjia; Hu, Guyue

2017-06-01

Prenatal diagnosis of fetal total anomalous pulmonary vein connection (TAPVC) remains challenging for most screening sonographers. The purpose of this study was to evaluate the use of four-dimensional echocardiography with high-definition flow imaging and spatiotemporal image correlation (4D-HDFI) in identifying pulmonary veins in normal and TAPVC fetuses. We retrospectively reviewed and performed 4D-HDFI in 204 normal and 12 fetuses with confirmed diagnosis of TAPVC. Cardiac volumes were available for postanalysis to obtain 4D-rendered images of the pulmonary veins. For the normal fetuses, two other traditional modalities including color Doppler and HDFI were used to detect the number of pulmonary veins and comparisons were made between each of these traditional methods and 4D-HDFI. For conventional echocardiography, HDFI modality was superior to color Doppler in detecting more pulmonary veins in normal fetuses throughout the gestational period. 4D-HDFI was the best method during the second trimester of pregnancy in identifying normal fetal pulmonary veins. 4D-HDFI images vividly depicted the figure, course, and drainage of pulmonary veins in both normal and TAPVC fetuses. HDFI and the advanced 4D-HDFI technique could facilitate identification of the anatomical features of pulmonary veins in both normal and TAPVC fetuses; 4D-HDFI therefore provides additional and more precise information than conventional echocardiography techniques. © 2017, Wiley Periodicals, Inc.

Vessel packaging effect in laser speckle contrast imaging and laser Doppler imaging.

PubMed

Fredriksson, Ingemar; Larsson, Marcus

2017-10-01

Laser speckle-based techniques are frequently used to assess microcirculatory blood flow. Perfusion estimates are calculated either by analyzing the speckle fluctuations over time as in laser Doppler flowmetry (LDF), or by analyzing the speckle contrast as in laser speckle contrast imaging (LSCI). The perfusion estimates depend on the amount of blood and its speed distribution. However, the perfusion estimates are commonly given in arbitrary units as they are nonlinear and depend on the magnitude and the spatial distribution of the optical properties in the tissue under investigation. We describe how the spatial confinement of blood to vessels, called the vessel packaging effect, can be modeled in LDF and LSCI, which affect the Doppler power spectra and speckle contrast, and the underlying bio-optical mechanisms for these effects. As an example, the perfusion estimate is reduced by 25% for LDF and often more than 50% for LSCI when blood is located in vessels with an average diameter of 40  μm, instead of being homogeneously distributed within the tissue. This significant effect can be compensated for only with knowledge of the average diameter of the vessels in the tissue. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Autonomous Sensors for Large Scale Data Collection

NASA Astrophysics Data System (ADS)

Noto, J.; Kerr, R.; Riccobono, J.; Kapali, S.; Migliozzi, M. A.; Goenka, C.

2017-12-01

Presented here is a novel implementation of a "Doppler imager" which remotely measures winds and temperatures of the neutral background atmosphere at ionospheric altitudes of 87-300Km and possibly above. Incorporating both recent optical manufacturing developments, modern network awareness and the application of machine learning techniques for intelligent self-monitoring and data classification. This system achieves cost savings in manufacturing, deployment and lifetime operating costs. Deployed in both ground and space-based modalities, this cost-disruptive technology will allow computer models of, ionospheric variability and other space weather models to operate with higher precision. Other sensors can be folded into the data collection and analysis architecture easily creating autonomous virtual observatories. A prototype version of this sensor has recently been deployed in Trivandrum India for the Indian Government. This Doppler imager is capable of operation, even within the restricted CubeSat environment. The CubeSat bus offers a very challenging environment, even for small instruments. The lack of SWaP and the challenging thermal environment demand development of a new generation of instruments; the Doppler imager presented is well suited to this environment. Concurrent with this CubeSat development is the development and construction of ground based arrays of inexpensive sensors using the proposed technology. This instrument could be flown inexpensively on one or more CubeSats to provide valuable data to space weather forecasters and ionospheric scientists. Arrays of magnetometers have been deployed for the last 20 years [Alabi, 2005]. Other examples of ground based arrays include an array of white-light all sky imagers (THEMIS) deployed across Canada [Donovan et al., 2006], oceans sensors on buoys [McPhaden et al., 2010], and arrays of seismic sensors [Schweitzer et al., 2002]. A comparable array of Doppler imagers can be constructed and deployed on the ground, to compliment the CubeSat data.

Ultrasound Biomicroscopy in Small Animal Research: Applications in Molecular and Preclinical Imaging

PubMed Central

Greco, A.; Mancini, M.; Gargiulo, S.; Gramanzini, M.; Claudio, P. P.; Brunetti, A.; Salvatore, M.

2012-01-01

Ultrasound biomicroscopy (UBM) is a noninvasive multimodality technique that allows high-resolution imaging in mice. It is affordable, widely available, and portable. When it is coupled to Doppler ultrasound with color and power Doppler, it can be used to quantify blood flow and to image microcirculation as well as the response of tumor blood supply to cancer therapy. Target contrast ultrasound combines ultrasound with novel molecular targeted contrast agent to assess biological processes at molecular level. UBM is useful to investigate the growth and differentiation of tumors as well as to detect early molecular expression of cancer-related biomarkers in vivo and to monitor the effects of cancer therapies. It can be also used to visualize the embryological development of mice in uterus or to examine their cardiovascular development. The availability of real-time imaging of mice anatomy allows performing aspiration procedures under ultrasound guidance as well as the microinjection of cells, viruses, or other agents into precise locations. This paper will describe some basic principles of high-resolution imaging equipment, and the most important applications in molecular and preclinical imaging in small animal research. PMID:22163379

21 CFR 892.1550 - Ultrasonic pulsed doppler imaging system.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ultrasonic pulsed doppler imaging system. 892.1550... system. (a) Identification. An ultrasonic pulsed doppler imaging system is a device that combines the... determine stationary body tissue characteristics, such as depth or location of tissue interfaces or dynamic...

Use of global ionospheric maps for HF Doppler measurements interpretation

NASA Astrophysics Data System (ADS)

Petrova, I. R.; Bochkarev, V. V.; Latypov, R. R.

2018-04-01

The HF Doppler technique, a method of measurement of Doppler frequency shift of ionospheric signal, is one of the well-known and widely used techniques of ionosphere research. It allows investigation of various disturbances in the ionosphere. There are different sources of disturbances in the ionosphere such as geomagnetic storms, solar flashes, meteorological effects and atmospheric waves. The HF Doppler technique allows us to find out the influence of earthquakes, explosions and other processes on the ionosphere, which occurs near the Earth. HF Doppler technique has high sensitivity to small frequency variations and high time resolution but interpretation of results is difficult. In this paper, we attempt to use GPS data for Doppler measurements interpretation. Modeling of Doppler frequency shift variations with use of TEC allows separation of ionosphere disturbances of medium scale.

Prostate: techniques, results, and potential applications of color Doppler US scanning.

PubMed

Rifkin, M D; Sudakoff, G S; Alexander, A A

1993-02-01

Color Doppler ultrasound (US) scanning and conventional endorectal gray-scale US of the prostate were performed in 619 patients. Pathologic correlation was available in all cases after US-guided transrectal biopsy. There were 132 cancers in 121 men, 13 foci of atypia in 10 men, 33 foci of inflammation in 31 men, and 469 benign lesions in 457 men. Two hundred seventy patients with abnormal areas of flow identified at color Doppler scanning also underwent spectral waveform analysis of the area of potential concern. No statistical difference in the mean resistive indexes was identified in any patient (P = .25; Scheffe F test, analysis of variance). All malignant lesions had abnormalities demonstrated at gray-scale US and/or focal or diffuse abnormal flow demonstrated at color Doppler scanning. Of the 132 cancers, 123 (93%) had corresponding gray-scale abnormalities and 114 (86%) demonstrated abnormal flow at color Doppler imaging. Nine of the 132 cancers (7%) had no obviously identifiable abnormality at gray-scale scanning but had distinctly abnormal flow at color Doppler scanning. Abnormal findings at color scanning without abnormal findings at gray-scale scanning occurred in eight of the 33 cases of inflammatory foci (24%) and in 24 of the 469 (5%) benign lesions.

Development of Time-Distance Helioseismology Data Analysis Pipeline for SDO/HMI

NASA Technical Reports Server (NTRS)

DuVall, T. L., Jr.; Zhao, J.; Couvidat, S.; Parchevsky, K. V.; Beck, J.; Kosovichev, A. G.; Scherrer, P. H.

2008-01-01

The Helioseismic and Magnetic Imager of SDO will provide uninterrupted 4k x 4k-pixel Doppler-shift images of the Sun with approximately 40 sec cadence. These data will have a unique potential for advancing local helioseismic diagnostics of the Sun's interior structure and dynamics. They will help to understand the basic mechanisms of solar activity and develop predictive capabilities for NASA's Living with a Star program. Because of the tremendous amount of data the HMI team is developing a data analysis pipeline, which will provide maps of subsurface flows and sound-speed distributions inferred form the Doppler data by the time-distance technique. We discuss the development plan, methods, and algorithms, and present the status of the pipeline, testing results and examples of the data products.

High Resolution Full-Aperture ISAR Processing through Modified Doppler History Based Motion Compensation

PubMed Central

Song, Jung-Hwan; Lee, Kee-Woong; Lee, Woo-Kyung; Jung, Chul-Ho

2017-01-01

A high resolution inverse synthetic aperture radar (ISAR) technique is presented using modified Doppler history based motion compensation. To this purpose, a novel wideband ISAR system is developed that accommodates parametric processing over extended aperture length. The proposed method is derived from an ISAR-to-SAR approach that makes use of high resolution spotlight SAR and sub-aperture recombination. It is dedicated to wide aperture ISAR imaging and exhibits robust performance against unstable targets having non-linear motions. We demonstrate that the Doppler histories of the full aperture ISAR echoes from disturbed targets are efficiently retrieved with good fitting models. Experiments have been conducted on real aircraft targets and the feasibility of the full aperture ISAR processing is verified through the acquisition of high resolution ISAR imagery. PMID:28555036

Applications of Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Xu, Zhiqiang

A major development in biomedical imaging in the last decade has been optical coherence tomography (OCT). This technique enables microscale resolution, depth resolved imaging of the detailed morphology of transparent and nontransparent biological tissue in a noncontact and quasi-noninvasive way. In the first part of this dissertation, we will describe the development and the performance of our home-made OCT systems working with different wavelength regions based on free-space and optical fiber Michelson interferometers. The second part will focus on Doppler OCT (DOCT), an important extension of OCT, which enables the simultaneous evaluation of the structural information and of the fluid flow distribution at a localized position beneath the sample surface. Much effort has been spent during the past few years in our laboratory aimed at providing more accurate velocity measurements with an extended dynamic range. We also applied our technique in different research areas such as microfluidics and hemodynamics. Investigations on the optical properties of the biological tissues (such as absorption and scattering) corresponding to different center wavelengths, have been performed in our laboratory. We used a 10 femtosecond Ti:sapphire laser centered at about 810 nm associated with a free-space Michelson interferometer. The infrared sources were centered at about 1310 and 1560 nm with all-fiber interferometers. Comparative studies using three different sources for several in vitro biological tissues based on a graphical method illustrated how the optical properties affect the quality of the OCT images in terms of the penetration depth and backscattering intensity. We have shown the advantage of working with 810-nm emission wavelength for good backscattering amplitude and contrast, while sources emitting at 1570 nm give good penetration depth. The 1330-nm sources provide a good compromise between the two. Therefore, the choice of the source will ultimately determine the longitudinal resolution and the imaging depth for OCT imaging. Doppler OCT is becoming an increasingly popular field of investigation within optical coherence tomography with potentially important applications in cardiovascular and microfluidic research. We have spent some of the effort on searching for accurate and efficient methods for processing the experimental data. We applied the pseudo Wigner time-frequency distribution method to the data processing of Doppler OCT and compared its performance to that of the short-time Fourier transform method, the Hilbert-based phase-resolved method and the autocorrelation method. We concluded that the pseudo Wigner-distribution signal processing method is overall more precise than other often-used methods in Doppler OCT for the analysis of cross-sectional velocity distributions, especially in the high velocity regime. We also discovered the advantage of using the time-domain instead of the frequency domain for Doppler OCT for some applications where precise Doppler-speed metrology is essential. Based on the fact that the obtained local OCT interference signal is almost a single periodic waveform, we have developed a novel, simple and less time-consuming processing method based on the zero-crossing points in an OCT signal for the measurement of the Doppler frequency in a laminar flow. This method was compared to other processing approaches currently used in Doppler OCT. The results show that in the case of laminar flow, the zero-crossing method gives the more precise results, especially in the higher velocity regime with a substantial economy in processing time and an increase in dynamic range which can reach 70 dB. This feature becomes a major advantage in metrology if one wants to measure velocities over several orders of magnitude. We have applied this technique to some real flow models and the preliminary results on flow velocity distributions obtained in the case of a microfluidic circuit and in that of a phantom of a blood vessel stenosis and bifurcation will be described in this thesis. We also proposed the method to successfully obtain the 2D velocity vector map in the phantom models by overlapping the Doppler OCT scalar velocity distributions of different incident angles. This quantitative knowledge of blood velocity profiles in the vessels can provide very important information in studying some cardiovascular diseases such as atherosclerosis. (Abstract shortened by UMI.)

Functional Spectral Domain Optical Coherence Tomography imaging

NASA Astrophysics Data System (ADS)

Bower, Bradley A.

Spectral Domain Optical Coherence Tomography (SDOCT) is a high-speed, high resolution imaging modality capable of structural and functional characterization of tissue microstructure. SDOCT fills a niche between histology and ultrasound imaging, providing non-contact, non-invasive backscattering amplitude and phase from a sample. Due to the translucent nature of the tissue, ophthalmic imaging is an ideal space for SDOCT imaging. Structural imaging of the retina has provided new insights into ophthalmic disease. The phase component of SDOCT images remains largely underexplored, though. While Doppler SDOCT has been explored in a research setting, it has yet to gain traction in the clinic. Other, functional exploitations of the phase are possible and necessary to expand the utility of SDOCT. Spectral Domain Phase Microscopy (SDPM) is an extension of SDOCT that is capable of resolving sub-wavelength displacements within a focal volume. Application of sub-wavelength displacement measurement imaging could provide a new method for non-invasive optophysiological measurement. This body of work encompasses both hardware and software design and development for implementation of SDOCT. Structural imaging was proven in both the lab and the clinic. Coarse phase changes associated with Doppler flow frequency shifts were recorded and a study was conducted to validate Doppler measurement. Fine phase changes were explored through SDPM applications. Preliminary optophysiology data was acquired to study the potential of sub-wavelength measurements in the retina. To remove the complexity associated with in-vivo human retinal imaging, a first principles approach using isolated nerve samples was applied using standard SDPM and a depthencoded technique for measuring conduction velocity. Results from amplitude as well as both coarse and fine phase processing are presented. In-vivo optophysiology using SDPM is a promising avenue for exploration, and projects furthering or extending this body of work are discussed.

Power Doppler evaluation of joint effusions: investigation in a rabbit model.

PubMed

Strouse, P J; DiPietro, M A; Teo, E L; Doi, K; Chrisp, C E

1999-08-01

To study the power Doppler findings of septic arthritis and noninfectious synovitis in an animal model. The right knees of 10 rabbits were inoculated with an aqueous suspension of Staphylococcus aureus. The right knees of 5 rabbits were injected with talc suspension. The right knees of 5 rabbits were injected with saline. All 20 left knees were injected with saline. Serial power Doppler images were obtained using constant-imaging parameters. Images were reviewed by blinded observers who assessed for increased power Doppler signal. All 10 knees inoculated with S. aureus developed septic arthritis. Each infected rabbit knee demonstrated increased signal on power Doppler on at least one examination, ranging from 1-6 days after inoculation. Only 23 of 45 examinations of infected knees were unequivocally positive by power Doppler on examinations performed 1 to 6 days after inoculation. No knee with talc synovitis demonstrated increased power Doppler signal. No control knee demonstrated increased power Doppler signal. Increased power Doppler signal may be seen with septic arthritis; however, its intensity and timing may vary from subject to subject. A normal power Doppler examination does not exclude septic arthritis.

Doppler Imaging of Exoplanets and Brown Dwarfs

NASA Astrophysics Data System (ADS)

Crossfield, I.; Biller, B.; Schlieder, J.; Deacon, N.; Bonnefoy, M.; Homeier, D.; Allard, F.; Buenzli, E.; Henning, T.; Brandner, W.; Goldman, Bertr; Kopytova, T.

2014-03-01

Doppler Imaging produces 2D global maps. When applied to cool planets or more massive brown dwarfs, it can map atmospheric features and track global weather patterns. The first substellar map, of the 2pc-distant brown dwarf Luhman 16B (Crossfeld et al. 2014), revealed patchy regions of thin & thick clouds. Here, I investigate the feasibility of future Doppler Imaging of additional objects. Searching the literature, I find that all 3 of P, v sin i, and variability are published for 22 brown dwarfs. At least one datum exists for 333 targets. The sample is very incomplete below ~L5; we need more surveys to find the best targets for Doppler Imaging! I estimate limiting magnitudes for Doppler Imaging with various hi-resolution near-infrared spectrographs. Only a handful of objects - at the M/L and L/T transitions - can be mapped with current tools. Large telescopes such as TMT and GMT will allow Doppler Imaging of many dozens of brown dwarfs and the brightest exoplanets. More targets beyond type L5 likely remain to be found. Future observations will let us probe the global atmospheric dynamics of many diverse objects.

Right Ventricular Tissue Doppler in Space Flight

NASA Technical Reports Server (NTRS)

Garcia, Kathleen M.; Hamilton, Douglas R.; Sargsyan, Ashot E.; Ebert, Douglas; Martin, David S.; Barratt, Michael R.; Martin, David S.; Bogomolov, Valery V.; Dulchavsky, Scott A.; Duncan, J. Michael

2010-01-01

The presentation slides review normal physiology of the right ventricle in space, general physiology of the right ventricle; difficulties in imaging the heart in space, imaging methods, tissue Doppler spectrum, right ventricle tissue Doppler, and Rt Tei Index.

Three-dimensional vascular imaging of proliferative diabetic retinopathy by Doppler optical coherence tomography.

PubMed

Miura, Masahiro; Hong, Young-Joo; Yasuno, Yoshiaki; Muramatsu, Daisuke; Iwasaki, Takuya; Goto, Hiroshi

2015-03-01

To evaluate the 3-dimensional architecture of neovascularization in proliferative diabetic retinopathy using Doppler optical coherence tomography (OCT). Prospective, nonrandomized clinical trial. Seventeen eyes of 14 patients with proliferative diabetic retinopathy were prospectively studied. Prototype Doppler OCT was used to evaluate the 3-dimensional vascular architecture at vitreoretinal adhesions. Proliferative membranes were detected in all eyes with proliferative diabetic retinopathy by standard OCT images. Doppler OCT images detected blood flow by neovascularization of the disc in 12 eyes and neovascularization elsewhere in 11 eyes. Doppler OCT images showed the 3-dimensional extent of new vessels at various stages of neovascularization, and the extent of new vessels could be clearly confirmed at vitreoretinal adhesions. Doppler OCT is useful for the detection and evaluation of the 3-dimensional vascular structure of neovascularization, and can assist in the noninvasive assessment of proliferative diabetic retinopathy. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

A quantitative comparison of transesophageal and epicardial color Doppler echocardiography in the intraoperative assessment of mitral regurgitation.

PubMed

Kleinman, J P; Czer, L S; DeRobertis, M; Chaux, A; Maurer, G

1989-11-15

Epicardial and transesophageal color Doppler echocardiography are both widely used for the intraoperative assessment of mitral regurgitation (MR); however, it has not been established whether grading of regurgitation is comparable when evaluated by these 2 techniques. MR jet size was quantitatively compared in 29 hemodynamically and temporally matched open-chest epicardial and transesophageal color Doppler echocardiography studies from 22 patients (18 with native and 4 with porcine mitral valves) scheduled to undergo mitral valve repair or replacement. Jet area, jet length and left atrial area were analyzed. Comparison of jet area measurements as assessed by epicardial and transesophageal color flow mapping revealed an excellent correlation between the techniques (r = 0.95, p less than 0.001). Epicardial and transesophageal jet length measurements were also similar (r = 0.77, p less than 0.001). Left atrial area could not be measured in 18 transesophageal studies (62%) due to foreshortening, and in 5 epicardial studies (17%) due to poor image resolution. Acoustic interference with left atrial and color flow mapping signals was noted in all patients with mitral valve prostheses when imaged by epicardial echocardiography, but this did not occur with transesophageal imaging. Thus, in patients undergoing valve repair or replacement, transesophageal and epicardial color flow mapping provide similar quantitative assessment of MR jet size. Jet area to left atrial area ratios have limited applicability in transesophageal color flow mapping, due to foreshortening of the left atrial borders in transesophageal views. Transesophageal color flow mapping may be especially useful in assessing dysfunctional mitral prostheses due to the lack of left atrial acoustic interference.

Remote defect imaging for plate-like structures based on the scanning laser source technique

NASA Astrophysics Data System (ADS)

Hayashi, Takahiro; Maeda, Atsuya; Nakao, Shogo

2018-04-01

In defect imaging with a scanning laser source technique, the use of a fixed receiver realizes stable measurements of flexural waves generated by laser at multiple rastering points. This study discussed the defect imaging by remote measurements using a laser Doppler vibrometer as a receiver. Narrow-band burst waves were generated by modulating laser pulse trains of a fiber laser to enhance signal to noise ratio in frequency domain. Averaging three images obtained at three different frequencies suppressed spurious distributions due to resonance. The experimental system equipped with these newly-devised means enabled us to visualize defects and adhesive objects in plate-like structures such as a plate with complex geometries and a branch pipe.

Complimentary use of epicardial echo imaging and Doppler in quantification of coronary artery stenoses

NASA Astrophysics Data System (ADS)

Richards, Kent L.; Cannon, Scott R.

1990-08-01

As more advanced therapeutic procedures are performed on coronary arteries during open chest surgery more advanced diagnostic procedures will be required to define the location and severity of coronary artery disease. This manuscript describes our preliminary experiences in identifying human coronary artery stenoses using epicardial two-dimensional color flow Doppler. Once the lesions were identified we used standard echo Doppler and imaging techniques to define their severity. The accuracy of stenotic cross sectional area calculated using the continuity equation and pressure gradient calculated using the Bernoulli equation were defined using a pulsatile flow model of the coronary circulation. Suggestions about further hardware development required to allow easy clinical application of this technique are described. 1 - CLINICAL NEED FOR INTRA-OPERATIVE EVAUJATION OFCORONARY ARTERIES The severity of coronary artery disease in adults who require coronary bypass surgery has changed significantly in the last ten years. More effective medications used to control angina pectoris and the wide use of percutaneous y artery angioplasty have delayed the timing of surgery until atherosclerotic involvement is more extensive. In addition patients who have had initial coronary bypass operations are now reaching ages at which atherosclerotic involvement of their bypass grafts and native vessels has progressed and reoperation is required. To meet the challenge of coronary arteries with multiple lesions or diffuse disease intraoperative angioplasty devices are being developed. Whether bypass surgery for advanced lesions or reoperation of

Pathological proof of cellular death in radiofrequency ablation therapy and correlation with flash echo imaging--an experiment study.

PubMed

Fujiki, Kei

2004-01-01

The aims of this study were to clarify the geographic distribution of complete cell death in the radiofrequency ablated area in a porcine liver experiment, and to evaluate the efficacy of ultrasonography using contrast media in detecting the area of Radiofrequency-induced cell death. Radiofrequency ablation was performed at 3 sites in each liver in seven swine with a RF2000TM radiofrequency generator using an expandable type needle electrode. The ablation area was investigated histologically by Hematoxylin-Eosin staining and NADH staining. The area of radiofrequency-induced cell death was correlated to the ultrasonographic findings using contrast media, by means of contrast harmonic imaging, flash echo imaging-subtraction and flash echo imaging-power Doppler. The ablation area showed three distinct regions. Although the HE staining did not indicate necrosis, the NADH staining showed a complete loss of cellular activity in the inner and middle layers of the ablation area. However, in the outer layer cells displaying cellular integrity were intermingled with the necrotic cells, indicating that some of the cells in this layer had a chance to survive. Further, in some cases the outer layer of the ablated area had irregular margins. The flash-echo power-doppler images were accurately correlated in size and shape to the pathologically proved region of complete cell death in the radiofrequency-induced lesions. In the marginal part of the radiofrequency ablation area, cell death was incomplete. Flash echo imaging-power doppler was a useful and sensitive real time imaging technique for accurate evaluation of the region of complete cell death.

Microvascular anastomosis guidance and evaluation using real-time three-dimensional Fourier-domain Doppler optical coherence tomography

PubMed Central

Ibrahim, Zuhaib; Tong, Dedi; Zhu, Shan; Mao, Qi; Pang, John; Andrew Lee, Wei Ping; Brandacher, Gerald; Kang, Jin U.

2013-01-01

Abstract. Vascular and microvascular anastomoses are critical components of reconstructive microsurgery, vascular surgery, and transplant surgery. Intraoperative surgical guidance using a surgical imaging modality that provides an in-depth view and three-dimensional (3-D) imaging can potentially improve outcome following both conventional and innovative anastomosis techniques. Objective postoperative imaging of the anastomosed vessel can potentially improve the salvage rate when combined with other clinical assessment tools, such as capillary refill, temperature, blanching, and skin turgor. Compared to other contemporary postoperative monitoring modalities—computed tomography angiograms, magnetic resonance (MR) angiograms, and ultrasound Doppler—optical coherence tomography (OCT) is a noninvasive high-resolution (micron-level), high-speed, 3-D imaging modality that has been adopted widely in biomedical and clinical applications. For the first time, to the best of our knowledge, the feasibility of real-time 3-D phase-resolved Doppler OCT (PRDOCT) as an assisted intra- and postoperative imaging modality for microvascular anastomosis of rodent femoral vessels is demonstrated, which will provide new insights and a potential breakthrough to microvascular and supermicrovascular surgery. PMID:23856833

OCT methods for capillary velocimetry

PubMed Central

Srinivasan, Vivek J.; Radhakrishnan, Harsha; Lo, Eng H.; Mandeville, Emiri T.; Jiang, James Y.; Barry, Scott; Cable, Alex E.

2012-01-01

To date, two main categories of OCT techniques have been described for imaging hemodynamics: Doppler OCT and OCT angiography. Doppler OCT can measure axial velocity profiles and flow in arteries and veins, while OCT angiography can determine vascular morphology, tone, and presence or absence of red blood cell (RBC) perfusion. However, neither method can quantify RBC velocity in capillaries, where RBC flow is typically transverse to the probe beam and single-file. Here, we describe new methods that potentially address these limitations. Firstly, we describe a complex-valued OCT signal in terms of a static scattering component, dynamic scattering component, and noise. Secondly, we propose that the time scale of random fluctuations in the dynamic scattering component are related to red blood cell velocity. Analysis was performed along the slow axis of repeated B-scans to parallelize measurements. We correlate our purported velocity measurements against two-photon microscopy measurements of RBC velocity, and investigate changes during hypercapnia. Finally, we image the ischemic stroke penumbra during distal middle cerebral artery occlusion (dMCAO), where OCT velocimetry methods provide additional insight that is not afforded by either Doppler OCT or OCT angiography. PMID:22435106

Planar Laser Imaging of Sprays for Liquid Rocket Studies

NASA Technical Reports Server (NTRS)

Lee, W.; Pal, S.; Ryan, H. M.; Strakey, P. A.; Santoro, Robert J.

1990-01-01

A planar laser imaging technique which incorporates an optical polarization ratio technique for droplet size measurement was studied. A series of pressure atomized water sprays were studied with this technique and compared with measurements obtained using a Phase Doppler Particle Analyzer. In particular, the effects of assuming a logarithmic normal distribution function for the droplet size distribution within a spray was evaluated. Reasonable agreement between the instrument was obtained for the geometric mean diameter of the droplet distribution. However, comparisons based on the Sauter mean diameter show larger discrepancies, essentially because of uncertainties in the appropriate standard deviation to be applied for the polarization ratio technique. Comparisons were also made between single laser pulse (temporally resolved) measurements with multiple laser pulse visualizations of the spray.

2D Doppler backscattering using synthetic aperture microwave imaging of MAST edge plasmas

NASA Astrophysics Data System (ADS)

Thomas, D. A.; Brunner, K. J.; Freethy, S. J.; Huang, B. K.; Shevchenko, V. F.; Vann, R. G. L.

2016-02-01

Doppler backscattering (DBS) is already established as a powerful diagnostic; its extension to 2D enables imaging of turbulence characteristics from an extended region of the cut-off surface. The Synthetic Aperture Microwave Imaging (SAMI) diagnostic has conducted proof-of-principle 2D DBS experiments of MAST edge plasma. SAMI actively probes the plasma edge using a wide (±40° vertical and horizontal) and tuneable (10-34.5 GHz) beam. The Doppler backscattered signal is digitised in vector form using an array of eight Vivaldi PCB antennas. This allows the receiving array to be focused in any direction within the field of view simultaneously to an angular range of 6-24° FWHM at 10-34.5 GHz. This capability is unique to SAMI and is a novel way of conducting DBS experiments. In this paper the feasibility of conducting 2D DBS experiments is explored. Initial observations of phenomena previously measured by conventional DBS experiments are presented; such as momentum injection from neutral beams and an abrupt change in power and turbulence velocity coinciding with the onset of H-mode. In addition, being able to carry out 2D DBS imaging allows a measurement of magnetic pitch angle to be made; preliminary results are presented. Capabilities gained through steering a beam using a phased array and the limitations of this technique are discussed.

A Planar-Fluorescence Imaging Technique for Studying Droplet-Turbulence Interactions in Vaporizing Sprays

NASA Technical Reports Server (NTRS)

Santavicca, Dom A.; Coy, E.

1990-01-01

Droplet turbulence interactions directly affect the vaporization and dispersion of droplets in liquid sprays and therefore play a major role in fuel oxidizer mixing in liquid fueled combustion systems. Proper characterization of droplet turbulence interactions in vaporizing sprays require measurement of droplet size velocity and size temperature correlations. A planar, fluorescence imaging technique is described which is being developed for simultaneously measuring the size, velocity, and temperature of individual droplets in vaporizing sprays. Preliminary droplet size velocity correlation measurements made with this technique are presented. These measurements are also compared to and show very good agreement with measurements made in the same spray using a phase Doppler particle analyzer.

Automated assessment of noninvasive filling pressure using color Doppler M-mode echocardiography

NASA Technical Reports Server (NTRS)

Greenberg, N. L.; Firstenberg, M. S.; Cardon, L. A.; Zuckerman, J.; Levine, B. D.; Garcia, M. J.; Thomas, J. D.

2001-01-01

Assessment of left ventricular filling pressure usually requires invasive hemodynamic monitoring to follow the progression of disease or the response to therapy. Previous investigations have shown accurate estimation of wedge pressure using noninvasive Doppler information obtained from the ratio of the wave propagation slope from color M-mode (CMM) images and the peak early diastolic filling velocity from transmitral Doppler images. This study reports an automated algorithm that derives an estimate of wedge pressure based on the spatiotemporal velocity distribution available from digital CMM Doppler images of LV filling.

Feedback mechanism for smart nozzles and nebulizers

DOEpatents

Montaser, Akbar [Potomac, MD; Jorabchi, Kaveh [Arlington, VA; Kahen, Kaveh [Kleinburg, CA

2009-01-27

Nozzles and nebulizers able to produce aerosol with optimum and reproducible quality based on feedback information obtained using laser imaging techniques. Two laser-based imaging techniques based on particle image velocimetry (PTV) and optical patternation map and contrast size and velocity distributions for indirect and direct pneumatic nebulizations in plasma spectrometry. Two pulses from thin laser sheet with known time difference illuminate droplets flow field. Charge coupled device (CCL)) captures scattering of laser light from droplets, providing two instantaneous particle images. Pointwise cross-correlation of corresponding images yields two-dimensional velocity map of aerosol velocity field. For droplet size distribution studies, solution is doped with fluorescent dye and both laser induced florescence (LIF) and Mie scattering images are captured simultaneously by two CCDs with the same field of view. Ratio of LIF/Mie images provides relative droplet size information, then scaled by point calibration method via phase Doppler particle analyzer.

High quality optical microangiography of ocular microcirculation and measurement of total retinal blood flow in mouse eye

NASA Astrophysics Data System (ADS)

Zhi, Zhongwei; Yin, Xin; Dziennis, Suzan; Alpers, Charles E.; Wang, Ruikang K.

2013-03-01

Visualization and measurement of retinal blood flow (RBF) is important to the diagnosis and management of different eye diseases, including diabetic retinopathy. Optical microangiography (OMAG) is developed for generating 3D dynamic microcirculation image and later refined into ultra-high sensitive OMAG (UHS-OMAG) for true capillary vessels imaging. Here, we present the application of OMAG imaging technique for visualization of depth-resolved vascular network within retina and choroid as well as measurement of total retinal blood flow in mice. A fast speed spectral domain OCT imaging system at 820nm with a line scan rate of 140 kHz was developed to image mouse posterior eye. By applying UHS-OMAG scanning protocol and processing algorithm, we achieved true capillary level imaging of retina and choroid vasculature in mouse eye. The vascular pattern within different retinal layers and choroid was presented. An en face Doppler OCT approach [1] without knowing Doppler angle was adopted for the measurement of total retinal blood flow. The axial blood flow velocity is measured in an en face plane by raster scanning and the flow is calculated by integrating over the vessel area of the central retinal artery.

One way Doppler extractor. Volume 1: Vernier technique

NASA Technical Reports Server (NTRS)

Blasco, R. W.; Klein, S.; Nossen, E. J.; Starner, E. R.; Yanosov, J. A.

1974-01-01

A feasibility analysis, trade-offs, and implementation for a One Way Doppler Extraction system are discussed. A Doppler error analysis shows that quantization error is a primary source of Doppler measurement error. Several competing extraction techniques are compared and a Vernier technique is developed which obtains high Doppler resolution with low speed logic. Parameter trade-offs and sensitivities for the Vernier technique are analyzed, leading to a hardware design configuration. A detailed design, operation, and performance evaluation of the resulting breadboard model is presented which verifies the theoretical performance predictions. Performance tests have verified that the breadboard is capable of extracting Doppler, on an S-band signal, to an accuracy of less than 0.02 Hertz for a one second averaging period. This corresponds to a range rate error of no more than 3 millimeters per second.

Multiparametric optical coherence tomography imaging of the inner retinal hemodynamic response to visual stimulation

NASA Astrophysics Data System (ADS)

Radhakrishnan, Harsha; Srinivasan, Vivek J.

2013-08-01

The hemodynamic response to neuronal activation is a well-studied phenomenon in the brain, due to the prevalence of functional magnetic resonance imaging. The retina represents an optically accessible platform for studying lamina-specific neurovascular coupling in the central nervous system; however, due to methodological limitations, this has been challenging to date. We demonstrate techniques for the imaging of visual stimulus-evoked hyperemia in the rat inner retina using Doppler optical coherence tomography (OCT) and OCT angiography. Volumetric imaging with three-dimensional motion correction, en face flow calculation, and normalization of dynamic signal to static signal are techniques that reduce spurious changes caused by motion. We anticipate that OCT imaging of retinal functional hyperemia may yield viable biomarkers in diseases, such as diabetic retinopathy, where the neurovascular unit may be impaired.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, S. A.; Plummer, G.; Fedor, J.

Mapping the distribution of currents inside a superconductor is usually performed indirectly through imaging of the stray magnetic fields above the surface. Here, we show that by direct imaging of the Doppler shift contribution to the quasiparticle excitation spectrum in the superconductor using low temperature scanning tunneling microscopy, we obtain directly the distribution of supercurrents inside the superconductor. We demonstrate the technique at the example of superconductor/ferromagnet hybrid structure that produces intricate current pattern consisting of combination Meissner shielding currents and Abrikosov vortex currents.

Temporal variability of vena contracta and jet areas with color Doppler in aortic regurgitation: a chronic animal model study.

PubMed

Ishii, M; Jones, M; Shiota, T; Yamada, I; Sinclair, B; Heinrich, R S; Yoganathan, A P; Sahn, D J

1998-11-01

The purpose of our study was to determine the temporal variability of regurgitant color Doppler jet areas and the width of the color Doppler imaged vena contracta for evaluating the severity of aortic regurgitation. Twenty-nine hemodynamically different states were obtained pharmacologically in 8 sheep 20 weeks after surgery to produce aortic regurgitation. Aortic regurgitation was quantified by peak and mean regurgitant flow rates, regurgitant stroke volumes, and regurgitant fractions determined using pulmonary and aortic electromagnetic flow probes and meters balanced against each other. The regurgitant jet areas and the widths of color Doppler imaged vena contracta were measured at 4 different times during diastole to determine the temporal variability of this parameter. When measured at 4 different temporal points in diastole, a significant change was observed in the size of the color Doppler imaged regurgitant jet (percent of difference: from 31.1% to 904%; 233% +/- 245%). Simple linear regression analysis between each color jet area at 4 different periods in diastole and flow meter-based severity of the aortic regurgitation showed only weak correlation (0.23 < r < 0.49). In contrast, for most conditions only a slight change was observed in the width of the color Doppler imaged vena contracta during the diastolic regurgitant period (percent of difference, vena contracta: from 2.4% to 12.9%, 5.8% +/- 3.2%). In addition, for each period the width of the color Doppler imaged vena contracta at the 4 different time periods in diastole correlated quite strongly with volumetric measures of the severity of aortic regurgitation (0.81 < r < 0.90) and with the instantaneous flow rate for the corresponding period (0.85 < r < 0.87). Color Doppler imaged vena contracta may provide a simple, practical, and accurate method for quantifying aortic regurgitation, even when using a single frame color Doppler flow mapping image.

Instantaneous Doppler Global Velocimetry Measurements of a Rotor Wake: Lessons Learned

NASA Technical Reports Server (NTRS)

Meyers, James; Fleming, Gary A.; Gorton, Susan Althoff; Berry, John D.

1998-01-01

A combined Doppler Global Velocimetry (DGV) and Projection Moir Interferometry (PMI) investigation of a helicopter rotor wake flow field and rotor blade deformation is presented. The three-component DGV system uses a single-frequency, frequency-doubled Nd:YAG laser to obtain instantaneous velocity measurements in the flow. The PMI system uses a pulsed laser-diode bar to obtain blade bending and twist measurements at the same instant that DGV measured the flow. The application of pulse lasers to DGV and PMI in large-scale wind tunnel applications represents a major step forward in the development of these technologies. As such, a great deal was learned about the difficulties of using these instruments to obtain instantaneous measurements in large facilities. Laser speckle and other image noise in the DGV data images were found to be traceable to the Nd:YAG laser. Although image processing techniques were used to virtually eliminate laser speckle noise, the source of low-frequency image noise is still under investigation. The PMI results agreed well with theoretical predictions of blade bending and twist.

Contrast-enhanced harmonic ultrasound imaging in ablation therapy for primary hepatocellular carcinoma.

PubMed

Minami, Yasunori; Kudo, Masatoshi

2009-12-31

The success rate of percutaneous radiofrequency (RF) ablation for hepatocellular carcinoma (HCC) depends on correct targeting via an imaging technique. However, RF electrode insertion is not completely accurate for residual HCC nodules because B-mode ultrasound (US), color Doppler, and power Doppler US findings cannot adequately differentiate between treated and viable residual tumor tissue. Electrode insertion is also difficult when we must identify the true HCC nodule among many large regenerated nodules in cirrhotic liver. Two breakthroughs in the field of US technology, harmonic imaging and the development of second-generation contrast agents, have recently been described and have demonstrated the potential to dramatically broaden the scope of US diagnosis of hepatic lesions. Contrast-enhanced harmonic US imaging with an intravenous contrast agent can evaluate small hypervascular HCC even when B-mode US cannot adequately characterize tumor. Therefore, contrast-enhanced harmonic US can facilitate RF ablation electrode placement in hypervascular HCC, which is poorly depicted by B-mode US. The use of contrast-enhanced harmonic US in ablation therapy for liver cancer is an efficient approach.

Laser Doppler Velocimetry Workshop

NASA Technical Reports Server (NTRS)

Owen, R. B.

1979-01-01

The potential of laser Doppler velocimetry as a technique for use in mapping flows in the several fluid systems under development for doing research on low-gravity processes, is investigated. Laser Doppler velocimetry techniques, equipment, and applications are summarized.

Update on imaging techniques in oculoplastics

PubMed Central

Cetinkaya, Altug

2012-01-01

Imaging is a beneficial aid to the oculoplastic surgeon especially in orbital and lacrimal disorders when the pathology is not visible from outside. It is a powerful tool that may be benefited in not only diagnosis but also management and follow-up. The most common imaging modalities required are CT and MRI, with CT being more frequently ordered by oculoplastic surgeons. Improvements in technology enabled the acquisition times to shorten incredibly. Radiologists can now obtain images with superb resolution, and isolate the site and tissue of interest from other structures with special techniques. Better contrast agents and 3D imaging capabilities make complicated cases easier to identify. Color Doppler imaging is becoming more popular both for research and clinical purposes. Magnetic resonance angiography (MRA) added so much to the vascular system imaging recently. Although angiography is still the gold standard, new software and techniques rendered MRA as valuable as angiography in most circumstances. Stereotactic navigation, although in use for a long time, recently became the focus of interest for the oculoplastic surgeon especially in orbital decompressions. Improvements in radiology and nuclear medicine techniques of lacrimal drainage system imaging provided more detailed analysis of the system. PMID:23961020

Development and Application of Multifunctional Optical Coherence Tomography

NASA Astrophysics Data System (ADS)

Zhi, Zhongwei

Microcirculation refers to the functions of capillaries and the neighboring lymphatic vessels. It plays a vital role in the pathophysiology of disorders in many clinical areas including cardiology, dermatology, neurology and ophthalmology, and so forth. It is crucial to develop imaging technologies that can provide both qualitative and quantitative information as to how microcirculation responds to certain injury and/or disease, and its treatment. Optical coherence tomography (OCT) is a non-invasive optical imaging technique for high-resolution cross-sectional imaging of specimens, with many applications in clinical medicine. Current state-of-the-art OCT systems operate in the Fourier domain, using either a broadband light source with a spectrometer, known as spectral domain OCT (SDOCT), or a rapidly tunable laser, known as swept source OCT (SSOCT). The current Fourier domain OCT systems have dramatically improvement in sensitivity, resolution and speed compared to time domain OCT. In addition to the improvement in the OCT system hardware, different methods for functional measurements of tissue beds have been developed and demonstrated. This includes but not limited to, i) Phase-resolved Doppler OCT for quantifying the blood flow, ii) OCT angiography for visualization of microvasculature, iii) Polarization sensitive OCT for measuring the intrinsic optical property/ birefringence of tissue, iv) spectroscopic OCT for measuring blood oxygenation, etc. Functional OCT can provide important clinical information that is not available in the typical intensity based structural OCT images. Among these functional OCT modalities, Doppler OCT and OCT angiography attract great interests as they show high capability for in vivo study of microvascular pathology. By analyzing the Doppler effect of a flowing particle on light frequency, Doppler OCT allows the quantification of the blood flow speed and blood flow rate. The most popular approach for Doppler OCT is achieved through analysis of the phase term in complex OCT signal which termed as Phase-resolved Doppler OCT. However, as limited by the phase noise and motion, Phase-resolved Doppler OCT can only be applied for relative large blood vessels, such as arterioles and venules. On the other hand, in order to visualize the microcirculation network, a number of strategies to enable better contrast of microvasculature components, which we termed OCT angiography, have been introduced during recent years. As a variation of Fourier domain OCT, optical microangiography (OMAG) is one of earliest proposed OCT angiography technique which is capable of generating 3D images of dynamic blood perfusion distribution within microcirculatory tissue beds. The OMAG algorithm works by separating the static and moving elements by high pass filtering on complex valued interferometric data after Fourier transform. Based on the conventional OMAG algorithm, we further developed ultra-high sensitive OMAG (UHS-OMAG) by switching the high-pass filtering from fast scan direction (adjacent A-lines within one B-frame) to slow scan direction (adjacent B-frames), which has a dramatically improved performance for capillary network imaging and analysis. Apart from the microvascular study with current available functional OCT for, visualization of the lymphatic system (lymph nodes and lymphatic vessels) plays a significant role in assessing patients with various malignancies and lymphedema. However, there is a lack of label-free and noninvasive method for lymphangiography. Hence, a cutting edge research to investigate the capability of OCT as a tool for non-invasive and label-free lymphangiography would be highly desired. The objective of my thesis is to develop a multiple-functional SDOCT system to image the microcirculation and quantify the several important parameters of microcirculation within microcirculatory tissue beds, and further apply it for pre-clinical research applications. The multifunctional OCT system provides modalities including structural OCT, OCT angiography, Doppler OCT and Optical lymphangiography, for multi-parametric study of tissue microstructure, blood vessel morphology, blood flow and lymphatic vessel all together. The thesis mainly focus on two parts: first, development of multi-functional OCT/optical microangiography (OMAG) system and methods for volumetric imaging of microvasculature and quantitative measurement of blood flow, and its application for pathological research in ophthalmology on rodent eye models; second, development of ultra-high resolution OCT system and algorithm for simultaneous label free imaging of blood and lymphatic vessel, and its application in wound healing study on mouse ear flap model. Objectives of my research are achieved through the following specific aims: Aim 1: Improve the sensitivity of OMAG for microvasculature imaging; perform volumetric and quantitative imaging of vasculature with combined OMAG and Phase-resolved Doppler OCT for in vivo study of vascular physiology. Aim 2: Develop high speed high resolution OCT system and method for rodent eye imaging. Apply the combined OMAG and Phase-resolved Doppler OCT approach to investigate the impact of elevated intraocular pressure on retinal, choroidal and optic nerve head blood flow in rat eye model, which aids to the better understanding of the mechanism and development of glaucoma. Aim 3: Apply the developed OCT system and ultra-high sensitive OMAG algorithm for noninvasive imaging of retinal morphology and microvasculature in obese mice, which may play an important role in early diagnosis of Diabetic retinopathy. Aim 4: Developing an ultra-high resolution SDOCT system using broadband Supercontinuum light source to achieve ultra-high resolution microvasculature imaging of biological tissue. Aim 5: Develop methods for simultaneous label free optical imaging of blood and lymphatic vessel and demonstrate its capability by monitoring the blood and lymph response to wound healing on mouse ear pinna model.

Echocardiography.

PubMed Central

Chambers, J. B.; Monaghan, M. J.; Jackson, G.

1988-01-01

Imaging echocardiography is an important extension of the clinical examination and will answer most questions in an emergency-for example, whether an enlarged cardiac shadow on the chest radiograph represents ventricular dilatation or an effusion. Doppler ultrasonography is essential for hospitals with an interest in cardiology because it provides direct haemodynamic data that are complementary to imaging. It requires more skill than imaging and may also be time consuming. Colour flow Doppler mapping is speedy and simple to use and aids the interpretation of continuous wave Doppler. It is therefore a natural companion to conventional Doppler, but there would have to be a high clinical load to justify its purchase. Images FIG 3 FIG 4 FIG 4 FIG 5 FIG 6 PMID:3143434

High speed, wide velocity dynamic range Doppler optical coherence tomography (Part III): in vivo endoscopic imaging of blood flow in the rat and human gastrointestinal tracts

NASA Astrophysics Data System (ADS)

Yang, Victor X. D.; Gordon, Maggie L.; Tang, Shou-Jiang; Marcon, Norman E.; Gardiner, Geoffrey; Qi, Bing; Bisland, Stuart; Seng-Yue, Emily; Lo, Stewart; Pekar, Julius; Wilson, Brian C.; Vitkin, I. Alex

2003-09-01

We previously described a fiber based Doppler optical coherence tomography system [1] capable of imaging embryo cardiac blood flow at 4~16 frames per second with wide velocity dynamic range [2]. Coupling this system to a linear scanning fiber optical catheter design that minimizes friction and vibrations, we report here the initial results of in vivo endoscopic Doppler optical coherence tomography (EDOCT) imaging in normal rat and human esophagus. Microvascular flow in blood vessels less than 100 µm diameter was detected using a combination of color-Doppler and velocity variance imaging modes, during clinical endoscopy using a mobile EDOCT system.

Doppler ultrasound surveillance in deep tunneling compressed-air work with Trimix breathing: bounce dive technique compared to saturation-excursion technique.

PubMed

Vellinga, T P van Rees; Sterk, W; de Boer, A G E M; van der Beek, A J; Verhoeven, A C; van Dijk, F J H

2008-01-01

The Western Scheldt Tunneling Project in The Netherlands provided a unique opportunity to evaluate two deep-diving techniques with Doppler ultrasound surveillance. Divers used the bounce diving techniques for repair and maintenance of the TBM. The tunnel boring machine jammed at its deepest depth. As a result the work time was not sufficient. The saturation diving technique was developed and permitted longer work time at great depth. Thirty-one divers were involved in this project. Twenty-three divers were examined using Doppler ultrasound. Data analysis addressed 52 exposures to Trimix at 4.6-4.8 bar gauge using the bounce technique and 354 exposures to Trimix at 4.0-6.9 bar gauge on saturation excursions. No decompression incidents occurred with either technique during the described phase of the project. Doppler ultrasound revealed that the bubble loads assessed in both techniques were generally low. We find out, that despite longer working hours, shorter decompression times and larger physical workloads, the saturation-excursion technique was associated with significant lower bubble grades than in the bounce technique using Doppler Ultrasound. We conclude that the saturation-excursion technique with Trimix is a good option for deep and long exposures in caisson work. The Doppler technique proved valuable, and it should be incorporated in future compressed-air work.

Using doppler radar images to estimate aircraft navigational heading error

DOEpatents

Doerry, Armin W [Albuquerque, NM; Jordan, Jay D [Albuquerque, NM; Kim, Theodore J [Albuquerque, NM

2012-07-03

A yaw angle error of a motion measurement system carried on an aircraft for navigation is estimated from Doppler radar images captured using the aircraft. At least two radar pulses aimed at respectively different physical locations in a targeted area are transmitted from a radar antenna carried on the aircraft. At least two Doppler radar images that respectively correspond to the at least two transmitted radar pulses are produced. These images are used to produce an estimate of the yaw angle error.

Novel techniques in stress echocardiography: a focus on the advantages and disadvantages.

PubMed

Vamvakidou, Anastasia; Gurunathan, Sothinathan; Senior, Roxy

2016-01-01

Stress echocardiography (SE) is an established tool not only for the assessment of coronary artery disease (CAD), but also for the evaluation of valvular disease and cardiomyopathy. New techniques, namely contrast echocardiography for function and perfusion including assessment of coronary flow reserve, strain imaging, 3-dimensional echocardiography, Doppler-derived coronary flow reserve and multimodality echocardiography, have been incorporated into stress protocols for improving assessment of cardiac disease. In this review, the advantages and disadvantages of these novel SE techniques are examined in terms of feasibility, accuracy, reproducibility and applications.

Laser Doppler velocimeter system simulation for sensing aircraft wake vortices

NASA Technical Reports Server (NTRS)

Thomson, J. A. L.; Meng, J. C. S.

1974-01-01

A hydrodynamic model of aircraft vortex wakes in an irregular wind shear field near the ground is developed and used as a basis for modeling the characteristics of a laser Doppler detection and vortex location system. The trailing vortex sheet and the wind shear are represented by discrete free vortices distributed over a two-dimensional grid. The time dependent hydrodynamic equations are solved by direct numerical integration in the Boussinesq approximation. The ground boundary is simulated by images, and fast Fourier Transform techniques are used to evaluate the vorticity stream function. The atmospheric turbulence was simulated by constructing specific realizations at time equal to zero, assuming that Kolmogoroff's law applies, and that the dissipation rate is constant throughout the flow field. The response of a simulated laser Doppler velocimeter is analyzed by simulating the signal return from the flow field as sensed by a simulation of the optical/electronic system.

Latin American Consensus on the use of transcranial Doppler in the diagnosis of brain death

PubMed Central

2014-01-01

Transcranial Doppler evaluates cerebral hemodynamics in patients with brain injury and is a useful technical tool in diagnosing cerebral circulatory arrest, usually present in the brain-dead patient. This Latin American Consensus was formed by a group of 26 physicians experienced in the use of transcranial Doppler in the context of brain death. The purpose of this agreement was to make recommendations regarding the indications, technique, and interpretation of the study of transcranial ultrasonography in patients with a clinical diagnosis of brain death or in the patient whose clinical diagnosis presents difficulties; a working group was formed to enable further knowledge and to strengthen ties between Latin American physicians working on the same topic. A review of the literature, concepts, and experiences were exchanged in two meetings and via the Internet. Questions about pathophysiology, equipment, techniques, findings, common problems, and the interpretation of transcranial Doppler in the context of brain death were answered. The basic consensus statements are the following: cerebral circulatory arrest is the final stage in the evolution of progressive intracranial hypertension, which is visualized with transcranial Doppler as a "pattern of cerebral circulatory arrest". The following are accepted as the standard of cerebral circulatory arrest: reverberant pattern, systolic spikes, and absence of previously demonstrated flow. Ultrasonography should be used - in acceptable hemodynamic conditions - in the anterior circulation bilaterally (middle cerebral artery) and in the posterior (basilar artery) territory. If no ultrasonographic images are found in any or all of these vessels, their proximal arteries are acceptable to be studied to look for a a pattern of cerebral circulatory arrest. PMID:25295818

Ultrahigh field magnetic resonance and colour Doppler real-time fusion imaging of the orbit--a hybrid tool for assessment of choroidal melanoma.

PubMed

Walter, Uwe; Niendorf, Thoralf; Graessl, Andreas; Rieger, Jan; Krüger, Paul-Christian; Langner, Sönke; Guthoff, Rudolf F; Stachs, Oliver

2014-05-01

A combination of magnetic resonance images with real-time high-resolution ultrasound known as fusion imaging may improve ophthalmologic examination. This study was undertaken to evaluate the feasibility of orbital high-field magnetic resonance and real-time colour Doppler ultrasound image fusion and navigation. This case study, performed between April and June 2013, included one healthy man (age, 47 years) and two patients (one woman, 57 years; one man, 67 years) with choroidal melanomas. All cases underwent 7.0-T magnetic resonance imaging using a custom-made ocular imaging surface coil. The Digital Imaging and Communications in Medicine volume data set was then loaded into the ultrasound system for manual registration of the live ultrasound image and fusion imaging examination. Data registration, matching and then volume navigation were feasible in all cases. Fusion imaging provided real-time imaging capabilities and high tissue contrast of choroidal tumour and optic nerve. It also allowed adding a real-time colour Doppler signal on magnetic resonance images for assessment of vasculature of tumour and retrobulbar structures. The combination of orbital high-field magnetic resonance and colour Doppler ultrasound image fusion and navigation is feasible. Multimodal fusion imaging promises to foster assessment and monitoring of choroidal melanoma and optic nerve disorders. • Orbital magnetic resonance and colour Doppler ultrasound real-time fusion imaging is feasible • Fusion imaging combines the spatial and temporal resolution advantages of each modality • Magnetic resonance and ultrasound fusion imaging improves assessment of choroidal melanoma vascularisation.

[Vascular complications following kidney transplant: the role of color-Doppler imaging].

PubMed

Granata, Antonio; Floccari, Fulvio; Lentini, Paolo; Vittoria, Salvatore; Di Pietro, Fabio; Zamboli, Pasquale; Fiorini, Fulvio; Fatuzzo, Pasquale

2012-01-01

The progressive decline in the incidence of graft rejection has made urological, surgical, parenchymal and vascular complications of kidney transplant more frequent. The latter, although accounting for only 5-10% of all post-transplant complications, are a frequent cause of graft loss. Ultrasonography, both in B-mode and with Doppler ultrasound, is an important diagnostic tool in case of clinical conditions which might impair kidney function. Even though ultrasonography is considered fundamental in the diagnosis of parenchymal and surgical complications of the transplanted kidney, its role is not fully understood in case of vascular complications of the graft. The specificity of Doppler ultrasound is very important in case of stenosis of the transplanted renal artery, pseudoaneurysms, arteriovenous fistulas, and thrombosis with complete or partial artery or vein occlusion. Doppler and color determinations present high diagnostic accuracy, which is higher in case of successive measurements performed during the follow-up of the graft. Modern techniques including contrast-enhanced ultrasound increase the diagnostic power of ultrasonography in case of vascular complications of the transplanted kidney, planted kidney.

Determining the near-surface current profile from measurements of the wave dispersion relation

NASA Astrophysics Data System (ADS)

Smeltzer, Benjamin; Maxwell, Peter; Aesøy, Eirik; Ellingsen, Simen

2017-11-01

The current-induced Doppler shifts of waves can yield information about the background mean flow, providing an attractive method of inferring the current profile in the upper layer of the ocean. We present measurements of waves propagating on shear currents in a laboratory water channel, as well as theoretical investigations of inversion techniques for determining the vertical current structure. Spatial and temporal measurements of the free surface profile obtained using a synthetic Schlieren method are analyzed to determine the wave dispersion relation and Doppler shifts as a function of wavelength. The vertical current profile can then be inferred from the Doppler shifts using an inversion algorithm. Most existing algorithms rely on a priori assumptions of the shape of the current profile, and developing a method that uses less stringent assumptions is a focus of this study, allowing for measurement of more general current profiles. The accuracy of current inversion algorithms are evaluated by comparison to measurements of the mean flow profile from particle image velocimetry (PIV), and a discussion of the sensitivity to errors in the Doppler shifts is presented.

Transcranial functional ultrasound imaging of the brain using microbubble-enhanced ultrasensitive Doppler

PubMed Central

Errico, Claudia; Osmanski, Bruno-Félix; Pezet, Sophie; Couture, Olivier; Lenkei, Zsolt; Tanter, Mickael

2016-01-01

Functional ultrasound (fUS) is a novel neuroimaging technique, based on high-sensitivity ultrafast Doppler imaging of cerebral blood volume, capable of measuring brain activation and connectivity in rodents with high spatiotemporal resolution (100 μm, 1 ms). However, the skull attenuates acoustic waves, so fUS in rats currently requires craniotomy or a thinned-skull window. Here we propose a non-invasive approach by enhancing the fUS signal with a contrast agent, inert gas microbubbles. Plane-wave illumination of the brain at high frame rate (500 Hz compounded sequence with three tilted plane waves, PRF = 1500Hz with a 128 element 15 MHz linear transducer), yields highly-resolved neurovascular maps. We compared fUS imaging performance through the intact skull bone (transcranial fUS) versus a thinned-skull window in the same animal. First, we show that the vascular network of the adult rat brain can be imaged transcranially only after a bolus intravenous injection of microbubbles, which leads to a 9 dB gain in the contrast-to-tissue ratio. Next, we demonstrate that functional increase in the blood volume of the primary sensory cortex after targeted electrical-evoked stimulations of the sciatic nerve is observable transcranially in presence of contrast agents, with high reproducibility (Pearson's coefficient ρ = 0.7 ± 0.1, p = 0.85). Our work demonstrates that the combination of ultrafast Doppler imaging and injection of contrast agent allows non-invasive functional brain imaging through the intact skull bone in rats. These results should ease non-invasive longitudinal studies in rodents and open a promising perspective for the adoption of highly resolved fUS approaches for the adult human brain. PMID:26416649

Feasibility of transabdominal Doppler sonography for studying uterine blood flow characteristics in cycling gilts.

PubMed

Herlta, Catherine; Starka, Rosa; Sigmarsson, Haukur L; Kauffold, Johannes

2018-06-01

To test for the feasibility of transabdominal Doppler sonography (color, power, pulse wave) to define uterine perfusion characteristics throughout the estrous cycle in gilts. A total of 15 gilts were synchronized for estrus and scanned in their following spontaneous cycle while being restrained in a purpose-designed mobile crate. To define uterine perfusion characteristics, vessels in between and within uterine cross-sections were imaged and recorded as video sequences to be analyzed by PixelFlux® software for perfused area (Amix), blood flow velocity (vmix) and intensity (Imix) as well as resistance (RIvmix) and pulsatility index (PIvmix). Color Doppler sonography proved to be the only feasible technique, as it was less affected by animal movements than power and pulse wave sonography. As determined by color Doppler sonography, all five parameters determined showed specific patterns through the estrous cycle, i. e. Amix, vmix, Imix were high in proestrus, decreased in estrus and remained low in midestrus and most parts of diestrus; RIvmix and PIvmix with inversely paralleled patterns. This study has demonstrated that transabdominal color Doppler but not power and pulse wave Doppler sonography is feasible to be performed in crate-restrained gilts for studying uterine perfusion characteristics during the estrous cycle, and that changes of uterine perfusion over the course of the estrous cycle can be clearly followed by color Doppler sonography. Results encourage the use of color Doppler sonography for studying i. e. uterine capacity or uterus related infertility such as for cases of clinically unapparent endometritis. Schattauer GmbH.

Doppler color imaging. Principles and instrumentation.

PubMed

Kremkau, F W

1992-01-01

DCI acquires Doppler-shifted echoes from a cross-section of tissue scanned by an ultrasound beam. These echoes are then presented in color and superimposed on the gray-scale anatomic image of non-Doppler-shifted echoes received during the scan. The flow echoes are assigned colors according to the color map chosen. Usually red, yellow, or white indicates positive Doppler shifts (approaching flow) and blue, cyan, or white indicates negative shifts (receding flow). Green is added to indicate variance (disturbed or turbulent flow). Several pulses (the number is called the ensemble length) are needed to generate a color scan line. Linear, convex, phased, and annular arrays are used to acquire the gray-scale and color-flow information. Doppler color-flow instruments are pulsed-Doppler instruments and are subject to the same limitations, such as Doppler angle dependence and aliasing, as other Doppler instruments. Color controls include gain, TGC, map selection, variance on/off, persistence, ensemble length, color/gray priority. Nyquist limit (PRF), baseline shift, wall filter, and color window angle, location, and size. Doppler color-flow instruments generally have output intensities intermediate between those of gray-scale imaging and pulsed-Doppler duplex instruments. Although there is no known risk with the use of color-flow instruments, prudent practice dictates that they be used for medical indications and with the minimum exposure time and instrument output required to obtain the needed diagnostic information.

Measurement Capabilities of Single-Pulse Planar Doppler Velocimetry

NASA Technical Reports Server (NTRS)

McKenzie, Robert L.; Kutler, Paul F. (Technical Monitor)

1994-01-01

Preliminary investigations are described of a method that is capable of measuring instantaneous, 3-D, velocity vectors everywhere in a light sheet generated by a pulsed laser. The technique, here called Planar Doppler Velocimetry (PDV), is a variation of a new concept for velocity measurements that was called Doppler Global Velocimetry (DGV) in its original disclosure. The concept relies on the use of a narrowband laser and measurements of the Doppler shift of scattered light from particles moving with a flow. The Doppler shift is recorded as a variation in transmission through a sharp-edged spectral filter provided by iodine vapor in a cell. Entire fields of velocity can be determined by using a solid-state camera to record the intensity variations throughout the field of view. However, the implementation of DGV has been centered principally on the use of high power, continuous-wave, ion lasers and measurement times that are determined by the 30-ms framing times of standard video cameras. Hence, they provide velocity fields that are averaged in time at least over that period. On the other hand, the PDV concept described in this presentation incorporates a high energy, repetitively pulsed, Nd-YAG laser that is injection-seeded to make it narrowband and then frequency-doubled to provide light at frequencies absorbed by the iodine vapor. The duration of each pulse is less than 10 nanoseconds. When used in combination with nonstandard, scientific quality, solid state cameras, a sequence of images can be obtained that provides instantaneous velocity vectors everywhere in the field of view. The investigations described in this paper include an accurate characterization of the iodine cell spectral behavior and its influence on the PDV measurements, a derivation of the PDV signal analysis requirements, and the unique aspects of the pulsed laser behavior related to this application. In addition, PDV measurements are to be demonstrated using data from a rotating wheel target and from the flow of a subsonic jet. Initially, single optical fiber light collection and photomultiplier detectors will be substituted for solid state cameras. Those results will allow the determination of the fundamental limitations of the PDV technique without the complications of image acquisition and processing. They will then be used to provide an analysis of the measurement capabilities of PDV both in small aerodynamic research wind tunnels and in large wind tunnels designed for production airframe and propulsion testing. Future plans include the implementation of solid state cameras and the development of the required image acquisition and processing software. Eventually, the PDV technique will be applied to an aerodynamic research program related to transonic wing flutter.

Magnetic Doppler imaging considering atmospheric structure modifications due to local abundances: a luxury or a necessity?

NASA Astrophysics Data System (ADS)

Kochukhov, O.; Wade, G. A.; Shulyak, D.

2012-04-01

Magnetic Doppler imaging is currently the most powerful method of interpreting high-resolution spectropolarimetric observations of stars. This technique has provided the very first maps of stellar magnetic field topologies reconstructed from time series of full Stokes vector spectra, revealing the presence of small-scale magnetic fields on the surfaces of Ap stars. These studies were recently criticised by Stift et al., who claimed that magnetic inversions are not robust and are seriously undermined by neglecting a feedback on the Stokes line profiles from the local atmospheric structure in the regions of enhanced metal abundance. We show that Stift et al. misinterpreted published magnetic Doppler imaging results and consistently neglected some of the most fundamental principles behind magnetic mapping. Using state-of-the-art opacity sampling model atmosphere and polarized radiative transfer codes, we demonstrate that the variation of atmospheric structure across the surface of a star with chemical spots affects the local continuum intensity but is negligible for the normalized local Stokes profiles except for the rare situation of a very strong line in an extremely Fe-rich atmosphere. For the disc-integrated spectra of an Ap star with extreme abundance variations, we find that the assumption of a mean model atmosphere leads to moderate errors in Stokes I but is negligible for the circular and linear polarization spectra. Employing a new magnetic inversion code, which incorporates the horizontal variation of atmospheric structure induced by chemical spots, we reconstructed new maps of magnetic field and Fe abundance for the bright Ap star α2 CVn. The resulting distribution of chemical spots changes insignificantly compared to the previous modelling based on a single model atmosphere, while the magnetic field geometry does not change at all. This shows that the assertions by Stift et al. are exaggerated as a consequence of unreasonable assumptions and extrapolations, as well as methodological flaws and inconsistencies of their analysis. Our discussion proves that published magnetic inversions based on a mean stellar atmosphere are highly robust and reliable, and that the presence of small-scale magnetic field structures on the surfaces of Ap stars is indeed real. Incorporating horizontal variations of atmospheric structure in Doppler imaging can marginally improve reconstruction of abundance distributions for stars showing very large iron overabundances. But this costly technique is unnecessary for magnetic mapping with high-resolution polarization spectra.

3D ultrafast ultrasound imaging in vivo.

PubMed

Provost, Jean; Papadacci, Clement; Arango, Juan Esteban; Imbault, Marion; Fink, Mathias; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

2014-10-07

Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32  ×  32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra--and inter-observer variability.

Noncoherent Doppler tracking: first flight results

NASA Astrophysics Data System (ADS)

DeBoy, Christopher C.; Robert Jensen, J.; Asher, Mark S.

2005-01-01

Noncoherent Doppler tracking has been devised as a means to achieve highly accurate, two-way Doppler measurements with a simple, transceiver-based communications system. This technique has been flown as an experiment on the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) spacecraft, (launched 7 December 2001), as the operational technique for Doppler tracking on CONTOUR, and is baselined on several future deep space missions at JHU/APL. This paper reports on initial results from a series of successful tests of this technique between the TIMED spacecraft and NASA ground stations in the Deep Space Network. It also examines the advantages that noncoherent Doppler tracking and a transceiver-based system may offer to small satellite systems, including reduced cost, mass, and power.

Four-dimensional ultrasonography of the fetal heart using color Doppler spatiotemporal image correlation.

PubMed

Gonçalves, Luís F; Romero, Roberto; Espinoza, Jimmy; Lee, Wesley; Treadwell, Marjorie; Chintala, Kavitha; Brandl, Helmut; Chaiworapongsa, Tinnakorn

2004-04-01

To describe clinical and research applications of 4-dimensional imaging of the fetal heart using color Doppler spatiotemporal image correlation. Forty-four volume data sets were acquired by color Doppler spatiotemporal image correlation. Seven subjects were examined: 4 fetuses without abnormalities, 1 fetus with ventriculomegaly and a hypoplastic cerebellum but normal cardiac anatomy, and 2 fetuses with cardiac anomalies detected by fetal echocardiography (1 case of a ventricular septal defect associated with trisomy 21 and 1 case of a double-inlet right ventricle with a 46,XX karyotype). The median gestational age at the time of examination was 21 3/7 weeks (range, 19 5/7-34 0/7 weeks). Volume data sets were reviewed offline by multiplanar display and volume-rendering methods. Representative images and online video clips illustrating the diagnostic potential of this technology are presented. Color Doppler spatiotemporal image correlation allowed multiplanar visualization of ventricular septal defects, multiplanar display and volume rendering of tricuspid regurgitation, volume rendering of the outflow tracts by color and power Doppler ultrasonography (both in a normal case and in a case of a double-inlet right ventricle with a double-outlet right ventricle), and visualization of venous streams at the level of the foramen ovale. Color Doppler spatiotemporal image correlation has the potential to simplify visualization of the outflow tracts and improve the evaluation of the location and extent of ventricular septal defects. Other applications include 3-dimensional evaluation of regurgitation jets and venous streams at the level of the foramen ovale.

Doppler synthetic aperture radar interferometry: a novel SAR interferometry for height mapping using ultra-narrowband waveforms

NASA Astrophysics Data System (ADS)

Yazıcı, Birsen; Son, Il-Young; Cagri Yanik, H.

2018-05-01

This paper introduces a new and novel radar interferometry based on Doppler synthetic aperture radar (Doppler-SAR) paradigm. Conventional SAR interferometry relies on wideband transmitted waveforms to obtain high range resolution. Topography of a surface is directly related to the range difference between two antennas configured at different positions. Doppler-SAR is a novel imaging modality that uses ultra-narrowband continuous waves (UNCW). It takes advantage of high resolution Doppler information provided by UNCWs to form high resolution SAR images. We introduce the theory of Doppler-SAR interferometry. We derive an interferometric phase model and develop the equations of height mapping. Unlike conventional SAR interferometry, we show that the topography of a scene is related to the difference in Doppler frequency between two antennas configured at different velocities. While the conventional SAR interferometry uses range, Doppler and Doppler due to interferometric phase in height mapping; Doppler-SAR interferometry uses Doppler, Doppler-rate and Doppler-rate due to interferometric phase in height mapping. We demonstrate our theory in numerical simulations. Doppler-SAR interferometry offers the advantages of long-range, robust, environmentally friendly operations; low-power, low-cost, lightweight systems suitable for low-payload platforms, such as micro-satellites; and passive applications using sources of opportunity transmitting UNCW.

Noninvasive diagnosis of right-sided extracardiac conduit obstruction by combined magnetic resonance imaging and continuous-wave Doppler echocardiography.

PubMed

Canter, C E; Gutierrez, F R; Molina, P; Hartmann, A F; Spray, T L

1991-04-01

Right-sided extracardiac conduits are frequently complicated by obstruction over time. We compared the utility of two-dimensional and Doppler echocardiography and magnetic resonance imaging in the diagnosis of postoperative right-sided obstruction with cardiac catheterization and angiography in 10 patients with xenograft or homograft conduits. Correlation (r = 0.95) between continuous-wave Doppler estimates and catheter pullback pressure gradients across the conduits was excellent. Echocardiography could only visualize five of 10 conduits in their entirety. Magnetic resonance imaging visualized all conduits and showed statistically significant (kappa = 0.58) agreement with angiography in the localization and estimation of severity of a variety of right-sided obstructions in these patients. However, flow voids created by the metallic ring around xenograft valves led to a false negative diagnosis of valvular stenosis in four patients when magnetic resonance imaging was used alone. Doppler studies correctly indicated obstruction in these patients. The combination of magnetic resonance imaging studies and continuous-wave Doppler echocardiography can be useful to noninvasively evaluate right-sided obstruction in postoperative patients with right-sided extracardiac conduits.

Cardiovascular imaging and image processing: Theory and practice - 1975; Proceedings of the Conference, Stanford University, Stanford, Calif., July 10-12, 1975

NASA Technical Reports Server (NTRS)

Harrison, D. C.; Sandler, H.; Miller, H. A.

1975-01-01

The present collection of papers outlines advances in ultrasonography, scintigraphy, and commercialization of medical technology as applied to cardiovascular diagnosis in research and clinical practice. Particular attention is given to instrumentation, image processing and display. As necessary concomitants to mathematical analysis, recently improved magnetic recording methods using tape or disks and high-speed computers of large capacity are coming into use. Major topics include Doppler ultrasonic techniques, high-speed cineradiography, three-dimensional imaging of the myocardium with isotopes, sector-scanning echocardiography, and commercialization of the echocardioscope. Individual items are announced in this issue.

Using local correlation tracking to recover solar spectral information from a slitless spectrograph

NASA Astrophysics Data System (ADS)

Courrier, Hans T.; Kankelborg, Charles C.

2018-01-01

The Multi-Order Solar EUV Spectrograph (MOSES) is a sounding rocket instrument that utilizes a concave spherical diffraction grating to form simultaneous images in the diffraction orders m=0, +1, and -1. MOSES is designed to capture high-resolution cotemporal spectral and spatial information of solar features over a large two-dimensional field of view. Our goal is to estimate the Doppler shift as a function of position for every MOSES exposure. Since the instrument is designed to operate without an entrance slit, this requires disentangling overlapping spectral and spatial information in the m=±1 images. Dispersion in these images leads to a field-dependent displacement that is proportional to Doppler shift. We identify these Doppler shift-induced displacements for the single bright emission line in the instrument passband by comparing images from each spectral order. We demonstrate the use of local correlation tracking as a means to quantify these differences between a pair of cotemporal image orders. The resulting vector displacement field is interpreted as a measurement of the Doppler shift. Since three image orders are available, we generate three Doppler maps from each exposure. These may be compared to produce an error estimate.

Live imaging of rat embryos with Doppler swept-source optical coherence tomography

NASA Astrophysics Data System (ADS)

Larina, Irina V.; Furushima, Kenryo; Dickinson, Mary E.; Behringer, Richard R.; Larin, Kirill V.

2009-09-01

The rat has long been considered an excellent system to study mammalian embryonic cardiovascular physiology, but has lacked the extensive genetic tools available in the mouse to be able to create single gene mutations. However, the recent establishment of rat embryonic stem cell lines facilitates the generation of new models in the rat embryo to link changes in physiology with altered gene function to define the underlying mechanisms behind congenital cardiovascular birth defects. Along with the ability to create new rat genotypes there is a strong need for tools to analyze phenotypes with high spatial and temporal resolution. Doppler OCT has been previously used for 3-D structural analysis and blood flow imaging in other model species. We use Doppler swept-source OCT for live imaging of early postimplantation rat embryos. Structural imaging is used for 3-D reconstruction of embryo morphology and dynamic imaging of the beating heart and vessels, while Doppler-mode imaging is used to visualize blood flow. We demonstrate that Doppler swept-source OCT can provide essential information about the dynamics of early rat embryos and serve as a basis for a wide range of studies on functional evaluation of rat embryo physiology.

Live imaging of rat embryos with Doppler swept-source optical coherence tomography

PubMed Central

Larina, Irina V.; Furushima, Kenryo; Dickinson, Mary E.; Behringer, Richard R.; Larin, Kirill V.

2009-01-01

The rat has long been considered an excellent system to study mammalian embryonic cardiovascular physiology, but has lacked the extensive genetic tools available in the mouse to be able to create single gene mutations. However, the recent establishment of rat embryonic stem cell lines facilitates the generation of new models in the rat embryo to link changes in physiology with altered gene function to define the underlying mechanisms behind congenital cardiovascular birth defects. Along with the ability to create new rat genotypes there is a strong need for tools to analyze phenotypes with high spatial and temporal resolution. Doppler OCT has been previously used for 3-D structural analysis and blood flow imaging in other model species. We use Doppler swept-source OCT for live imaging of early postimplantation rat embryos. Structural imaging is used for 3-D reconstruction of embryo morphology and dynamic imaging of the beating heart and vessels, while Doppler-mode imaging is used to visualize blood flow. We demonstrate that Doppler swept-source OCT can provide essential information about the dynamics of early rat embryos and serve as a basis for a wide range of studies on functional evaluation of rat embryo physiology. PMID:19895102

Comparative study evaluating the role of color Doppler sonography and computed tomography in predicting chest wall invasion by lung tumors.

PubMed

Sripathi, Smiti; Mahajan, Abhishek

2013-09-01

To analyze qualitative and quantitative parameters of lung tumors by color Doppler sonography, determine the role of color Doppler sonography in predicting chest wall invasion by lung tumors using spectral waveform analysis, and compare color Doppler sonography and computed tomography (CT) for predicting chest wall invasion by lung tumors. Between March and September 2007, 55 patients with pleuropulmonary lesions on chest radiography were assessed by grayscale and color Doppler sonography for chest wall invasion. Four patients were excluded from the study because of poor acoustic windows. Quantitative and qualitative sonographic examinations of the lesions were performed using grayscale and color Doppler imaging. The correlation between the color Doppler and CT findings was determined, and the final outcomes were correlated with the histopathologic findings. Of a total of 51 lesions, 32 were malignant. Vascularity was present on color Doppler sonography in 28 lesions, and chest wall invasion was documented in 22 cases. Computed tomography was performed in 24 of 28 evaluable malignant lesions, and the findings were correlated with the color Doppler findings for chest wall invasion. Of the 24 patients who underwent CT, 19 showed chest wall invasion. The correlation between the color Doppler and CT findings revealed that color Doppler sonography had sensitivity of 95.6% and specificity of 100% for assessing chest wall invasion, whereas CT had sensitivity of 85.7% and specificity of 66.7%. Combined qualitative and quantitative color Doppler sonography can predict chest wall invasion by lung tumors with better sensitivity and specificity than CT. Although surgery is the reference standard, color Doppler sonography is a readily available, affordable, and noninvasive in vivo diagnostic imaging modality that is complementary to CT and magnetic resonance imaging for lung cancer staging.

A quantitative damage imaging technique based on enhanced CCRTM for composite plates using 2D scan

NASA Astrophysics Data System (ADS)

He, Jiaze; Yuan, Fuh-Gwo

2016-10-01

A two-dimensional (2D) non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique. The system comprises a single piezoelectric wafer mounted on the composite plate and a laser Doppler vibrometer (LDV) for scanning a region in the vicinity of the PZT to capture the scattered wavefield. The proposed damage imaging technique takes into account the amplitude, phase, geometric spreading, and all of the frequency content of the Lamb waves propagating in the plate; thus, a reflectivity coefficients of the delamination is calculated and potentially related to damage severity. Comparisons are made in terms of damage imaging quality between 2D areal scans and 1D line scans as well as between the proposed and existing imaging conditions. The experimental results show that the 2D E-CCRTM performs robustly when imaging and quantifying impact damage in large-scale composites using a single PZT actuator with a nearby areal scan using LDV.

An enhanced CCRTM (E-CCRTM) damage imaging technique using a 2D areal scan for composite plates

NASA Astrophysics Data System (ADS)

He, Jiaze; Yuan, Fuh-Gwo

2016-04-01

A two-dimensional (2-D) non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique. The system comprises a single piezoelectric actuator mounted on the composite plate and a laser Doppler vibrometer (LDV) for scanning a region to capture the scattered wavefield in the vicinity of the PZT. The proposed damage imaging technique takes into account the amplitude, phase, geometric spreading, and all of the frequency content of the Lamb waves propagating in the plate; thus, the reflectivity coefficients of the delamination can be calculated and potentially related to damage severity. Comparisons are made in terms of damage imaging quality between 2-D areal scans and linear scans as well as between the proposed and existing imaging conditions. The experimental results show that the 2-D E-CCRTM performs robustly when imaging and quantifying impact damage in large-scale composites using a single PZT actuator with a nearby areal scan using LDV.

Performance analysis of multiple PRF technique for ambiguity resolution

NASA Technical Reports Server (NTRS)

Chang, C. Y.; Curlander, J. C.

1992-01-01

For short wavelength spaceborne synthetic aperture radar (SAR), ambiguity in Doppler centroid estimation occurs when the azimuth squint angle uncertainty is larger than the azimuth antenna beamwidth. Multiple pulse recurrence frequency (PRF) hopping is a technique developed to resolve the ambiguity by operating the radar in different PRF's in the pre-imaging sequence. Performance analysis results of the multiple PRF technique are presented, given the constraints of the attitude bound, the drift rate uncertainty, and the arbitrary numerical values of PRF's. The algorithm performance is derived in terms of the probability of correct ambiguity resolution. Examples, using the Shuttle Imaging Radar-C (SIR-C) and X-SAR parameters, demonstrate that the probability of correct ambiguity resolution obtained by the multiple PRF technique is greater than 95 percent and 80 percent for the SIR-C and X-SAR applications, respectively. The success rate is significantly higher than that achieved by the range cross correlation technique.

Imaging nanoparticle flow using magneto-motive optical Doppler tomography.

PubMed

Kim, Jeehyun; Oh, Junghwan; Milner, Thomas E; Nelson, J Stuart

2007-01-24

We introduce a novel approach for imaging solutions of superparamagnetic iron oxide (SPIO) nanoparticles using magneto-motive optical Doppler tomography (MM-ODT). MM-ODT combines an externally applied temporally oscillating high-strength magnetic field with ODT to detect nanoparticles flowing through a microfluidic channel. A solenoid with a cone-shaped ferrite core extensively increased the magnetic field strength (B(max) = 1 T, [Formula: see text]) at the tip of the core and also focused the magnetic field in microfluidic channels containing nanoparticle solutions. Nanoparticle contrast was demonstrated in a microfluidic channel filled with an SPIO solution by imaging the Doppler frequency shift which was observed independently of the nanoparticle flow rate and direction. Results suggest that MM-ODT may be applied to image Doppler shift of SPIO nanoparticles in microfluidic flows with high contrast.

Critical Review of Noninvasive Optical Technologies for Wound Imaging

PubMed Central

Jayachandran, Maanasa; Rodriguez, Suset; Solis, Elizabeth; Lei, Jiali; Godavarty, Anuradha

2016-01-01

Significance: Noninvasive imaging approaches can provide greater information about a wound than visual inspection during the wound healing and treatment process. This review article focuses on various optical imaging techniques developed to image different wound types (more specifically ulcers). Recent Advances: The noninvasive optical imaging approaches in this review include hyperspectral imaging, multispectral imaging, near-infrared spectroscopy (NIRS), diffuse reflectance spectroscopy, optical coherence tomography, laser Doppler imaging, laser speckle imaging, spatial frequency domain imaging, and fluorescence imaging. The various wounds imaged using these techniques include open wounds, chronic wounds, diabetic foot ulcers, decubitus ulcers, venous leg ulcers, and burns. Preliminary work in the development and implementation of a near-infrared optical scanner for wound imaging as a noncontact hand-held device is briefly described. The technology is based on NIRS and has demonstrated its potential to differentiate a healing from nonhealing wound region. Critical Issues: While most of the optical imaging techniques can penetrate few hundred microns to a 1–2 mm from the wound surface, NIRS has the potential to penetrate deeper, demonstrating the potential to image internal wounds. Future Directions: All the technologies are currently at various stages of translational efforts to the clinic, with NIRS holding a greater promise for physiological assessment of the wounds internal, beyond the gold-standard visual assessment. PMID:27602254

Comparison of Hemispheric Activation during Mental Word and Rhyme Generation Using Transcranial Doppler Sonography

ERIC Educational Resources Information Center

Krach, Soren; Hartje, Wolfgang

2006-01-01

The Wada test is at present the method of choice for preoperative assessment of patients who require surgery close to cortical language areas. It is, however, an invasive test with an attached morbidity risk. By now, an alternative to the Wada test is to combine a lexical word generation paradigm with non-invasive imaging techniques. However,…

Skin perfusion evaluation between laser speckle contrast imaging and laser Doppler flowmetry

NASA Astrophysics Data System (ADS)

Humeau-Heurtier, Anne; Mahe, Guillaume; Durand, Sylvain; Abraham, Pierre

2013-03-01

In the biomedical field, laser Doppler flowmetry (LDF) and laser speckle contrast imaging (LSCI) are two optical techniques aiming at monitoring - non-invasively - the microvascular blood perfusion. LDF has been used for nearly 40 years whereas LSCI is a recent technique that overcomes some drawbacks of LDF. Both LDF and LSCI give perfusion assessments in arbitrary units. However, the possible relationship existing between perfusions given by LDF and by LSCI over large blood flow values has not been completely studied yet. We therefore herein evaluate the relationship between the LDF and LSCI perfusion values across a broad range of skin blood flows. For this purpose, LDF and LSCI data were acquired simultaneously on the forearm of 12 healthy subjects, at rest, during different durations of vascular occlusion and during reactive hyperemia. For the range of skin blood flows studied, the power function fits the data better than the linear function: powers for individual subjects go from 1.2 to 1.7 and the power is close to 1.3 when all the subjects are studied together. We thus suggest distinguishing perfusion values given by the two optical systems.

The modern role of transoesophageal echocardiography in the assessment of valvular pathologies

PubMed Central

Bull, Sacha; Newton, James

2017-01-01

Despite significant advancements in the field of cardiovascular imaging, transoesophageal echocardiography remains the key imaging modality in the management of valvular pathologies. This paper provides echocardiographers with an overview of the modern role of TOE in the diagnosis and management of valvular disease. We describe how the introduction of 3D techniques has changed the detection and grading of valvular pathologies and concentrate on its role as a monitoring tool in interventional cardiology. In addition, we focus on the echocardiographic and Doppler techniques used in the assessment of prosthetic valves and provide guidance for the evaluation of prosthetic valves. Finally, we summarise quantitative methods used for the assessment of valvular stenosis and regurgitation and highlight the key areas where echocardiography remains superior over other novel imaging modalities. PMID:28096184

The modern role of transoesophageal echocardiography in the assessment of valvular pathologies.

PubMed

Wamil, Malgorzata; Bull, Sacha; Newton, James

2017-01-17

Despite significant advancements in the field of cardiovascular imaging, transoesophageal echocardiography remains the key imaging modality in the management of valvular pathologies. This paper provides echocardiographers with an overview of the modern role of TOE in the diagnosis and management of valvular disease. We describe how the introduction of 3D techniques has changed detection and grading of valvular pathologies and concentrate on its role as a monitoring tool in interventional cardiology. In addition, we focus on the echocardiographic and Doppler techniques used in the assessment of prosthetic valves, and provide guidance for evaluation of prosthetic valves. Finally, we summarise quantitative methods used for the assessment of valvular stenosis and regurgitation and highlight the key areas where echocardiography remains superior over other novel imaging modalities. © 2017 The authors.

Evaluation of a Delay-Doppler Imaging Algorithm Based on the Wigner-Ville Distribution

DTIC Science & Technology

1989-10-18

exchanging the frequency and time variables. 2.3 PROPERTIES OF THE WIGNER - VILLE DISTRIBUTION A partial list of the properties of the WVD is provided...ESD-TH-89-163 N Technical Report (N R55 00 Lfl Evaluation of a Delay-Doppler Imaging Algorithm Based on the Wigner - Ville Distribution K.I. Schultz 18...DOPPLER IMAGING ALGORITHM BASED ON THE WIGNER - VILLE DISTRIBUTION K.I. SCHULTZ Group 52 TECHNICAL REPORT 855 18 OCTOBER 1989 Approved for public release

Comparison between laser speckle contrast imaging and laser Doppler imaging to assess skin blood flow in humans.

PubMed

Millet, C; Roustit, M; Blaise, S; Cracowski, J L

2011-09-01

We tested the linearity between skin blood flux recorded with laser speckle contrast imaging (LSCI) and laser Doppler imaging (LDI), comparing different ways of expressing data. A secondary objective was to test within-subject variability of baseline flux with the two techniques. We performed local heating at 36, 39, 42, and 44°C on the forearm of healthy volunteers, and measured cutaneous blood flux with LDI and LSCI. Biological zero (BZ) was obtained by occluding the brachial artery. We expressed data as raw arbitrary perfusion units (APUs) and as a percentage increase from baseline (%BL), with and without subtracting BZ. Inter-site variability was expressed as a within subject coefficient of variation (CV). Twelve participants were enrolled. Inter-site variability at baseline was lower with LSCI (CV=9.2%) than with LDI (CV=20.7%). We observed an excellent correlation between both techniques when data were expressed as raw APUs or APU-BZ (R=0.90; p<0.001). The correlation remained correct for %BL (R=0.77, p<0.001), but decreased for %BL-BZ (R=0.44, p=0.003). Bland-Altman plots revealed a major proportional bias between the two techniques. This study suggests that skin blood flux measured with LSCI is linearly related to the LDI signal over a wide range of perfusion. Subtracting BZ does not affect this linearity but introduces variability in baseline flux, thus decreasing the correlation when data are expressed as a function of baseline. Finally, systematic bias makes it impossible to assimilate arbitrary perfusion units provided by the two systems. Copyright © 2011 Elsevier Inc. All rights reserved.

Detection of Early Right Ventricular Dysfunction in Young Patients With Thalassemia Major Using Tissue Doppler Imaging

PubMed Central

Bornaun, Helen; Dedeoglu, Reyhan; Oztarhan, Kazim; Dedeoglu, Savas; Erfidan, Erkan; Gundogdu, Muge; Aydogan, Gonul; Cengiz, Dicle

2016-01-01

Background Myocardial iron overload is the most common cause of mortality in patients with thalassemia major (TM), also known as beta-thalassemia. T2* cardiovascular magnetic resonance imaging (MRI) is the best way of monitoring cardiac iron, and new echocardiographic techniques can be used to assess cardiac function. Objectives The aim of this study was to assess the systolic and diastolic right ventricular (RV) function of patients with TM using tissue Doppler imaging (TDI) and to determine whether this echocardiographic technique is an adequate diagnostic tool for the screening and detection of subclinical cardiac dysfunction. Patients and Methods Eighty-four patients with TM were evaluated by conventional echocardiography and pulse-wave TDI. The data of the TM group (Group 1) were compared with that of 85 age- and sex-matched healthy controls (Group 2). Cardiovascular T2* MRI examinations were performed in 49 of the 85 patients. Results The patients with TM had significantly lower values for weight, height, body mass index, systolic arterial pressure, deceleration time, E’/A’, and ejection time (ET) than the controls. Group 1 also had significantly higher values for peak early diastolic velocity (E) over peak late diastolic velocity (A), peak early diastolic velocity of TDI (E’), peak late diastolic velocity of TDI (A’), E/E’, isovolumetric relaxation time, isovolumetric contraction time, and RV magnetic perfusion imaging (MPI) than Group 2. Conclusions RV diastolic dysfunction occurs before systolic deterioration in patients with TM and cannot be screened with conventional echocardiographic techniques. In routine practice, TDI measurements, MPI (for global function) and the E/E’ parameter (for diastolic function) can be used to screen and detect early RV dysfunction. PMID:27617076

High-frequency Ultrasound Imaging of Mouse Cervical Lymph Nodes.

PubMed

Walk, Elyse L; McLaughlin, Sarah L; Weed, Scott A

2015-07-25

High-frequency ultrasound (HFUS) is widely employed as a non-invasive method for imaging internal anatomic structures in experimental small animal systems. HFUS has the ability to detect structures as small as 30 µm, a property that has been utilized for visualizing superficial lymph nodes in rodents in brightness (B)-mode. Combining power Doppler with B-mode imaging allows for measuring circulatory blood flow within lymph nodes and other organs. While HFUS has been utilized for lymph node imaging in a number of mouse  model systems, a detailed protocol describing HFUS imaging and characterization of the cervical lymph nodes in mice has not been reported. Here, we show that HFUS can be adapted to detect and characterize cervical lymph nodes in mice. Combined B-mode and power Doppler imaging can be used to detect increases in blood flow in immunologically-enlarged cervical nodes. We also describe the use of B-mode imaging to conduct fine needle biopsies of cervical lymph nodes to retrieve lymph tissue for histological  analysis. Finally, software-aided steps are described to calculate changes in lymph node volume and to visualize changes in lymph node morphology following image reconstruction. The ability to visually monitor changes in cervical lymph node biology over time provides a simple and powerful technique for the non-invasive monitoring of cervical lymph node alterations in preclinical mouse models of oral cavity disease.

Clinical utility of eco-color-power Doppler ultrasonography and contrast enhanced magnetic resonance imaging for interpretation and quantification of joint synovitis: a review.

PubMed

Carotti, Marina; Galeazzi, Vittoria; Catucci, Francesca; Zappia, Marcello; Arrigoni, Francesco; Barile, Antonio; Giovagnoni, Andrea

2018-01-19

With the introduction of new biologics such as anti-TNF-alpha antibodies and other therapies in the treatment of inflammatory arthritis, capable of halting joint destruction and functional disability, there are new pressures on diagnostic and prognostic imaging. Early demonstration of pre-erosive inflammatory features and monitoring of the long-term effects of treatment are becoming increasingly important. Early detection of synovitis offers advantages in terms of allowing early instigation of therapy and may allow the identification of those patients displaying more aggressive disease who might benefit from early intervention with expensive DMARD therapy. Advanced imaging techniques such as ultrasound (US) and magnetic resonance imaging (MRI) have focussed on the demonstration and quantification of synovitis and allow early diagnosis of inflammatory arthropathies such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Synovitis represents a potential surrogate measure of disease activity that can be monitored using either MRI or US; the techniques have, generally, focused on monitoring synovial volume or quality as assessed by its vascularity. However to achieve these goals, standardisation and validation of US and MRI are required to ensure accurate diagnosis, reproducibility and reliability. Each modality has different strengths and weaknesses and levels of validation. This article aims to increase the awareness of radiologists and rheumatologists about this field and to encourage them to participate and contribute to the ongoing development of these modalities. Without this collaboration, it is unlikely that these modalities will reach their full potential in the field of rheumatological imaging. This review is in two parts. The first part addresses the role of US and colour or power Doppler sonography (PDUS) in the detection and monitoring of synovitis in inflammatory arthropathies. The second part will look at advanced MR imaging and Dynamic contrast-enhanced MRI techniques and in particular how they are applied to the monitoring of the disease process.

A micro-Doppler sonar for acoustic surveillance in sensor networks

NASA Astrophysics Data System (ADS)

Zhang, Zhaonian

Wireless sensor networks have been employed in a wide variety of applications, despite the limited energy and communication resources at each sensor node. Low power custom VLSI chips implementing passive acoustic sensing algorithms have been successfully integrated into an acoustic surveillance unit and demonstrated for detection and location of sound sources. In this dissertation, I explore active and passive acoustic sensing techniques, signal processing and classification algorithms for detection and classification in a multinodal sensor network environment. I will present the design and characterization of a continuous-wave micro-Doppler sonar to image objects with articulated moving components. As an example application for this system, we use it to image gaits of humans and four-legged animals. I will present the micro-Doppler gait signatures of a walking person, a dog and a horse. I will discuss the resolution and range of this micro-Doppler sonar and use experimental results to support the theoretical analyses. In order to reduce the data rate and make the system amenable to wireless sensor networks, I will present a second micro-Doppler sonar that uses bandpass sampling for data acquisition. Speech recognition algorithms are explored for biometric identifications from one's gait, and I will present and compare the classification performance of the two systems. The acoustic micro-Doppler sonar design and biometric identification results are the first in the field as the previous work used either video camera or microwave technology. I will also review bearing estimation algorithms and present results of applying these algorithms for bearing estimation and tracking of moving vehicles. Another major source of the power consumption at each sensor node is the wireless interface. To address the need of low power communications in a wireless sensor network, I will also discuss the design and implementation of ultra wideband transmitters in a three dimensional silicon on insulator process. Lastly, a prototype of neuromorphic interconnects using ultra wideband radio will be presented.

Tissue Doppler Imaging can be useful to distinguish pathological from physiological left ventricular hypertrophy: a study in master athletes and mild hypertensive subjects

PubMed Central

Galanti, Giorgio; Toncelli, Loira; Del Furia, Francesca; Stefani, Laura; Cappelli, Brunello; De Luca, Alessio; Vono, Maria Concetta Roberta

2009-01-01

Background Transthoracic echocardiography left ventricular wall thickness is often increased in master athletes and it results by intense physical training. Left Ventricular Hypertrophy can also be due to a constant pressure overload. Conventional Pulsed Wave (PW) Doppler analysis of diastolic function sometimes fails to distinguish physiological from pathological LVH. The aim of this study is to evaluate the role of Pulsed Wave Tissue Doppler Imaging in differentiating pathological from physiological LVH in the middle-aged population. Methods we selected a group of 80 master athletes, a group of 80 sedentary subjects with essential hypertension and an apparent normal diastolic function at standard PW Doppler analysis. The two groups were comparable for increased left ventricular wall thickness and mass index (134.4 ± 19.7 vs 134.5 ± 22.1 gr/m2; p > .05). Diastolic function indexes using the PW technique were in the normal range for both. Results Pulsed Wave TDI study of diastolic function immediately distinguished the two groups. While in master athletes the diastolic TDI-derived parameters remained within normal range (E' 9.4 ± 3.1 cm/sec; E/E' 7.8 ± 2.1), in the hypertensive group these parameters were found to be constantly altered, with mean values and variation ranges always outside normal validated limits (E' 7.2 ± 2.4 cm/sec; E/E' 10.6 ± 3.2), and with E' and E/E' statistically different in the two groups (p < .001). Conclusion Our study showed that the TDI technique can be an easy and validated method to assess diastolic function in differentiating normal from pseudonormal diastolic patterns and it can distinguish physiological from pathological LVH emphasizing the eligibility certification required by legal medical legislation as in Italy. PMID:19845938

[Non-palpable testicular tumors in adults: A management based on imaging? Issue from the French Urologic Association Genital Cancer committee's edit].

PubMed

Rocher, L; Feretti, L; Camparo, P; Savoie, P H; Morel-Journel, N; Murez, T; Sebe, P; Flechon, A; Méjean, A; Durand, X

2018-04-09

Help in management of non-palpable testicular tumors. French Urologic Association Genital cancer committee's Edit. To review their characterization at imaging findings of non-palpable testicular tumors. Literature review (PubMed, Medline) of urological and radiological studies dealing with testicular tumors using keywords: non-palpable/incidental testicular tumors; color Doppler ultrasound; US elastography; magnetic resonance imaging; contrast enhanced sonography; partial surgery. Color Doppler is the basic exam. The size, the presence of microlithts/microlithiasis/macrocalcifications, the vascular architecture are major semiological findings to suggest the benign or the malignant nature of the lesion. Other techniques like multiparametric MRI, contrast-enhanced sonography, sonographic elastography are still in evaluation. The frequency of benign tumors such as Leydig cell tumors lead to preservation management, through improved characterization, monitoring or tumorectomy. Non-randomized study - a very few prospective studies. The era of total orchiectomy for any uncertain testicular lesion is over. We try the challenge of characterization, and define management's algorithms based on the suspected nature of the tumors. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

In vivo visualization method by absolute blood flow velocity based on speckle and fringe pattern using two-beam multipoint laser Doppler velocimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyoden, Tomoaki, E-mail: kyouden@nc-toyama.ac.jp; Naruki, Shoji; Akiguchi, Shunsuke

Two-beam multipoint laser Doppler velocimetry (two-beam MLDV) is a non-invasive imaging technique able to provide an image of two-dimensional blood flow and has potential for observing cancer as previously demonstrated in a mouse model. In two-beam MLDV, the blood flow velocity can be estimated from red blood cells passing through a fringe pattern generated in the skin. The fringe pattern is created at the intersection of two beams in conventional LDV and two-beam MLDV. Being able to choose the depth position is an advantage of two-beam MLDV, and the position of a blood vessel can be identified in a three-dimensionalmore » space using this technique. Initially, we observed the fringe pattern in the skin, and the undeveloped or developed speckle pattern generated in a deeper position of the skin. The validity of the absolute velocity value detected by two-beam MLDV was verified while changing the number of layers of skin around a transparent flow channel. The absolute velocity value independent of direction was detected using the developed speckle pattern, which is created by the skin construct and two beams in the flow channel. Finally, we showed the relationship between the signal intensity and the fringe pattern, undeveloped speckle, or developed speckle pattern based on the skin depth. The Doppler signals were not detected at deeper positions in the skin, which qualitatively indicates the depth limit for two-beam MLDV.« less

A Computer-Aided Diagnosis System for Measuring Carotid Artery Intima-Media Thickness (IMT) Using Quaternion Vectors.

PubMed

Kutbay, Uğurhan; Hardalaç, Fırat; Akbulut, Mehmet; Akaslan, Ünsal; Serhatlıoğlu, Selami

2016-06-01

This study aims investigating adjustable distant fuzzy c-means segmentation on carotid Doppler images, as well as quaternion-based convolution filters and saliency mapping procedures. We developed imaging software that will simplify the measurement of carotid artery intima-media thickness (IMT) on saliency mapping images. Additionally, specialists evaluated the present images and compared them with saliency mapping images. In the present research, we conducted imaging studies of 25 carotid Doppler images obtained by the Department of Cardiology at Fırat University. After implementing fuzzy c-means segmentation and quaternion-based convolution on all Doppler images, we obtained a model that can be analyzed easily by the doctors using a bottom-up saliency model. These methods were applied to 25 carotid Doppler images and then interpreted by specialists. In the present study, we used color-filtering methods to obtain carotid color images. Saliency mapping was performed on the obtained images, and the carotid artery IMT was detected and interpreted on the obtained images from both methods and the raw images are shown in Results. Also these results were investigated by using Mean Square Error (MSE) for the raw IMT images and the method which gives the best performance is the Quaternion Based Saliency Mapping (QBSM). 0,0014 and 0,000191 mm(2) MSEs were obtained for artery lumen diameters and plaque diameters in carotid arteries respectively. We found that computer-based image processing methods used on carotid Doppler could aid doctors' in their decision-making process. We developed software that could ease the process of measuring carotid IMT for cardiologists and help them to evaluate their findings.

The utility of ultrasound superb microvascular imaging for evaluation of breast tumour vascularity: comparison with colour and power Doppler imaging regarding diagnostic performance.

PubMed

Park, A Y; Seo, B K; Woo, O H; Jung, K S; Cho, K R; Park, E K; Cha, S H; Cha, J

2018-03-01

To investigate the utility of superb microvascular imaging (SMI) for evaluating the vascularity of breast masses in comparison with colour or power Doppler ultrasound (US) and the effect on diagnostic performance. A total of 191 biopsy-proven masses (99 benign and 92 malignant) in 166 women with greyscale, colour Doppler, power Doppler, and SMI images were enrolled in this retrospective study. Three radiologists analysed the vascular images using a three-factor scoring system to evaluate the number, morphology, and distribution of tumour vessels. They assessed the Breast Imaging-Reporting and Data System categories for greyscale US alone and combinations of greyscale US and each type of vascular US. The Kruskal-Wallis test was performed and the area under the receiver-operating characteristic curve (AUC) measured. On SMI, vascular scores were compared between benign and malignant masses and the optimal cut-off value for the overall score was determined. SMI showed higher vascular scores than colour or power Doppler US and malignant masses had higher scores than benign masses (p<0.001). The diagnostic performance of the combination of greyscale US and SMI was higher than those of greyscale US alone and greyscale and colour or power Doppler US (AUC, 0.815 versus 0.774, 0.789, 0.791; p<0.001). The optimal cut-off value of the overall vascular score was 5 with a sensitivity of 82.3% and a specificity of 65.3% (AUC, 0.808). SMI is superior to colour or power Doppler US for characterising the vascularity in breast masses and improving diagnostic performance. Copyright © 2017 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Real-time clinically oriented array-based in vivo combined photoacoustic and power Doppler imaging

NASA Astrophysics Data System (ADS)

Harrison, Tyler; Jeffery, Dean; Wiebe, Edward; Zemp, Roger J.

2014-03-01

Photoacoustic imaging has great potential for identifying vascular regions for clinical imaging. In addition to assessing angiogenesis in cancers, there are many other disease processes that result in increased vascularity that present novel targets for photoacoustic imaging. Doppler imaging can provide good localization of large vessels, but poor imaging of small or low flow speed vessels and is susceptible to motion artifacts. Photoacoustic imaging can provide visualization of small vessels, but due to the filtering effects of ultrasound transducers, only shows the edges of large vessels. Thus, we have combined photoacoustic imaging with ultrasound power Doppler to provide contrast agent- free vascular imaging. We use a research-oriented ultrasound array system to provide interlaced ultrasound, Doppler, and photoacoustic imaging. This system features realtime display of all three modalities with adjustable persistence, rejection, and compression. For ease of use in a clinical setting, display of each mode can be disabled. We verify the ability of this system to identify vessels with varying flow speeds using receiver operating characteristic curves, and find that as flow speed falls, photoacoustic imaging becomes a much better method for identifying blood vessels. We also present several in vivo images of the thyroid and several synovial joints to assess the practicality of this imaging for clinical applications.

Use of speckle for determining the response characteristics of Doppler imaging radars

NASA Technical Reports Server (NTRS)

Tilley, D. G.

1986-01-01

An optical model is developed for imaging optical radars such as the SAR on Seasat and the Shuttle Imaging Radar (SIR-B) by analyzing the Doppler shift of individual speckles in the image. The signal received at the spacecraft is treated in terms of a Fresnel-Kirchhoff integration over all backscattered radiation within a Huygen aperture at the earth. Account is taken of the movement of the spacecraft along the orbital path between emission and reception. The individual points are described by integration of the point source amplitude with a Green's function scattering kernel. Doppler data at each point furnishes the coordinates for visual representations. A Rayleigh-Poisson model of the surface scattering characteristics is used with Monte Carlo methods to generate simulations of Doppler radar speckle that compare well with Seasat SAR data SIR-B data.

Added value products for imaging remote sensing by processing actual GNSS reflectometry delay doppler maps

NASA Astrophysics Data System (ADS)

Schiavulli, Domenico; Frappart, Frédéric; Ramilien, Guillaume; Darrozes, José; Nunziata, Ferdinando; Migliaccio, Maurizio

2016-04-01

Global Navigation Satellite System Reflectometry (GNSS-R) is an innovative and promising tool for remote sensing. It is based on the exploitation of GNSS signals reflected off Earth's surface as signals of opportunity to infer geophysical information of the reflecting surface. The main advantages of GNSS-R with respect dedicated sensors are: the unprecedented spatial-temporal coverage due to the availability of a great amount of transmitting satellite, e.g. GPS, Galileo, Glonass, etc…, long term GNSS mission life and cost effectiveness. In fact only a simple receiver is needed. In the last years several works demonstrated the meaningful of this technique in several Earth Observation applications. All these applications presented results obtained by using a receiver mounted on an aircraft or on a fixed platform. Moreover, space borne missions have been launched or are planned: UK-DMC, TechDemoSat-1 (TDS-1), NASA CYGNSS, Geros ISS. Practically, GNSS-R can be seen as a bistatic radar system where the GNSS satellites continuously transmit the L-band all-weather night-and-day signals that are reflected off a surface, called Glistening Zone (GZ), and a receiver measures the scattered microwave signals in terms of Delay-Doppler maps (DDMs) or delay waveforms. These two products have been widely studied in the literature to extract compact parameters for different remote sensing applications. However, products measured in the Delay Doppler (DD) domain are not able to provide any spatial information of the scattering scene. This could represent a drawback for applications related to imaging remote sensing, e.g. target detection, sea/land and sea/ice transition, oil spill detection, etc…. To overcome these limitations some deconvolution techniques have been proposed in the state of the art aiming at the reconstruction of a radar image of the observed scene by processing the measured DDMs. These techniques have been tested on DDMs related to simulated marine scenario including areas with different wind speed, oil spill, non-homogeneous area and cyclone. In this work a deconvolution technique based on the 2-D Truncated Singular Value Decomposition (TSVD) approach is used to process, for the first time, a real DDM measured by the TDS-1 mission to generate a radar image of the observed scene. The considered DDMs are related to marine scenario including non-homogenous area, i.e. sea/land and sea/ice transition. These non-homogeneous area provide a strong scattering contribution in the DD domain but it is not possible to extract any other information by analyzing the DDM. In the other hand, after the 2-D TSVD technique application a radar image of the observed scenario is provided where the transition between sea and non-homogeneous elements is reconstructed and well located in the spatial domain. Finally, in this work we demonstrate the soundness of the proposed approach able to provide an added value product for imaging remote sensing to improve/complement dedicated sensors.

Real-time, high-resolution ultrasonography of the vocal folds--a prospective pilot study in patients before and after thyroidectomy.

PubMed

Dedecjus, Marek; Adamczewski, Zbigniew; Brzeziński, Jan; Lewiński, Andrzej

2010-09-01

The aim of the study was to evaluate the functionality of vocal folds (VF) by real-time, high-resolution ultrasonography (US) and to correlate the imaged features to results of laryngological examination (LE). The study group comprised 50 patients (41 females and nine males), qualified to thyroidectomy. All the patients had LE and US examination before and 2 days, 2 months, and 3 months after the surgery. We used high-resolution US imaging to identify VFs and, subsequently, a pulsed Doppler and Doppler gate to quantify the tissue displacement velocity in the vibrating VF section. LE revealed unilateral VF paralysis in two patients. VF dysfunction was diagnosed in other four subjects. In simultaneously performed US examination, changes in VF displacement velocity (VFDV) were observed in ten patients. In two subjects, VFDV was below 30 cm/s- patients with VF paralysis, diagnosed in LE. In a further eight cases, we observed VFDV decrease by 50%, comparing to preoperative values. Both US-imaging and LE, performed after the 3-month follow-up, confirmed the transitional character of the above-mentioned pathologies. US imaging of the VFs correlated with LE results, while being a minimally invasive, easily reproducible, and inexpensive method of examining VF functionality. Thanks to many recording options, it may soon become a perfect tool for an early identification of postoperative VF dysfunction with its later monitoring. To our knowledge, it is the first application of US and Doppler gate modes for VFDF quantification; however, an analysis on a larger group of patients is necessary to standardize the technique.

Laser Doppler measurement techniques for spacecraft

NASA Technical Reports Server (NTRS)

Kinman, Peter W.; Gagliardi, Robert M.

1986-01-01

Two techniques are proposed for using laser links to measure the relative radial velocity of two spacecraft. The first technique determines the relative radial velocity from a measurement of the two-way Doppler shift on a transponded radio-frequency subcarrier. The subcarrier intensity-modulates reciprocating laser beams. The second technique determines the relative radial velocity from a measurement of the two-way Doppler shift on an optical frequency carrier which is transponded between spacecraft using optical Costas loops. The first technique might be used in conjunction with noncoherent optical communications, while the second technique is compatible with coherent optical communications. The first technique simultaneously exploits the diffraction advantage of laser beams and the maturity of radio-frequency phase-locked loop technology. The second technique exploits both the diffraction advantage of laser beams and the large Doppler effect at optical frequencies. The second technique has the potential for greater accuracy; unfortunately, it is more difficult to implement since it involves optical Costas loops.

Micro-Doppler analysis of multiple frequency continuous wave radar signatures

NASA Astrophysics Data System (ADS)

Anderson, Michael G.; Rogers, Robert L.

2007-04-01

Micro-Doppler refers to Doppler scattering returns produced by non rigid-body motion. Micro-Doppler gives rise to many detailed radar image features in addition to those associated with bulk target motion. Targets of different classes (for example, humans, animals, and vehicles) produce micro-Doppler images that are often distinguishable even by nonexpert observers. Micro-Doppler features have great potential for use in automatic target classification algorithms. Although the potential benefit of using micro-Doppler in classification algorithms is high, relatively little experimental (non-synthetic) micro-Doppler data exists. Much of the existing experimental data comes from highly cooperative targets (human or vehicle targets directly approaching the radar). This research involved field data collection and analysis of micro-Doppler radar signatures from non-cooperative targets. The data was collected using a low cost Xband multiple frequency continuous wave (MFCW) radar with three transmit frequencies. The collected MFCW radar signatures contain data from humans, vehicles, and animals. The presented data includes micro-Doppler signatures previously unavailable in the literature such as crawling humans and various animal species. The animal micro-Doppler signatures include deer, dog, and goat datasets. This research focuses on the analysis of micro-Doppler from noncooperative targets approaching the radar at various angles, maneuvers, and postures.

Light and sound - emerging imaging techniques for inflammatory bowel disease

PubMed Central

Knieling, Ferdinand; Waldner, Maximilian J

2016-01-01

Patients with inflammatory bowel disease are known to have a high demand of recurrent evaluation for therapy and disease activity. Further, the risk of developing cancer during the disease progression is increasing from year to year. New, mostly non-radiant, quick to perform and quantitative methods are challenging, conventional endoscopy with biopsy as gold standard. Especially, new physical imaging approaches utilizing light and sound waves have facilitated the development of advanced functional and molecular modalities. Besides these advantages they hold the promise to predict personalized therapeutic responses and to spare frequent invasive procedures. Within this article we highlight their potential for initial diagnosis, assessment of disease activity and surveillance of cancer development in established techniques and recent advances such as wide-view full-spectrum endoscopy, chromoendoscopy, autofluorescence endoscopy, endocytoscopy, confocal laser endoscopy, multiphoton endoscopy, molecular imaging endoscopy, B-mode and Doppler ultrasound, contrast-enhanced ultrasound, ultrasound molecular imaging, and elastography. PMID:27433080

Doppler Ultrasound: What Is It Used for?

MedlinePlus

... During a Doppler ultrasound, a technician trained in ultrasound imaging (sonographer) presses a small hand-held device (transducer), ... neurologic-disorders/neurologic-tests-and-procedures/other-neurologic-imaging-studies. Accessed Oct. 18, 2016. ... . Mayo Clinic Footer Legal ...

Laser-Based Diagnostic Measurements of Low Emissions Combustor Concepts

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.

2011-01-01

This presentation provides a summary of primarily laser-based measurement techniques we use at NASA Glenn Research Center to characterize fuel injection, fuel/air mixing, and combustion. The report highlights using Planar Laser-Induced Fluorescence, Particle Image Velocimetry, and Phase Doppler Interferometry to obtain fuel injector patternation, fuel and air velocities, and fuel drop sizes and turbulence intensities during combustion. We also present a brief comparison between combustors burning standard JP-8 Jet fuel and an alternative fuels. For this comparison, we used flame chemiluminescence and high speed imaging.

Study of Raynaud’s Phenomenon by Means of Infrared Functional Imaging

DTIC Science & Technology

2001-10-25

Scleroderma and 20 Primary Raynaud’s Phenomenon patients were studied subsequently to clinical evaluation and nailfold capillaroscopy . This new...severity of Raynaud�s phenomenon, Br J Rheumatol 30(3):190- 5,1991. 6. Javanetti S, et al.: Thermography and nailfold capillaroscopy as...completely exhaustive in focusing primary or secondary RP [4]. Moreover, these techniques -as nailfold capillary microscopy, cutaneous laser-Doppler

Multibeam synthetic aperture radar for global oceanography

NASA Technical Reports Server (NTRS)

Jain, A.

1979-01-01

A single-frequency multibeam synthetic aperture radar concept for large swath imaging desired for global oceanography is evaluated. Each beam iilluminates a separate range and azimuth interval, and images for different beams may be separated on the basis of the Doppler spectrum of the beams or their spatial azimuth separation in the image plane of the radar processor. The azimuth resolution of the radar system is selected so that the Doppler spectrum of each beam does not interfere with the Doppler foldover due to the finite pulse repetition frequency of the radar system.

One way Doppler Extractor. Volume 2: Digital VCO technique

NASA Technical Reports Server (NTRS)

Nossen, E. J.; Starner, E. R.

1974-01-01

A feasibility analysis and trade-offs for a one-way Doppler extractor using digital VCO techniques is presented. The method of Doppler measurement involves the use of a digital phase lock loop; once this loop is locked to the incoming signal, the precise frequency and hence the Doppler component can be determined directly from the contents of the digital control register. The only serious error source is due to internally generated noise. Techniques are presented for minimizing this error source and achieving an accuracy of 0.01 Hz in a one second averaging period. A number of digitally controlled oscillators were analyzed from a performance and complexity point of view. The most promising technique uses an arithmetic synthesizer as a digital waveform generator.

Secondary benefit of maintaining normal transcranial Doppler velocities when using hydroxyurea for prevention of severe sickle cell anemia.

PubMed

Ghafuri, Djamila Labib; Chaturvedi, Shruti; Rodeghier, Mark; Stimpson, Sarah-Jo; McClain, Brandi; Byrd, Jeannie; DeBaun, Michael R

2017-07-01

In a retrospective cohort study, we tested the hypothesis that when prescribing hydroxyurea (HU) to children with sickle cell anemia (SCA) to prevent vaso-occlusive events, there will be a secondary benefit of maintaining low transcranial Doppler (TCD) velocity, measured by imaging technique (TCDi). HU was prescribed for 90.9% (110 of 120) of children with SCA ≥5 years of age and followed for a median of 4.4 years, with 70% (n = 77) receiving at least one TCDi evaluation after starting HU. No child prescribed HU had a conditional or abnormal TCDi measurement. HU initiation for disease severity prevention decreases the prevalence of abnormal TCDi velocities. © 2016 Wiley Periodicals, Inc.

Extraction of convective cloud parameters from Doppler Weather Radar MAX(Z) product using Image Processing Technique

NASA Astrophysics Data System (ADS)

Arunachalam, M. S.; Puli, Anil; Anuradha, B.

2016-07-01

In the present work continuous extraction of convective cloud optical information and reflectivity (MAX(Z) in dBZ) using online retrieval technique for time series data production from Doppler Weather Radar (DWR) located at Indian Meteorological Department, Chennai has been developed in MATLAB. Reflectivity measurements for different locations within the DWR range of 250 Km radii of circular disc area can be retrieved using this technique. It gives both time series reflectivity of point location and also Range Time Intensity (RTI) maps of reflectivity for the corresponding location. The Graphical User Interface (GUI) developed for the cloud reflectivity is user friendly; it also provides the convective cloud optical information such as cloud base height (CBH), cloud top height (CTH) and cloud optical depth (COD). This technique is also applicable for retrieving other DWR products such as Plan Position Indicator (Z, in dBZ), Plan Position Indicator (Z, in dBZ)-Close Range, Volume Velocity Processing (V, in knots), Plan Position Indicator (V, in m/s), Surface Rainfall Intensity (SRI, mm/hr), Precipitation Accumulation (PAC) 24 hrs at 0300UTC. Keywords: Reflectivity, cloud top height, cloud base, cloud optical depth

Effects of implanted Doppler flowmeters on femoral vein autografts.

PubMed Central

Michie, D D; Cowan, D F; Cain, C P; Bell, C C

1976-01-01

Thirteen femoral vein autografts were placed into the corresponding ipsilateral femoral arteries of 8 mongrel dogs. Cuff-type Doppler (ultrasonic) flowmeters were placed around six of the grafts. None of the vessels thrombosed. Blood flow velocities were measured in all vessels up until the time of sacrifice (mean 95 +/- 5 days after surgery) or accidental death (one dog, 49 days after surgery). The only case of graft failure was attributed to infection at the flowmeter site. With this single exception, the vein grafts exhibited uniformity in histological appearance from dog to dog. These data suggest that implantation of properly designed Doppler flow transducers may have clinical applications. This technique permits continuous or intermittent assessment of blood flow characteristics through a graft without additional trauma or cost to the patient. It is free of the many inherent disadvantages of chronically implanted electromagnetic flowmeters and may negate the need in some instances for followup angiographic studies. Images Fig. 1. Fig. 2. Fig. 3. PMID:130843

Comprasion of ovarian stromal blood flow measured by color Doppler ultrasonography in polycystic ovary syndrome patients and healthy women with ultrasonographic evidence of polycystic.

PubMed

Ozdemir, Ozhan; Sari, Mustafa Erkan; Kalkan, Dilek; Koc, Esra Meltem; Ozdemir, Seyda; Atalay, Cemal Resat

2015-04-01

To compare ovarian stromal artery blood flows measured by Doppler ultrasonography of polycystic ovary syndrome (PCOS) patients and healthy women with polycystic ovarian image in ultrasonography. Forty-two patients diagnosed with PCOS according to the criteria of 2003 Rotterdam Concencus Conferance on PCOS and 38 healthy volunteers with polycystic ovarian image in ultrasonography were included in the study. Ovarian volumes and ovarian stromal artery blood flows were measured by 3-dimensional (3-D) ultrasonography and Doppler ultrasonography in all patients. In patients with PCOS, ovarian stromal artery pulsatility index (PI) and resistivity index (RI) were found significantly different from healthy women with polycystic ovarian image in ultrasonography (p < 0.05). 3-D ovarian volumes were found significantly higher in patients with PCOS (p < 0.05), and a negative correlation was also obtained between ovarian volumes and ovarian stromal artery resistivity indices. Ovarian stromal artery Doppler examination could have an importance to explain the pathophysiology of PCOS, but there are few publications in the literature about PCOS and the details of ovarian stromal artery Doppler parameters in patients with polycystic ovarian image only. We conclude that Doppler ultrasonography findings of PCOS patients might be helpful in understanding the clinical follow-up and etiology of the disease.

Transdural doppler ultrasonography monitors cerebral blood flow changes in relation to motor tasks.

PubMed

Hatanaka, Nobuhiko; Tokuno, Hironobu; Nambu, Atsushi; Takada, Masahiko

2009-04-01

Monitoring changes in cerebral blood flow in association with neuronal activity has widely been used to evaluate various brain functions. However, current techniques do not directly measure blood flow changes in specified blood vessels. The present study identified arterioles within the cerebral cortex by echoencephalography and color Doppler imaging, and then measured blood flow velocity (BFV) changes in pulsed-wave Doppler mode. We applied this "transdural Doppler ultrasonography (TDD)" to examine BFV changes in the cortical motor-related areas of monkeys during the performance of unimanual (right or left) and bimanual key-press tasks. BFV in the primary motor cortex (MI) was increased in response to contralateral movement. In each of the unimanual and bimanual tasks, bimodal BFV increases related to both the instruction signal and the movement were observed in the supplementary motor area (SMA). Such BFV changes in the SMA were prominent during the early stage of task training and gradually decreased with improvements in task performance, leaving those in the MI unchanged. Moreover, BFV changes in the SMA depended on task difficulty. The present results indicate that TDD is useful for evaluating regional brain functions.

Doppler optical coherence microscopy and tomography applied to inner ear mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Page, Scott; Freeman, Dennis M.; Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts

While it is clear that cochlear traveling waves underlie the extraordinary sensitivity, frequency selectivity, and dynamic range of mammalian hearing, the underlying micromechanical mechanisms remain unresolved. Recent advances in low coherence measurement techniques show promise over traditional laser Doppler vibrometry and video microscopy, which are limited by low reflectivities of cochlear structures and restricted optical access. Doppler optical coherence tomography (DOCT) and Doppler optical coherence microscopy (DOCM) both utilize a broadband source to limit constructive interference of scattered light to a small axial depth called a coherence gate. The coherence gate can be swept axially to image and measure sub-nanometermore » motions of cochlear structures throughout the cochlear partition. The coherence gate of DOCT is generally narrower than the confocal gate of the focusing optics, enabling increased axial resolution (typically 15 μm) within optical sections of the cochlear partition. DOCM, frequently implemented in the time domain, centers the coherence gate on the focal plane, achieving enhanced lateral and axial resolution when the confocal gate is narrower than the coherence gate. We compare these two complementary systems and demonstrate their utility in studying cellular and micromechanical mechanisms involved in mammalian hearing.« less

Three-dimensional color Doppler imaging of the carotid artery

NASA Astrophysics Data System (ADS)

Picot, Paul A.; Rickey, Daniel W.; Mitchell, Ross; Rankin, Richard N.; Fenster, Aaron

1991-05-01

Stroke is the third leading cause of death in the United States. It is caused by ischemic injury to the brain, usually resulting from emboli from atherosclerotic plaques. The carotid bifurcation in humans is prone to atherosclerotic disease and is a site where emboli may originate. Currently, carotid stenoses are evaluated by non-invasive duplex Doppler ultrasound, with preoperative verification by intra-arterial angiography. We have developed a system that uses a color Doppler ultrasound imaging system to acquire in-vivo 3-D color Doppler images of the human carotid artery, with the aim of increasing the diagnostic accuracy of ultrasound and decreasing the use of angiography for verification. A clinical TL Ultramark 9 color Doppler ultrasound system was modified by mounting the hand-held ultrasound scan head on a motor-driven translation stage. The stage allows planar ultrasound images to be acquired over 45 mm along the neck between the clavicle and the mandible. A 3- D image is acquired by digitizing, in synchrony with the cardiac cycle, successive color ultrasound video images as the scan head is stepped along the neck. A complete volume set of 64 frames, comprising some 15 megabytes of data, requires approximately 2 minutes to acquire. The volume image is reformatted and displayed on a Sun 4/360 workstation equipped with a TAAC-1 graphics accelerator. The 3-D image may be manipulated in real time to yield the best view of blood flow in the bifurcation.

Absolute atomic hydrogen densities in a radio frequency discharge measured by two-photon laser induced fluorescence imaging

NASA Astrophysics Data System (ADS)

Chérigier, L.; Czarnetzki, U.; Luggenhölscher, D.; Schulz-von der Gathen, V.; Döbele, H. F.

1999-01-01

Absolute atomic hydrogen densities were measured in the gaseous electronics conference reference cell parallel plate reactor by Doppler-free two-photon absorption laser induced fluorescence spectroscopy (TALIF) at λ=205 nm. The capacitively coupled radio frequency discharge was operated at 13.56 MHz in pure hydrogen under various input power and pressure conditions. The Doppler-free excitation technique with an unfocused laser beam together with imaging the fluorescence radiation by an intensified charge coupled device camera allows instantaneous spatial resolution along the radial direction. Absolute density calibration is obtained with the aid of a flow tube reactor and titration with NO2. The influence of spatial intensity inhomogenities along the laser beam and subsequent fluorescence are corrected by TALIF in xenon. A full mapping of the absolute density distribution between the electrodes was obtained. The detection limit for atomic hydrogen amounts to about 2×1018 m-3. The dissociation degree is of the order of a few percent.

Listening to speech recruits specific tongue motor synergies as revealed by transcranial magnetic stimulation and tissue-Doppler ultrasound imaging

PubMed Central

D'Ausilio, A.; Maffongelli, L.; Bartoli, E.; Campanella, M.; Ferrari, E.; Berry, J.; Fadiga, L.

2014-01-01

The activation of listener's motor system during speech processing was first demonstrated by the enhancement of electromyographic tongue potentials as evoked by single-pulse transcranial magnetic stimulation (TMS) over tongue motor cortex. This technique is, however, technically challenging and enables only a rather coarse measurement of this motor mirroring. Here, we applied TMS to listeners’ tongue motor area in association with ultrasound tissue Doppler imaging to describe fine-grained tongue kinematic synergies evoked by passive listening to speech. Subjects listened to syllables requiring different patterns of dorso-ventral and antero-posterior movements (/ki/, /ko/, /ti/, /to/). Results show that passive listening to speech sounds evokes a pattern of motor synergies mirroring those occurring during speech production. Moreover, mirror motor synergies were more evident in those subjects showing good performances in discriminating speech in noise demonstrating a role of the speech-related mirror system in feed-forward processing the speaker's ongoing motor plan. PMID:24778384

Scleroderma in children: an update.

PubMed

Zulian, Francesco; Cuffaro, Giorgio; Sperotto, Francesca

2013-09-01

Scleroderma, in its localized and systemic presentation, represents the third most frequent rheumatic condition in childhood after juvenile idiopathic arthritis and systemic lupus erythematosus. Early diagnosis, appropriate assessment and effective treatment are crucial to improve the long-term outcome. Recent studies, concerning histopathology and clinical associations with other conditions, open new horizons on the etiopathogenesis of scleroderma. New developments have been also reached in the field of outcome measures. In juvenile localized scleroderma (JLS), new techniques such as Doppler and laser Doppler imaging have shown their usefulness for the daily monitoring of the patients. In juvenile systemic sclerosis (JSSc), a new severity score has been developed and needs to be validated in future trials. Finally, a randomized, double-blind controlled trial, a multicenter consensus statement and long-term follow-up studies have confirmed the important role of methotrexate (MTX) for the treatment of JLS. Studies over recent years highlighted the role of imaging as outcome measures for JLS and introduced a severity score for JSSc. New studies on MTX confirmed its important role for the treatment of JLS.

Laser Doppler perfusion imaging: a method for measuring female sexual response.

PubMed

Styles, S J; Maclean, A B; Reid, W M N; Sultana, S R

2006-05-01

To develop a new noninvasive technique to measure vulval blood flow changes during sexual arousal; 18 healthy volunteers between the age of 20 and 33 years were studied. Each subject underwent two experimental sessions at least 2 weeks apart to coincide with the proliferative and luteal phases of her menstrual cycle. An initial laser Doppler perfusion imaging (LDPI) scan of the vulva was performed. The subject was then given a chapter of erotic fiction to read and a repeat LDPI scan was performed immediately after. The percentage change in flux were calculated: the clitoral skin blood flow increased by 26.4% (P < 0.05), labial skin blood flow by 24.9% (P < 0.05) and the posterior fourchette skin blood flow by 35.3% (P < 0.05). LDPI can detect changes in vulval perfusion during the sexual arousal response and could be used to compare healthy subjects with female sexual dysfunction patients, as well as for assessing the benefits of any treatment for this condition.

Chromospherically active stars. III - HD 26337 = EI Eri: An RS CVn candidate for the Doppler-imaging technique

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Quigley, Robert; Gillies, Kim; Africano, John L.

1987-01-01

Spectroscopic observations of the chromospherically active G5 IV single-lined binary HD 26337 = EI Eri are presented. An orbital period of 1.94722 days is found for the star. It has moderately strong Ca II H and K emission and strong ultraviolet emission features, while H-alpha is a weak absorption feature that is variable in strength. The inclination of the system is 46 + or - 12 deg, and the unseen secondary is probably a late K or early M dwarf. The v sin i of the primary is 50 + or - 3 km/s, resulting in a minimum radius of 1.9 + or - 0.1 solar radius. The star is within the required limits for Doppler imaging. The primary is close to filling its Roche lobe, resulting in a strong constraint that the mass ratio is 2.6 or greater, with a primary mass of at least 1.4 solar mass. The distance to the system is estimated at 75 pc.

To assess the intimal thickness, flow velocities, and luminal diameter of carotid arteries using high-resolution B-mode ultrasound doppler imaging

NASA Astrophysics Data System (ADS)

Vemuru, Madhuri; Jabbar, Afzal; Chandra, Suman

2004-04-01

Carotid imaging is a Gold Standard test that provides useful information about the structure and functions of carotid arteries. Spectral imaging helps to evaluate the vessel and hemodynamic changes. High resolution B-mode imaging has emerged as one of the methods of choice for determining the anatomic extent of atherosclerosis and its progression and for assessing cardiovascular risks. The measurements made with Doppler correlate well with pathologic measurements. Recent prospective studies have clearly demonstrated that these measurements of carotid intimal thickness are potent predictors of Myocardial Infarction and Stroke. This method appears very attractive as it is non-invasive, extremely safe, well accepted by the patient and relatively inexpensive. It can be performed serially and has the advantage of visualizing the arterial wall in contrast to angiographic techniques which provide only an outline of the arterial lumen. Recently, there has been an interest in the clinical use of this technique in making difficult clinical decisions like deciding on preventive therapies. 30 subjects aged 21-60 years and 30 subjects aged 61-85 years of both sexes are selected after doing a baseline study to exclude Hypertension, Diabetes, Obesity and Hyperlipidemia. The carotid arteries were examined for intimal thickening, blood flow velocities and luminal diameter. With aging there is a narrowing of the carotid vessels and significant increase in intimal thickening with a consequent increase in the blood flow velocities. Inter-observer, intra-observer and instrument variations are seen and there is no significant change in the values when the distal flow pattern is considered for measurements. Aging produces major cardiovascular changes including decreased elasticity and compliance of great arteries leading to structural and functional alterations in heart and vessels. With aging there is increased intimal thickness and increased pulse wave velocity which is clearly understood by using high resolution B-Mode carotid imaging techniques.

Digital PIV Measurements in the Diffuser of a High Speed Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Wernet, Mark P.

1998-01-01

Particle Imaging Velocimetry (PIV) is a powerful measurement technique which can be used as an alternative or complementary approach to Laser Doppler Velocimetry (LDV) in a wide range of research applications. PIV data are measured simultaneously at multiple points in space, which enables the investigation of the non-stationary spatial structures typically encountered in turbomachinery. Obtaining ample optical access, sufficiently high seed particle concentrations and accurate synchronization of image acquisition relative to impeller position are the most formidable tasks in the successful implementation of PIV in turbomachinery. Preliminary results from the successful application of the standard 2-D digital PIV technique in the diffuser of a high speed centrifugal compressor are presented. Instantaneous flow. measurements were also obtained during compressor surge.

Noninvasive imaging analysis of biological tissue associated with laser thermal injury.

PubMed

Chang, Cheng-Jen; Yu, De-Yi; Hsiao, Yen-Chang; Ho, Kuang-Hua

2017-04-01

The purpose of our study is to use a noninvasive tomographic imaging technique with high spatial resolution to characterize and monitor biological tissue responses associated with laser thermal injury. Optical doppler tomography (ODT) combines laser doppler flowmetry (LDF) with optical coherence tomography (OCT) to obtain high resolution tomographic velocity and structural images of static and moving constituents in highly scattering biological tissues. A SurgiLase XJ150 carbon dioxide (CO 2 ) laser using a continuous mode of 3 watts (W) was used to create first, second or third degree burns on anesthetized Sprague-Dawley rats. Additional parameters for laser thermal injury were assessed as well. The rationale for using ODT in the evaluation of laser thermal injury offers a means of constructing a high resolution tomographic image of the structure and perfusion of laser damaged skin. In the velocity images, the blood flow is coded at 1300 μm/s and 0 velocity, 1000 μm/s and 0 velocity, 700 μm/s and 0 velocity adjacent to the first, second, and third degree injuries, respectively. ODT produces exceptional spatial resolution while having a non-invasive way of measurement, therefore, ODT is an accurate measuring method for high-resolution fluid flow velocity and structural images for biological tissue with laser thermal injury. Copyright © 2017 Chang Gung University. Published by Elsevier B.V. All rights reserved.

Molecular filter based planar Doppler velocimetry

NASA Astrophysics Data System (ADS)

Elliott, Gregory S.; Beutner, Thomas J.

1999-11-01

Molecular filter based diagnostics are continuing to gain popularity as a research tool for investigations in areas of aerodynamics, fluid mechanics, and combustion. This class of diagnostics has gone by many terms including Filtered Rayleigh Scattering, Doppler Global Velocimetry, and Planar Doppler Velocimetry. The majority of this article reviews recent advances in Planar Doppler Velocimetry in measuring up to three velocity components over a planar region in a flowfield. The history of the development of these techniques is given with a description of typical systems, components, and levels of uncertainty in the measurement. Current trends indicate that uncertainties on the order of 1 m/s are possible with these techniques. A comprehensive review is also given on the application of Planar Doppler Velocimetry to laboratory flows, supersonic flows, and large scale subsonic wind tunnels. The article concludes with a description of future trends, which may simplify the technique, followed by a description of techniques which allow multi-property measurements (i.e. velocity, density, temperature, and pressure) simultaneously.

Echocardiographic Techniques of Deformation Imaging in the Evaluation of Maternal Cardiovascular System in Patients with Complicated Pregnancies.

PubMed

Visentin, Silvia; Palermo, Chiara; Camerin, Martina; Daliento, Luciano; Muraru, Denisa; Cosmi, Erich; Badano, Luigi P

2017-01-01

Cardiovascular diseases (CVD) represent the leading cause of maternal mortality and morbidity. Knowledge of CVD in women is constantly evolving and data are emerging that female-specific risk factors as complications of pregnancy are conditions associated with an increased risk for the long-term development of CVD. Echocardiography is a safe and effective imaging technique indicated in symptomatic or asymptomatic pregnant women with congenital heart diseases who require close monitoring of cardiac function. Deformation imaging is an echocardiographic technique used to assess myocardial function by measuring the actual deformation of the myocardium through the cardiac cycle. Speckle-tracking echocardiography (STE) is a two-dimensional (2D) technique which has been found to be more accurate than tissue Doppler to assess both left ventricular (LV) and right ventricular (RV) myocardial function. The use of 2D STE however might present some technical issues due to the tomographic nature of the technique and the motion in the three-dimensional space of the myocardial speckles. This has promoted the use of 3D STE to track the motion of the speckles in the 3D space. This review will focus on the clinical value of the new echocardiographic techniques of deformation imaging used to assess the maternal cardiovascular system in complicated pregnancies.

Doppler Fourier Domain Optical Coherence Tomography for Label-Free Tissue Angiography

NASA Astrophysics Data System (ADS)

Leitgeb, Rainer A.; Szkulmowski, Maciej; Blatter, Cedric; Wojtkowski, Maciej

Information about tissue perfusion and the vascular structure is certainly most important for assessment of tissue state or personal health and the diagnosis of any pathological conditions. It is therefore of key medical interest to have tools available for both quantitative blood flow assessment as well as qualitative vascular imaging. The strength of optical techniques is the unprecedented level of detail even for small capillary structures or microaneurysms and the possibility to combine different techniques for additional tissue spectroscopy giving insight into tissue metabolism. There is an immediate diagnostic and pharmacological demand for high-resolution, label-free, tissue angiography and flow assessment that in addition allow for precise depth gating of flow information. The most promising candidate is Doppler optical coherence tomography (DOCT) being noncontact, label free, and without employing hazardous radiation. DOCT provides fully quantitative volumetric information about blood flow together with the vascular and structural anatomy. Besides flow quantification, analysis of OCT signal fluctuations allows to contrast moving scatterers in tissue such as red blood cells from static tissue. This allows for non-invasive optical angiography and yields high resolution even for smallest capillaries. Because of the huge potential of DOCT and lable-free optical angiography for diagnosis, the last years saw a rapid increase of publications in this field with many different approaches. The present chapter gives an overview over existing Doppler OCT approaches and angiography techniques. It furthermore discusses limitations and noise issues, and gives examples for angiography in the eye and the skin.

Twelve-hour reproducibility of retinal and optic nerve blood flow parameters in healthy individuals.

PubMed

Luksch, Alexandra; Lasta, Michael; Polak, Kaija; Fuchsjäger-Mayrl, Gabriele; Polska, Elzbieta; Garhöfer, Gerhard; Schmetterer, Leopold

2009-11-01

The aim of the present study was to investigate the reproducibility and potential diurnal variation of optic nerve head and retinal blood flow parameters in healthy individuals over a period of 12 hr. We measured optic nerve head and retinal blood flow parameters in 16 healthy male non-smoking individuals at five time-points during the day (08:00, 11:00, 14:00, 17:00 and 20:00 hr). Outcome parameters were perimacular white blood cell flux (as assessed with the blue field entoptic technique), blood velocities in retinal veins (as assessed with bi-directional laser Doppler velocimetry), retinal arterial and venous diameters (as assessed with the retinal vessel analyser), optic nerve head blood flow, volume and velocity (as assessed with single point and scanning laser Doppler flowmetry) and blood velocities in the central retinal artery (as assessed with colour Doppler imaging). The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. No diurnal variation in optic nerve head or retinal blood flow was observed with any of the techniques employed. Coefficients of variation were between 1.6% and 18.5% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 3.7% to 78.2%. Our data indicate that in healthy individuals the selected techniques provide adequate reproducibility to be used in clinical studies. However, in patients with eye diseases and reduced vision the reproducibility may be considerably worse.

The Place of Nailfold Capillaroscopy Among Instrumental Methods for Assessment of Some Peripheral Ischaemic Syndromes in Rheumatology.

PubMed

Lambova, Sevdalina N

2016-01-01

Micro- and macrovascular pathology is a frequent finding in a number of common rheumatic diseases. Secondary Raynaud's phenomenon (RP) is among the most common symptoms in systemic sclerosis and several other systemic autoimmune diseases including a broad differential diagnosis. It should be also differential from other peripheral vascular syndromes such as embolism, thrombosis, etc., some of which lead to clinical manifestation of the blue toe syndrome. The current review discusses the instrumental methods for vascular assessments. Nailfold capillaroscopy is the only method among the imaging techniques that can be used for morphological assessment of the nutritive capillaries in the nailfold area. Laser-Doppler flowmetry and laser-Doppler imaging are methods for functional assessment of microcirculation, while thermography and plethysmography reflect both blood flow in peripheral arteries and microcirculation. Doppler ultrasound and angiography visualize peripheral arteries. The choice of the appropriate instrumental method is guided by the clinical presentation. The main role of capillaroscopy is to provide differential diagnosis between primary and secondary RP. In rheumatology, capillaroscopic changes in systemic sclerosis have been recently defined as diagnostic. The appearance of abnormal capillaroscopic pattern inherits high positive predictive value for the development of a connective tissue disease that is higher than the predictive value of antinuclear antibodies. In cases of abrupt onset of peripheral ischaemia, clinical signs of critical ischaemia, unilateral or lower limb involvement, Doppler ultrasound and angiography are indicated. The most common causes for such clinical picture that may be referred to rheumatologic consultation are the antiphospholipid syndrome, mimickers of vasculitides such as atherosclerosis with cholesterol emboli, and neoplasms.

Tissue Doppler imaging and echo-Doppler findings associated with a mitral valve stenosis with an immobile posterior valve leaflet in a bull terrier.

PubMed

Tidholm, A; Nicolle, A P; Carlos, C; Gouni, V; Caruso, J L; Pouchelon, J L; Chetboul, V

2004-04-01

A mitral valve stenosis was diagnosed in a 2-year-old female Bull Terrier by use of two-dimensional (2-D) and M-mode echocardiography, colour-flow imaging and spectral Doppler examinations. Tissue Doppler Imaging was also performed to assess the segmental radial myocardial motion. The mitral valve stenosis was characterized by a decreased mitral orifice area/left ventricle area ratio (0.14), an increased early diastolic flow velocity (E wave = 1.9 m/s), a prolonged pressure half-time (106 ms) and a decreased E-F slope (4.5 cm/s) on pulsed-wave Doppler examination. This mitral stenosis was associated with an immobile posterior leaflet, as seen on 2-D and M-mode echocardiography. Immobility of the posterior mitral leaflet is considered to be a rare finding in humans and, to our knowledge, has not been precisely documented in dogs with mitral valve stenosis.

Doppler Feature Based Classification of Wind Profiler Data

NASA Astrophysics Data System (ADS)

Sinha, Swati; Chandrasekhar Sarma, T. V.; Lourde. R, Mary

2017-01-01

Wind Profilers (WP) are coherent pulsed Doppler radars in UHF and VHF bands. They are used for vertical profiling of wind velocity and direction. This information is very useful for weather modeling, study of climatic patterns and weather prediction. Observations at different height and different wind velocities are possible by changing the operating parameters of WP. A set of Doppler power spectra is the standard form of WP data. Wind velocity, direction and wind velocity turbulence at different heights can be derived from it. Modern wind profilers operate for long duration and generate approximately 4 megabytes of data per hour. The radar data stream contains Doppler power spectra from different radar configurations with echoes from different atmospheric targets. In order to facilitate systematic study, this data needs to be segregated according the type of target. A reliable automated target classification technique is required to do this job. Classical techniques of radar target identification use pattern matching and minimization of mean squared error, Euclidean distance etc. These techniques are not effective for the classification of WP echoes, as these targets do not have well-defined signature in Doppler power spectra. This paper presents an effective target classification technique based on range-Doppler features.

Assessing the usefulness of B-mode and colour Doppler sonography, and measurements of circulating progesterone concentrations for determining ovarian responses in superovulated ewes.

PubMed

Oliveira, Mef; Ribeiro, I F; Rodriguez, Mgk; Maciel, G S; Fonseca, J F; Brandão, F Z; Bartlewski, P M

2018-06-01

The main goal of this study was to assess the usefulness of two imaging modalities, namely the B-mode and colour Doppler sonography, and serum progesterone (P 4 ) concentrations for determining the ovarian response in superovulated ewes. Twenty-four sexually mature Santa Inês ewes underwent the superovulatory treatment consisting of eight injections of porcine FSH (total dose of 200 or 133 or 100 mg; n = 8 ewes/total dose) given at 12-hr intervals and initiated 48 hr before CIDR ® (Pfizer Inc., Auckland, New Zealand) removal. Six days after natural mating, the ovaries of all donor ewes were visualized and examined with transrectal ultrasonography and then with videolaparoscopy to identify and enumerate corpora lutea (CL) and luteinized unovulated follicles (LUFs). Jugular blood samples were collected just prior to ovarian examinations. The total number of CL (r = .78 and 0.83, p < .0001) and LUFs (r = .74 and 0.90, p < .0001) enumerated using the B-mode and colour Doppler ultrasonographic technique, respectively, were correlated with that ascertained by videolaparoscopy. Circulating concentrations of P 4 were related directly to the number of healthy CL (r = .73, p = .0002) and inversely to the number of prematurely regressing CL (r = -.46, p = .03), but the accuracy of predicting the number of short-lived CL with serum P 4 concentrations was very poor. The present results indicate that ultrasonographic imaging and serum P 4 measurements on the day of embryo recovery are useful indicators of total/normal CL numbers and both ultrasonographic techniques can be used to quantify LUFs in superovulated ewes. © 2018 Blackwell Verlag GmbH.

Real-time, high-resolution ultrasonography of the vocal folds—a prospective pilot study in patients before and after thyroidectomy

PubMed Central

Adamczewski, Zbigniew; Brzeziński, Jan; Lewiński, Andrzej

2010-01-01

Purpose The aim of the study was to evaluate the functionality of vocal folds (VF) by real-time, high-resolution ultrasonography (US) and to correlate the imaged features to results of laryngological examination (LE). Methods The study group comprised 50 patients (41 females and nine males), qualified to thyroidectomy. All the patients had LE and US examination before and 2 days, 2 months, and 3 months after the surgery. We used high-resolution US imaging to identify VFs and, subsequently, a pulsed Doppler and Doppler gate to quantify the tissue displacement velocity in the vibrating VF section. Results LE revealed unilateral VF paralysis in two patients. VF dysfunction was diagnosed in other four subjects. In simultaneously performed US examination, changes in VF displacement velocity (VFDV) were observed in ten patients. In two subjects, VFDV was below 30 cm/s— patients with VF paralysis, diagnosed in LE. In a further eight cases, we observed VFDV decrease by 50%, comparing to preoperative values. Both US-imaging and LE, performed after the 3-month follow-up, confirmed the transitional character of the above-mentioned pathologies. Conclusions US imaging of the VFs correlated with LE results, while being a minimally invasive, easily reproducible, and inexpensive method of examining VF functionality. Thanks to many recording options, it may soon become a perfect tool for an early identification of postoperative VF dysfunction with its later monitoring. To our knowledge, it is the first application of US and Doppler gate modes for VFDF quantification; however, an analysis on a larger group of patients is necessary to standardize the technique. PMID:20640934

Demonstration of PIV in a Transonic Compressor

NASA Technical Reports Server (NTRS)

Wernet, Mark P.

1997-01-01

Particle Imaging Velocimetry (PIV) is a powerful measurement technique which can be used as an alternative or complementary approach to Laser Doppler Velocimetry (LDV) in a wide range of research applications. PIV data are measured simultaneously at multiple points in space, which enables the investigation of the non-stationary spatial structures typically encountered in turbomachinery. Many of the same issues encountered in the application of LDV techniques to rotating machinery apply in the application of PIV. Preliminary results from the successful application of the standard 2-D PIV technique to a transonic axial compressor are presented. The lessons learned from the application of the 2-D PIV technique will serve as the basis for applying 3-component PIV techniques to turbomachinery.

Automatic extraction of disease-specific features from Doppler images

NASA Astrophysics Data System (ADS)

Negahdar, Mohammadreza; Moradi, Mehdi; Parajuli, Nripesh; Syeda-Mahmood, Tanveer

2017-03-01

Flow Doppler imaging is widely used by clinicians to detect diseases of the valves. In particular, continuous wave (CW) Doppler mode scan is routinely done during echocardiography and shows Doppler signal traces over multiple heart cycles. Traditionally, echocardiographers have manually traced such velocity envelopes to extract measurements such as decay time and pressure gradient which are then matched to normal and abnormal values based on clinical guidelines. In this paper, we present a fully automatic approach to deriving these measurements for aortic stenosis retrospectively from echocardiography videos. Comparison of our method with measurements made by echocardiographers shows large agreement as well as identification of new cases missed by echocardiographers.

Tissue Doppler Imaging in the evaluation of abdominal aortic pulsatility: a useful tool for the neonatologist.

PubMed

Valerio, Enrico; Grison, Alessandra; Capretta, Anna; Golin, Rosanna; Ferrarese, Paola; Bellettato, Massimo

2017-03-01

Sonographic cardiac evaluation of newborns with suspected aortic coarctation (AoC) should tend to demonstrate a good phasic and pulsatile flow and the absence of pressure gradient along a normally conformed aortic arch from the modified left parasternal and suprasternal echocardiographic views; these findings, however, may not necessarily rule out a more distal coarctation in the descending aorta. For this reason, the sonographic exam of newborns with suspected AoC should always include a Doppler evaluation of abdominal aortic blood flow from the subcostal view. Occasionally, however, a clearly pulsatile Doppler flow trace in abdominal aorta may be difficult to obtain due to the bad insonation angle existing between the probe and the vessel. In such suboptimal ultrasonic alignment situation, the use of Tissue Doppler Imaging instead of classic Doppler flow imaging may reveal a preserved aortic pulsatility by sampling the aortic wall motion induced by normal flow. We propose to take advantage of the TDI pattern as a surrogate of a normal pulsatile Doppler flow trace in abdominal aorta when the latter is difficult to obtain due to malalignment with the insonated vessel.

Wireless ultrasonic wavefield imaging via laser for hidden damage detection inside a steel box girder bridge

NASA Astrophysics Data System (ADS)

An, Yun-Kyu; Song, Homin; Sohn, Hoon

2014-09-01

This paper presents a wireless ultrasonic wavefield imaging (WUWI) technique for detecting hidden damage inside a steel box girder bridge. The proposed technique allows (1) complete wireless excitation of piezoelectric transducers and noncontact sensing of the corresponding responses using laser beams, (2) autonomous damage visualization without comparing against baseline data previously accumulated from the pristine condition of a target structure and (3) robust damage diagnosis even for real structures with complex structural geometries. First, a new WUWI hardware system was developed by integrating optoelectronic-based signal transmitting and receiving devices and a scanning laser Doppler vibrometer. Next, a damage visualization algorithm, self-referencing f-k filter (SRF), was introduced to isolate and visualize only crack-induced ultrasonic modes from measured ultrasonic wavefield images. Finally, the performance of the proposed technique was validated through hidden crack visualization at a decommissioned Ramp-G Bridge in South Korea. The experimental results reveal that the proposed technique instantaneously detects and successfully visualizes hidden cracks even in the complex structure of a real bridge.

Doppler imaging of the young late-type star LO Pegasi (BD+22°4409) in 2003 September

NASA Astrophysics Data System (ADS)

Piluso, N.; Lanza, A. F.; Pagano, I.; Lanzafame, A. C.; Donati, J.-F.

2008-06-01

A Doppler image of the zero-age main-sequence (ZAMS) late-type rapidly rotating star LO Pegasi, based on spectra acquired between 2003 September 12 and 15 is presented. The least-squares deconvolution technique is applied to enhance the signal-to-noise ratio of the mean rotational broadened line profiles extracted from the observed spectra. In the present application, an unbroadened spectrum is used as a reference, instead of a simple line list, to improve the deconvolution technique applied to extract the mean profiles. The reconstructed image is similar to those previously obtained from observations taken in 1993 and 1998, and shows that LO Peg photospheric activity is dominated by high-latitude spots with a non-uniform polar cap. The latter seems to be a persistent feature as it has been observed since 1993 with little modifications. Small spots, observed between ~10° and ~60° of latitude, appears to be different with respect to those present in the 1993 and 1998 maps. Based on observations made with the Italian Telescopio Nazionale Galileo operated on the island of La Palma by the Centro Galileo Galilei of INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque del los Muchachos of the Instituto de Astrofísica de Canarias. E-mail: nicolo.piluso@oact.inaf.it (NP); nuccio.lanza@oact.inaf.it (AFL); isabella.pagano@oact.inaf.it (IP); alessandro.lanzafame@oact.inaf.it (ACL); donati@ast.obs-mip.fr (J-FD)

A real-time device for converting Doppler ultrasound audio signals into fluid flow velocity

PubMed Central

Hogeman, Cynthia S.; Koch, Dennis W.; Krishnan, Anandi; Momen, Afsana; Leuenberger, Urs A.

2010-01-01

A Doppler signal converter has been developed to facilitate cardiovascular and exercise physiology research. This device directly converts audio signals from a clinical Doppler ultrasound imaging system into a real-time analog signal that accurately represents blood flow velocity and is easily recorded by any standard data acquisition system. This real-time flow velocity signal, when simultaneously recorded with other physiological signals of interest, permits the observation of transient flow response to experimental interventions in a manner not possible when using standard Doppler imaging devices. This converted flow velocity signal also permits a more robust and less subjective analysis of data in a fraction of the time required by previous analytic methods. This signal converter provides this capability inexpensively and requires no modification of either the imaging or data acquisition system. PMID:20173048

Design and Ground Calibration of the Helioseismic and Magnetic Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)

NASA Technical Reports Server (NTRS)

Schou, J.; Scherrer, P. H.; Bush, R. I.; Wachter, R.; Couvidat, S.; Rabello-Soares, M. C.; Bogart, R. S.; Hoeksema, J. T.; Liu, Y.; Duvall, T. L., Jr.;

Laser Doppler imaging of cutaneous blood flow through transparent face masks: a necessary preamble to computer-controlled rapid prototyping fabrication with submillimeter precision.

PubMed

Allely, Rebekah R; Van-Buendia, Lan B; Jeng, James C; White, Patricia; Wu, Jingshu; Niszczak, Jonathan; Jordan, Marion H

2008-01-01

A paradigm shift in management of postburn facial scarring is lurking "just beneath the waves" with the widespread availability of two recent technologies: precise three-dimensional scanning/digitizing of complex surfaces and computer-controlled rapid prototyping three-dimensional "printers". Laser Doppler imaging may be the sensible method to track the scar hyperemia that should form the basis of assessing progress and directing incremental changes in the digitized topographical face mask "prescription". The purpose of this study was to establish feasibility of detecting perfusion through transparent face masks using the Laser Doppler Imaging scanner. Laser Doppler images of perfusion were obtained at multiple facial regions on five uninjured staff members. Images were obtained without a mask, followed by images with a loose fitting mask with and without a silicone liner, and then with a tight fitting mask with and without a silicone liner. Right and left oblique images, in addition to the frontal images, were used to overcome unobtainable measurements at the extremes of face mask curvature. General linear model, mixed model, and t tests were used for data analysis. Three hundred seventy-five measurements were used for analysis, with a mean perfusion unit of 299 and pixel validity of 97%. The effect of face mask pressure with and without the silicone liner was readily quantified with significant changes in mean cutaneous blood flow (P < .5). High valid pixel rate laser Doppler imager flow data can be obtained through transparent face masks. Perfusion decreases with the application of pressure and with silicone. Every participant measured differently in perfusion units; however, consistent perfusion patterns in the face were observed.

Method and apparatus for optical Doppler tomographic imaging of fluid flow velocity in highly scattering media

DOEpatents

Nelson, John Stuart; Milner, Thomas Edward; Chen, Zhongping

1999-01-01

Optical Doppler tomography permits imaging of fluid flow velocity in highly scattering media. The tomography system combines Doppler velocimetry with high spatial resolution of partially coherent optical interferometry to measure fluid flow velocity at discrete spatial locations. Noninvasive in vivo imaging of blood flow dynamics and tissue structures with high spatial resolutions of the order of 2 to 10 microns is achieved in biological systems. The backscattered interference signals derived from the interferometer may be analyzed either through power spectrum determination to obtain the position and velocity of each particle in the fluid flow sample at each pixel, or the interference spectral density may be analyzed at each frequency in the spectrum to obtain the positions and velocities of the particles in a cross-section to which the interference spectral density corresponds. The realized resolutions of optical Doppler tomography allows noninvasive in vivo imaging of both blood microcirculation and tissue structure surrounding the vessel which has significance for biomedical research and clinical applications.

High-Frame-Rate Doppler Ultrasound Using a Repeated Transmit Sequence

PubMed Central

Podkowa, Anthony S.; Oelze, Michael L.; Ketterling, Jeffrey A.

2018-01-01

The maximum detectable velocity of high-frame-rate color flow Doppler ultrasound is limited by the imaging frame rate when using coherent compounding techniques. Traditionally, high quality ultrasonic images are produced at a high frame rate via coherent compounding of steered plane wave reconstructions. However, this compounding operation results in an effective downsampling of the slow-time signal, thereby artificially reducing the frame rate. To alleviate this effect, a new transmit sequence is introduced where each transmit angle is repeated in succession. This transmit sequence allows for direct comparison between low resolution, pre-compounded frames at a short time interval in ways that are resistent to sidelobe motion. Use of this transmit sequence increases the maximum detectable velocity by a scale factor of the transmit sequence length. The performance of this new transmit sequence was evaluated using a rotating cylindrical phantom and compared with traditional methods using a 15-MHz linear array transducer. Axial velocity estimates were recorded for a range of ±300 mm/s and compared to the known ground truth. Using these new techniques, the root mean square error was reduced from over 400 mm/s to below 50 mm/s in the high-velocity regime compared to traditional techniques. The standard deviation of the velocity estimate in the same velocity range was reduced from 250 mm/s to 30 mm/s. This result demonstrates the viability of the repeated transmit sequence methods in detecting and quantifying high-velocity flow. PMID:29910966

Laser Doppler flowmetry for measurement of laminar capillary blood flow in the horse

NASA Astrophysics Data System (ADS)

Adair, Henry S., III

1998-07-01

Current methods for in vivo evaluation of digital hemodynamics in the horse include angiography, scintigraphy, Doppler ultrasound, electromagnetic flow and isolated extracorporeal pump perfused digit preparations. These techniques are either non-quantifiable, do not allow for continuous measurement, require destruction of the horse orare invasive, inducing non- physiologic variables. In vitro techniques have also been reported for the evaluation of the effects of vasoactive agents on the digital vessels. The in vitro techniques are non-physiologic and have evaluated the vasculature proximal to the coronary band. Lastly, many of these techniques require general anesthesia or euthanasia of the animal. Laser Doppler flowmetry is a non-invasive, continuous measure of capillary blood flow. Laser Doppler flowmetry has been used to measure capillary blood flow in many tissues. The principle of this method is to measure the Doppler shift, that is, the frequency change that light undergoes when reflected by moving objects, such as red blood cells. Laser Doppler flowmetry records a continuous measurement of the red cell motion in the outer layer of the tissue under study, with little or no influence on physiologic blood flow. This output value constitutes the flux of red cells and is reported as capillary perfusion units. No direct information concerning oxygen, nutrient or waste metabolite exchange in the surrounding tissue is obtained. The relationship between the flowmeter output signal and the flux of red blood cells is linear. The principles of laser Doppler flowmetry will be discussed and the technique for laminar capillary blood flow measurements will be presented.

Tissue Pulsatility Imaging of Cerebral Vasoreactivity during Hyperventilation

PubMed Central

Kucewicz, John C.; Dunmire, Barbrina; Giardino, Nicholas D.; Leotta, Daniel F.; Paun, Marla; Dager, Stephen R.; Beach, Kirk W.

2008-01-01

Tissue Pulsatility Imaging (TPI) is an ultrasonic technique that is being developed at the University of Washington to measure tissue displacement or strain due to blood flow over the cardiac and respiratory cycles. This technique is based in principle on plethysmography, an older non-ultrasound technology for measuring expansion of a whole limb or body part due to perfusion. TPI adapts tissue Doppler signal processing methods to measure the “plethysmographic” signal from hundreds or thousands of sample volumes in an ultrasound image plane. This paper presents a feasibility study to determine if TPI can be used to assess cerebral vasoreactivity. Ultrasound data were collected transcranially through the temporal acoustic window from four subjects before, during, and after voluntary hyperventilation. In each subject, decreases in tissue pulsatility during hyperventilation were observed that were statistically correlated with the subject’s end-tidal CO2 measurements. PMID:18336991

Spaceborne Imaging Radar-C instrument

NASA Technical Reports Server (NTRS)

Huneycutt, Bryan L.

1993-01-01

The Spaceborne Imaging Radar-C is the next radar in the series of spaceborne radar experiments, which began with Seasat and continued with SIR-A and SIR-B. The SIR-C instrument has been designed to obtain simultaneous multifrequency and simultaneous multipolarization radar images from a low earth orbit. It is a multiparameter imaging radar that will be flown during at least two different seasons. The instrument operates in the squint alignment mode, the extended aperture mode, the scansar mode, and the interferometry mode. The instrument uses engineering techniques such as beam nulling for echo tracking, pulse repetition frequency hopping for Doppler centroid tracking, generating the frequency step chirp for radar parameter flexibility, block floating-point quantizing for data rate compression, and elevation beamwidth broadening for increasing the swath illumination.

Computer-generated imagery for 4-D meteorological data

NASA Technical Reports Server (NTRS)

Hibbard, William L.

1986-01-01

The University of Wisconsin-Madison Space Science and Engineering Center is developing animated stereo display terminals for use with McIDAS (Man-computer Interactive Data Access System). This paper describes image-generation techniques which have been developed to take maximum advantage of these terminals, integrating large quantities of four-dimensional meteorological data from balloon and satellite soundings, satellite images, Doppler and volumetric radar, and conventional surface observations. The images have been designed to use perspective, shading, hidden-surface removal, and transparency to augment the animation and stereo-display geometry. They create an illusion of a moving three-dimensional model of the atmosphere. This paper describes the design of these images and a number of rules of thumb for generating four-dimensional meteorological displays.

Instantaneous flow measurements in a supersonic wind tunnel using spectrally resolved Rayleigh scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.; Buggele, Alvin E.; Reeder, Mark F.

1995-01-01

Results of a feasibility study to apply laser Rayleigh scattering to non-intrusively measure flow properties in a small supersonic wind tunnel are presented. The technique uses an injection seeded, frequency doubled Nd:YAG laser tuned to an absorption band of iodine. The molecular Rayleigh scattered light is filtered with an iodine cell to block light at the laser frequency. The Doppler-shifted Rayleigh scattered light that passes through the iodine cell is analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode. An intensified CCD camera is used to record the images. The images are analyzed at several subregions, where the flow velocity is determined. Each image is obtained with a single laser pulse, giving instantaneous measurements.

Finnish Meteorological Institute Doppler Lidar

DOE Data Explorer

Ewan OConnor

2015-03-27

This doppler lidar system provides co-polar and cross polar attenuated backscatter coefficients,signal strength, and doppler velocities in the cloud and in the boundary level, including uncertainties for all parameters. Using the doppler beam swinging DBS technique, and Vertical Azimuthal Display (VAD) this system also provides vertical profiles of horizontal winds.

Imaging doppler lidar for wind turbine wake profiling

DOEpatents

Bossert, David J.

2015-11-19

An imaging Doppler lidar (IDL) enables the measurement of the velocity distribution of a large volume, in parallel, and at high spatial resolution in the wake of a wind turbine. Because the IDL is non-scanning, it can be orders of magnitude faster than conventional coherent lidar approaches. Scattering can be obtained from naturally occurring aerosol particles. Furthermore, the wind velocity can be measured directly from Doppler shifts of the laser light, so the measurement can be accomplished at large standoff and at wide fields-of-view.

High-frequency dual mode pulsed wave Doppler imaging for monitoring the functional regeneration of adult zebrafish hearts

PubMed Central

Kang, Bong Jin; Park, Jinhyoung; Kim, Jieun; Kim, Hyung Ham; Lee, Changyang; Hwang, Jae Youn; Lien, Ching-Ling; Shung, K. Kirk

2015-01-01

Adult zebrafish is a well-known small animal model for studying heart regeneration. Although the regeneration of scars made by resecting the ventricular apex has been visualized with histological methods, there is no adequate imaging tool for tracking the functional recovery of the damaged heart. For this reason, high-frequency Doppler echocardiography using dual mode pulsed wave Doppler, which provides both tissue Doppler (TD) and Doppler flow in a same cardiac cycle, is developed with a 30 MHz high-frequency array ultrasound imaging system. Phantom studies show that the Doppler flow mode of the dual mode is capable of measuring the flow velocity from 0.1 to 15 cm s−1 with high accuracy (p-value = 0.974 > 0.05). In the in vivo study of zebrafish, both TD and Doppler flow signals were simultaneously obtained from the zebrafish heart for the first time, and the synchronized valve motions with the blood flow signals were identified. In the longitudinal study on the zebrafish heart regeneration, the parameters for diagnosing the diastolic dysfunction, for example, E/Em < 10, E/A < 0.14 for wild-type zebrafish, were measured, and the type of diastolic dysfunction caused by the amputation was found to be similar to the restrictive filling. The diastolic function was fully recovered within four weeks post-amputation. PMID:25505135

Comparison of the Diagnostic Performance of Power Doppler Ultrasound and a New Microvascular Doppler Ultrasound Technique (AngioPLUS) for Differentiating Benign and Malignant Breast Masses.

PubMed

Jung, Hae Kyoung; Park, Ah Young; Ko, Kyung Hee; Koh, Jieun

2018-03-12

This study was performed to compare the diagnostic performance of power Doppler ultrasound (US) and a new microvascular Doppler US technique (AngioPLUS; SuperSonic Imagine, Aix-en-Provence, France) for differentiating benign and malignant breast masses. Power Doppler US and AngioPLUS findings were available in 124 breast masses with confirmed pathologic results (benign, 80 [64.5%]; malignant, 44 [35.5%]). The diagnostic performance of each tool was calculated to distinguish benign from malignant masses using a receiver operating characteristic curve analysis and compared. The area under the curve showed that AngioPLUS was superior to power Doppler US in differentiating benign from malignant breast masses, but the difference was not statistically significant. © 2018 by the American Institute of Ultrasound in Medicine.

Implementation of laser speckle contrast analysis as connection kit for mobile phone for assessment of skin blood flow

NASA Astrophysics Data System (ADS)

Jakovels, Dainis; Saknite, Inga; Spigulis, Janis

2014-05-01

Laser speckle contrast analysis (LASCA) offers a non-contact, full-field, and real-time mapping of capillary blood flow and can be considered as an alternative method to Laser Doppler perfusion imaging. LASCA technique has been implemented in several commercial instruments. However, these systems are still too expensive and bulky to be widely available. Several optical techniques have found new implementations as connection kits for mobile phones thus offering low cost screening devices. In this work we demonstrate simple implementation of LASCA imaging technique as connection kit for mobile phone for primary low-cost assessment of skin blood flow. Stabilized 650 nm and 532 nm laser diode modules were used for LASCA illumination. Dual wavelength illumination could provide additional information about skin hemoglobin and oxygenation level. The proposed approach was tested for arterial occlusion and heat test. Besides, blood flow maps of injured and provoked skin were demonstrated.

The development of a combined b-mode, ARFI, and spectral Doppler ultrasound imaging system for investigating cardiovascular stiffness and hemodynamics

NASA Astrophysics Data System (ADS)

Doherty, Joshua R.; Dumont, Douglas M.; Trahey, Gregg E.

2011-03-01

The progression of atherosclerotic disease, caused by the formation of plaques within arteries, is a complex process believed to be a function of the localized mechanical properties and hemodynamic loading associated with the arterial wall. It is hypothesized that measurements of vascular stiffness and wall-shear rate (WSR) may provide important information regarding vascular remodeling, endothelial function, and the growth of soft-lipid filled plaques that could help a clinician better diagnose a patient's risk of clinical events such as stroke. To that end, the approach taken in this work was to combine conventional B-mode, Acoustic Radiation Force Impulse (ARFI), Shear Wave Elasticity Imaging (SWEI), and spectral Doppler techniques into a single imaging system capable of simultaneously measuring the tissue displacements and WSR throughout the cardiac cycle and over several heartbeats. Implemented on a conventional scanner, the carotid arteries of human subjects were scanned to demonstrate the initial in vivo feasibility of the method. Two non-invasive ultrasound based imaging methods, SAD-SWEI and SAD-Gated Imaging, were developed that measure ARF-induced on-axis tissue displacements, off-axis transverse wave velocities, and WSR throughout the cardiac cycle. Human carotid artery scans were performed in vivo on 5 healthy subjects. Statistical differences were observed in both on-axis proximal wall displacements and transverse wave velocities during diastole compared to systole.

The Surface of V410 Tauri

NASA Astrophysics Data System (ADS)

Rice, J. B.; Strassmeier, K. G.; Kopf, M.

2011-02-01

We present Doppler images of the weak-lined T Tauri star V410 Tau obtained with two different Doppler-imaging codes. The images are consistent and show a cool extended spot, symmetric about the pole, at a temperature approximately 750 K below the average photospheric value. Smaller cool spots are found fairly uniformly distributed at latitudes below the polar cap with temperatures about 450 K below the average photospheric temperature. Resolution on the stellar surface is limited to about 7° of arc, so structure within these spots is not visible. Also at lower latitudes are hotter features with temperatures up to 1000 K above the photosphere. A trial Doppler image using a TiO molecular feature reproduced the cool polar cap at a temperature about 100 K below the value from the atomic line images. The equatorial features, however, were not properly reproduced since Doppler imaging relies on information in the wings of lines for reconstructing equatorial features, and for V410 Tau these molecular band lines overlap. In 1993, V410 Tau had a large photometric amplitude resulting from the concentration of cool spots on the hemisphere of the star visible at phase 0°, a phenomenon known as preferred longitude. In contrast, the small photometric amplitude observed currently is due to a strong symmetric polar spot and the uniform distribution in longitude of equatorial cool and warm spots. This redistribution of surface features may be the beginning of a slow "flip-flop" for V410 Tau where spot locations alternate between preferred longitudes. Flare events linked to two of the hotter spots in the Doppler image were observed.

Titan's dunes revealed by the delay/Doppler processing of the Cassini radar altimeter data

NASA Astrophysics Data System (ADS)

Poggiali, V.; Mastrogiuseppe, M.; Hayes, A.; Seu, R.; Bonnefoy, L.; Mullen, J.; Lunine, J. I.

2017-12-01

Doppler Beam Sharpened techniques can be exploited for the Cassini radar altimeter data to resolve features far smaller than the footprint in the along-track direction [1]. We applied the delay/Doppler algorithm [2] which performs an incoherent sum of the echoes relative to specific along-track Doppler-limited areas. The algorithm allows to preserve the radiometric resolution and to improve the geometric one by a factor of ten with respect to the conventional processing. The generation of topographic profiles with km-scale along-track spacing is essential to our understanding of the processes that shape Titan's surfaces and lead to the formation of morphologic units like dunes, hummocks, fluvial valleys, and lacustrine basins. Dunes are one of the most extensive units on Titan, covering vast portions of Titan's equatorial latitudes and almost all longitudes. In SAR images, they have a linear bright-dark pattern extending hundreds of kilometers. Delay/Doppler processing of the altimetry data allows us to resolve individual longitudinal dunes both spatially and vertically for the first time. Comparing radar altimetry backscatter to the dune backscattering from SAR images, we can obtain new information about their geometric and dielectric characteristics. Current models using radarclinometry [3], SAR swath pairs [4], or unresolved altimetry [5] estimate dune heights of 40-150 m, but are unable to resolve the topography of individual dune crests. This will permit also a more accurate estimation of the sediment budget of the dunes, a necessary step towards understanding their formation and evolution. References: [1] Picardi, G. et al., IGARSS `98 Proc., vol. 5, pp. 2643-2645, 1998; [2] Raney, R.K., IEEE TGRS 36, n. 5, 1998; [3] Lorenz, R.D. et al., Science 312, 724-727, 2006; [4] Callegari, M. et al., IEEE vol. 8, n. 3, p. 1295-1306; [5] Mastrogiuseppe, M. et al., Icarus 230, p. 191-197, 2014.

[Basic laws of blood screw motion in human common carotid arteries].

PubMed

Kulikov, V P; Kirsanov, R I

2008-08-01

The basic laws of blood screw motion in common carotid arteries in people were determined by means of modern ultrasound techniques for the first time. 92 healthy adults, aged 18-30, were examined. The blood flow in the middle one-third of common carotid arteries was registered by means of Color Doppler Imaging and impulse Doppler with the help of ultrasound Medison 8000EX scanner by linear transducer of 5-9 MHz. The steady registration of blood screw motion in both common carotid arteries in Color Doppler Imaging regimen was observed in 54.3 % of cases. The direction of screw stream rotation in most cases (54%) was multi-directed: in the right common carotid artery it was right, in the left common carotid artery--left (48%), and in 6% of cases it was reverse. For 46% of cases blood rotation in both common carotid arteries was one-directed (26%--right, 20%--left). The velocity parameters of rotation component of blood motion were determined, maximum velocity being 19.68 +/- 5.84 cm/sec, minimum--4.57 +/- 2.89 cm/sec, average--7.48 +/- 2.49 cm/sec, angular--10.7 +/- 2.49 sec(-1). The rated velocity of blood cells motion in screw motion with regard of screw current lines to the vessel vertical axis makes up from 158.67 +/- 32.79 to 224.39 +/- 46.37 cm/sec.

Applications of Doppler-free saturation spectroscopy for edge physics studies (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, E. H., E-mail: martineh@ornl.gov; Caughman, J. B. O.; Isler, R. C.

Doppler-free saturation spectroscopy provides a very powerful method to obtain detailed information about the electronic structure of the atom through measurement of the spectral line profile. This is achieved through a significant decrease in the Doppler broadening and essentially an elimination of the instrument broadening inherent to passive spectroscopic techniques. In this paper we present the technique and associated physics of Doppler-free saturation spectroscopy in addition to how one selects the appropriate transition. Simulations of H{sub δ} spectra are presented to illustrate the increased sensitivity to both electric field and electron density measurements.

Applications of Doppler-free saturation spectroscopy for edge physics studies (invited).

PubMed

Martin, E H; Zafar, A; Caughman, J B O; Isler, R C; Bell, G L

2016-11-01

Doppler-free saturation spectroscopy provides a very powerful method to obtain detailed information about the electronic structure of the atom through measurement of the spectral line profile. This is achieved through a significant decrease in the Doppler broadening and essentially an elimination of the instrument broadening inherent to passive spectroscopic techniques. In this paper we present the technique and associated physics of Doppler-free saturation spectroscopy in addition to how one selects the appropriate transition. Simulations of H δ spectra are presented to illustrate the increased sensitivity to both electric field and electron density measurements.

Ambiguity Of Doppler Centroid In Synthetic-Aperture Radar

NASA Technical Reports Server (NTRS)

Chang, Chi-Yung; Curlander, John C.

1991-01-01

Paper discusses performances of two algorithms for resolution of ambiguity in estimated Doppler centroid frequency of echoes in synthetic-aperture radar. One based on range-cross-correlation technique, other based on multiple-pulse-repetition-frequency technique.

Cardiovascular dysfunction in obesity and new diagnostic imaging techniques: the role of noninvasive image methods.

PubMed

Barbosa, José Augusto A; Rodrigues, Alexandre B; Mota, Cleonice Carvalho C; Barbosa, Márcia M; Simões e Silva, Ana C

2011-01-01

Obesity is a major public health problem affecting adults and children in both developed and developing countries. This condition often leads to metabolic syndrome, which increases the risk of cardiovascular disease. A large number of studies have been carried out to understand the pathogenesis of cardiovascular dysfunction in obese patients. Endothelial dysfunction plays a key role in the progression of atherosclerosis and the development of coronary artery disease, hypertension and congestive heart failure. Noninvasive methods in the field of cardiovascular imaging, such as measuring intima-media thickness, flow-mediated dilatation, tissue Doppler, and strain, and strain rate, constitute new tools for the early detection of cardiac and vascular dysfunction. These techniques will certainly enable a better evaluation of initial cardiovascular injury and allow the correct, timely management of obese patients. The present review summarizes the main aspects of cardiovascular dysfunction in obesity and discusses the application of recent noninvasive imaging methods for the early detection of cardiovascular alterations.

Detection and three-dimensional visualization of lesion models using sonoelastography

NASA Astrophysics Data System (ADS)

Taylor, Lawrence S.; Gaborski, Thomas R.; Strang, John G.; Rubens, Deborah; Parker, Kevin J.

2002-04-01

Sonoelastography is a vibration Doppler technique for imaging the relative elasticity of tissues. Detectability of hard lesions of various sizes has previously been demonstrated in tissue phantoms by our group. Because real tissue differs from phantom material, the injection of formaldehyde in fresh liver tissue is being used as an in-vitro lesion model. Pieces of fresh calf liver were embedded in an agar gel then injected with a bolus of 37% formaldehyde to create a stiff lesion. Two and three-dimensional sonoelastography and b-mode images were acquired. The lesions were visible in each sonoelastography image as a region of reduced vibration. After imaging, lesions were dissected and measured for size and volume. One 0.4 cc bolus injection of formaldehyde created a lesion with a volume of 10.3 cc in the sonoelastography image compared to 9.3 cc using fluid displacement of the dissected lesion. A 0.33 cc injection of formaldehyde lesion created a volume of 5 cc in the sonoelastography image compared to 4.4 cc using fluid displacement. Sonoelastography imaging techniques for imaging hard lesions in phantoms can be successfully extended to imaging formaldehyde induced lesions in real tissue.

Power cavitation-guided blood-brain barrier opening with focused ultrasound and microbubbles

NASA Astrophysics Data System (ADS)

Burgess, M. T.; Apostolakis, I.; Konofagou, E. E.

2018-03-01

Image-guided monitoring of microbubble-based focused ultrasound (FUS) therapies relies on the accurate localization of FUS-stimulated microbubble activity (i.e. acoustic cavitation). Passive cavitation imaging with ultrasound arrays can achieve this, but with insufficient spatial resolution. In this study, we address this limitation and perform high-resolution monitoring of acoustic cavitation-mediated blood-brain barrier (BBB) opening with a new technique called power cavitation imaging. By synchronizing the FUS transmit and passive receive acquisition, high-resolution passive cavitation imaging was achieved by using delay and sum beamforming with absolute time delays. Since the axial image resolution is now dependent on the duration of the received acoustic cavitation emission, short pulses of FUS were used to limit its duration. Image sets were acquired at high-frame rates for calculation of power cavitation images analogous to power Doppler imaging. Power cavitation imaging displays the mean intensity of acoustic cavitation over time and was correlated with areas of acoustic cavitation-induced BBB opening. Power cavitation-guided BBB opening with FUS could constitute a standalone system that may not require MRI guidance during the procedure. The same technique can be used for other acoustic cavitation-based FUS therapies, for both safety and guidance.

Power cavitation-guided blood-brain barrier opening with focused ultrasound and microbubbles.

PubMed

Burgess, M T; Apostolakis, I; Konofagou, E E

2018-03-15

Image-guided monitoring of microbubble-based focused ultrasound (FUS) therapies relies on the accurate localization of FUS-stimulated microbubble activity (i.e. acoustic cavitation). Passive cavitation imaging with ultrasound arrays can achieve this, but with insufficient spatial resolution. In this study, we address this limitation and perform high-resolution monitoring of acoustic cavitation-mediated blood-brain barrier (BBB) opening with a new technique called power cavitation imaging. By synchronizing the FUS transmit and passive receive acquisition, high-resolution passive cavitation imaging was achieved by using delay and sum beamforming with absolute time delays. Since the axial image resolution is now dependent on the duration of the received acoustic cavitation emission, short pulses of FUS were used to limit its duration. Image sets were acquired at high-frame rates for calculation of power cavitation images analogous to power Doppler imaging. Power cavitation imaging displays the mean intensity of acoustic cavitation over time and was correlated with areas of acoustic cavitation-induced BBB opening. Power cavitation-guided BBB opening with FUS could constitute a standalone system that may not require MRI guidance during the procedure. The same technique can be used for other acoustic cavitation-based FUS therapies, for both safety and guidance.

Clinical, echocardiographic, and Doppler imaging characteristics of mitral valve stenosis in two dogs.

PubMed

Fox, P R; Miller, M W; Liu, S K

1992-11-15

Mitral stenosis was diagnosed noninvasively by echocardiography and Doppler imaging in 2 Bull Terriers. Two-dimensional echocardiography revealed severe atrial and moderate left ventricular dilatation; severely reduced mitral valve opening excursion; doming of the cranial mitral valve leaflet into the left ventricle during diastole; thickened, nodular cranial mitral valve leaflets; and reduced mitral valve orifice. M-mode echocardiographic findings additionally indicated greatly diminished mitral valve E to F slope and abnormal caudal mitral valve leaflet motion. Color flow Doppler imaging revealed bright bursts of color with aliasing originating from the stenotic mitral valve orifice, extending into the left atrium during systole, and into the left atrium during diastole. Spectral Doppler recordings revealed transvalvular mitral valve gradients and prolonged pressure half-times. Necropsy performed on 1 dog revealed extremely thickened, nodular, and stiff mitral valves with short, thickened, and fused chordae tendineae. The diagnosis of mitral valve stenosis was easily facilitated with diagnostic ultrasonography.

Advantages and limits of hemorrhoidal dearterialization in the treatment of symptomatic hemorrhoids

PubMed Central

Giamundo, Paolo

2016-01-01

In the last two decades, hemorrhoidal dearterialization has become universally accepted as a treatment option for symptomatic hemorrhoids. The rationale for this procedure is based on the assumption that arterial blood overflow is mainly responsible for dilatation of the hemorrhoidal plexus due to the absence of capillary interposition between the arterial and venous systems within the anal canal. Dearterialization, with either suture ligation (Doppler-guided hemorrhoid artery ligation/transanal hemorrhoidal dearterialization) or laser (hemorrhoidal laser procedure), may be successfully performed alone or with mucopexy. Although the added value of Doppler-guidance in association with dearterialization has recently been challenged, this imaging method still plays an important role in localizing hemorrhoidal arteries and, therefore, minimizing the effect of anatomic variation among patients. However, it is important to employ the correct Doppler transducer. Some Doppler transducers may not easily detect superficial arteries due to inadequate frequency settings. All techniques of dearterialization have the advantage of preserving the anatomy and physiology of the anal canal, when compared to other surgical treatments for hemorrhoids. This advantage cannot be underestimated as impaired anal function, including fecal incontinence and other defecation disorders, may occur following surgical treatment for hemorrhoids. Furthermore, this potentially devastating problem can occur in patients of all ages, including younger patients. PMID:26843909

Advantages and limits of hemorrhoidal dearterialization in the treatment of symptomatic hemorrhoids.

PubMed

Giamundo, Paolo

2016-01-27

In the last two decades, hemorrhoidal dearterialization has become universally accepted as a treatment option for symptomatic hemorrhoids. The rationale for this procedure is based on the assumption that arterial blood overflow is mainly responsible for dilatation of the hemorrhoidal plexus due to the absence of capillary interposition between the arterial and venous systems within the anal canal. Dearterialization, with either suture ligation (Doppler-guided hemorrhoid artery ligation/transanal hemorrhoidal dearterialization) or laser (hemorrhoidal laser procedure), may be successfully performed alone or with mucopexy. Although the added value of Doppler-guidance in association with dearterialization has recently been challenged, this imaging method still plays an important role in localizing hemorrhoidal arteries and, therefore, minimizing the effect of anatomic variation among patients. However, it is important to employ the correct Doppler transducer. Some Doppler transducers may not easily detect superficial arteries due to inadequate frequency settings. All techniques of dearterialization have the advantage of preserving the anatomy and physiology of the anal canal, when compared to other surgical treatments for hemorrhoids. This advantage cannot be underestimated as impaired anal function, including fecal incontinence and other defecation disorders, may occur following surgical treatment for hemorrhoids. Furthermore, this potentially devastating problem can occur in patients of all ages, including younger patients.

Transcranial power M-mode Doppler ultrasound for diagnosis of patent foramen ovale

NASA Astrophysics Data System (ADS)

Moehring, Mark; Spencer, Merrill

2005-04-01

Patent foramen ovale (PFO) is a right-to-left shunt (RLS) which communicates blood from the right to left atrium of the heart. PFO has been associated with stroke and, more recently, with migraine headache. Diagnosis of RLS can be accomplished effectively with transcranial power M-mode Doppler ultrasound (PMD). PMD is a modality which can be performed without the sedation required by the more invasive diagnostic technique using transesophageal echocardiography. PMD for this application consists of 2 MHz pulse Doppler ultrasound with placement of sample gates at 2 mm intervals along the single-transducer beam axis, and 8 kHz pulse repetition rate (PMD100M, Spencer Technologies). Doppler power versus depth is constructed every 4ms, using 33 sample gates. Bubble microemboli injected in the venous system and moving across a PFO present as high intensity tracks on a PMD image, as emboli transit from the heart to the brain and through the observed cerebral vasculature. Use of PMD in this context has been reported in the clinical literature [M. P. Spencer, M. A. Moehring, J. Jesurum et al, J. Neuroimaging 14, 342-349 (2004)]. This talk surveys the basic technical features of PMD for sensing PFO-related showers of bubble microemboli, and how these features provide clues to the severity of PFO.

A feasability study of color flow doppler vectorization for automated blood flow monitoring.

PubMed

Schorer, R; Badoual, A; Bastide, B; Vandebrouck, A; Licker, M; Sage, D

2017-12-01

An ongoing issue in vascular medicine is the measure of the blood flow. Catheterization remains the gold standard measurement method, although non-invasive techniques are an area of intense research. We hereby present a computational method for real-time measurement of the blood flow from color flow Doppler data, with a focus on simplicity and monitoring instead of diagnostics. We then analyze the performance of a proof-of-principle software implementation. We imagined a geometrical model geared towards blood flow computation from a color flow Doppler signal, and we developed a software implementation requiring only a standard diagnostic ultrasound device. Detection performance was evaluated by computing flow and its determinants (flow speed, vessel area, and ultrasound beam angle of incidence) on purposely designed synthetic and phantom-based arterial flow simulations. Flow was appropriately detected in all cases. Errors on synthetic images ranged from nonexistent to substantial depending on experimental conditions. Mean errors on measurements from our phantom flow simulation ranged from 1.2 to 40.2% for angle estimation, and from 3.2 to 25.3% for real-time flow estimation. This study is a proof of concept showing that accurate measurement can be done from automated color flow Doppler signal extraction, providing the industry the opportunity for further optimization using raw ultrasound data.

Composition Independent Thermometry in Gaseous Combustion Using Spectral Lineshape Information

NASA Astrophysics Data System (ADS)

Zelenak, Dominic

2016-11-01

Temperature is an important thermochemical property that holds the key to revealing several combustion phenomena such as pollutant formation, flame extinction, and heat release. In a practical combusting environment, the local composition is unknown, hindering the effectiveness of established non-intrusive thermometry techniques. This study aims to offset this limitation by developing laser thermometry techniques that do not require prior knowledge of the local composition. Multiple methods for obtaining temperature are demonstrated, which make use of the spectral line broadening of an absorbing species (Kr) seeded into the flow. These techniques involve extracting the Doppler broadening from the Voight profile and utilizing compositional scaling of collisional broadening and shift to determine temperature. Doppler broadening-temperature scaling of two photon Kr-PLIF is provided. Lean-premixed and diffusion jet flames of CH4 will serve as the test bed for experimentation, and validation of the two methods will be made using the corresponding temperature determined from Rayleigh scattering imaging with adiabatic mixing and unity Lewis number assumptions. A ratiometric dual lineshape thermometry method for turbulent flames will also be introduced. AFOSR Grant FA9550-16-1-0190 with Dr. Chiping Li as Program Manager.

Temporal enhancement of two-dimensional color doppler echocardiography

NASA Astrophysics Data System (ADS)

Terentjev, Alexey B.; Settlemier, Scott H.; Perrin, Douglas P.; del Nido, Pedro J.; Shturts, Igor V.; Vasilyev, Nikolay V.

2016-03-01

Two-dimensional color Doppler echocardiography is widely used for assessing blood flow inside the heart and blood vessels. Currently, frame acquisition time for this method varies from tens to hundreds of milliseconds, depending on Doppler sector parameters. This leads to low frame rates of resulting video sequences equal to tens of Hz, which is insufficient for some diagnostic purposes, especially in pediatrics. In this paper, we present a new approach for reconstruction of 2D color Doppler cardiac images, which results in the frame rate being increased to hundreds of Hz. This approach relies on a modified method of frame reordering originally applied to real-time 3D echocardiography. There are no previous publications describing application of this method to 2D Color Doppler data. The approach has been tested on several in-vivo cardiac 2D color Doppler datasets with approximate duration of 30 sec and native frame rate of 15 Hz. The resulting image sequences had equivalent frame rates to 500Hz.

Ultrasonographic imaging of inflammatory bowel disease in pediatric patients

PubMed Central

Chiorean, Liliana; Schreiber-Dietrich, Dagmar; Braden, Barbara; Cui, Xin-Wu; Buchhorn, Reiner; Chang, Jian-Min; Dietrich, Christoph F

2015-01-01

Inflammatory bowel disease (IBD) is one of the most common chronic gastrointestinal diseases in pediatric patients. Choosing the optimal imaging modality for the assessment of gastrointestinal disease in pediatric patients can be challenging. The invasiveness and patient acceptance, the radiation exposure and the quality performance of the diagnostic test need to be considered. By reviewing the literature regarding imaging in inflammatory bowel disease the value of ultrasound in the clinical management of pediatric patients is highlighted. Transabdominal ultrasound is a useful, noninvasive method for the initial diagnosis of IBD in children; it also provides guidance for therapeutic decisions and helps to characterize and predict the course of the disease in individual patients. Ultrasound techniques including color Doppler imaging and contrast-enhanced ultrasound are promising imaging tools to determine disease activity and complications. Comparative studies between different imaging methods are needed. PMID:25954096

21 CFR 892.1550 - Ultrasonic pulsed doppler imaging system.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ultrasonic pulsed doppler imaging system. 892.1550 Section 892.1550 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... include signal analysis and display equipment, patient and equipment supports, component parts, and...

21 CFR 892.1550 - Ultrasonic pulsed doppler imaging system.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ultrasonic pulsed doppler imaging system. 892.1550 Section 892.1550 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... include signal analysis and display equipment, patient and equipment supports, component parts, and...

Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique: A test case of the Mars Express Phobos Flyby. II. Doppler tracking: Formulation of observed and computed values, and noise budget

NASA Astrophysics Data System (ADS)

Bocanegra-Bahamón, T. M.; Molera Calvés, G.; Gurvits, L. I.; Duev, D. A.; Pogrebenko, S. V.; Cimò, G.; Dirkx, D.; Rosenblatt, P.

2018-01-01

Context. Closed-loop Doppler data obtained by deep space tracking networks, such as the NASA Deep Space Network (DSN) and the ESA tracking station network (Estrack), are routinely used for navigation and science applications. By shadow tracking the spacecraft signal, Earth-based radio telescopes involved in the Planetary Radio Interferometry and Doppler Experiment (PRIDE) can provide open-loop Doppler tracking data only when the dedicated deep space tracking facilities are operating in closed-loop mode. Aims: We explain the data processing pipeline in detail and discuss the capabilities of the technique and its potential applications in planetary science. Methods: We provide the formulation of the observed and computed values of the Doppler data in PRIDE tracking of spacecraft and demonstrate the quality of the results using an experiment with the ESA Mars Express spacecraft as a test case. Results: We find that the Doppler residuals and the corresponding noise budget of the open-loop Doppler detections obtained with the PRIDE stations compare to the closed-loop Doppler detections obtained with dedicated deep space tracking facilities.

Interferometric imaging of acoustical phenomena using high-speed polarization camera and 4-step parallel phase-shifting technique

NASA Astrophysics Data System (ADS)

Ishikawa, K.; Yatabe, K.; Ikeda, Y.; Oikawa, Y.; Onuma, T.; Niwa, H.; Yoshii, M.

2017-02-01

Imaging of sound aids the understanding of the acoustical phenomena such as propagation, reflection, and diffraction, which is strongly required for various acoustical applications. The imaging of sound is commonly done by using a microphone array, whereas optical methods have recently been interested due to its contactless nature. The optical measurement of sound utilizes the phase modulation of light caused by sound. Since light propagated through a sound field changes its phase as proportional to the sound pressure, optical phase measurement technique can be used for the sound measurement. Several methods including laser Doppler vibrometry and Schlieren method have been proposed for that purpose. However, the sensitivities of the methods become lower as a frequency of sound decreases. In contrast, since the sensitivities of the phase-shifting technique do not depend on the frequencies of sounds, that technique is suitable for the imaging of sounds in the low-frequency range. The principle of imaging of sound using parallel phase-shifting interferometry was reported by the authors (K. Ishikawa et al., Optics Express, 2016). The measurement system consists of a high-speed polarization camera made by Photron Ltd., and a polarization interferometer. This paper reviews the principle briefly and demonstrates the high-speed imaging of acoustical phenomena. The results suggest that the proposed system can be applied to various industrial problems in acoustical engineering.

Noninvasive Techniques for Intracranial Pressure Assessment: A Review from Aerospace Medicine Perspective

NASA Technical Reports Server (NTRS)

Hamilton, Douglas R.; Sargsyan, Ashot E.; Fogarty, Jennifer; Ebert, Douglas J. W.; Polk, J. D.

2010-01-01

Microgravity-induced changes in fluid distribution and other physiological factors due to space flight have been implicated as the cause of increased intracranial pressure (ICP) in a number of space crewmembers. The modest levels of ICP elevation and absence of severe symptoms in this group do not warrant invasive diagnostic interventions. However, the long-term trends and residual or consequential changes secondary to the observed ICP elevation in this group are not yet known. Therefore, close attention is needed to evaluate the potential techniques of noninvasively assessing ICP, including those feasible for in-flight use. Of particular interest is continuity between ground and in-flight testing, whereby data from the same or different techniques allow reasonably dependable estimation of ICP trends and responses. Methods: A thorough review of current literature, analysis of NASA data, and interviews with subject matter experts were conducted to construct a presentation that reflects the state of the art for noninvasive ICP measurement and monitoring. Results: Multiple imaging and non-imaging modalities are available to assess ICP in terrestrial clinical and experimental environments. Imaging alternatives include magnetic resonance imaging (MRI) and high-resolution sonography. Non-imaging techniques include transcranial Doppler, certain audiological methods, and venous ophthalmodynamometry, among others. Special functional techniques have been proposed recently that allow the use of advanced MRI methods to calculate ICP in addition to the acquisition of high-resolution images. Our data include many of these applications, with several cases of correlation with lumbar puncture, the invasive "gold standard" measurement of ICP.

Methodological approach for the assessment of ultrasound reproducibility of cardiac structure and function: a proposal of the study group of Echocardiography of the Italian Society of Cardiology (Ultra Cardia SIC) Part I

PubMed Central

2011-01-01

When applying echo-Doppler imaging for either clinical or research purposes it is very important to select the most adequate modality/technology and choose the most reliable and reproducible measurements. Quality control is a mainstay to reduce variability among institutions and operators and must be obtained by using appropriate procedures for data acquisition, storage and interpretation of echo-Doppler data. This goal can be achieved by employing an echo core laboratory (ECL), with the responsibility for standardizing image acquisition processes (performed at the peripheral echo-labs) and analysis (by monitoring and optimizing the internal intra- and inter-reader variability of measurements). Accordingly, the Working Group of Echocardiography of the Italian Society of Cardiology decided to design standardized procedures for imaging acquisition in peripheral laboratories and reading procedures and to propose a methodological approach to assess the reproducibility of echo-Doppler parameters of cardiac structure and function by using both standard and advanced technologies. A number of cardiologists experienced in cardiac ultrasound was involved to set up an ECL available for future studies involving complex imaging or including echo-Doppler measures as primary or secondary efficacy or safety end-points. The present manuscript describes the methodology of the procedures (imaging acquisition and measurement reading) and provides the documentation of the work done so far to test the reproducibility of the different echo-Doppler modalities (standard and advanced). These procedures can be suggested for utilization also in non referall echocardiographic laboratories as an "inside" quality check, with the aim at optimizing clinical consistency of echo-Doppler data. PMID:21943283

The high-resolution Doppler imager on the Upper Atmosphere Research Satellite

NASA Technical Reports Server (NTRS)

Hays, Paul B.; Abreu, Vincent J.; Dobbs, Michael E.; Gell, David A.; Grassl, Heinz J.; Skinner, Wilbert R.

1993-01-01

The high-resolution Doppler imager (HRDI) on the Upper Atmosphere Research Satellite is a triple-etalon Fabry-Perot interferometer designed to measure winds in the stratosphere, mesosphere, and lower thermosphere. Winds are determined by measuring the Doppler shifts of rotational lines of the O2 atmospheric band, which are observed in emission in the mesosphere and lower thermosphere and in absorption in the stratosphere. The interferometer has high resolution (0.05/cm), good offhand rejection, aud excellent stability. This paper provides details of the design and capabilities of the HRDI instrument.

Two-dimensional color tissue Doppler imaging detects myocardial dysfunction before occurrence of hypertrophy in a young Maine Coon cat.

PubMed

Chetboul, Valerie; Sampedrano, Carolina Carlos; Gouni, Vassiliki; Nicolle, Audrey P; Pouchelon, Jean-Louis

2006-01-01

A 20-month-old healthy male Maine Coon cat was referred for a cardiovascular evaluation. Physical examination and electrocardiogram were normal. The end-diastolic subaortic interventricular septal thickness (6 mm; reference range: < or = 6mm) and the mitral flow late diastolic velocity (0.89 m/s; reference range: 0.2-0.8m/s) were within the upper ranges. However, M-mode echocardiography did not reveal any sign of hypertrophic cardiomyopathy (HCM). Tissue Doppler imaging (TDI) identified a marked left ventricular free wall dysfunction characterized by decreased myocardial velocities in early diastole, increased myocardial velocities in late diastole and the presence of postsystolic contractions both at the base and the apex for the longitudinal motion. One year later, the diagnosis of HCM was confirmed by conventional echocardiography and the cat died suddenly 2 months later. This report demonstrates for the first time in spontaneous HCM the sensitivity of TDI for early diagnosis of myocardial dysfunction and suggests that TDI should form part of the screening techniques for early diagnosis of feline HCM.

Characterization of intraventricular flow patterns in healthy neonates from conventional color-Doppler ultrasound

NASA Astrophysics Data System (ADS)

Tejman-Yarden, Shai; Rzasa, Callie; Benito, Yolanda; Alhama, Marta; Leone, Tina; Yotti, Raquel; Bermejo, Javier; Printz, Beth; Del Alamo, Juan C.

2012-11-01

Left ventricular vortices have been difficult to visualize in the clinical setting due to the lack of quantitative non-invasive modalities, and this limitation is especially important in pediatrics. We have developed and validated a new technique to reconstruct two-dimensional time-resolved velocity fields in the LV from conventional transthoracic color-Doppler images. This non-invasive modality was used to image LV flow in 10 healthy full-term neonates, ages 24-48 hours. Our results show that, in neonates, a diastolic vortex developed during LV filling, was maintained during isovolumic contraction, and decayed during the ejection period. The vortex was created near the base of the ventricle, moved toward the apex, and then back toward the base and LVOT during ejection. In conclusion, we have characterized for the first time the properties of the LV filling vortex in normal neonates, demonstrating that this vortex channels blood from the inflow to the outflow tract of the LV. Together with existing data from adults, our results confirm that the LV vortex is conserved through adulthood. Funded by NIH Grant R21HL108268.

Speckle tracking evaluation of right ventricular functions in children with sickle cell disease.

PubMed

Tolba, Osama Abd Rab Elrasol; El-Shanshory, Mohamed Ramadan; El-Gamasy, Mohamed Abd Elaziz; El-Shehaby, Walid Ahmed

2017-01-01

Cardiac dysfunction is a risk factor for death in patients with sickle cell disease (SCD). Aim of the work is to evaluate the right ventricular systolic and diastolic functions by tissue Doppler and speckling tracking imaging in children with SCD. Thirty children with SCD and thirty controls were subjected to clinical, laboratory evaluations, and echocardiographic study using GE Vivid 7 (GE Medical System, Horten, Norway with a 3.5-MHz multifrequency transducer) including; Two-dimensional and tissue Doppler echocardiographic study (lateral tricuspid valve annulus peak E' velocity, lateral tricuspid valve annulus peak A' velocity, E'/A' ratio, isovolumetric relaxation time, lateral tricuspid valve annulus S' and septal S' waves and peak longitudinal systolic strain [PLSS] and time to PLSS) were done in six right ventricular segments. There was a significant decrease in right ventricular systolic and diastolic function in patients group when compared to controls. Children with SCD have impaired right ventricular systolic and diastolic functions when compared to healthy children with early evaluation of the systolic dysfunction by speckle tracking imaging technique.

Ultrasound: medical imaging and beyond (an invited review).

PubMed

Azhari, Haim

2012-09-01

Medical applications of ultrasound were first investigated about seventy years ago. It has rapidly evolved since then, becoming an essential tool in medical imaging. Ultrasound ability to provide real time images with frame rates exceeding several hundred frames per second allows one to view rapid anatomical changes as well as to guide minimal invasive procedures. By, combining Doppler techniques with anatomical images ultrasound provides real time quantitative flow information as well. It is portable, versatile, cost effective and considered sufficiently hazardless to monitor pregnancy. Moreover, ultrasound has the unique capacity to offer therapeutic capabilities in addition to its outstanding imaging abilities. It can be used for physiotherapy, lithotripsy, and thermal ablation, and recent studies have demonstrated its usefulness in drug delivery, gene therapy and molecular imaging. The purpose of this article is to provide an introductory review of the field covering briefly topics from basic physics through current imaging methods to therapeutic applications.

Cartographie des disques

NASA Astrophysics Data System (ADS)

Hameury, Jean-Marie

2001-01-01

Two techniques are frequently used to produce images of the accretion disc in an eclipsing binary: eclipse mapping and Doppler tomography. From the light curve, one can deduce the radial distribution of the effective temperature, assuming axial symmetry. On the other hand, from the variation of the line profile one can reconstruct an image in the velocity space, which can be converted into a real image if one knows the kinematics of the system. Deux techniques sont couramment utilisées pour obtenir des images des disques dans les systèmes binaires à éclipses. En utilisant la courbe de lumière, on peut remonter à la distribution radiale de la brillance de surface, en supposant que celle-ci a une symètrie axiale. D'autre part, les profils de raies renseignent sur la distribution de vitesse des régions émissives leur variation temporelle permet de réaliser une image dans l'espace des vitesses, que l'on peut ensuite transformer en carte dans l'espace (x,y) si on connaît la cinématique du système.

Novel Applications of Ultrasound Technology to Visualize and Characterize Myofascial Trigger Points and Surrounding Soft Tissue

PubMed Central

Sikdar, Siddhartha; Shah, Jay P.; Gebreab, Tadesse; Yen, Ru-Huey; Gilliams, Elizabeth; Danoff, Jerome; Gerber, Lynn H.

2009-01-01

Objective Apply ultrasound (US) imaging techniques to better describe the characteristics of myofascial trigger points (MTrPs) and the immediately adjacent soft tissue. Design Descriptive (exploratory) study. Setting Biomedical research center. Participants 9 subjects meeting Travell and Simons’s criteria for MTrPs in a taut band in the upper trapezius. Interventions (None) Main Outcome Measures MTrPs were evaluated by 1) physical examination, 2) pressure algometry, and 3) three types of ultrasound imaging including grayscale (2D US), vibration sonoelastography (VSE), and Doppler. Methods Four sites in each patient were labeled based on physical examination as either active MTrP (spontaneously-painful, A-MTrP), latent MTrP (non-painful, L-MTrP), or normal myofascial tissue. US examination was performed on each subject by a team blinded to the physical findings. A 12-5 MHz US transducer was used. VSE was performed by color Doppler variance imaging while simultaneously inducing vibrations (~92Hz) with a handheld massage vibrator. Each site was assigned a tissue imaging score (TIS) as follows: 0 = uniform echogenicity and stiffness; 1 = focal hypoechoic region with stiff nodule; 2 = multiple hypoechoic regions with stiff nodules. Blood flow in the neighborhood of MTrPs was assessed using Doppler imaging. Each site was assigned a blood flow waveform score (BFS) as follows: 0 = normal arterial flow in muscle; 1 = elevated diastolic flow; 2 = high-resistance flow waveform with retrograde diastolic flow. Results MTrPs appeared as focal, hypoechoic regions on 2D US, indicating local changes in tissue echogenicity, and as focal regions of reduced vibration amplitude on VSE, indicating a localized stiff nodule. MTrPs were elliptical in shape, with a size of 0.16 ± 0.11 cm2. There were no significant differences in size between A-MTrPs and L-MTrPs. Sites containing MTrPs were more likely to have higher TIS compared to normal myofascial tissue (p<0.002). Small arteries (or enlarged arterioles) near A-MTrPs showed retrograde flow in diastole indicating a highly resistive vascular bed. A-MTrP sites were more likely to have higher BFS compared to L-MTrPs (p<0.021). Conclusions Preliminary findings show that, under the conditions of this investigation, US imaging techniques can be used to distinguish myofascial tissue containing MTrPs from normal myofascial tissue (lacking trigger points). Ultrasound enables visualization and some characterization of MTrPs and adjacent soft tissue. PMID:19887205

Locoregional spread of cutaneous melanoma: sonography findings.

PubMed

Catalano, Orlando; Caracò, Corrado; Mozzillo, Nicola; Siani, Alfredo

2010-03-01

This article reviews various aspects of locoregional spread of malignant cutaneous melanoma, as imaged with gray-scale sonography and Doppler techniques. The scenarios illustrated include disease staging (primary melanoma, satellite metastasis, in-transit metastasis, and lymphadenopathies), sentinel lymph node biopsy procedure, patient follow-up, recurrence detection, cutaneous metastasis, and sonographically guided intervention. High-resolution sonography allows recognition of small, clinically-occult melanomatous foci. It plays a major role in locoregional staging and follow-up of patients with cutaneous melanoma.

Summary of SAR (Synthetic Aperture Radar) Ocean Wave Data Archived at ERIM (Environmental Research Institute of Michigan).

DTIC Science & Technology

1984-05-01

transform (FFT) techniques achieve the required azi- muthal compression of the SAR Doppler history (Ausherman, 1980). Specially- designed digital...processors have also been designed for 3 -[RIM RADAR DIVISION real-time processing of SAR data aboard the aircraft for display or transmission to a ground...included a multi-sided box pattern designed to image the dominant waves from various directions. Figure 2 presents the results obtained as a function of

Speckle tracking analysis: a new tool for left atrial function analysis in systemic hypertension: an overview.

PubMed

Cameli, Matteo; Ciccone, Marco M; Maiello, Maria; Modesti, Pietro A; Muiesan, Maria L; Scicchitano, Pietro; Novo, Salvatore; Palmiero, Pasquale; Saba, Pier S; Pedrinelli, Roberto

2016-05-01

Speckle tracking echocardiography (STE) is an imaging technique applied to the analysis of left atrial function. STE provides a non-Doppler, angle-independent and objective quantification of left atrial myocardial deformation. Data regarding feasibility, accuracy and clinical applications of left atrial strain are rapidly gathering. This review describes the fundamental concepts of left atrial STE, illustrates its pathophysiological background and discusses its emerging role in systemic arterial hypertension.

Insights into the use of thermography to assess burn wound healing potential: a reliable and valid technique when compared to laser Doppler imaging

NASA Astrophysics Data System (ADS)

Jaspers, Mariëlle E. H.; Maltha, Ilse; Klaessens, John H. G. M.; de Vet, Henrica C. W.; Verdaasdonk, Rudolf M.; van Zuijlen, Paul P. M.

2016-09-01

Adequate assessment of burn wounds is crucial in the management of burn patients. Thermography, as a noninvasive measurement tool, can be utilized to detect the remaining perfusion over large burn wound areas by measuring temperature, thereby reflecting the healing potential (HP) (i.e., number of days that burns require to heal). The objective of this study was to evaluate the clinimetric properties (i.e., reliability and validity) of thermography for measuring burn wound HP. To evaluate reliability, two independent observers performed a thermography measurement of 50 burns. The intraclass correlation coefficient (ICC), the standard error of measurement (SEM), and the limits of agreement (LoA) were calculated. To assess validity, temperature differences between burned and nonburned skin (ΔT) were compared to the HP found by laser Doppler imaging (serving as the reference standard). By applying a visual method, one ΔT cutoff point was identified to differentiate between burns requiring conservative versus surgical treatment. The ICC was 0.99, expressing an excellent correlation between two measurements. The SEM was calculated at 0.22°C, the LoA at -0.58°C and 0.64°C. The ΔT cutoff point was -0.07°C (sensitivity 80% specificity 80%). These results show that thermography is a reliable and valid technique in the assessment of burn wound HP.

Noninvasive Imaging of the Coronary Vasculature Using Ultrafast Ultrasound.

PubMed

Maresca, David; Correia, Mafalda; Villemain, Olivier; Bizé, Alain; Sambin, Lucien; Tanter, Mickael; Ghaleh, Bijan; Pernot, Mathieu

2017-08-11

The aim of this study was to investigate the potential of coronary ultrafast Doppler angiography (CUDA), a novel vascular imaging technique based on ultrafast ultrasound, to image noninvasively with high sensitivity the intramyocardial coronary vasculature and quantify the coronary blood flow dynamics. Noninvasive coronary imaging techniques are currently limited to the observation of the epicardial coronary arteries. However, many studies have highlighted the importance of the coronary microcirculation and microvascular disease. CUDA was performed in vivo in open-chest procedures in 9 swine. Ultrafast plane-wave imaging at 2,000 frames/s was combined to an adaptive spatiotemporal filtering to achieve ultrahigh-sensitive imaging of the coronary blood flows. Quantification of the flow change was performed during hyperemia after a 30-s left anterior descending (LAD) artery occlusion followed by reperfusion and was compared to gold standard measurements provided by a flowmeter probe placed at a proximal location on the LAD (n = 5). Coronary flow reserve was assessed during intravenous perfusion of adenosine. Vascular damages were evaluated during a second set of experiments in which the LAD was occluded for 90 min, followed by 150 min of reperfusion to induce myocardial infarction (n = 3). Finally, the transthoracic feasibility of CUDA was assessed on 2 adult and 2 pediatric volunteers. Ultrahigh-sensitive cine loops of venous and arterial intramyocardial blood flows were obtained within 1 cardiac cycle. Quantification of the coronary flow changes during hyperemia was in good agreement with gold standard measurements (r 2  = 0.89), as well as the assessment of coronary flow reserve (2.35 ± 0.65 vs. 2.28 ± 0.84; p = NS). On the infarcted animals, CUDA images revealed the presence of strong hyperemia and the appearance of abnormal coronary vessel structures in the reperfused LAD territory. Finally, the feasibility of transthoracic coronary vasculature imaging was shown on 4 human volunteers. Ultrafast Doppler imaging can map the coronary vasculature with high sensitivity and quantify intramural coronary blood flow changes. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Applicability of the iterative technique for cardiac resynchronization therapy optimization: full-disclosure, 50-sequential-patient dataset of transmitral Doppler traces, with implications for future research design and guidelines.

PubMed

Jones, Siana; Shun-Shin, Matthew J; Cole, Graham D; Sau, Arunashis; March, Katherine; Williams, Suzanne; Kyriacou, Andreas; Hughes, Alun D; Mayet, Jamil; Frenneaux, Michael; Manisty, Charlotte H; Whinnett, Zachary I; Francis, Darrel P

2014-04-01

Full-disclosure study describing Doppler patterns during iterative atrioventricular delay (AVD) optimization of biventricular pacemakers (cardiac resynchronization therapy, CRT). Doppler traces of the first 50 eligible patients undergoing iterative Doppler AVD optimization in the BRAVO trial were examined. Three experienced observers classified conformity to guideline-described patterns. Each observer then selected the optimum AVD on two separate occasions: blinded and unblinded to AVD. Four Doppler E-A patterns occurred: A (always merged, 18% of patients), B (incrementally less fusion at short AVDs, 12%), C (full separation at short AVDs, as described by the guidelines, 28%), and D (always separated, 42%). In Groups A and D (60%), the iterative guidelines therefore cannot specify one single AVD. On the kappa scale (0 = chance alone; 1 = perfect agreement), observer agreement for the ideal AVD in Classes B and C was poor (0.32) and appeared worse in Groups A and D (0.22). Blinding caused the scattering of the AVD selected as optimal to widen (standard deviation rising from 37 to 49 ms, P < 0.001). By blinding 28% of the selected optimum AVDs were ≤60 or ≥200 ms. All 50 Doppler datasets are presented, to support future methodological testing. In most patients, the iterative method does not clearly specify one AVD. In all the patients, agreement on the ideal AVD between skilled observers viewing identical images is poor. The iterative protocol may successfully exclude some extremely unsuitable AVDs, but so might simply accepting factory default. Irreproducibility of the gold standard also prevents alternative physiological optimization methods from being validated honestly.

Photogrammetry and optical methods in structural dynamics - A review

NASA Astrophysics Data System (ADS)

Baqersad, Javad; Poozesh, Peyman; Niezrecki, Christopher; Avitabile, Peter

2017-03-01

In the last few decades, there has been a surge of research in the area of non-contact measurement techniques. Photogrammetry has received considerable attention due to its ability to achieve full-field measurement and its robustness to work in testing environments and on testing articles in which using other measurement techniques may not be practical. More recently, researchers have used this technique to study transient phenomena and to perform measurements on vibrating structures. The current paper reviews the most current trends in the photogrammetry technique (point tracking, digital image correlation, and target-less approaches) and compares the applications of photogrammetry to other measurement techniques used in structural dynamics (e.g. laser Doppler vibrometry and interferometry techniques). The paper does not present the theoretical background of the optical techniques, but instead presents the general principles of each approach and highlights the novel structural dynamic measurement concepts and applications that are enhanced by utilizing optical techniques.

Quantitative analysis of thyroid tumors vascularity: A comparison between 3-D contrast-enhanced ultrasound and 3-D Power Doppler on benign and malignant thyroid nodules.

PubMed

Caresio, Cristina; Caballo, Marco; Deandrea, Maurilio; Garberoglio, Roberto; Mormile, Alberto; Rossetto, Ruth; Limone, Paolo; Molinari, Filippo

2018-05-15

To perform a comparative quantitative analysis of Power Doppler ultrasound (PDUS) and Contrast-Enhancement ultrasound (CEUS) for the quantification of thyroid nodules vascularity patterns, with the goal of identifying biomarkers correlated with the malignancy of the nodule with both imaging techniques. We propose a novel method to reconstruct the vascular architecture from 3-D PDUS and CEUS images of thyroid nodules, and to automatically extract seven quantitative features related to the morphology and distribution of vascular network. Features include three tortuosity metrics, the number of vascular trees and branches, the vascular volume density, and the main spatial vascularity pattern. Feature extraction was performed on 20 thyroid lesions (ten benign and ten malignant), of which we acquired both PDUS and CEUS. MANOVA (multivariate analysis of variance) was used to differentiate benign and malignant lesions based on the most significant features. The analysis of the extracted features showed a significant difference between the benign and malignant nodules for both PDUS and CEUS techniques for all the features. Furthermore, by using a linear classifier on the significant features identified by the MANOVA, benign nodules could be entirely separated from the malignant ones. Our early results confirm the correlation between the morphology and distribution of blood vessels and the malignancy of the lesion, and also show (at least for the dataset used in this study) a considerable similarity in terms of findings of PDUS and CEUS imaging for thyroid nodules diagnosis and classification. © 2018 American Association of Physicists in Medicine.

Evaluation of the microcirculation in a sheep island pedicle flap with laser Doppler flowmeter and 99m-Tc-labelled red blood cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banic, A.; Kouris, K.; Lewis, D.H.

1990-10-01

The aim of the study was experimentally to evaluate the capability and reliability of laser Doppler flowmetry (LDF) in conditions of circulatory deficiency, by correlating it to flow-related parameters measured by a radionuclide-imaging technique and using 99m-Tc red blood cells (RBCs). For this purpose, a pedicle island flap in the sheep was used, with well-perfused proximal parts and with evident stasis in the distal third of the flap. No correlation was found between results obtained with the two techniques. In regions with evident stasis, falsely high LDF readings were recorded. This may be due to a back-and-forth motion of themore » RBCs under the probe, rather than to true flow. It was concluded that, while LDF seems reliable in detecting complete arterial occlusion, it is unreliable in predicting either complete venous occlusion or partial obstruction of the flow to and from the flap. Clinical use for this purpose cannot be recommended.« less

Results of vardenafil mediated power Doppler ultrasound, contrast enhanced ultrasound and systematic random biopsies to detect prostate cancer.

PubMed

Morelli, Girolamo; Pagni, Riccardo; Mariani, Chiara; Minervini, Riccardo; Morelli, Andrea; Gori, Francesco; Ferdeghini, Ezio Maria; Paterni, Marco; Mauro, Eva; Guidi, Elisa; Armillotta, Nicola; Canale, Domenico; Vitti, Paolo; Caramella, Davide; Minervini, Andrea

2011-06-01

We evaluated the ability of the phosphodiesterase-5 inhibitor vardenafil to increase prostate microcirculation during power Doppler ultrasound. We also evaluated the results of contrast and vardenafil enhanced targeted biopsies compared to those of standard 12-core random biopsies to detect cancer. Between May 2008 and January 2010, 150 consecutive patients with prostate specific antigen more than 4 ng/ml at first diagnosis with negative digital rectal examination and transrectal ultrasound, and no clinical history of prostatitis underwent contrast enhanced power Doppler ultrasound (bolus injection of 2.4 ml SonoVue® contrast agent), followed by vardenafil enhanced power Doppler ultrasound (1 hour after oral administration of vardenafil 20 mg). All patients underwent standard 12-core transrectal ultrasound guided random prostate biopsy plus 1 further sampling from each suspected hypervascular lesion detected by contrast and vardenafil enhanced power Doppler ultrasound. Prostate cancer was detected in 44 patients (29.3%). Contrast and vardenafil enhanced power Doppler ultrasound detected suspicious, contrast enhanced and vardenafil enhanced areas in 112 (74.6%) and 110 patients (73.3%), and was diagnostic for cancer in 32 (28.5%) and 42 (38%), respectively. Analysis of standard technique, and contrast and vardenafil enhanced power Doppler ultrasound findings by biopsy core showed significantly higher detection using vardenafil vs contrast enhanced power Doppler ultrasound and standard technique (41.2% vs 22.7% and 8.1%, p <0.005 and <0.001, respectively). The detection rate of standard plus contrast or vardenafil enhanced power Doppler ultrasound was 10% and 11.7% (p not significant). Vardenafil enhanced power Doppler ultrasound enables excellent visualization of the microvasculature associated with cancer and can improve the detection rate compared to contrast enhanced power Doppler ultrasound and the random technique. Copyright © 2011 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

High Dynamic Velocity Range Particle Image Velocimetry Using Multiple Pulse Separation Imaging

PubMed Central

Persoons, Tim; O’Donovan, Tadhg S.

2011-01-01

The dynamic velocity range of particle image velocimetry (PIV) is determined by the maximum and minimum resolvable particle displacement. Various techniques have extended the dynamic range, however flows with a wide velocity range (e.g., impinging jets) still challenge PIV algorithms. A new technique is presented to increase the dynamic velocity range by over an order of magnitude. The multiple pulse separation (MPS) technique (i) records series of double-frame exposures with different pulse separations, (ii) processes the fields using conventional multi-grid algorithms, and (iii) yields a composite velocity field with a locally optimized pulse separation. A robust criterion determines the local optimum pulse separation, accounting for correlation strength and measurement uncertainty. Validation experiments are performed in an impinging jet flow, using laser-Doppler velocimetry as reference measurement. The precision of mean flow and turbulence quantities is significantly improved compared to conventional PIV, due to the increase in dynamic range. In a wide range of applications, MPS PIV is a robust approach to increase the dynamic velocity range without restricting the vector evaluation methods. PMID:22346564

The Novel Nonlinear Adaptive Doppler Shift Estimation Technique and the Coherent Doppler Lidar System Validation Lidar

NASA Technical Reports Server (NTRS)

Beyon, Jeffrey Y.; Koch, Grady J.

2006-01-01

The signal processing aspect of a 2-m wavelength coherent Doppler lidar system under development at NASA Langley Research Center in Virginia is investigated in this paper. The lidar system is named VALIDAR (validation lidar) and its signal processing program estimates and displays various wind parameters in real-time as data acquisition occurs. The goal is to improve the quality of the current estimates such as power, Doppler shift, wind speed, and wind direction, especially in low signal-to-noise-ratio (SNR) regime. A novel Nonlinear Adaptive Doppler Shift Estimation Technique (NADSET) is developed on such behalf and its performance is analyzed using the wind data acquired over a long period of time by VALIDAR. The quality of Doppler shift and power estimations by conventional Fourier-transform-based spectrum estimation methods deteriorates rapidly as SNR decreases. NADSET compensates such deterioration in the quality of wind parameter estimates by adaptively utilizing the statistics of Doppler shift estimate in a strong SNR range and identifying sporadic range bins where good Doppler shift estimates are found. The authenticity of NADSET is established by comparing the trend of wind parameters with and without NADSET applied to the long-period lidar return data.

Investigation of erectile dysfunction.

PubMed

Patel, D V; Halls, J; Patel, U

2012-11-01

Erectile dysfunction (ED) represents a common and debilitating condition with a wide range of organic and non-organic causes. Physical aetiologies can be divided into disorders affecting arterial inflow, the venous occlusion mechanism or the penile structure itself. Various imaging modalities can be utilised to investigate the physical causes of ED, but penile Doppler sonography (PDS) is the most informative technique, indicated in those patients with ED who do not respond to oral pharmacological agents (e.g. phosphodiesterase type 5 inhibitors). This review will examine the anatomical and physiological basis of penile erection, the method for performing PDS and features of specific causes of ED, and will also consider the alternative imaging modalities available.

Techniques in processing multi-frequency multi-polarization spaceborne SAR data

NASA Technical Reports Server (NTRS)

Curlander, John C.; Chang, C. Y.

1991-01-01

This paper presents the algorithm design of the SIR-C ground data processor, with emphasis on the unique elements involved in the production of registered multifrequency polarimetric data products. A quick-look processing algorithm used for generation of low-resolution browse image products and estimation of echo signal parameters is also presented. Specifically the discussion covers: (1) azimuth reference function generation to produce registered polarimetric imagery; (2) geometric rectification to accommondate cross-track and along-track Doppler drifts; (3) multilook filtering designed to generate output imagery with a uniform resolution; and (4) efficient coding to compress the polarimetric image data for distribution.

Noninvasive imaging techniques in the assessment of scleroderma spectrum disorders.

PubMed

Murray, Andrea K; Moore, Tonia L; Manning, Joanne B; Taylor, Christopher; Griffiths, Christopher E M; Herrick, Ariane L

2009-08-15

Systemic sclerosis (SSc) affects both microvascular structure and function. Laser Doppler imaging (LDI) and thermal imaging can be used to measure cutaneous blood vessel function. Nailfold capillaroscopy (NC) measures capillary morphology. The aim of this study was to investigate the relationship between capillary morphology and blood flow, and to determine which combination of techniques allows the best discrimination between patients with SSc, primary Raynaud's phenomenon (RP), and healthy controls. NC was performed in 16 patients with SSc, 14 patients with primary RP, and 16 healthy controls. In addition, participants underwent cold stimulus with cold water. Hands were imaged to monitor rewarming and reperfusion. Nailfold morphologic features were measured and baseline images and rewarming curves were analyzed. Significant differences were found between groups (analysis of variance) for capillary morphologic features and rewarming curve characteristics. A correlation (P < 0.001) was found between LDI and thermal imaging at baseline (0.667) and maximum (0.729) blood flow and skin temperature, and for the areas under the rewarming curves (0.684). Receiver operating characteristic curves indicated that NC, thermal imaging, and LDI allowed 89%, 74%, and 72%, respectively, of SSc patient data to be correctly classified versus primary RP patients and controls. NC, LDI, and thermal imaging each independently provide good discrimination between patients with SSc and those with primary RP and healthy controls (NC being the most suitable technique for classifying patient groups). However, a combination of all 3 techniques improves classification. LDI and thermal imaging give equivalent information on dynamic changes in the cutaneous microcirculation; however, these only weakly correspond to capillary morphology.

Ship dynamics for maritime ISAR imaging.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doerry, Armin Walter

2008-02-01

Demand is increasing for imaging ships at sea. Conventional SAR fails because the ships are usually in motion, both with a forward velocity, and other linear and angular motions that accompany sea travel. Because the target itself is moving, this becomes an Inverse- SAR, or ISAR problem. Developing useful ISAR techniques and algorithms is considerably aided by first understanding the nature and characteristics of ship motion. Consequently, a brief study of some principles of naval architecture sheds useful light on this problem. We attempt to do so here. Ship motions are analyzed for their impact on range-Doppler imaging using Inversemore » Synthetic Aperture Radar (ISAR). A framework for analysis is developed, and limitations of simple ISAR systems are discussed.« less

Advanced MR Imaging of the Placenta: Exploring the in utero placenta-brain connection

PubMed Central

Andescavage, Nickie Niforatos; DuPlessis, Adre; Limperopoulos, Catherine

2015-01-01

The placenta is a vital organ necessary for the healthy neurodevelopment of the fetus. Despite the known associations between placental dysfunction and neurologic impairment, there is a paucity of tools available to reliably assess in vivo placental health and function. Existing clinical tools for placental assessment remain insensitive in predicting and assessing placental well-being. Advanced MRI techniques hold significant promise for the dynamic, non-invasive, real-time assessment of placental health and identification of early placental-based disorders. In this review, we summarize the available clinical tools for placental assessment including ultrasound, Doppler, and conventional MRI. We then explore the emerging role of advanced placental MR imaging techniques for supporting the developing fetus, appraise the strengths and limitations of quantitative MRI in identifying early markers of placental dysfunction for improved pregnancy monitoring and fetal outcomes. PMID:25765905

Doppler Imaging and Chemical Abundance Analysis of EK Dra: Capabilities of Small Telescopes

NASA Astrophysics Data System (ADS)

Kilicoglu, Tolgahan; Senavci, H. V.; Bahar, E.; Isik, E.; Montes, D.; Hussain, G. A. J.

2018-04-01

We investigate the chromospheric and spot activity behaviour of the young Solar-like star EK Dra via Doppler imaging and spectral synthesis methods, using mid-resolution time series spectra of the system. We also present the atmospheric parameters and detailed elemental photospheric abundances of the star. The chemical abundance pattern of EK Dra do not suggest any remarkable peculiarities except few elements. The Titanium Oxide (TiO) bandheads at 7000 - 7100 A region also give clues about the spot temperature that may be cooler than 4000 K. In addition, we also discuss the capabilities of small telescopes (40 cm in our case) and medium resolution spectrographs in terms of Doppler imaging and chemical abundance analysis.

Anthropomorphic cardiac ultrasound phantom.

PubMed

Smith, S W; Rinaldi, J E

1989-10-01

A new phantom is described which simulates the human cardiac anatomy for applications in ultrasound imaging, ultrasound Doppler, and color-flow Doppler imaging. The phantom consists of a polymer left ventricle which includes a prosthetic mitral and aortic valve and is connected to a mock circulatory loop. Aerated tap water serves as a blood simulating fluid and ultrasound contrast medium within the circulatory loop. The left ventricle is housed in a Lexan ultrasound visualization chamber which includes ultrasound viewing ports and acoustic absorbers. A piston pump connected to the visualization chamber by a single port pumps degassed water within the chamber which in turn pumps the left ventricle. Real-time ultrasound images and Doppler studies measure flow patterns through the valves and within the left ventricle.

Color doppler in clinical cardiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duncan, W.J.

1987-01-01

A presentation of color doppler, which enables physicians to pinpoint problems and develop effective treatment. State-of-the-art illustrations and layout, with color images and explanatory text are included.

Right ventricular diastolic performance in children with pulmonary arterial hypertension associated with congenital heart disease: correlation of echocardiographic parameters with invasive reference standards by high-fidelity micromanometer catheter.

PubMed

Okumura, Kenichi; Slorach, Cameron; Mroczek, Dariusz; Dragulescu, Andreea; Mertens, Luc; Redington, Andrew N; Friedberg, Mark K

2014-05-01

Right ventricular diastolic dysfunction influences outcomes in pulmonary arterial hypertension (PAH), but echocardiographic parameters have not been investigated in relation to invasive reference standards in pediatric PAH. We investigated echocardiographic parameters of right ventricular diastolic function in children with PAH in relation to simultaneously measured invasive reference measures. We prospectively recruited children undergoing a clinically indicated cardiac catheterization for evaluation of PAH and pulmonary vasoreactivity testing. Echocardiography was performed simultaneously with invasive reference measurements by high-fidelity micromanometer catheter. For analysis, patients were divided into shunt and nonshunt groups. Sixteen children were studied. In the group as a whole, significant correlations were found among τ and tricuspid deceleration time, E', E/E', TimeE-E', A wave velocity, and global early and late diastolic strain rate. dp/dt minimum correlated significantly with late diastolic tricuspid annular velocity (A'), tissue Doppler imaging-derived systolic:diastolic duration ratio, and global late diastolic strain rate. End-diastolic pressure correlated significantly with tissue Doppler imaging-derived systolic:diastolic duration ratio. On multivariate analysis, tricuspid deceleration time, TimeE-E', and global early diastolic strain rate were independent predictors of τ, whereas tissue Doppler imaging-derived systolic:diastolic duration ratio was an independent predictor of dp/dt minimum. In general, correlations between echocardiographic and invasive parameters were better in the shunt group than in the nonshunt group. Echocardiography correlates with invasive reference measures of right ventricular diastolic function in children with PAH, although it does not differentiate between early versus late diastolic abnormalities. Newer echocardiographic techniques may have added value to assess right ventricular diastolic dysfunction in this population. © 2014 American Heart Association, Inc.

Radio Occultation Experiments with Venus Express and Mars Express using the Planetary Radio Interferometry and Doppler Experiment (PRIDE) Technique

NASA Astrophysics Data System (ADS)

Bocanegra Bahamon, T.; Gurvits, L.; Molera Calves, G.; Cimo, G.; Duev, D.; Pogrebenko, S.; Dirkx, D.; Rosenblatt, P.

2017-12-01

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can be used to enhance multiple radio science experiments of planetary missions. By 'eavesdropping' on the spacecraft signal using radio telescopes from different VLBI networks around the world, the PRIDE technique provides precise open-loop Doppler and VLBI observables to able to reconstruct the spacecraft's orbit. The application of this technique for atmospheric studies has been assessed by observing ESA's Venus Express (VEX) and Mars Express (MEX) during multiple Venus and Mars occultation events between 2012 and 2014. From these observing sessions density, temperature and pressure profiles of Venus and Mars neutral atmosphere and ionosphere have been retrieved. We present an error propagation analysis where the uncertainties of the atmospheric properties measured with this technique have been derived. These activities serve as demonstration of the applicability of the PRIDE technique for radio occultation studies, and provides a benchmark against the traditional Doppler tracking provided by the NASA's DSN and ESA's Estrack networks for these same purposes, in the framework of the upcoming ESA JUICE mission to the Jovian system.

Low-frequency high-definition power Doppler in visualizing and defining fetal pulmonary venous connections.

PubMed

Liu, Lin; He, Yihua; Li, Zhian; Gu, Xiaoyan; Zhang, Ye; Zhang, Lianzhong

2014-07-01

The use of low-frequency high-definition power Doppler in assessing and defining pulmonary venous connections was investigated. Study A included 260 fetuses at gestational ages ranging from 18 to 36 weeks. Pulmonary veins were assessed by performing two-dimensional B-mode imaging, color Doppler flow imaging (CDFI), and low-frequency high-definition power Doppler. A score of 1 was assigned if one pulmonary vein was visualized, 2 if two pulmonary veins were visualized, 3 if three pulmonary veins were visualized, and 4 if four pulmonary veins were visualized. The detection rate between Exam-1 and Exam-2 (intra-observer variability) and between Exam-1 and Exam-3 (inter-observer variability) was compared. In study B, five cases with abnormal pulmonary venous connection were diagnosed and compared to their anatomical examination. In study A, there was a significant difference between CDFI and low-frequency high-definition power Doppler for the four pulmonary veins observed (P < 0.05). The detection rate of each pulmonary vein when employing low-frequency high-definition power Doppler was higher than that when employing two-dimensional B-mode imaging or CDFI. There was no significant difference between the intra- and inter-observer variabilities using low-frequency high-definition power Doppler display of pulmonary veins (P > 0.05). The coefficient correlation between Exam-1 and Exam-2 was 0.844, and the coefficient correlation between Exam-1 and Exam-3 was 0.821. In study B, one case of total anomalous pulmonary venous return and four cases of partial anomalous pulmonary venous return were diagnosed by low-frequency high-definition power Doppler and confirmed by autopsy. The assessment of pulmonary venous connections by low-frequency high-definition power Doppler is advantageous. Pulmonary venous anatomy can and should be monitored during fetal heart examination.

Structural and functional optical coherence tomography imaging of the colon

NASA Astrophysics Data System (ADS)

Welge, Weston Anthony

Colorectal cancer (CRC) remains the second deadliest cancer in the United States, despite steady reduction in mortality rate over the last three decades. Colonoscopy is the gold-standard screening modality with high sensitivity and specificity to mature polyps. However, the miss rate for small (< 5 mm) lesions is estimated to be as high as 26%. Because the five-year survival rate for CRC detected at the local stage is 90%, there is a clear need for a screening procedure that is sensitive to these small lesions. Optical coherence tomography (OCT) has become a major biomedical imaging modality since its invention in 1991. As the optical analog to ultrasound, OCT provides information in both lateral and depth dimensions with resolution < 10 ?m and an imaging depth of about 1.5 mm in scattering tissue. In this dissertation, I describe my efforts to develop new uses of OCT for improved early detection of adenoma in the azoxymethane mouse model of CRC. In recent years, commercial OCT systems have reached imaging speeds sufficiently high for in vivo volumeric imaging while laterally sampling the tissue at the Nyquist limit. First, I describe the design of a miniature endoscope and the integration of this probe with a commercial OCT system. Then I describe the development of two OCT imaging methods, one structural and one functional, that could be used for future work in diagnostic or therapeutic studies. The structural method produces en face images of the colon surface showing the colonic crypts, the first such demonstration of crypt visualization in the mouse. Changes in the crypt pattern are correlated with adenoma and are one of the earliest morphological changes. The functional method uses a Doppler OCT algorithm and image processing to detect the colon microvasculature. This technique can be used for vessel counting and blood flow measurements. Angiogenesis occurs at the beginning of tumorigenesis, and the tumor-originated arterioles are incapable of regular vasodilation. This Doppler OCT technique could potentially detect tumors at the earliest stages by measuring the change in local blood flow velocity in response to vasodilatory stimuli.

Radar signal analysis of ballistic missile with micro-motion based on time-frequency distribution

NASA Astrophysics Data System (ADS)

Wang, Jianming; Liu, Lihua; Yu, Hua

2015-12-01

The micro-motion of ballistic missile targets induces micro-Doppler modulation on the radar return signal, which is a unique feature for the warhead discrimination during flight. In order to extract the micro-Doppler feature of ballistic missile targets, time-frequency analysis is employed to process the micro-Doppler modulated time-varying radar signal. The images of time-frequency distribution (TFD) reveal the micro-Doppler modulation characteristic very well. However, there are many existing time-frequency analysis methods to generate the time-frequency distribution images, including the short-time Fourier transform (STFT), Wigner distribution (WD) and Cohen class distribution, etc. Under the background of ballistic missile defence, the paper aims at working out an effective time-frequency analysis method for ballistic missile warhead discrimination from the decoys.

Ultrasound Thermal Field Imaging of Opaque Fluids

NASA Technical Reports Server (NTRS)

Andereck, C. David

1999-01-01

We have initiated an experimental program to develop an ultrasound system for non-intrusively imaging the thermal field in opaque fluids under an externally imposed temperature gradient. Many industrial processes involve opaque fluids, such as molten metals, semiconductors, and polymers, often in situations in which thermal gradients are important. For example, one may wish to understand semiconductor crystal growth dynamics in a Bridgman apparatus. Destructive testing of the crystal after the process is completed gives only indirect information about the fluid dynamics of the formation process. Knowledge of the coupled thermal and velocity fields during the growth process is then essential. Most techniques for non-intrusive velocity and temperature measurement in fluids are optical in nature, and hence the fluids studied must be transparent. In some cases (for example, LDV (laser Doppler velocimetry) and PIV (particle imaging velocimetry)) the velocities of small neutrally buoyant seed particles suspended in the fluid, are measured. Without particle seeding one can use the variation of the index of refraction of the fluid with temperature to visualize, through interferometric, Schlieren or shadowgraph techniques, the thermal field. The thermal field in turn gives a picture of the pattern existing in the fluid. If the object of study is opaque, non-optical techniques must be used. In this project we focus on the use of ultrasound, which propagates easily through opaque liquids and solids. To date ultrasound measurements have almost exclusively relied on the detection of sound scattered from density discontinuities inside the opaque material of interest. In most cases it has been used to visualize structural properties, but more recently the ultrasound Doppler velocimeter has become available. As in the optical case, it relies on seed particles that scatter Doppler shifted sound back to the detector. Doppler ultrasound techniques are, however, not useful for studying convective fluid flow in crystal growth, because particle seeding is unacceptable and flow velocities are typically too low to be resolved, and may be even lower in microgravity conditions where buoyancy forces are negligible. We will investigate a different use of ultrasound to probe the flows of opaque fluids non-intrusively and without the use of seed particles: our goal is to ultrasonically visualize the thermal field of opaque fluids with relatively high spatial resolution. The proposed technique relies upon the variation of sound speed with temperature of the fluid. A high frequency ultra-sound pulse passing through a fluid-filled chamber will traverse the chamber in a time determined by the relevant chamber dimension and the temperature of the fluid through which the pulse passes. With high time-resolution instrumentation that compares the excitation signal with the received pulse we can detect the influence of the fluid temperature on the pulse travel time. This is effectively an interferometric system, which in its optical form is an extremely sensitive approach to measuring thermal fields in fluids. Moreover, the temperature dependence of sound velocity in liquid metals is comparable to the temperature dependence of the speed of light required for accurate interferometric thermal images in transparent fluids. With an array of transducers scanned electronically a map of the thermal field over the chamber could be produced. An alternative approach would be to use the ultrasound analog of the shadowgraph technique. In the optical version, collimated light passes through the fluid, where it is focused or defocused locally by temperature field induced variations of the index of refraction. The resulting image reveals the thermal field through the spatial pattern of light intensity variations. By analogy, an ultrasound plane wave traversing an opaque fluid sample would be also locally focused or defocused depending on the speed of sound variations, giving rise to spatial variations in sound intensity that will reveal the thermal field pattern. These approaches could be applied to any situation in which temperature differences are expected to occur, and will rapidly provide information about the flow that simply cannot be obtained by any current intrusive or non-intrusive diagnostic technique. As materials processing in microgravity matures it will become increasingly important to have available simple and versatile diagnostic tools, such as we will develop, for studying the flows of opaque fluids under thermal forcing.

The role of modern diagnostic imaging in diagnosing and differentiating kidney diseases in children.

PubMed

Maliborski, Artur; Zegadło, Arkadiusz; Placzyńska, Małgorzata; Sopińska, Małgorzata; Lichosik, Marianna; Jobs, Katarzyna

2018-01-01

Urinary tract diseases are in the group of the most commonly diagnosed medical conditions in pediatric patients. Many diseases with different etiologies are accompanied by pain, fever, hematuria, or urinary tract dysfunction. Those most common ones in children are urinary tract infections and congenital malformation. They can also represent tumors or changes caused by systemic diseases. Clinical tests and even more often additional imaging studies are required to make a proper diagnosis of urinary tract diseases. Just a few decades ago urography, cystography or voiding cystourethrography were the main methods in diagnostic imaging of the urinary tract. Today's imaging methods supported by digital radiographic and fluoroscopy systems, high sensitivity detectors with quantum detection, advanced algorithms eliminating motion artifacts, modern medical imaging monitors with a resolution of three or even eight megapixels significantly differ from conventional radiographic methods. The methods that are currently usually performed are: computed tomography, magnetic resonance imaging, isotopic methods and ultrasonography using elastography and new solutions in Doppler imaging. Modern techniques are currently focused on reducing radiation exposure with better imaging capabilities. The development of these techniques became an essential diagnostic aid in nephrological and urological practice. The aim of this paper is to present the latest solutions that are currently used in the diagnostic imaging of urinary tract diseases.

Real time 3D structural and Doppler OCT imaging on graphics processing units

NASA Astrophysics Data System (ADS)

Sylwestrzak, Marcin; Szlag, Daniel; Szkulmowski, Maciej; Gorczyńska, Iwona; Bukowska, Danuta; Wojtkowski, Maciej; Targowski, Piotr

2013-03-01

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.

The use of indium-111 labeled platelet scanning for the detection of asymptomatic deep venous thrombosis in a high risk population

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siegel, R.S.; Rae, J.L.; Ryan, N.L.

Five hundred indium-111 labeled platelet imaging studies (387 donor and 113 autologous) were performed postoperatively in 473 patients who had undergone total hip replacement, total knee replacement, or internal fixation of a hip fracture to detect occult deep venous thrombosis. All patients had been anticoagulated prophylactically with aspirin, warfarin sodium (Coumadin), or dextran. Thirty-four possible cases of proximal deep venous thrombosis were identified in 28 asymptomatic patients. To verify the scan results, 31 venograms were performed in 25 patients (three refused). In 21 of 31 cases, totally occlusive thrombi were detected; in 5 cases, partially occlusive thrombi were detected; inmore » 5 cases, no thrombus was seen. No patient who had a negative scan nor any patient who had a verified positive scan (and received appropriate heparin therapy) subsequently developed symptoms or signs of pulmonary embolism. One hundred forty-one indium study patients also underwent Doppler ultrasonography/impedance plethysmography (Doppler/IPG) as a comparative non-invasive technique. In 137 cases, the results of the indium study and Doppler/IPG studies were congruent. The indium study had no false negative results that were detected by Doppler/IPG. No patient had any clinically evident toxicity. These results suggest that indium-111 labeled platelet scanning is a safe, noninvasive means for identifying DVT in high risk patients.« less

Swirling flow in a model of the carotid artery: Numerical and experimental study

NASA Astrophysics Data System (ADS)

Kotmakova, Anna A.; Gataulin, Yakov A.; Yukhnev, Andrey D.

2018-05-01

The present contribution is aimed at numerical and experimental study of inlet swirling flow in a model of the carotid artery. Flow visualization is performed both with the ultrasound color Doppler imaging mode and with CFD data postprocessing of swirling flows in a carotid artery model. Special attention is paid to obtaining data for the secondary motion in the internal carotid artery. Principal errors of the measurement technique developed are estimated using the results of flow calculations.

Developments in echocardiographic techniques for the evaluation of ventricular function in children.

PubMed

Dragulescu, Andreea; Mertens, Luc L

2010-01-01

Echocardiography is a very important tool for the diagnosis and follow-up of children with congenital and acquired heart disease. One of the challenges that remains in paediatric heart disease is the assessment of systolic and diastolic function in children, as this is influenced by growth, morphology and loading conditions. New echocardiographic techniques, such as tissue Doppler, deformation imaging and three-dimensional echocardiography, have great potential application in this field. They may provide new insights into the influence of growth, morphology and loading on cardiac mechanics, and could become useful clinical tools. In this review, we discuss the potential use and limitations of these new echocardiographic techniques in paediatric and congenital heart disease. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Arterial and Venous Doppler in Evaluation of the "At-Risk" Fetus.

PubMed

Turan, Sifa; Turan, Ozhan M

2017-09-01

Our practice utilizes Doppler ultrasound as one of the most objective and effective methods to assess at-risk pregnancies. This review will discuss the application of arterial and venous Doppler techniques in assessing and managing various diseases and conditions for high-risk fetuses.

Ultrafast Ultrasound Imaging of Ocular Anatomy and Blood Flow

PubMed Central

Urs, Raksha; Ketterling, Jeffrey A.; Silverman, Ronald H.

2016-01-01

Purpose Ophthalmic ultrasound imaging is currently performed with mechanically scanned single-element probes. These probes have limited capabilities overall and lack the ability to image blood flow. Linear-array systems are able to detect blood flow, but these systems exceed ophthalmic acoustic intensity safety guidelines. Our aim was to implement and evaluate a new linear-array–based technology, compound coherent plane-wave ultrasound, which offers ultrafast imaging and depiction of blood flow at safe acoustic intensity levels. Methods We compared acoustic intensity generated by a 128-element, 18-MHz linear array operated in conventionally focused and plane-wave modes and characterized signal-to-noise ratio (SNR) and lateral resolution. We developed plane-wave B-mode, real-time color-flow, and high-resolution depiction of slow flow in postprocessed data collected continuously at a rate of 20,000 frames/s. We acquired in vivo images of the posterior pole of the eye by compounding plane-wave images acquired over ±10° and produced images depicting orbital and choroidal blood flow. Results With the array operated conventionally, Doppler modes exceeded Food and Drug Administration safety guidelines, but plane-wave modalities were well within guidelines. Plane-wave data allowed generation of high-quality compound B-mode images, with SNR increasing with the number of compounded frames. Real-time color-flow Doppler readily visualized orbital blood flow. Postprocessing of continuously acquired data blocks of 1.6-second duration allowed high-resolution depiction of orbital and choroidal flow over the cardiac cycle. Conclusions Newly developed high-frequency linear arrays in combination with plane-wave techniques present opportunities for the evaluation of ocular anatomy and blood flow, as well as visualization and analysis of other transient phenomena such as vessel wall motion over the cardiac cycle and saccade-induced vitreous motion. PMID:27428169

Effects of red blood cell aggregates dissociation on the estimation of ultrasound speckle image velocimetry.

PubMed

Yeom, Eunseop; Nam, Kweon-Ho; Paeng, Dong-Guk; Lee, Sang-Joon

2014-08-01

Ultrasound speckle image of blood is mainly attributed by red blood cells (RBCs) which tend to form RBC aggregates. RBC aggregates are separated into individual cells when the shear force is over a certain value. The dissociation of RBC aggregates has an influence on the performance of ultrasound speckle image velocimetry (SIV) technique in which a cross-correlation algorithm is applied to the speckle images to get the velocity field information. The present study aims to investigate the effect of the dissociation of RBC aggregates on the estimation quality of SIV technique. Ultrasound B-mode images were captured from the porcine blood circulating in a mock-up flow loop with varying flow rate. To verify the measurement performance of SIV technique, the centerline velocity measured by the SIV technique was compared with that measured by Doppler spectrograms. The dissociation of RBC aggregates was estimated by using decorrelation of speckle patterns in which the subsequent window was shifted as much as the speckle displacement to compensate decorrelation caused by in-plane loss of speckle patterns. The decorrelation of speckles is considerably increased according to shear rate. Its variations are different along the radial direction. Because the dissociation of RBC aggregates changes ultrasound speckles, the estimation quality of SIV technique is significantly correlated with the decorrelation of speckles. This degradation of measurement quality may be improved by increasing the data acquisition rate. This study would be useful for simultaneous measurement of hemodynamic and hemorheological information of blood flows using only speckle images. Copyright © 2014 Elsevier B.V. All rights reserved.

Detection of cortical optical changes during seizure activity using optical coherence tomography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ornelas, Danielle; Hasan, Md.; Gonzalez, Oscar; Krishnan, Giri; Szu, Jenny I.; Myers, Timothy; Hirota, Koji; Bazhenov, Maxim; Binder, Devin K.; Park, Boris H.

2017-02-01

Electrophysiology has remained the gold standard of neural activity detection but its resolution and high susceptibility to noise and motion artifact limit its efficiency. Imaging techniques, including fMRI, intrinsic optical imaging, and diffuse optical imaging, have been used to detect neural activity, but rely on indirect measurements such as changes in blood flow. Fluorescence-based techniques, including genetically encoded indicators, are powerful techniques, but require introduction of an exogenous fluorophore. A more direct optical imaging technique is optical coherence tomography (OCT), a label-free, high resolution, and minimally invasive imaging technique that can produce depth-resolved cross-sectional and 3D images. In this study, we sought to examine non-vascular depth-dependent optical changes directly related to neural activity. We used an OCT system centered at 1310 nm to search for changes in an ex vivo brain slice preparation and an in vivo model during 4-AP induced seizure onset and propagation with respect to electrical recording. By utilizing Doppler OCT and the depth-dependency of the attenuation coefficient, we demonstrate the ability to locate and remove the optical effects of vasculature within the upper regions of the cortex from in vivo attenuation calculations. The results of this study show a non-vascular decrease in intensity and attenuation in ex vivo and in vivo seizure models, respectively. Regions exhibiting decreased optical changes show significant temporal correlation to regions of increased electrical activity during seizure. This study allows for a thorough and biologically relevant analysis of the optical signature of seizure activity both ex vivo and in vivo using OCT.

Analysing Simple Motions Using the Doppler Effect--"Seeing" Sound

ERIC Educational Resources Information Center

Stonawski, Tamás; Gálik, Tamás

2017-01-01

The Doppler effect has seen widespread use in the past hundred years. It is used for medical imaging, for measuring speed, temperature, direction, etc, and it makes the spatial relations of motion easy to map. The Doppler effect also allows GPS receivers to measure the speed of a vehicle significantly more accurately than dashboard speedometers.…

Photonic Doppler velocimetry lens array probe incorporating stereo imaging

DOEpatents

Malone, Robert M.; Kaufman, Morris I.

2015-09-01

A probe including a multiple lens array is disclosed to measure velocity distribution of a moving surface along many lines of sight. Laser light, directed to the moving surface is reflected back from the surface and is Doppler shifted, collected into the array, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to the multiple lens array. Numerous fibers in a fiber array project numerous rays to establish many measurement points at numerous different locations. One or more lens groups may be replaced with imaging lenses so a stereo image of the moving surface can be recorded. Imaging a portion of the surface during initial travel can determine whether the surface is breaking up.

Real-time microstructural and functional imaging and image processing in optical coherence tomography

NASA Astrophysics Data System (ADS)

Westphal, Volker

Optical Coherence Tomography (OCT) is a noninvasive optical imaging technique that allows high-resolution cross-sectional imaging of tissue microstructure, achieving a spatial resolution of about 10 mum. OCT is similar to B-mode ultrasound (US) except that it uses infrared light instead of ultrasound. In contrast to US, no coupling gel is needed, simplifying the image acquisition. Furthermore, the fiber optic implementation of OCT is compatible with endoscopes. In recent years, the transition from slow imaging, bench-top systems to real-time clinical systems has been under way. This has lead to a variety of applications, namely in ophthalmology, gastroenterology, dermatology and cardiology. First, this dissertation will demonstrate that OCT is capable of imaging and differentiating clinically relevant tissue structures in the gastrointestinal tract. A careful in vitro correlation study between endoscopic OCT images and corresponding histological slides was performed. Besides structural imaging, OCT systems were further developed for functional imaging, as for example to visualize blood flow. Previously, imaging flow in small vessels in real-time was not possible. For this research, a new processing scheme similar to real-time Doppler in US was introduced. It was implemented in dedicated hardware to allow real-time acquisition and overlayed display of blood flow in vivo. A sensitivity of 0.5mm/s was achieved. Optical coherence microscopy (OCM) is a variation of OCT, improving the resolution even further to a few micrometers. Advances made in the OCT scan engine for the Doppler setup enabled real-time imaging in vivo with OCM. In order to generate geometrical correct images for all the previous applications in real-time, extensive image processing algorithms were developed. Algorithms for correction of distortions due to non-telecentric scanning, nonlinear scan mirror movements, and refraction were developed and demonstrated. This has led to interesting new applications, as for example in imaging of the anterior segment of the eye.

As-built performance of the monolithic interferometers for MIGHTI, the thermsopheric wind and temperature instrument on the Ionospheric Connection Explorer (ICON)

NASA Astrophysics Data System (ADS)

Harlander, J.; Englert, C. R.; Brown, C. M.; Marr, K. D.; Miller, I. J.; Zastera, V.; Bach, B.; Mende, S. B.

2016-12-01

The Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) is one of four instruments on the NASA-sponsored Ionospheric Connection (ICON) Explorer mission. ICON investigates the extreme variability of the Earth's ionosphere with a unique combination of sensors on-board a low Earth orbit satellite. MIGHTI uses the Doppler Asymmetric Spatial Heterodyne (DASH) Spectroscopy technique to derive thermospheric winds by measuring Doppler shifts of atomic oxygen airglow emission lines in the visible spectrum over an altitude range generally not accessible to in-situ probes. Specifically, MIGHTI measures neutral winds utilizing the atomic oxygen O(1S - 1D) transition at 557.7 nm (green line) and the O(1D - 3P) transition at 630.0 nm (red line). In addition, it uses a multiband photometric technique to derive thermospheric temperatures from the spectral shape of the molecular oxygen A-band in the near infrared near 760 nm. Two identical MIGHTI interferometers, oriented on the spacecraft to view a common atmospheric volume from orthogonal lines of sight. Both instruments use the Doppler Asymmetric Spatial Heterodyne (DASH) approach with low order Echelle gratings optimized for the red, green, and near infrared wavelengths detected by MIGHTI. The design of the monolithic DASH interferometers which are the heart of the MIGHTI instrument will be reviewed followed by a description of the interferometer element fabrication, assembly and their as-built performance.

Detecting and mitigating wind turbine clutter for airspace radar systems.

PubMed

Wang, Wen-Qin

2013-01-01

It is well recognized that a wind turbine has a large radar cross-section (RCS) and, due to the movement of the blades, the wind turbine will generate a Doppler frequency shift. This scattering behavior may cause severe interferences on existing radar systems including static ground-based radars and spaceborne or airborne radars. To resolve this problem, efficient techniques or algorithms should be developed to mitigate the effects of wind farms on radars. Herein, one transponder-based mitigation technique is presented. The transponder is not a new concept, which has been proposed for calibrating high-resolution imaging radars. It modulates the radar signal in a manner that the retransmitted signals can be separated from the scene echoes. As wind farms often occupy only a small area, mitigation processing in the whole radar operation will be redundant and cost inefficient. Hence, this paper uses a transponder to determine whether the radar is impacted by the wind farms. If so, the effects of wind farms are then mitigated with subsequent Kalman filtering or plot target extraction algorithms. Taking airborne synthetic aperture radar (SAR) and pulse Doppler radar as the examples, this paper provides the corresponding system configuration and processing algorithms. The effectiveness of the mitigation technique is validated by numerical simulation results.

Detecting and Mitigating Wind Turbine Clutter for Airspace Radar Systems

PubMed Central

2013-01-01

It is well recognized that a wind turbine has a large radar cross-section (RCS) and, due to the movement of the blades, the wind turbine will generate a Doppler frequency shift. This scattering behavior may cause severe interferences on existing radar systems including static ground-based radars and spaceborne or airborne radars. To resolve this problem, efficient techniques or algorithms should be developed to mitigate the effects of wind farms on radars. Herein, one transponder-based mitigation technique is presented. The transponder is not a new concept, which has been proposed for calibrating high-resolution imaging radars. It modulates the radar signal in a manner that the retransmitted signals can be separated from the scene echoes. As wind farms often occupy only a small area, mitigation processing in the whole radar operation will be redundant and cost inefficient. Hence, this paper uses a transponder to determine whether the radar is impacted by the wind farms. If so, the effects of wind farms are then mitigated with subsequent Kalman filtering or plot target extraction algorithms. Taking airborne synthetic aperture radar (SAR) and pulse Doppler radar as the examples, this paper provides the corresponding system configuration and processing algorithms. The effectiveness of the mitigation technique is validated by numerical simulation results. PMID:24385880

Neovascularity in patellar tendinopathy and the response to eccentric training: a case report using Power Doppler ultrasound.

PubMed

McCreesh, Karen M; Riley, Sara J; Crotty, James M

2013-12-01

This report describes the case of an amateur soccer player with chronic patellar tendinopathy who underwent ultrasound imaging before and after engaging in an 8-week programme of eccentric exercise. On initial assessment, greyscale ultrasound imaging demonstrated tendon thickening and reduced echogenicity, while Power Doppler imaging demonstrated a large amount of neovascularity. After 8 weeks of an eccentric loading programme, the patient reported significantly improved symptoms and functional scores, while follow-up imaging demonstrated improvement in the echo appearance of the tendon and complete resolution of the neovascularity. The association between neovascularity and symptoms in tendinopathy research is conflicting, with a paucity of research in the area of patellar tendinopathy. While further research is needed to clarify the significance of greyscale and Power Doppler ultrasound changes in relation to symptoms in patellar tendinopathy, ultrasound imaging was shown to be a useful adjunct to diagnosis and outcome assessment in this case. Copyright © 2012 Elsevier Ltd. All rights reserved.

Velocity Statistics and Spectra in Three-Stream Jets

NASA Technical Reports Server (NTRS)

Ecker, Tobias; Lowe, K. Todd; Ng, Wing F.; Henderson, Brenda; Leib, Stewart

2016-01-01

Velocimetry measurements were obtained in three-stream jets at the NASA Glenn Research Center Nozzle Acoustics Test Rig using the time-resolved Doppler global velocimetry technique. These measurements afford exceptional frequency response, to 125 kHz bandwidth, in order to study the detailed dynamics of turbulence in developing shear flows. Mean stream-wise velocity is compared to measurements acquired using particle image velocimetry for validation. Detailed results for convective velocity distributions throughout an axisymmetric plume and the thick side of a plume with an offset third-stream duct are provided. The convective velocity results exhibit that, as expected, the eddy speeds are reduced on the thick side of the plume compared to the axisymmetric case. The results indicate that the time-resolved Doppler global velocimetry method holds promise for obtaining results valuable to the implementation and refinement of jet noise prediction methods being developed for three-stream jets.

[The temporomandibular joint in juvenile idiopathic arthritis: what radiologists need to look for on magnetic resonance imaging].

PubMed

De La Hoz Polo, M; Navallas, M

2014-01-01

The term "juvenile idiopathic arthritis" (JIA) encompasses a group of arthritis of unknown cause with onset before the age of 16 years that last for at least 6 weeks. The prevalence of temporomandibular joint involvement in published series ranges from 17% to 87%. Temporomandibular joint involvement is difficult to detect clinically, so imaging plays a key role in diagnosis and monitoring treatment. MRI is the technique of choice for the study of arthritis of the temporomandibular joint because it is the most sensitive technique for detecting acute synovitis and bone edema. Power Doppler ultrasonography can also detect active synovitis by showing the hypervascularization of the inflamed synovial membrane, but it cannot identify bone edema. This article describes the MRI technique for evaluating the temporomandibular joint in patients with juvenile idiopathic arthritis, defines the parameters to look for, and illustrates the main findings. Copyright © 2013 SERAM. Published by Elsevier Espana. All rights reserved.

Combined DEM Extration Method from StereoSAR and InSAR

NASA Astrophysics Data System (ADS)

Zhao, Z.; Zhang, J. X.; Duan, M. Y.; Huang, G. M.; Yang, S. C.

2015-06-01

A pair of SAR images acquired from different positions can be used to generate digital elevation model (DEM). Two techniques exploiting this characteristic have been introduced: stereo SAR and interferometric SAR. They permit to recover the third dimension (topography) and, at the same time, to identify the absolute position (geolocation) of pixels included in the imaged area, thus allowing the generation of DEMs. In this paper, StereoSAR and InSAR combined adjustment model are constructed, and unify DEM extraction from InSAR and StereoSAR into the same coordinate system, and then improve three dimensional positioning accuracy of the target. We assume that there are four images 1, 2, 3 and 4. One pair of SAR images 1,2 meet the required conditions for InSAR technology, while the other pair of SAR images 3,4 can form stereo image pairs. The phase model is based on InSAR rigorous imaging geometric model. The master image 1 and the slave image 2 will be used in InSAR processing, but the slave image 2 is only used in the course of establishment, and the pixels of the slave image 2 are relevant to the corresponding pixels of the master image 1 through image coregistration coefficient, and it calculates the corresponding phase. It doesn't require the slave image in the construction of the phase model. In Range-Doppler (RD) model, the range equation and Doppler equation are a function of target geolocation, while in the phase equation, the phase is also a function of target geolocation. We exploit combined adjustment model to deviation of target geolocation, thus the problem of target solution is changed to solve three unkonwns through seven equations. The model was tested for DEM extraction under spaceborne InSAR and StereoSAR data and compared with InSAR and StereoSAR methods respectively. The results showed that the model delivered a better performance on experimental imagery and can be used for DEM extraction applications.

A New Era in Diagnostic Ultrasound, Superb Microvascular Imaging: Preliminary Results in Pediatric Hepato-Gastrointestinal Disorders.

PubMed

Ohno, Yasuharu; Fujimoto, Tamotsu; Shibata, Yukari

2017-02-01

Introduction  Superb microvascular imaging is a new ultrasound image processing technique that uses advanced clutter suppression to extract flow signals from vessels and which helps us visualize very small vascular structures that were not previously visible without the use of a contrast agent. We herein analyzed the usefulness of superb microvascular imaging in the diagnosis of hepato-gastrointestinal disorders in pediatric patients. Materials and Methods  Fifty-six pediatric patients who underwent a total of 81 superb microvascular imaging examinations with an Aplio 300 ultrasound system (Toshiba Medical Systems, Tokyo, Japan) were enrolled in this study. The subjects underwent conventional ultrasound examinations, including Doppler imaging followed by superb microvascular imaging. The superb microvascular imaging findings and standard imaging were compared. All of the examinations were performed without sedation. Results  The average age of the patients (male, n  = 38; female, n  = 18) was 4 years. The clinical diagnoses included hepatobiliary disorders ( n  = 29), acute appendicitis ( n  = 10), and other intestinal disorders ( n  = 17). The target organs for superb microvascular imaging were the liver, appendix, rectum, intestine, gallbladder, and lymph node. In most of the patients, superb microvascular imaging achieved the excellent visualization of microvascular structures, revealing abnormal vasculature in 21 out of 46 (45.7%) examinations of the liver, 9/9 (100%) examinations of the appendix, 0/11 (0%) examinations of the rectum, 9/11 (81.8%) examinations of the intestine, 0/1 (0%) examinations of the gallbladder, and 3/3 (100%) examinations of the lymph nodes. Superb microvascular imaging was superior to Doppler imaging for depicting the microvascular structures. Conclusions  Superb microvascular imaging is especially useful for depicting the microvascular flow and can aid in the diagnosis and treatment planning for pediatric patients with hepato-gastrointestinal disorders. Georg Thieme Verlag KG Stuttgart · New York.

Feasibility assessment of Doppler radar long-term physiological measurements.

PubMed

Massagram, Wansuree; Lubecke, Victor M; Boric-Lubecke, Olga

2011-01-01

In this paper we examine the feasibility of applying doppler radar technique for a long-term health monitoring. Doppler radar was used to detect and eliminate periods of significant motion. This technique was verified using a human study on 17 subjects, and it was determined that for 15 out of 17 subjects there was no significant motion for over 85% of the measurement interval in supine positions. Majority of subjects exhibited significantly less motion in supine position, which is promising for sleep monitoring, and monitoring of hospitalized patients.

Magnetic Doppler imaging of the chemically peculiar star HD 125248

NASA Astrophysics Data System (ADS)

Rusomarov, N.; Kochukhov, O.; Ryabchikova, T.; Ilyin, I.

2016-04-01

Context. Intermediate-mass, chemically peculiar stars with strong magnetic fields provide an excellent opportunity to study the topology of their surface magnetic fields and the interplay between magnetic geometries and abundance inhomogeneities in the atmospheres of these stars. Aims: We reconstruct detailed maps of the surface magnetic field and abundance distributions for the magnetic Ap star HD 125248. Methods: We performed the analysis based on phase-resolved, four Stokes parameter spectropolarimetric observations obtained with the HARPSpol instrument. These data were interpreted with the help of magnetic Doppler imaging techniques and model atmospheres taking the effects of strong magnetic fields and nonsolar chemical composition into account. Results: We improved the atmospheric parameters of the star, Teff = 9850 ± 250 K and log g = 4.05 ± 0.10. We performed detailed abundance analysis, which confirmed that HD 125248 has abundances typical of other Ap stars, and discovered significant vertical stratification effects for the Fe II and Cr II ions. We computed LSD Stokes profiles using several line masks corresponding to Fe-peak and rare earth elements, and studied their behavior with rotational phase. Combining previous longitudinal field measurements with our own observations, we improved the rotational period of the star Prot = 9.29558 ± 0.00006 d. Magnetic Doppler imaging of HD 125248 showed that its magnetic field is mostly poloidal and quasi-dipolar with two large spots of different polarity and field strength. The chemical maps of Fe, Cr, Ce, Nd, Gd, and Ti show abundance contrasts of 0.9-3.5 dex. Among these elements, the Fe abundance map does not show high-contrast features. Cr is overabundant around the negative magnetic pole and has 3.5 dex abundance range. The rare earth elements and Ti are overabundant near the positive magnetic pole. Conclusions: The magnetic field of HD 125248 has strong deviations from the classical oblique dipole field geometry. A comparison of the magnetic field topology of HD 125248 with the results derived for other stars using four Stokes magnetic Doppler imaging suggests evidence that the field topology becomes simpler with increasing age. The abundance maps show weak correlation with magnetic field geometry, but they do not agree with the theoretical atomic diffusion calculations, which predict element accumulation in the horizontal field regions. Based on observations collected at the European Southern Observatory, Chile (ESO programs 088.D-0066, 090.D-0256).

Combined use of Doppler OCT and en face OCT functions for discrimination of an aneurysm in the lamina cribrosa from a disc hemorrhage.

PubMed

Holló, Gábor

2015-12-01

In addition to retinal nerve fiber layer thickness measurements, the recently introduced AngioVue optical coherence tomography (OCT) offers corresponding layer-by-layer Doppler OCT and en face OCT functions, for simultaneous evaluation of perfusion and structure of the optic nerve head. We investigated the clinical usefulness of combined use of Doppler and en face Fourier-domain OCT functions of the AngioVue Fourier-domain OCT for discrimination of a disc hemorrhage and a disc hemorrhage-like atypical vessel structure located deep in the lamina cribrosa. We present our findings with AngioVue OCT on a disc hemorrhage and a spatially related retinal nerve fiber layer bundle defect in a glaucomatous eye (case 1). Both alterations were detected on en face OCT images without any Doppler OCT signal. We also report on an aneurysm suggestive for a disc hemorrhage on clinical examination and disc photography in a treated ocular hypertensive eye (case 2). The aneurysm was within the lamina cribrosa tissue at the border of the cup and the neuroretinal rim. This vascular structure produced strong Doppler signals but no structurally detectable signs on the en face OCT images. Combined evaluation of corresponding Doppler OCT and en face OCT images enables ophthalmologists to easily separate true disc hemorrhages from disc hemorrhage-like deep vascular structures. This is of clinical significance in preventing unnecessary intensification of pressure-lowering treatment in glaucoma.

Two-dimensional multi-frequency imaging of a tumor inclusion in a homogeneous breast phantom using the harmonic motion Doppler imaging method.

PubMed

Tafreshi, Azadeh Kamali; Top, Can Barış; Gençer, Nevzat Güneri

2017-06-21

Harmonic motion microwave Doppler imaging (HMMDI) is a novel imaging modality for imaging the coupled electrical and mechanical properties of body tissues. In this paper, we used two experimental systems with different receiver configurations to obtain HMMDI images from tissue-mimicking phantoms at multiple vibration frequencies between 15 Hz and 35 Hz. In the first system, we used a spectrum analyzer to obtain the Doppler data in the frequency domain, while in the second one, we used a homodyne receiver that was designed to acquire time-domain data. The developed phantoms mimicked the elastic and dielectric properties of breast fat tissue, and included a [Formula: see text] mm cylindrical inclusion representing the tumor. A focused ultrasound probe was mechanically scanned in two lateral dimensions to obtain two-dimensional HMMDI images of the phantoms. The inclusions were resolved inside the fat phantom using both experimental setups. The image resolution increased with increasing vibration frequency. The designed receiver showed higher sensitivity than the spectrum analyzer measurements. The results also showed that time-domain data acquisition should be used to fully exploit the potential of the HMMDI method.

Two-dimensional multi-frequency imaging of a tumor inclusion in a homogeneous breast phantom using the harmonic motion Doppler imaging method

NASA Astrophysics Data System (ADS)

Kamali Tafreshi, Azadeh; Barış Top, Can; Güneri Gençer, Nevzat

2017-06-01

Harmonic motion microwave Doppler imaging (HMMDI) is a novel imaging modality for imaging the coupled electrical and mechanical properties of body tissues. In this paper, we used two experimental systems with different receiver configurations to obtain HMMDI images from tissue-mimicking phantoms at multiple vibration frequencies between 15 Hz and 35 Hz. In the first system, we used a spectrum analyzer to obtain the Doppler data in the frequency domain, while in the second one, we used a homodyne receiver that was designed to acquire time-domain data. The developed phantoms mimicked the elastic and dielectric properties of breast fat tissue, and included a 14~\\text{mm}× 9 mm cylindrical inclusion representing the tumor. A focused ultrasound probe was mechanically scanned in two lateral dimensions to obtain two-dimensional HMMDI images of the phantoms. The inclusions were resolved inside the fat phantom using both experimental setups. The image resolution increased with increasing vibration frequency. The designed receiver showed higher sensitivity than the spectrum analyzer measurements. The results also showed that time-domain data acquisition should be used to fully exploit the potential of the HMMDI method.

Augmented reality and dynamic infrared thermography for perforator mapping in the anterolateral thigh.

PubMed

Cifuentes, Ignacio Javier; Dagnino, Bruno Leonardo; Salisbury, María Carolina; Perez, María Eliana; Ortega, Claudia; Maldonado, Daniela

2018-05-01

Dynamic infrared thermography (DIRT) has been used for the preoperative mapping of cutaneous perforators. This technique has shown a positive correlation with intraoperative findings. Our aim was to evaluate the accuracy of perforator mapping with DIRT and augmented reality using a portable projector. For this purpose, three volunteers had both of their anterolateral thighs assessed for the presence and location of cutaneous perforators using DIRT. The obtained image of these "hotspots" was projected back onto the thigh and the presence of Doppler signals within a 10-cm diameter from the midpoint between the lateral patella and the anterior superior iliac spine was assessed using a handheld Doppler device. Hotspots were identified in all six anterolateral thighs and were successfully projected onto the skin. The median number of perforators identified within the area of interest was 5 (range, 3-8) and the median time needed to identify them was 3.5 minutes (range, 3.3-4.0 minutes). Every hotspot was correlated to a Doppler sound signal. In conclusion, augmented reality can be a reliable method for transferring the location of perforators identified by DIRT onto the thigh, facilitating its assessment and yielding a reliable map of potential perforators for flap raising.

[Parenchymal complications of the transplanted kidney: the role of color-Doppler imaging].

PubMed

Granata, Antonio; Clementi, Silvia; Clementi, Anna; Di Pietro, Fabio; Scarfia, Viviana R; Insalaco, Monica; Aucella, Filippo; Prencipe, Michele; Fiorini, Fulvio; Sicurezza, Elvia

2012-01-01

Kidney transplantation is the treatment of choice for end-stage renal disease, given the better quality of life of transplanted patients when compared to patients on maintenance dialysis. In spite of surgical improvements and new immunosuppressive regimens, part of the transplanted grafts still develop chronic dysfunction. Ultrasonography, both in B-mode and with Doppler ultrasound, is an important diagnostic tool in case of clinical conditions which might impair kidney function. Even though ultrasonography is considered fundamental in the diagnosis of vascular and surgical complications of the transplanted kidney, its role is not fully understood in case of parenchymal complications of the graft. The specificity of Doppler ultrasound is low both in case of acute complications such as acute tubular necrosis, drug toxicity and acute rejection, and in case of chronic conditions such as chronic allograft nephropathy. Single determinations of resistance indices present low diagnostic accuracy, which is higher in case of successive measurements performed during the follow-up of the graft. Modern techniques including tissue pulsatility index, maximal fractional area and contrast-enhanced ultrasound increase the diagnostic power of ultrasonography in case of parenchymal complications of the transplanted kidney.

[Ultrasound and color Doppler applications in nephrology. The normal kidney: anatomy, vessels and congenital anomalies].

PubMed

Meola, Mario; Petrucci, Ilaria; Giovannini, Lisa; Samoni, Sara; Dellafiore, Carolina

2012-01-01

Gray-scale ultrasound is the diagnostic technique of choice in patients with suspected or known renal disease. Knowledge of the normal and abnormal sonographic morphology of the kidney and urinary tract is essential for a successful diagnosis. Conventional sonography must always be complemented by Doppler sampling of the principal arterial and venous vessels. B-mode scanning is performed with the patient in supine, prone or side position. The kidney can be imaged by the anterior, lateral or posterior approach using coronal, transverse and oblique scanning planes. Morphological parameters that must be evaluated are the coronal diameter, the parenchymal thickness and echogenicity, the structure and state of the urinary tract, and the presence of congenital anomalies that may mimic a pseudomass. The main renal artery and the hilar-intraparenchymal branches of the arterial and venous vessels should be accurately evaluated using color Doppler. Measurement of intraparenchymal resistance indices (IP, IR) provides an indirect and quantitative parameter of the stiffness and eutrophic or dystrophic remodeling of the intrarenal microvasculature. These parameters differ depending on age, diabetic and hypertensive disease, chronic renal glomerular disease, and interstitial, vascular and obstructive nephropathy.

The effects of probe placement on measured flow velocity in transcranial Doppler ultrasound imaging in-vitro and in-vivo experiments

NASA Astrophysics Data System (ADS)

de Jong, Daan L. K.; Meel-van den Abeelen, Aisha S. S.; Lagro, Joep; Claassen, Jurgen A. H. R.; Slump, Cornelis H.

2014-03-01

The measurement of the blood flow in the middle cerebral artery (MCA) using transcranial Doppler ultrasound (US) imaging is clinically relevant for the study of cerebral autoregulation. Especially in the aging population, impairement of the autoregulation may coincide or relate to loss of perfusion and consequently loss of brain function. The cerebral autoregulation can be assessed by relating the blood pressure to the blood flow in the brain. Doppler US is a widely used, non-invasive method to measure the blood flow in the MCA. However, Doppler flow imaging is known to produce results that are dependent of the operator. The angle of the probe insonation with respect to the centerline of the blood vessel is a well known factor for output variability. In patients also the skull must be traversed and the MCA must be detected, influencing the US signal intensity. In this contribution we report two studies. We describe first an in-vitro setup to study the Doppler flow in a situation where the ground truth is known. Secondly, we report on a study with healthy volunteers where the effects of small probe displacements on the flow velocity signals are investigated. For the latter purpose, a special probe holder was designed to control the experiment.

Intrahepatic portosystemic venous shunt: diagnosis by color Doppler imaging.

PubMed

Kudo, M; Tomita, S; Tochio, H; Minowa, K; Todo, A

1993-05-01

Intrahepatic portosystemic venous shunt is a rare clinical entity; only 33 such cases have been reported. It may be congenital, or secondary to portal hypertension. Five patients with this disorder are presented, each of whom was diagnosed by color Doppler imaging, including waveform spectral analysis. One patient with clinical evidence of cirrhosis and portal hypertension had episodes of hepatic encephalopathy and elevated blood levels of ammonia. This patient had a large tubular shunt between the posterior branch of the portal vein and the inferior vena cava. Shunts of this type are considered to be collateral pathways which develop in the hepatic parenchyma as a result of portal hypertension. The other four patients had no evidence of liver disease, and all four evidenced an aneurysmal portohepatic venous shunt within the liver parenchyma. Shunts of this type are considered congenital. The diagnosis of intrahepatic portosystemic venous shunts was established by color Doppler imaging, which demonstrated a direct communication of color flow signals between the portal vein and hepatic vein, in addition to the characterization of the Doppler spectrum at each sampling point from a continuous waveform signal (portal vein) to a turbulent signal (aneurysmal cavity), and finally, to a biphasic waveform signal (hepatic vein). As demonstrated by the five patients, color Doppler imaging is useful in the diagnosis of an intrahepatic portosystemic hepatic venous shunt, and the measurement of shunt ratio may be useful in the follow-up and determining the therapeutic option.

Oxygen consumption estimation with combined color doppler ultrasound and photoacoustic microscopy: a phantom study

NASA Astrophysics Data System (ADS)

Jiang, Yan; Harrison, Tyler; Forbrich, Alex; Zemp, Roger J.

2011-03-01

The metabolic rate of oxygen consumption (MRO2) quantifies tissue metabolism, which is important for diagnosis of many diseases. For a single vessel model, the MRO2 can be estimated in terms of the mean flow velocity, vessel crosssectional area, total concentration of hemoglobin (CHB), and the difference between the oxygen saturation (sO2) of blood flowing into and out of the tissue region. In this work, we would like to show the feasibility to estimate MRO2 with our combined photoacoustic and high-frequency ultrasound imaging system. This system uses a swept-scan 25-MHz ultrasound transducer with confocal dark-field laser illumination optics. A pulse-sequencer enables ultrasonic and laser pulses to be interlaced so that photoacoustic and Doppler ultrasound images are co-registered. Since the mean flow velocity can be measured by color Doppler ultrasound, the vessel cross-sectional area can be measured by power Doppler or photoacoustic imaging, and multi-wavelength photoacoustic methods can be used to estimate sO2 and CHB, all of these parameters necessary for MRO2 estimation can be provided by our system. Experiments have been performed on flow phantoms to generate co-registered color Doppler and photoacoustic images. To verify the sO2 estimation, two ink samples (red and blue) were mixed in various concentration ratios to mimic different levels of sO2, and the result shows a good match between the calculated concentration ratios and actual values.

The Supraclavicular Artery Perforator Flap: A Comparative Study of Imaging Techniques Used in Preoperative Mapping.

PubMed

Sheriff, Hemin Oathman; Mahmood, Kawa Abdullah; Hamawandi, Nzar; Mirza, Aram Jamal; Hawas, Jawad; Moreno, Esther Granell; Clavero, Juan Antonio; Hankins, Christopher; Masia, Jaume

2018-05-18

 The supraclavicular artery flap is an excellent flap for head and neck reconstruction. The aim of this study is to assess imaging techniques to define the precise vascular boundaries of this flap.  Six imaging techniques were used for supraclavicular artery mapping in 65 cases; handheld Doppler, triplex ultrasound, computed tomography angiography, magnetic resonance angiography, digital subtraction angiography, and indocyanine green angiography. We checked the site of the perforators, the course of a supraclavicular artery, and anatomical mapping of the supraclavicular artery.  Handheld Doppler identified perforators' sites in 80% of the cases but showed no results for the course of the vessel. Triplex ultrasound identified the site of perforators in 52.9%, and partial mapping of the course of a supraclavicular artery in 64.7% of the cases. Computerized tomography angiography showed the site of perforators in 60%, and the course of supraclavicular artery completely in 45%, and partially in an additional 30%of the cases examined. Magnetic resonance angiography showed negative results for all parameters. Digital subtraction angiography showed the partial course of a supraclavicular artery in 62.5%, but showed no perforators. Indocyanine green angiography showed the site of perforators in 60% and a partial course of supraclavicular artery distal to perforators in 60%.Anatomical mapping of the vessel was possible with computerized tomography angiogram completely in 45%, and partially in 30%, and was also possible with indocyanine green angiography partially in 60%.  Computerized tomography angiography showed best results in the mapping of the supraclavicular artery, but with an inability to define the perforator perfusion territories, and also with risks of irradiation, while indocyanine green angiography is a good alternative as it could precisely map the superficial course of the artery and angiosomes, with no radiation exposure. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Linear prediction data extrapolation superresolution radar imaging

NASA Astrophysics Data System (ADS)

Zhu, Zhaoda; Ye, Zhenru; Wu, Xiaoqing

1993-05-01

Range resolution and cross-range resolution of range-doppler imaging radars are related to the effective bandwidth of transmitted signal and the angle through which the object rotates relatively to the radar line of sight (RLOS) during the coherent processing time, respectively. In this paper, linear prediction data extrapolation discrete Fourier transform (LPDEDFT) superresolution imaging method is investigated for the purpose of surpassing the limitation imposed by the conventional FFT range-doppler processing and improving the resolution capability of range-doppler imaging radar. The LPDEDFT superresolution imaging method, which is conceptually simple, consists of extrapolating observed data beyond the observation windows by means of linear prediction, and then performing the conventional IDFT of the extrapolated data. The live data of a metalized scale model B-52 aircraft mounted on a rotating platform in a microwave anechoic chamber and a flying Boeing-727 aircraft were processed. It is concluded that, compared to the conventional Fourier method, either higher resolution for the same effective bandwidth of transmitted signals and total rotation angle of the object or equal-quality images from smaller bandwidth and total angle may be obtained by LPDEDFT.

Three-dimensional power Doppler sonography in screening for carotid artery disease.

PubMed

Keberle, M; Jenett, M; Beissert, M; Jahns, R; Haerten, R; Hahn, D

2000-01-01

Color Doppler sonography has gained considerable recognition as a noninvasive method to detect carotid artery disease and to assess the degree of carotid artery stenosis. However, results are highly operator-dependent and cannot be presented as survey images. The purpose of this study was to evaluate real-time 3-dimensional (3D) power Doppler sonography as a method for screening for atherosclerosis in the carotid arteries. We prospectively screened 75 patients for carotid artery disease using both conventional color Doppler sonography and 3D power Doppler sonography, and the results from the 2 modalities were compared. A total of 150 common carotid arteries, 150 internal carotid arteries, and 150 external carotid arteries were examined utilizing a 7.5-MHz linear-array transducer combined with tissue harmonic imaging. Color Doppler sonography detected 297 normal or atherosclerotic arteries without stenosis, 57 arteries with mild (1-49%) stenosis, 41 with moderate (50-69%) stenosis, 32 with severe (70-99%) stenosis, and 9 with occlusions. The degree of stenosis determined by color Doppler sonography correlated with that determined by 3D power Doppler sonography (r = 0.982-0.998). Moreover, there was a good correlation between the measurements for both the length of the lesion and its distance from the bulb as determined by the 3D volume surveys and by color Doppler sonography (r = 0.986). The interobserver variability rate was 3.7% +/- 0.5%. Generally, the acquisition and reconstruction of the 3D data took less than 5 minutes. 3D power Doppler sonography is easy to perform and is an accurate method in screening for atherosclerotic lesions of the carotid arteries. Moreover, it provides excellent 3D volume surveys that may be helpful in the planning of surgical treatment. Copyright 2000 John Wiley & Sons, Inc.

Coherent Doppler lidar for measurements of wind fields

NASA Technical Reports Server (NTRS)

Menzies, Robert T.; Hardesty, R. Michael

1989-01-01

The signal-processing techniques for obtaining the velocity estimates and the fundamental factors that influence coherent lidar performance are considered. The similarities and distinctions between Doppler lidar and Doppler radars are discussed. The capability of coherent Doppler lidars for mapping wind fields over selected regions in the lower atmosphere and greatly enhancing the capability to visualize flow patterns in real time is discussed, and examples are given. Salient features of a concept for an earth-orbiting Doppler lidar to be launched in the late 1990s are examined.

A unique case of "double-orifice aortic valve"-comprehensive assessment by 2-, 3-dimensional, and color Doppler echocardiography.

PubMed

Stirrup, James E; Cowburn, Peter J; Pousios, Dimitrios; Ohri, Sunil K; Shah, Benoy N

2016-09-01

Transesophageal echocardiography (TEE) is a powerful imaging tool for the comprehensive assessment of valvular structure and function. TEE may be of added benefit when anatomy is difficult to delineate accurately by transthoracic echocardiography. In this article, we present 2-, 3-dimensional, and color Doppler TEE images from a male patient with aortic stenosis. A highly unusual and complex pattern of valvular calcification created a functionally "double-orifice" valve. Such an abnormality may have implications for the accuracy of continuous-wave Doppler echocardiography, which assumes a single orifice valve in native aortic valves. © 2016, Wiley Periodicals, Inc.

A study on the measurement of radar cross section of flighting model based on the range-Doppler imaging

NASA Astrophysics Data System (ADS)

Hashimoto, Osamu; Mizokami, Osamu

The method for measuring radar cross section (RCS) based on Range-Doppler Imaging is discussed. In this method, the measured targets are rotated and the Doppler frequencies caused by each scattering element along the targets are analyzed by FFT. Using this method, each scattered power peak along the flying model is measured. It is found that each part of the RCS of a flying model can be measured and its RCS of a main wing (about 46 dB/sq cm) is greater than of its body (about 20-30 dB/sq cm).

Power Doppler ultrasonography and synovitis: correlating ultrasound imaging with histopathological findings and evaluating the performance of ultrasound equipments.

PubMed

Koski, J M; Saarakkala, S; Helle, M; Hakulinen, U; Heikkinen, J O; Hermunen, H

2006-12-01

To examine the validity of power Doppler ultrasound imaging to identify synovitis, using histopathology as gold standard, and to assess the performance of ultrasound equipments. 44 synovial sites in small and large joints, bursae and tendon sheaths were depicted with ultrasound. A synovial biopsy was performed on the site depicted and a synovial sample was taken for histopathological evaluation. The performance of three ultrasound devices was tested using flow phantoms. A positive Doppler signal was detected in 29 of 35 (83%) of the patients with active histological inflammation. In eight additional samples, histological examination showed other pathological synovial findings and a Doppler signal was detected in five of them. No significant correlation was found between the amount of Doppler signal and histological synovitis score (r = 0.239, p = NS). The amount of subsynovial infiltration of polymorphonuclear leucocytes and surface fibrin correlated significantly with the amount of power Doppler signal: r = 0.397 (p<0.01) and 0.328 (p<0.05), respectively. The ultrasound devices differed in showing the smallest detectable flow. A negative Doppler signal does not exclude the possibility of synovitis. A positive Doppler signal in the synovium is an indicator of an active synovial inflammation in patients. A Doppler signal does not correlate with the extent of the inflammation and it can also be seen in other synovial reactions. It is important that the quality measurements of ultrasound devices are reported, because the results should be evaluated against the quality of the device used.

Comparison of Techniques for Non-Intrusive Fuel Drop Size Measurements in a Subscale Gas Turbine Combustor

NASA Technical Reports Server (NTRS)

Zaller, Michelle; Anderson, Robert C.; Hicks, Yolanda R.; Locke, Randy J.

1999-01-01

In aviation gas turbine combustors, many factors, such as the degree and extent of fuel/air mixing and fuel vaporization achieved prior to combustion, influence the formation of undesirable pollutants. To assist in analyzing the extent of fuel/air mixing, flow visualization techniques have been used to interrogate the fuel distributions during subcomponent tests of lean-burning fuel injectors. Discrimination between liquid and vapor phases of the fuel was determined by comparing planar laser-induced fluorescence (PLIF) images, elastically-scattered light images, and phase/Doppler interferometer measurements. Estimates of Sauter mean diameters are made by ratioing PLIF and Mie scattered intensities for various sprays, and factors affecting the accuracy of these estimates are discussed. Mie calculations of absorption coefficients indicate that the fluorescence intensities of individual droplets are proportional to their surface areas, instead of their volumes, due to the high absorbance of the liquid fuel for the selected excitation wavelengths.

Noise Equalization for Ultrafast Plane Wave Microvessel Imaging.

PubMed

Song, Pengfei; Manduca, Armando; Trzasko, Joshua D; Chen, Shigao

2017-11-01

Ultrafast plane wave microvessel imaging significantly improves ultrasound Doppler sensitivity by increasing the number of Doppler ensembles that can be collected within a short period of time. The rich spatiotemporal plane wave data also enable more robust clutter filtering based on singular value decomposition. However, due to the lack of transmit focusing, plane wave microvessel imaging is very susceptible to noise. This paper was designed to: 1) study the relationship between ultrasound system noise (primarily time gain compensation induced) and microvessel blood flow signal and 2) propose an adaptive and computationally cost-effective noise equalization method that is independent of hardware or software imaging settings to improve microvessel image quality.

Effects of exercise training on systo-diastolic ventricular dysfunction in patients with hypertension: an echocardiographic study with tissue velocity and strain imaging evaluation.

PubMed

Leggio, Massimo; Mazza, Andrea; Cruciani, Giancarlo; Sgorbini, Luca; Pugliese, Marco; Bendini, Maria Grazia; Severi, Paolo; Jesi, Anna Patrizia

2014-07-01

There is a lack of detailed data regarding the effect of exercise training in pharmacologically treated hypertensive patients. Therefore, the aim of this study was to evaluate the effects of exercise training on left and right ventricular morphologic and functional parameters by means of conventional echocardiography and sensitive new echocardiographic techniques including tissue Doppler velocity and strain imaging, that were performed in pharmacologically treated hypertensive patients at baseline and at the end of a specific exercise training protocol for primary prevention of cardiovascular disease. We selected 116 pharmacologically treated hypertensive patients who completed the exercise training protocol. All patients underwent a clinical history and examination; transthoracic echocardiography and exercise testing were performed at baseline and at the end of the exercise training protocol. Conventional echocardiography revealed a mild degree of diastolic dysfunction without significant differences or variations from baseline to the end of the exercise training protocol. In contrast, tissue Doppler velocity and strain imaging measurements demonstrated and highlighted the positive influence of exercise training: for both left and right ventricle myocardial early peak diastolic velocities (Em), the ratio of myocardial early-late peak diastolic velocity (Em/Am), myocardial peak systolic velocities (Sm) and peak strain and strain rate values significantly increased at the end of the exercise training protocol, suggesting a relationship between exercise capacity and both left and right ventricular systo-diastolic function. Our study, by means of newer more sensitive echocardiographic techniques, clearly demonstrated the positive impact of exercise training on both left and right ventricular systo-diastolic function, in terms of adjunctive subclinical improvement, in pharmacologically treated hypertensive patients.

De-Dopplerization of Acoustic Measurements

DTIC Science & Technology

2017-08-10

band energy obtained from fractional octave band digital filters generates a de-Dopplerized spectrum without complex resampling algorithms. An...energy obtained from fractional octave band digital filters generates a de-Dopplerized spectrum without complex resampling algorithms. An equation...fractional octave representation and smearing that occurs within the spectrum11, digital filtering techniques were not considered by these earlier

Editorial special issue on "Laser Doppler vibrometry"

NASA Astrophysics Data System (ADS)

Vanlanduit, Steve; Dirckx, Joris

2017-12-01

The invention of the laser in 1960 has opened up many opportunities in the field of measurement science and technology. Just a few years after the invention of the laser, a novel fluid flow measurement technique based on the Doppler effect was introduced: at that moment the laser Doppler anemometer or shortly LDA [1] was born. The technique enabled fluid velocity measurement by using the light of a He-Ne beam which was scattered by very small polystyrene spheres entrained in the fluid. Later on, in the late nineteen seventees it was recognized that the detection of the Doppler frequency shift that occurs when light is scattered by a moving surface can also be used to measure the vibration velocity of an object. The instrument to perform these vibration measurements was called the laser Doppler vibrometer or LDV [2]. In the last decades several technological advances were made in the field of laser Doppler vibrometry. The result is that nowadays, velocity measurements of fluids (using LDA) and vibrating objects (using LDV) are performed in many challenging applications in different fields (microelectronics, civil structures, biomedical engineering, material science, etc.).

Oscillations in the wake of a flare blast wave

NASA Astrophysics Data System (ADS)

Tothova, D.; Innes, D. E.; Stenborg, G.

2011-04-01

Context. Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift oscillations. The Doppler-shift oscillations are commonly interpreted as longitudinal modes. Aims: Our aim is to investigate the relationship between loop dynamics and flows seen in TRACE 195 Å images and Doppler shifts observed by SUMER in Si iii 1113.2 Å and FeXIX 1118.1 Å at the time of a C.8-class limb flare and an associated CME. Methods: We carefully co-aligned the sequence of TRACE 195 Å images to structures seen in the SUMER Si iii, CaX, and FeXIX emission lines. Additionally, Hα observations of a lifting prominence associated with the flare and the coronal mass ejection (CME) are available in three bands around 6563.3 Å. They give constraints on the timing and geometry. Results: Large-scale Doppler-shift oscillations in FeXIX and transverse oscillations in intensity images were observed over a large region of the corona after the passage of a wide bright extreme-ultraviolet (EUV) disturbance, which suggests ionization, heating, and acceleration of hot plasma in the wake of a blast wave. The online movie associated to Fig. 2 is available at http://www.aanda.org and at http://www.mps.mpg.de/data/outgoing/tothova/movie.gif

Promise of new imaging technologies for assessing ovarian function.

PubMed

Singh, Jaswant; Adams, Gregg P; Pierson, Roger A

2003-10-15

Advancements in imaging technologies over the last two decades have ushered a quiet revolution in research approaches to the study of ovarian structure and function. The most significant changes in our understanding of the ovary have resulted from the use of ultrasonography which has enabled sequential analyses in live animals. Computer-assisted image analysis and mathematical modeling of the dynamic changes within the ovary has permitted exciting new avenues of research with readily quantifiable endpoints. Spectral, color-flow and power Doppler imaging now facilitate physiologic interpretations of vascular dynamics over time. Similarly, magnetic resonance imaging (MRI) is emerging as a research tool in ovarian imaging. New technologies, such as three-dimensional ultrasonography and MRI, ultrasound-based biomicroscopy and synchrotron-based techniques each have the potential to enhance our real-time picture of ovarian function to the near-cellular level. Collectively, information available in ultrasonography, MRI, computer-assisted image analysis and mathematical modeling heralds a new era in our understanding of the basic processes of female and male reproduction.

Precise Tracking of the Magellan and Pioneer Venus Orbiters by Same-Beam Interferometry. Part 2: Orbit Determination Analysis

NASA Technical Reports Server (NTRS)

Folkner, W. M.; Border, J. S.; Nandi, S.; Zukor, K. S.

1993-01-01

A new radio metric positioning technique has demonstrated improved orbit determination accuracy for the Magellan and Pioneer Venus Orbiter orbiters. The new technique, known as Same-Beam Interferometry (SBI), is applicable to the positioning of multiple planetary rovers, landers, and orbiters which may simultaneously be observed in the same beamwidth of Earth-based radio antennas. Measurements of carrier phase are differenced between spacecraft and between receiving stations to determine the plane-of-sky components of the separation vector(s) between the spacecraft. The SBI measurements complement the information contained in line-of-sight Doppler measurements, leading to improved orbit determination accuracy. Orbit determination solutions have been obtained for a number of 48-hour data arcs using combinations of Doppler, differenced-Doppler, and SBI data acquired in the spring of 1991. Orbit determination accuracy is assessed by comparing orbit solutions from adjacent data arcs. The orbit solution differences are shown to agree with expected orbit determination uncertainties. The results from this demonstration show that the orbit determination accuracy for Magellan obtained by using Doppler plus SBI data is better than the accuracy achieved using Doppler plus differenced-Doppler by a factor of four and better than the accuracy achieved using only Doppler by a factor of eighteen. The orbit determination accuracy for Pioneer Venus Orbiter using Doppler plus SBI data is better than the accuracy using only Doppler data by 30 percent.

V405 ANDROMEDA REVISITED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribeiro, T.; Baptista, R.; Kafka, S.

We present a multi-epoch time-resolved high-resolution optical spectroscopy study of the short-period (P{sub orb} = 11.2 hr) eclipsing M0V+M5V RS CVn binary V405 Andromeda. By means of indirect imaging techniques, namely Doppler imaging, we study the surface activity features of the M0V component of the system. A modified version of a Doppler imaging code, which takes into account the tidal distortion of the surface of the star, is applied to the multi-epoch data set in order to provide indirect images of the stellar surface. The multi-epoch surface brightness distributions show a low intensity 'belt' of spots at latitudes {+-}40{sup 0}more » and a noticeable absence of high latitude features or polar spots on the primary star of V405 Andromeda. They also reveal slow evolution of the spot distribution over {approx}4 yr. An entropy landscape procedure is used in order to find the set of binary parameters that lead to the smoothest surface brightness distributions. As a result, we find M{sub 1} = 0.51 {+-} 0.03 M{sub sun}, M{sub 2} = 0.21 {+-} 0.01 M{sub sun}, R{sub 1} = 0.71 {+-} 0.01 R{sub sun}, and an inclination i = 65{sup 0} {+-} 1{sup 0}. The resulting systemic velocity is distinct for different epochs, raising the possibility of the existence of a third body in the system.« less

Visualization of hepatic arteries with 3D ultrasound during intra-arterial therapies

NASA Astrophysics Data System (ADS)

Gérard, Maxime; Tang, An; Badoual, Anaïs.; Michaud, François; Bigot, Alexandre; Soulez, Gilles; Kadoury, Samuel

2016-03-01

Liver cancer represents the second most common cause of cancer-related mortality worldwide. The prognosis is poor with an overall mortality of 95%. Moreover, most hepatic tumors are unresectable due to their advanced stage at discovery or poor underlying liver function. Tumor embolization by intra-arterial approaches is the current standard of care for advanced cases of hepatocellular carcinoma. These therapies rely on the fact that the blood supply of primary hepatic tumors is predominantly arterial. Feedback on blood flow velocities in the hepatic arteries is crucial to ensure maximal treatment efficacy on the targeted masses. Based on these velocities, the intra-arterial injection rate is modulated for optimal infusion of the chemotherapeutic drugs into the tumorous tissue. While Doppler ultrasound is a well-documented technique for the assessment of blood flow, 3D visualization of vascular anatomy with ultrasound remains challenging. In this paper we present an image-guidance pipeline that enables the localization of the hepatic arterial branches within a 3D ultrasound image of the liver. A diagnostic Magnetic resonance angiography (MRA) is first processed to automatically segment the hepatic arteries. A non-rigid registration method is then applied on the portal phase of the MRA volume with a 3D ultrasound to enable the visualization of the 3D mesh of the hepatic arteries in the Doppler images. To evaluate the performance of the proposed workflow, we present initial results from porcine models and patient images.

Magnetic Doppler imaging of 53 Camelopardalis in all four Stokes parameters

NASA Astrophysics Data System (ADS)

Kochukhov, O.; Bagnulo, S.; Wade, G. A.; Sangalli, L.; Piskunov, N.; Landstreet, J. D.; Petit, P.; Sigut, T. A. A.

2004-02-01

We present the first investigation of the structure of the stellar surface magnetic field using line profiles in all four Stokes parameters. We extract the information about the magnetic field geometry and abundance distributions of the chemically peculiar star 53 Cam by modelling time-series of high-resolution spectropolarimetric observations with the help of a new magnetic Doppler imaging code. This combination of the unique four Stokes parameter data and state-of-the-art magnetic imaging technique makes it possible to infer the stellar magnetic field topology directly from the rotational variability of the Stokes spectra. In the magnetic imaging of 53 Cam we discard the traditional multipolar assumptions about the structure of magnetic fields in Ap stars and explore the stellar magnetic topology without introducing any global a priori constraints on the field structure. The complex magnetic model of 53 Cam derived with our magnetic Doppler imaging method achieves a good fit to the observed intensity, circular and linear polarization profiles of strong magnetically sensitive Fe II spectral lines. Such an agreement between observations and model predictions was not possible with any earlier multipolar magnetic models, based on modelling Stokes I spectra and fitting surface averaged magnetic observables (e.g., longitudinal field, magnetic field modulus, etc.). Furthermore, we demonstrate that even the direct inversion of the four Stokes parameters of 53 Cam assuming a low-order multipolar magnetic geometry is incapable of achieving an adequate fit to our spectropolarimetric observations. Thus, as a main result of our investigation, we discover that the magnetic field topology of 53 Cam is considerably more complex than any low-order multipolar expansion, raising a general question about the validity of the multipolar assumption in the studies of magnetic field structures of Ap stars. In addition to the analysis of the magnetic field of 53 Cam, we reconstruct surface abundance distributions of Si, Ca, Ti, Fe and Nd. These abundance maps confirm results of the previous studies of 53 Cam, in particular dramatic antiphase variation of Ca and Ti abundances. Based on observations obtained with the Bernard Lyot telescope of the Pic du Midi Observatory and Isaac Newton Telescope of the La Palma Observatory.

Quantification of absolute blood velocity using LDA

NASA Astrophysics Data System (ADS)

Borozdova, M. A.; Fedosov, I. V.; Tuchin, V. V.

2018-04-01

We developed novel schematics of a Laser Doppler anemometer where measuring volume is comparable with the red blood cell (RBC) size and a small period of interference fringes improves device resolution. The technique was used to estimate Doppler frequency shift at flow velocity measurements. It has been shown that technique is applicable for measurements in whole blood.

The use of laser Doppler imaging as an aid in clinical management decision making in the treatment of vesicant burns.

PubMed

Brown, R F; Rice, P; Bennett, N J

1998-12-01

Vesicants are a group of chemicals recognised, under the terms of the Chemical Weapons Convention, as potential chemical warfare agents whose prime effect on the skin is to cause burns and blistering. Experience of the clinical management of these injuries is not readily available and therefore an accurate assessment of the severity of the lesion and extent of tissue involvement is an important factor when determining the subsequent clinical management strategy for such lesions. This study was performed to assess the use of laser Doppler imaging (LDI) as a noninvasive means of assessing wound microvascular perfusion following challenge with the vesicant agents (sulphur mustard or lewisite) by comparing the images obtained with histopathological analysis of the lesion. Large white pigs were challenged with sulphur mustard (1.91 mg cm(-2)) or lewisite (0.3 mg.cm(-2)) vapour for periods of up to 6 h At intervals of between 1 h and 7 days following vesicant challenge, LDI images were acquired and samples for routine histopathology were taken. The results from this study suggest that LDI was: (i) a simple, reproducible and noninvasive means of assessing changes in tissue perfusion, and hence tissue viability, in developing and healing vesicant burns; (ii) the LDI images correlates well with histopathological assessment of the resulting lesions and the technique was sufficiently sensitive enough to discriminate between skin lesions of different aetiology. These attributes suggest that LDI would be a useful investigative tool that could aid clinical management decision making in the early treatment of vesicant agent-induced skin burns.

Very high spatial resolution two-dimensional solar spectroscopy with video CCDs

NASA Technical Reports Server (NTRS)

Johanneson, A.; Bida, T.; Lites, B.; Scharmer, G. B.

1992-01-01

We have developed techniques for recording and reducing spectra of solar fine structure with complete coverage of two-dimensional areas at very high spatial resolution and with a minimum of seeing-induced distortions. These new techniques permit one, for the first time, to place the quantitative measures of atmospheric structure that are afforded only by detailed spectral measurements into their proper context. The techniques comprise the simultaneous acquisition of digital spectra and slit-jaw images at video rates as the solar scene sweeps rapidly by the spectrograph slit. During data processing the slit-jaw images are used to monitor rigid and differential image motion during the scan, allowing measured spectrum properties to be remapped spatially. The resulting quality of maps of measured properties from the spectra is close to that of the best filtergrams. We present the techniques and show maps from scans over pores and small sunspots obtained at a resolution approaching 1/3 arcsec in the spectral region of the magnetically sensitive Fe I lines at 630.15 and 630.25 nm. The maps shown are of continuum intensity and calibrated Doppler velocity. More extensive spectral inversion of these spectra to yield the strength of the magnetic field and other parameters is now underway, and the results of that analysis will be presented in a following paper.

Simultaneous multispectral reflectance imaging and laser speckle flowmetry of cerebral blood flow and oxygen metabolism in focal cerebral ischemia

PubMed Central

Jones, Phill B.; Shin, Hwa Kyoung; Boas, David A.; Hyman, Bradley T.; Moskowitz, Michael A.; Ayata, Cenk; Dunn, Andrew K.

2009-01-01

Real-time investigation of cerebral blood flow (CBF), and oxy- and deoxyhemoglobin concentration (HbO, HbR) dynamics has been difficult until recently due to limited spatial and temporal resolution of techniques like laser Doppler flowmetry and magnetic resonance imaging (MRI). The combination of laser speckle flowmetry (LSF) and multispectral reflectance imaging (MSRI) yields high-resolution spatiotemporal maps of hemodynamic and metabolic changes in response to functional cortical activation. During acute focal cerebral ischemia, changes in HbO and HbR are much larger than in functional activation, resulting in the failure of the Beer-Lambert approximation to yield accurate results. We describe the use of simultaneous LSF and MSRI, using a nonlinear Monte Carlo fitting technique, to record rapid changes in CBF, HbO, HbR, and cerebral metabolic rate of oxygen (CMRO2) during acute focal cerebral ischemia induced by distal middle cerebral artery occlusion (dMCAO) and reperfusion. This technique captures CBF and CMRO2 changes during hemodynamic and metabolic events with high temporal and spatial resolution through the intact skull and demonstrates the utility of simultaneous LSF and MSRI in mouse models of cerebrovascular disease. PMID:19021335

A comparative study of colour and perfusion between two different post surgical scars. Do the laser Doppler imager and the colorimeter measure the same features of a scar?

PubMed

Mermans, J F; Peeters, W J; Dikmans, R; Serroyen, J; van der Hulst, R R J W; Van den Kerckhove, E

2013-05-01

The purpose of this study was to investigate the influence of different located post surgical scars on both perfusion and redness. The pattern of change and correlation between perfusion and redness of post surgical scars is also examined. In this study, we measured redness and perfusion of the abdominal and breast scar of 24 women undergoing breast reconstruction with Deep Inferior Epigastric Perforator Free Flap surgery with the Minolta Chromameter CR-400/410 and the Moor Instruments laser Doppler imager 12IR, respectively, at different intervals post-operatively. The laser Doppler imager gives significantly higher values for the abdominal compared with the breast scar. There was no consistent correlation found between perfusion and redness at the different test moments for both locations. The scores of both parameters were significantly associated after 9 months follow-up for both locations. Scars closed with higher mechanical force show higher perfusion and prolonged activity; and more redness is associated with more perfusion for both post surgical scars. Nevertheless, there was no consistent correlation found between these parameters making the laser Doppler imager and the Colorimeter still non-replaceable instruments. © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

Complex regression Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Elahi, Sahar; Gu, Shi; Thrane, Lars; Rollins, Andrew M.; Jenkins, Michael W.

2018-04-01

We introduce a new method to measure Doppler shifts more accurately and extend the dynamic range of Doppler optical coherence tomography (OCT). The two-point estimate of the conventional Doppler method is replaced with a regression that is applied to high-density B-scans in polar coordinates. We built a high-speed OCT system using a 1.68-MHz Fourier domain mode locked laser to acquire high-density B-scans (16,000 A-lines) at high enough frame rates (˜100 fps) to accurately capture the dynamics of the beating embryonic heart. Flow phantom experiments confirm that the complex regression lowers the minimum detectable velocity from 12.25 mm / s to 374 μm / s, whereas the maximum velocity of 400 mm / s is measured without phase wrapping. Complex regression Doppler OCT also demonstrates higher accuracy and precision compared with the conventional method, particularly when signal-to-noise ratio is low. The extended dynamic range allows monitoring of blood flow over several stages of development in embryos without adjusting the imaging parameters. In addition, applying complex averaging recovers hidden features in structural images.

Feasibility of heart rate variability measurement from quadrature Doppler radar using arctangent demodulation with DC offset compensation.

PubMed

Massagram, Wansuree; Hafner, Noah M; Park, Byung-Kwan; Lubecke, Victor M; Host-Madsen, Anders; Boric-Lubecke, Olga

2007-01-01

This paper describes the experimental results of the beat-to-beat interval measurement from a quadrature Doppler radar system utilizing arctangent demodulation with DC offset compensation techniques. The comparison in SDNN and in RMSDD of both signals demonstrates the potential of using quadrature Doppler radar for HRV analysis.

Effect of scanline orientation on ventricular flow propagation: assessment using high frame-rate color Doppler echocardiography

NASA Technical Reports Server (NTRS)

Greenberg, N. L.; Castro, P. L.; Drinko, J.; Garcia, M. J.; Thomas, J. D.

2000-01-01

Color M-mode echocardiography has recently been utilized to describe diastolic flow propagation velocity (Vp) in the left ventricle. While increasing temporal resolution from 15 to 200 Hz, this M-mode technique requires the user to select a single scanline, potentially limiting quantification of Vp due to the complex three-dimensional inflow pattern. We previously performed computational fluid dynamics simulations to demonstrate the insignificance of the scanline orientation, however geometric complexity was limited. The purpose of this study was to utilize high frame-rate 2D color Doppler images to investigate the importance of scanline selection in patients for the quantification of Vp. 2D color Doppler images were digitally acquired at 50 frames/s in 6 subjects from the apical 4-chamber window (System 5, GE/Vingmed, Milwaukee, WI). Vp was determined for a set of scanlines positioned through 5 locations across the mitral annulus (from the anterior to posterior mitral annulus). An analysis of variance was performed to examine the differences in Vp as a function of scanline position. Vp was not effected by scanline position in sampled locations from the center of the mitral valve towards the posterior annulus. Although not statistically significant, there was a trend to slower propagation velocities on the anterior side of the valve (60.8 +/- 16.7 vs. 54.4 +/- 13.6 cm/s). This study clinically validates our previous numerical experiment showing that Vp is insensitive to small perturbations of the scanline through the mitral valve. However, further investigation is necessary to examine the impact of ventricular geometry in pathologies including dilated cardiomyopathy.

Intracardiac Vortex Dynamics by High-Frame-Rate Doppler Vortography-In Vivo Comparison With Vector Flow Mapping and 4-D Flow MRI.

PubMed

Faurie, Julia; Baudet, Mathilde; Assi, Kondo Claude; Auger, Dominique; Gilbert, Guillaume; Tournoux, Francois; Garcia, Damien

2017-02-01

Recent studies have suggested that intracardiac vortex flow imaging could be of clinical interest to early diagnose the diastolic heart function. Doppler vortography has been introduced as a simple color Doppler method to detect and quantify intraventricular vortices. This method is able to locate a vortex core based on the recognition of an antisymmetric pattern in the Doppler velocity field. Because the heart is a fast-moving organ, high frame rates are needed to decipher the whole blood vortex dynamics during diastole. In this paper, we adapted the vortography method to high-frame-rate echocardiography using circular waves. Time-resolved Doppler vortography was first validated in vitro in an ideal forced vortex. We observed a strong correlation between the core vorticity determined by high-frame-rate vortography and the ground-truth vorticity. Vortography was also tested in vivo in ten healthy volunteers using high-frame-rate duplex ultrasonography. The main vortex that forms during left ventricular filling was tracked during two-three successive cardiac cycles, and its core vorticity was determined at a sampling rate up to 80 duplex images per heartbeat. Three echocardiographic apical views were evaluated. Vortography-derived vorticities were compared with those returned by the 2-D vector flow mapping approach. Comparison with 4-D flow magnetic resonance imaging was also performed in four of the ten volunteers. Strong intermethod agreements were observed when determining the peak vorticity during early filling. It is concluded that high-frame-rate Doppler vortography can accurately investigate the diastolic vortex dynamics.

Directional ocean wave measurements in a coastal setting using a focused array imaging radar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frasier, S.J.; Liu, Y.; Moller, D.

1995-03-01

A unique focused array imaging Doppler radar was used to measure directional spectra of ocean surface waves in a nearshore experiment performed on the North Carolina Outer Banks. Radar images of the ocean surface`s Doppler velocity were used to generate two dimensional spectra of the radial component of the ocean surface velocity field. These are compared to simultaneous in-situ measurements made by a nearby array of submerged pressure sensors. Analysis of the resulting two-dimensional spectra include comparisons of dominant wave lengths, wave directions, and wave energy accounting for relative differences in water depth at the measurement locations. Limited estimates ofmore » the two-dimensional surface displacement spectrum are derived from the radar data. The radar measurements are analogous to those of interferometric synthetic aperture radars (INSAR), and the equivalent INSAR parameters are shown. The agreement between the remote and in-situ measurements suggests that an imaging Doppler radar is effective for these wave measurements at near grazing incidence angles.« less

Ultrasonography of the biliary tract - up to date. The importance of correlation between imaging methods and patients' signs and symptoms.

PubMed

Badea, Radu; Zaro, Răzvan; Tanțău, Marcel; Chiorean, Liliana

2015-09-01

Ultrasonography is generally accepted and performed as a first choice imaging technique in patients with jaundice. The method allows the discrimination between cholestatic and mechanical jaundice. The existing procedures are multiple: gray scale, Doppler, i.v. contrast enhancement, elastography, tridimensional ultrasonography, each of these with different contribution to the positive and differential diagnosis regarding the nature of the jaundice. The final diagnosis is a multimodal one and the efficiency is dependent on the level of the available technology, the examiner's experience, the degree and modality of integration of the data within the clinical context, as well as on the portfolio of available imaging procedures. This review shows the main ultrasonographic methods consecrated in the evaluation of the biliary tree. It also underlines the integrated character of the procedures, as well as the necessity to correlate with other imaging methods and the clinical situation.

Imaging the cool stars in the interacting binaries AE Aqr, BV Cen and V426 Oph

NASA Astrophysics Data System (ADS)

Watson, C. A.; Steeghs, D.; Dhillon, V. S.; Shahbaz, T.

2007-10-01

It is well known that magnetic activity in late-type stars increases with increasing rotation rate. Using inversion techniques akin to medical imaging, the rotationally broadened profiles from such stars can be used to reconstruct `Doppler images' of the distribution of cool, dark starspots on their stellar surfaces. Interacting binaries, however, contain some of the most rapidly rotating late-type stars known and thus provide important tests of stellar dynamo models. Furthermore, magnetic activity is thought to play a key role in their evolution, behaviour and accretion dynamics. Despite this, we know comparatively little about the magnetic activity and its influence on such binaries. In this review we summarise the concepts behind indirect imaging of these systems, and present movies of the starspot distributions on the cool stars in some interacting binaries. We conclude with a look at the future opportunities that such studies may provide.

B-Flow Imaging in Lower Limb Peripheral Arterial Disease and Bypass Graft Ultrasonography.

PubMed

D'Abate, Fabrizio; Ramachandran, Veni; Young, Mark A; Farrah, John; Ahmed, Mudasar H; Jones, Keith; Hinchliffe, Robert J

2016-09-01

Doppler ultrasonography plays a key role in the diagnosis of peripheral arterial disease, but is often limited by pitfalls that may be overcome by B-flow imaging. Thus far, there is little information on B-flow imaging for the assessment of peripheral arterial disease and bypass grafts in lower limbs. This article describes the authors' early experience with B-flow in the lower extremities. Sixty patients were included among a large cohort of patients routinely referred to the vascular laboratory for peripheral arterial disease and bypass graft assessments. Two experienced vascular sonographers performed all scans, comparing color Doppler ultrasonography with B-flow imaging. All scans were performed using a combination of the 9 L linear and C2-9 curvilinear transducers with the LOGIQ E9 system (GE Healthcare, Waukesha, WI, USA). Our experience indicates that this relatively unexplored technology has the potential to significantly improve peripheral blood flow evaluation. Nevertheless, B-flow imaging is not exempt from limitations and should be considered complementary to color Doppler ultrasonography. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Evaluation of gastrointestinal activity patterns in healthy horses using B mode and Doppler ultrasonography

PubMed Central

2005-01-01

Abstract Healthy adult horses were examined by using transabdominal ultrasonography to quantitatively and qualitatively evaluate activity of the jejunum, cecum, and colon with B mode and Doppler techniques. Doppler ultrasound was used to assess jejunal peristaltic activity. Examinations were performed on multiple occasions under imposed colic evaluation conditions, including fasting, nasogastric intubation, and xylazine sedation. In fasted horses, jejunal visibility was increased and jejunal, cecal, and colonic activity was decreased. The stomach was displaced ventrally and was visualized ventral to the costochondral junction. Xylazine sedation in fed horses had minimal effects; however, in fasted horses, xylazine significantly decreased jejunal and cecal activity. Nasogastric intubation in fasted horses had no observable effects on activity, but moved the stomach dorsally. B mode and Doppler jejunal activity were strongly correlated. Prior feeding and sedation status need to be considered when interpreting the results of equine abdominal ultrasound examinations. Doppler techniques may be useful for assessing jejunal activity. PMID:15825515

A method to validate quantitative high-frequency power doppler ultrasound with fluorescence in vivo video microscopy.

PubMed

Pinter, Stephen Z; Kim, Dae-Ro; Hague, M Nicole; Chambers, Ann F; MacDonald, Ian C; Lacefield, James C

2014-08-01

Flow quantification with high-frequency (>20 MHz) power Doppler ultrasound can be performed objectively using the wall-filter selection curve (WFSC) method to select the cutoff velocity that yields a best-estimate color pixel density (CPD). An in vivo video microscopy system (IVVM) is combined with high-frequency power Doppler ultrasound to provide a method for validation of CPD measurements based on WFSCs in mouse testicular vessels. The ultrasound and IVVM systems are instrumented so that the mouse remains on the same imaging platform when switching between the two modalities. In vivo video microscopy provides gold-standard measurements of vascular diameter to validate power Doppler CPD estimates. Measurements in four image planes from three mice exhibit wide variation in the optimal cutoff velocity and indicate that a predetermined cutoff velocity setting can introduce significant errors in studies intended to quantify vascularity. Consistent with previously published flow-phantom data, in vivo WFSCs exhibited three characteristic regions and detectable plateaus. Selection of a cutoff velocity at the right end of the plateau yielded a CPD close to the gold-standard vascular volume fraction estimated using IVVM. An investigator can implement the WFSC method to help adapt cutoff velocity to current blood flow conditions and thereby improve the accuracy of power Doppler for quantitative microvascular imaging. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Letters: Noise Equalization for Ultrafast Plane Wave Microvessel Imaging

PubMed Central

Song, Pengfei; Manduca, Armando; Trzasko, Joshua D.

2017-01-01

Ultrafast plane wave microvessel imaging significantly improves ultrasound Doppler sensitivity by increasing the number of Doppler ensembles that can be collected within a short period of time. The rich spatiotemporal plane wave data also enables more robust clutter filtering based on singular value decomposition (SVD). However, due to the lack of transmit focusing, plane wave microvessel imaging is very susceptible to noise. This study was designed to: 1) study the relationship between ultrasound system noise (primarily time gain compensation-induced) and microvessel blood flow signal; 2) propose an adaptive and computationally cost-effective noise equalization method that is independent of hardware or software imaging settings to improve microvessel image quality. PMID:28880169

Development of a Duplex Ultrasound Simulator and Preliminary Validation of Velocity Measurements in Carotid Artery Models.

PubMed

Zierler, R Eugene; Leotta, Daniel F; Sansom, Kurt; Aliseda, Alberto; Anderson, Mark D; Sheehan, Florence H

2016-07-01

Duplex ultrasound scanning with B-mode imaging and both color Doppler and Doppler spectral waveforms is relied upon for diagnosis of vascular pathology and selection of patients for further evaluation and treatment. In most duplex ultrasound applications, classification of disease severity is based primarily on alterations in blood flow velocities, particularly the peak systolic velocity (PSV) obtained from Doppler spectral waveforms. We developed a duplex ultrasound simulator for training and assessment of scanning skills. Duplex ultrasound cases were prepared from 2-dimensional (2D) images of normal and stenotic carotid arteries by reconstructing the common carotid, internal carotid, and external carotid arteries in 3 dimensions and computationally simulating blood flow velocity fields within the lumen. The simulator displays a 2D B-mode image corresponding to transducer position on a mannequin, overlaid by color coding of velocity data. A spectral waveform is generated according to examiner-defined settings (depth and size of the Doppler sample volume, beam steering, Doppler beam angle, and pulse repetition frequency or scale). The accuracy of the simulator was assessed by comparing the PSV measured from the spectral waveforms with the true PSV which was derived from the computational flow model based on the size and location of the sample volume within the artery. Three expert examiners made a total of 36 carotid artery PSV measurements based on the simulated cases. The PSV measured by the examiners deviated from true PSV by 8% ± 5% (N = 36). The deviation in PSV did not differ significantly between artery segments, normal and stenotic arteries, or examiners. To our knowledge, this is the first simulation of duplex ultrasound that can create and display real-time color Doppler images and Doppler spectral waveforms. The results demonstrate that an examiner can measure PSV from the spectral waveforms using the settings on the simulator with a mean absolute error in the velocity measurement of less than 10%. With the addition of cases with a range of pathologies, this duplex ultrasound simulator will be a useful tool for training health-care providers in vascular ultrasound applications and for assessing their skills in an objective and quantitative manner. © The Author(s) 2016.

The uses of two-dimensional Doppler echocardiographic techniques preoperatively and postoperatively in a ventricular septal defect caused by penetrating trauma.

PubMed

Goldman, A P; Kotler, M N; Goldberg, S E; Parameswaran, R; Parry, W

1985-12-01

Doppler echocardiography was used to determine the site and size of a ventricular septal defect in a patient with a penetrating wound of the heart. Additional physiological measurements by Doppler study, including pulmonary artery pressure and degree of left-to-right shunting, were helpful in deciding on surgical closure of the defect as the definitive therapy in this patient. Associated intracardiac defects (e.g., mitral or tricuspid regurgitation) can be excluded by Doppler echocardiography.

Development of a spectroscopic technique for simultaneous magnetic field, electron density, and temperature measurements in ICF-relevant plasmas.

PubMed

Dutra, E C; Koch, J A; Presura, R; Angermeier, W A; Darling, T; Haque, S; Mancini, R C; Covington, A M

2016-11-01

Spectroscopic techniques in the visible range are often used in plasma experiments to measure B-field induced Zeeman splitting, electron densities via Stark broadening, and temperatures from Doppler broadening. However, when electron densities and temperatures are sufficiently high, the broadening of the Stark and Doppler components can dominate the emission spectra and obscure the Zeeman component. In this research, we are developing a time-resolved multi-axial technique for measuring the Zeeman, Stark, and Doppler broadened line emission of dense magnetized plasmas for Z-pinch and Dense Plasma Focus (DPF) accelerators. The line emission is used to calculate the electron densities, temperatures, and B-fields. In parallel, we are developing a line-shape modeling code that incorporates the broadening effects due to Stark, Doppler, and Zeeman effects for dense magnetized plasma. This manuscript presents the details of the experimental setup and line shape code, along with the results obtained from an Al iii doublet at the University of Nevada, Reno at Nevada Terawatt Facility. Future tests are planned to further evaluate the technique and modeling on other material wire array, gas puff, and DPF platforms.

A Microfluidics-based Pulpal Arteriole Blood Flow Phantom for Validation of Doppler Ultrasound Devices in Pulpal Blood Flow Velocity Measurement.

PubMed

Kim, Dohyun; Park, Sung-Ho

2016-11-01

Recently, Doppler ultrasound has been used for the measurement of pulpal blood flow in human teeth. However, the reliability of this method has not been verified. In this study, we developed a model to simulate arteriole blood flow within the dental pulp by using microfluidics. This arteriole simulator, or flow phantom, was used to determine the reliability of measurements obtained by using a Doppler ultrasound device. A microfluidic chip was fabricated by using the soft lithography technique, and blood-mimicking fluid was pumped through the channel by a microfluidic system. A Doppler ultrasound device was used for the measurement of flow velocity. The peak, mean, and minimal flow velocities obtained from the phantom and the Doppler ultrasound device were compared by using linear regression analysis and Pearson correlation coefficient. Bland-Altman analyses were performed to evaluate the velocity differences between the flow generated by the phantom and the flow measurements made with the Doppler ultrasound device. The microfluidic system was able to generate the flow profiles as intended, and the fluid flow could be monitored and controlled by the software program. There were excellent linear correlations between the peak, mean, and minimal flow velocities of the phantom and those of the Doppler ultrasound device (r = 0.94-0.996, P < .001). However, the velocities were overestimated by the Doppler ultrasound device. This phantom provides opportunities for research and education involving the Doppler ultrasound technique in dentistry. Although Doppler ultrasound can be an effective tool for the measurement of pulpal blood flow velocity, it is essential to validate and calibrate the device before clinical use. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

4D in vivo ultrafast ultrasound imaging using a row-column addressed matrix and coherently-compounded orthogonal plane waves

NASA Astrophysics Data System (ADS)

Flesch, M.; Pernot, M.; Provost, J.; Ferin, G.; Nguyen-Dinh, A.; Tanter, M.; Deffieux, T.

2017-06-01

4D ultrafast ultrasound imaging was recently shown using a 2D matrix (i.e. fully populated) connected to a 1024-channel ultrafast ultrasound scanner. In this study, we investigate the row-column addressing (RCA) matrix approach, which allows a reduction of independent channels from N  ×  N to N  +  N, with a dedicated beamforming strategy for ultrafast ultrasound imaging based on the coherent compounding of orthogonal plane wave (OPW). OPW is based on coherent compounding of plane wave transmissions in one direction with receive beamforming along the orthogonal direction and its orthogonal companion sequence. Such coherent recombination of complementary orthogonal sequences leads to the virtual transmit focusing in both directions which results into a final isotropic point spread function (PSF). In this study, a 32  ×  32 2D matrix array probe (1024 channels), centered at 5 MHz was considered. An RCA array, of same footprint with 32  +  32 elements (64 channels), was emulated by summing the elements either along a line or a column in software prior to beamforming. This approach allowed for the direct comparison of the 32  +  32 RCA scheme to the optimal fully sampled 32  ×  32 2D matrix configuration, which served as the gold standard. This approach was first studied through PSF simulations and then validated experimentally on a phantom consisting of anechoic cysts and echogenic wires. The contrast-to-noise ratio and the lateral resolution of the RCA approach were found to be approximately equal to half (in decibel) and twice the values, respectively, obtained when using the 2D matrix approach. Results in a Doppler phantom and the human humeral artery in vivo confirmed that ultrafast Doppler imaging can be achieved with reduced performances when compared against the equivalent 2D matrix. Volumetric anatomic Doppler rendering and voxel-based pulsed Doppler quantification are presented as well. OPW compound imaging using emulated RCA matrix can achieve a power Doppler with sufficient contrast to recover the vein shape and provides an accurate Doppler spectrum.

4D in vivo ultrafast ultrasound imaging using a row-column addressed matrix and coherently-compounded orthogonal plane waves.

PubMed

Flesch, M; Pernot, M; Provost, J; Ferin, G; Nguyen-Dinh, A; Tanter, M; Deffieux, T

2017-06-07

4D ultrafast ultrasound imaging was recently shown using a 2D matrix (i.e. fully populated) connected to a 1024-channel ultrafast ultrasound scanner. In this study, we investigate the row-column addressing (RCA) matrix approach, which allows a reduction of independent channels from N  ×  N to N  +  N, with a dedicated beamforming strategy for ultrafast ultrasound imaging based on the coherent compounding of orthogonal plane wave (OPW). OPW is based on coherent compounding of plane wave transmissions in one direction with receive beamforming along the orthogonal direction and its orthogonal companion sequence. Such coherent recombination of complementary orthogonal sequences leads to the virtual transmit focusing in both directions which results into a final isotropic point spread function (PSF). In this study, a 32  ×  32 2D matrix array probe (1024 channels), centered at 5 MHz was considered. An RCA array, of same footprint with 32  +  32 elements (64 channels), was emulated by summing the elements either along a line or a column in software prior to beamforming. This approach allowed for the direct comparison of the 32  +  32 RCA scheme to the optimal fully sampled 32  ×  32 2D matrix configuration, which served as the gold standard. This approach was first studied through PSF simulations and then validated experimentally on a phantom consisting of anechoic cysts and echogenic wires. The contrast-to-noise ratio and the lateral resolution of the RCA approach were found to be approximately equal to half (in decibel) and twice the values, respectively, obtained when using the 2D matrix approach. Results in a Doppler phantom and the human humeral artery in vivo confirmed that ultrafast Doppler imaging can be achieved with reduced performances when compared against the equivalent 2D matrix. Volumetric anatomic Doppler rendering and voxel-based pulsed Doppler quantification are presented as well. OPW compound imaging using emulated RCA matrix can achieve a power Doppler with sufficient contrast to recover the vein shape and provides an accurate Doppler spectrum.

C-band radar pulse Doppler error: Its discovery, modeling, and elimination

NASA Technical Reports Server (NTRS)

Krabill, W. B.; Dempsey, D. J.

1978-01-01

The discovery of a C Band radar pulse Doppler error is discussed and use of the GEOS 3 satellite's coherent transponder to isolate the error source is described. An analysis of the pulse Doppler tracking loop is presented and a mathematical model for the error was developed. Error correction techniques were developed and are described including implementation details.

Development of the One-Sided Nonlinear Adaptive Doppler Shift Estimation

NASA Technical Reports Server (NTRS)

Beyon, Jeffrey Y.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.; Serror, Judith A.

2009-01-01

The new development of a one-sided nonlinear adaptive shift estimation technique (NADSET) is introduced. The background of the algorithm and a brief overview of NADSET are presented. The new technique is applied to the wind parameter estimates from a 2-micron wavelength coherent Doppler lidar system called VALIDAR located in NASA Langley Research Center in Virginia. The new technique enhances wind parameters such as Doppler shift and power estimates in low Signal-To-Noise-Ratio (SNR) regimes using the estimates in high SNR regimes as the algorithm scans the range bins from low to high altitude. The original NADSET utilizes the statistics in both the lower and the higher range bins to refine the wind parameter estimates in between. The results of the two different approaches of NADSET are compared.

Imaging the Surfaces of Stars from Space

NASA Astrophysics Data System (ADS)

Carpenter, Kenneth; Rau, Gioia

2018-04-01

Imaging of Stellar Surfacess has been dominated to-date by ground-based observations, but space-based facilities offer tremendous potential for extending the wavelength coverage and ultimately the resolution of such efforts. We review the imaging accomplished so far from space and then talk about exciting future prospects. The earliest attempts from space indirectly produced surface maps via the Doppler Imaging Technique, using UV spectra obtained with the International Ultraviolet Explorer (IUE). Later, the first direct UV images were obtained with the Hubble Space Telescope (HST), of Mira and Betelgeuse, using the Faint Object Camera (FOC). We will show this work and then investigate prospects for IR imaging with the James Webb Space Telescope (JWST). The real potential of space-based Imaging of Stellar Surfacess, however, lies in the future, when large-baseline Fizeau interferometers, such as the UV-optical Stellar Imager (SI) Vision Mission, with a 30-element array and 500m max baseline, are flown. We describe SI and its science goals, which include 0.1 milli-arcsec spectral Imaging of Stellar Surfacess and the probing of internal structure and flows via asteroseismology.

Quantitative 3-d diagnostic ultrasound imaging using a modified transducer array and an automated image tracking technique.

PubMed

Hossack, John A; Sumanaweera, Thilaka S; Napel, Sandy; Ha, Jun S

2002-08-01

An approach for acquiring dimensionally accurate three-dimensional (3-D) ultrasound data from multiple 2-D image planes is presented. This is based on the use of a modified linear-phased array comprising a central imaging array that acquires multiple, essentially parallel, 2-D slices as the transducer is translated over the tissue of interest. Small, perpendicularly oriented, tracking arrays are integrally mounted on each end of the imaging transducer. As the transducer is translated in an elevational direction with respect to the central imaging array, the images obtained by the tracking arrays remain largely coplanar. The motion between successive tracking images is determined using a minimum sum of absolute difference (MSAD) image matching technique with subpixel matching resolution. An initial phantom scanning-based test of a prototype 8 MHz array indicates that linear dimensional accuracy of 4.6% (2 sigma) is achievable. This result compares favorably with those obtained using an assumed average velocity [31.5% (2 sigma) accuracy] and using an approach based on measuring image-to-image decorrelation [8.4% (2 sigma) accuracy]. The prototype array and imaging system were also tested in a clinical environment, and early results suggest that the approach has the potential to enable a low cost, rapid, screening method for detecting carotid artery stenosis. The average time for performing a screening test for carotid stenosis was reduced from an average of 45 minutes using 2-D duplex Doppler to 12 minutes using the new 3-D scanning approach.

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.

Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance ( w' 2) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w' 2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skillmore » in correcting for volume-averaging effects in the calculation of w' 2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w' 2. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w' 2. After the autocovariance technique is applied, values of w' 2 from the Doppler lidars are generally in close agreement ( R 2≈0.95-0.98) with those calculated from sonic anemometer measurements.« less

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.

Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance ( w' 2) from zenith stares. But, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w' 2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skillmore » in correcting for volume-averaging effects in the calculation of w' 2 is also assessed. In addition, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w' 2. And through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w' 2. After the autocovariance technique is applied, values of w' 2 from the Doppler lidars are generally in close agreement ( R 2 ≈ 0.95 -0.98) with those calculated from sonic anemometer measurements.« less

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

DOE PAGES

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; ...

2016-12-06

Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance ( w' 2) from zenith stares. But, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w' 2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skillmore » in correcting for volume-averaging effects in the calculation of w' 2 is also assessed. In addition, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w' 2. And through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w' 2. After the autocovariance technique is applied, values of w' 2 from the Doppler lidars are generally in close agreement ( R 2 ≈ 0.95 -0.98) with those calculated from sonic anemometer measurements.« less

Association Between Echocardiography Laboratory Accreditation and the Quality of Imaging and Reporting for Valvular Heart Disease.

PubMed

Thaden, Jeremy J; Tsang, Michael Y; Ayoub, Chadi; Padang, Ratnasari; Nkomo, Vuyisile T; Tucker, Stephen F; Cassidy, Cynthia S; Bremer, Merri; Kane, Garvan C; Pellikka, Patricia A

2017-08-01

It is presumed that echocardiographic laboratory accreditation leads to improved quality, but there are few data. We sought to compare the quality of echocardiographic examinations performed at accredited versus nonaccredited laboratories for the evaluation of valvular heart disease. We enrolled 335 consecutive valvular heart disease subjects who underwent echocardiography at our institution and an external accredited or nonaccredited institution within 6 months. Completeness and quality of echocardiographic reports and images were assessed by investigators blinded to the external laboratory accreditation status and echocardiographic results. Compared with nonaccredited laboratories, accredited sites more frequently reported patient sex (94% versus 78%; P <0.001), height and weight (96% versus 63%; P <0.001), blood pressure (86% versus 39%; P <0.001), left ventricular size (96% versus 83%; P <0.001), right ventricular size (94% versus 80%; P =0.001), and right ventricular function (87% versus 73%; P =0.006). Accredited laboratories had higher rates of complete and diagnostic color (58% versus 35%; P =0.002) and spectral Doppler imaging (45% versus 21%; P <0.0001). Concordance between external and internal grading of external studies was improved when diagnostic quantification was performed (85% versus 69%; P =0.003), and in patients with mitral regurgitation, reproducibility was improved with higher quality color Doppler imaging. Accredited echocardiographic laboratories had more complete reporting and better image quality, while echocardiographic quantification and color Doppler image quality were associated with improved concordance in grading valvular heart disease. Future quality improvement initiatives should highlight the importance of high-quality color Doppler imaging and echocardiographic quantification to improve the accuracy, reproducibility, and quality of echocardiographic studies for valvular heart disease. © 2017 American Heart Association, Inc.

Specialized Diagnostic Investigations to Assess Ocular Status in Hypertensive Diseases of Pregnancy.

PubMed

Bakhda, Rahul Navinchandra

2016-04-22

This review describes specialized diagnostic investigations to assess ocular status in hypertensive diseases of pregnancy. Ocular assessment can aid in early detection for prompt multidisciplinary treatment, obstetric intervention and follow-up. The investigations accurately predict the possible causes of blindness in hypertensive diseases of pregnancy. The investigations include fluorescein angiography, ophthalmodynamometry, fluorophotometry, imaging modalities, OCT, ultrasonography, doppler velocimetry and blood chemistry analysis. The review includes a summary of imaging techniques and related recent developments to assess the neuro-ophthalmic aspects of the disease. The imaging modalities have been instrumental in understanding the complex neuropathophysiological mechanisms of eclamptic seizures. The importance of blood chemistry analysis in hypertensive diseases of pregnancy has been emphasized. The investigations have made a significant contribution in improving the standards of antenatal care and reducing maternal and fetal morbidity and mortality.

Specialized Diagnostic Investigations to Assess Ocular Status in Hypertensive Diseases of Pregnancy

PubMed Central

Bakhda, Rahul Navinchandra

2016-01-01

This review describes specialized diagnostic investigations to assess ocular status in hypertensive diseases of pregnancy. Ocular assessment can aid in early detection for prompt multidisciplinary treatment, obstetric intervention and follow-up. The investigations accurately predict the possible causes of blindness in hypertensive diseases of pregnancy. The investigations include fluorescein angiography, ophthalmodynamometry, fluorophotometry, imaging modalities, OCT, ultrasonography, doppler velocimetry and blood chemistry analysis. The review includes a summary of imaging techniques and related recent developments to assess the neuro-ophthalmic aspects of the disease. The imaging modalities have been instrumental in understanding the complex neuropathophysiological mechanisms of eclamptic seizures. The importance of blood chemistry analysis in hypertensive diseases of pregnancy has been emphasized. The investigations have made a significant contribution in improving the standards of antenatal care and reducing maternal and fetal morbidity and mortality. PMID:28933399

Echocardiography Practice: Insights into Appropriate Clinical Use, Technical Competence and Quality Improvement Program

PubMed Central

Kossaify, Antoine; Grollier, Gilles

2014-01-01

Echocardiography accounts for nearly half of all cardiac imaging techniques. It is a widely available and adaptable tool, as well as being a cost-effective and mainly a non-invasive test. In addition, echocardiography provides extensive clinical data, which is related to the presence or advent of different modalities (tissue Doppler imaging, speckle tracking imaging, three-dimensional mode, contrast echo, etc.), different approaches (transesophageal, intravascular, etc.), and different applications (ie, heart failure/resynchronization studies, ischemia/stress echo, etc.). In view of this, it is essential to conform to criteria of appropriate use and to keep standards of competence. In this study, we sought to review and discuss clinical practice of echocardiography in light of the criteria of appropriate clinical use, also we present an insight into echocardiographic technical competence and quality improvement project. PMID:24516342

A new technique for monitoring the water vapor in the atmosphere

NASA Technical Reports Server (NTRS)

Black, H. D.; Eisner, A.

1984-01-01

In the correction of satellite Doppler data for tropospheric effects the precipitable water vapor (PWV) is inferred at the tracking site. The technique depends on: (1) an ephemeris for the satellite; (2) an analytic model for the refraction range effect that is good to a few centimeters; (3) Doppler data with noise level below 10 centimeters; and (4) a surface pressure/temperature measurement at the tracking site. The PWV is a by product of the computation necessary to correct the Doppler data for tropospheric effects. A formulation of the refraction integral minimizes the necessity for explicit water vapor, temperature and pressure profiles.

Wind field measurement in the nonprecipitous regions surrounding storms by an airborne pulsed Doppler lidar system, appendix A

NASA Technical Reports Server (NTRS)

Bilbro, J. W.; Vaughan, W. W.

1980-01-01

Coherent Doppler lidar appears to hold great promise in contributing to the basic store of knowledge concerning flow field characteristics in the nonprecipitous regions surrounding severe storms. The Doppler lidar, through its ability to measure clear air returns, augments the conventional Doppler radar system, which is most useful in the precipitous regions of the storm. A brief description of the Doppler lidar severe storm measurement system is provided along with the technique to be used in performing the flow field measurements. The application of the lidar is addressed, and the planned measurement program is outlined.

Eyeballing oscillators for pulsed Doppler radar

NASA Astrophysics Data System (ADS)

Goldman, S.

1985-03-01

The visibility of small targets to a Doppler radar system in the presence of large targets is limited by phase noise. Such limitations occur when an airborne radar searches the ground for a mobile vehicle. Under these conditions, the performance of the Doppler radar depends greatly on the specifications of its phased-locked oscillator. Goldman (1984) has discussed the steps required to evaluate the noise resulting from a pulsed Doppler radar system. In the present investigation, these techniques are applied in reverse to determine system specifications for oscillator noise. A 95-GHz pulsed Doppler radar system is used as an example of specifying system phase noise.

High PRF ultrafast sliding compound doppler imaging: fully qualitative and quantitative analysis of blood flow

NASA Astrophysics Data System (ADS)

Kang, Jinbum; Jang, Won Seuk; Yoo, Yangmo

2018-02-01

Ultrafast compound Doppler imaging based on plane-wave excitation (UCDI) can be used to evaluate cardiovascular diseases using high frame rates. In particular, it provides a fully quantifiable flow analysis over a large region of interest with high spatio-temporal resolution. However, the pulse-repetition frequency (PRF) in the UCDI method is limited for high-velocity flow imaging since it has a tradeoff between the number of plane-wave angles (N) and acquisition time. In this paper, we present high PRF ultrafast sliding compound Doppler imaging method (HUSDI) to improve quantitative flow analysis. With the HUSDI method, full scanline images (i.e. each tilted plane wave data) in a Doppler frame buffer are consecutively summed using a sliding window to create high-quality ensemble data so that there is no reduction in frame rate and flow sensitivity. In addition, by updating a new compounding set with a certain time difference (i.e. sliding window step size or L), the HUSDI method allows various Doppler PRFs with the same acquisition data to enable a fully qualitative, retrospective flow assessment. To evaluate the performance of the proposed HUSDI method, simulation, in vitro and in vivo studies were conducted under diverse flow circumstances. In the simulation and in vitro studies, the HUSDI method showed improved hemodynamic representations without reducing either temporal resolution or sensitivity compared to the UCDI method. For the quantitative analysis, the root mean squared velocity error (RMSVE) was measured using 9 angles (-12° to 12°) with L of 1-9, and the results were found to be comparable to those of the UCDI method (L  =  N  =  9), i.e.  ⩽0.24 cm s-1, for all L values. For the in vivo study, the flow data acquired from a full cardiac cycle of the femoral vessels of a healthy volunteer were analyzed using a PW spectrogram, and arterial and venous flows were successfully assessed with high Doppler PRF (e.g. 5 kHz at L  =  4). These results indicate that the proposed HUSDI method can improve flow visualization and quantification with a higher frame rate, PRF and flow sensitivity in cardiovascular imaging.

High PRF ultrafast sliding compound doppler imaging: fully qualitative and quantitative analysis of blood flow.

PubMed

Kang, Jinbum; Jang, Won Seuk; Yoo, Yangmo

2018-02-09

Ultrafast compound Doppler imaging based on plane-wave excitation (UCDI) can be used to evaluate cardiovascular diseases using high frame rates. In particular, it provides a fully quantifiable flow analysis over a large region of interest with high spatio-temporal resolution. However, the pulse-repetition frequency (PRF) in the UCDI method is limited for high-velocity flow imaging since it has a tradeoff between the number of plane-wave angles (N) and acquisition time. In this paper, we present high PRF ultrafast sliding compound Doppler imaging method (HUSDI) to improve quantitative flow analysis. With the HUSDI method, full scanline images (i.e. each tilted plane wave data) in a Doppler frame buffer are consecutively summed using a sliding window to create high-quality ensemble data so that there is no reduction in frame rate and flow sensitivity. In addition, by updating a new compounding set with a certain time difference (i.e. sliding window step size or L), the HUSDI method allows various Doppler PRFs with the same acquisition data to enable a fully qualitative, retrospective flow assessment. To evaluate the performance of the proposed HUSDI method, simulation, in vitro and in vivo studies were conducted under diverse flow circumstances. In the simulation and in vitro studies, the HUSDI method showed improved hemodynamic representations without reducing either temporal resolution or sensitivity compared to the UCDI method. For the quantitative analysis, the root mean squared velocity error (RMSVE) was measured using 9 angles (-12° to 12°) with L of 1-9, and the results were found to be comparable to those of the UCDI method (L  =  N  =  9), i.e.  ⩽0.24 cm s -1 , for all L values. For the in vivo study, the flow data acquired from a full cardiac cycle of the femoral vessels of a healthy volunteer were analyzed using a PW spectrogram, and arterial and venous flows were successfully assessed with high Doppler PRF (e.g. 5 kHz at L  =  4). These results indicate that the proposed HUSDI method can improve flow visualization and quantification with a higher frame rate, PRF and flow sensitivity in cardiovascular imaging.

Reconstruction of an acoustic pressure field in a resonance tube by particle image velocimetry.

PubMed

Kuzuu, K; Hasegawa, S

2015-11-01

A technique for estimating an acoustic field in a resonance tube is suggested. The estimation of an acoustic field in a resonance tube is important for the development of the thermoacoustic engine, and can be conducted employing two sensors to measure pressure. While this measurement technique is known as the two-sensor method, care needs to be taken with the location of pressure sensors when conducting pressure measurements. In the present study, particle image velocimetry (PIV) is employed instead of a pressure measurement by a sensor, and two-dimensional velocity vector images are extracted as sequential data from only a one- time recording made by a video camera of PIV. The spatial velocity amplitude is obtained from those images, and a pressure distribution is calculated from velocity amplitudes at two points by extending the equations derived for the two-sensor method. By means of this method, problems relating to the locations and calibrations of multiple pressure sensors are avoided. Furthermore, to verify the accuracy of the present method, the experiments are conducted employing the conventional two-sensor method and laser Doppler velocimetry (LDV). Then, results by the proposed method are compared with those obtained with the two-sensor method and LDV.

Laser speckle imaging of rat retinal blood flow with hybrid temporal and spatial analysis method

NASA Astrophysics Data System (ADS)

Cheng, Haiying; Yan, Yumei; Duong, Timothy Q.

2009-02-01

Noninvasive monitoring of blood flow in retinal circulation will reveal the progression and treatment of ocular disorders, such as diabetic retinopathy, age-related macular degeneration and glaucoma. A non-invasive and direct BF measurement technique with high spatial-temporal resolution is needed for retinal imaging. Laser speckle imaging (LSI) is such a method. Currently, there are two analysis methods for LSI: spatial statistics LSI (SS-LSI) and temporal statistical LSI (TS-LSI). Comparing these two analysis methods, SS-LSI has higher signal to noise ratio (SNR) and TSLSI is less susceptible to artifacts from stationary speckle. We proposed a hybrid temporal and spatial analysis method (HTS-LSI) to measure the retinal blood flow. Gas challenge experiment was performed and images were analyzed by HTS-LSI. Results showed that HTS-LSI can not only remove the stationary speckle but also increase the SNR. Under 100% O2, retinal BF decreased by 20-30%. This was consistent with the results observed with laser Doppler technique. As retinal blood flow is a critical physiological parameter and its perturbation has been implicated in the early stages of many retinal diseases, HTS-LSI will be an efficient method in early detection of retina diseases.

Medical ultrasound: imaging of soft tissue strain and elasticity

PubMed Central

Wells, Peter N. T.; Liang, Hai-Dong

2011-01-01

After X-radiography, ultrasound is now the most common of all the medical imaging technologies. For millennia, manual palpation has been used to assist in diagnosis, but it is subjective and restricted to larger and more superficial structures. Following an introduction to the subject of elasticity, the elasticity of biological soft tissues is discussed and published data are presented. The basic physical principles of pulse-echo and Doppler ultrasonic techniques are explained. The history of ultrasonic imaging of soft tissue strain and elasticity is summarized, together with a brief critique of previously published reviews. The relevant techniques—low-frequency vibration, step, freehand and physiological displacement, and radiation force (displacement, impulse, shear wave and acoustic emission)—are described. Tissue-mimicking materials are indispensible for the assessment of these techniques and their characteristics are reported. Emerging clinical applications in breast disease, cardiology, dermatology, gastroenterology, gynaecology, minimally invasive surgery, musculoskeletal studies, radiotherapy, tissue engineering, urology and vascular disease are critically discussed. It is concluded that ultrasonic imaging of soft tissue strain and elasticity is now sufficiently well developed to have clinical utility. The potential for further research is examined and it is anticipated that the technology will become a powerful mainstream investigative tool. PMID:21680780

Optical coherence tomography of dental structures

NASA Astrophysics Data System (ADS)

Baumgartner, Angela; Hitzenberger, Christoph K.; Dichtl, Sabine; Sattmann, Harald; Moritz, Andreas; Sperr, Wolfgang; Fercher, Adolf F.

1998-04-01

In the past ten years Partial Coherence Interferometry (PCI) and Optical Coherence Tomography (OCT) have been successfully developed for high precision biometry and tomography of biological tissues. OCT employs the partial coherence properties of a superluminescent diode and the Doppler principle yielding resolution and precision figures of the order of a few microns. Presently, the main application fields of this technique are biometry and imaging of ocular structures in vivo, as well as its clinical use in dermatology and endoscopic applications. This well established length measuring and imaging technique has now been applied to dentistry. First in vitro OCT images of the cemento (dentine) enamel junction of extracted sound and decayed human teeth have been recorded. These images distinguish dentine and enamel structures that are important for assessing enamel thickness and diagnosing caries. Individual optical A-Scans show that the penetration depth into enamel is considerably larger than into dentine. First polarization sensitive OCT recordings show localized changes of the polarization state of the light backscattered by dental material. Two-dimensional maps of the magnitude of the interference intensity and of the total phase difference between two orthogonal polarization states as a function of depth can reveal important structural information.

Servomechanism for Doppler shift compensation in optical correlator for synthetic aperture radar

NASA Technical Reports Server (NTRS)

Constaninides, N. J.; Bicknell, T. J. (Inventor)

1980-01-01

A method and apparatus for correcting Doppler shifts in synthetic aperture radar data is described. An optical correlator for synthetic aperture radar data has a means for directing a laser beam at a signal film having radar return pulse intensity information recorded on it. A resultant laser beam passes through a range telescope, an azimuth telescope, and a Fourier transform filter located between the range and azimuth telescopes, and forms an image for recording on an image film. A compensation means for Doppler shift in the radar return pulse intensity information includes a beam splitter for reflecting the modulated laser beam, after having passed through the Fourier transform filter, to a detection screen having two photodiodes mounted on it.

Three-dimensional high-definition flow in the diagnosis of placental lakes.

PubMed

Inubashiri, Eisuke; Deguchi, Keizou; Abe, Kiyotaka; Saitou, Atushi; Watanabe, Yukio; Akutagawa, Noriyuki; Kuroki, Katumaru; Sugawara, Masaki; Maeda, Nobuhiko

2014-10-01

Placental lakes are sonolucent areas often found in the normal placenta. Most of them are asymptomatic. They are sometimes related to placenta accreta or intrauterine fetal growth restriction, among other conditions. Although Doppler sonography is useful for evaluating noxious placental lakes, it is not easy to adapt Doppler studies to conventional two-dimensional color Doppler sonography because of the low-velocity blood flow and high vascularity in the placenta. Here, we demonstrate how three-dimensional high-definition imaging of flow provides a novel visual depiction of placental lakes, which helps substantially with the differential diagnosis. As far as we know, there have been no previous reports of observation of placental lakes using three-dimensional high-definition imaging of flow.

Comparison of numerical techniques for the evaluation of the Doppler broadening functions psi(x,theta) and chi(x,theta)

NASA Technical Reports Server (NTRS)

Canright, R. B., Jr.; Semler, T. T.

1972-01-01

Several approximations to the Doppler broadening functions psi(x, theta) and chi(x, theta) are compared with respect to accuracy and speed of evaluation. A technique, due to A. M. Turning (1943), is shown to be at least as accurate as direct numerical quadrature and somewhat faster than Gaussian quadrature. FORTRAN 4 listings are included.

Augmented reality and dynamic infrared thermography for perforator mapping in the anterolateral thigh

PubMed Central

Cifuentes, Ignacio Javier; Dagnino, Bruno Leonardo; Salisbury, María Carolina; Perez, María Eliana; Ortega, Claudia; Maldonado, Daniela

2018-01-01

Dynamic infrared thermography (DIRT) has been used for the preoperative mapping of cutaneous perforators. This technique has shown a positive correlation with intraoperative findings. Our aim was to evaluate the accuracy of perforator mapping with DIRT and augmented reality using a portable projector. For this purpose, three volunteers had both of their anterolateral thighs assessed for the presence and location of cutaneous perforators using DIRT. The obtained image of these “hotspots” was projected back onto the thigh and the presence of Doppler signals within a 10-cm diameter from the midpoint between the lateral patella and the anterior superior iliac spine was assessed using a handheld Doppler device. Hotspots were identified in all six anterolateral thighs and were successfully projected onto the skin. The median number of perforators identified within the area of interest was 5 (range, 3–8) and the median time needed to identify them was 3.5 minutes (range, 3.3–4.0 minutes). Every hotspot was correlated to a Doppler sound signal. In conclusion, augmented reality can be a reliable method for transferring the location of perforators identified by DIRT onto the thigh, facilitating its assessment and yielding a reliable map of potential perforators for flap raising. PMID:29788686

Clinical use of ultrasonography associated with color Doppler in the diagnosis and follow-up of acute pyelonephritis.

PubMed

Dell'Atti, Lucio; Borea, Pier Andrea; Ughi, Gianni; Russo, Gian Rosario

2010-12-01

The purpose of this study is to evaluate the current role of the Ultrasound associated with the color-Doppler in the diagnosis of acute pyelonephritis (APN) and to compare ultrasound images with CT images in order to reduce the amount radiation absorbe without significant loss of diagnostic efficacy, since this disease in most cases affects young adults. We studied 38 patients (aged 17-65 years) who presented from September 2007 to March 2010 to the emergency department with suspected diagnosis of APN. All patients underwent first to an ultrasound study, then to abdominal CT. Renal, perirenal and extrarenal tomographic findings usually associated with acute pyelonephritis were analyzed, in an attempt to identify what are the differences with respect to the images obtained with an ultrasound study. All patients then performed ultrasonography and/or abdominal CT evaluation one month later, 25 patients repeated both examinations, while the other 13 repeated only ultrasound. In 38 subjects with suspected APN, CT assessed the presence in 79% and in 21% the absence of the disease. Ultrasonography in 68% of cases diagnosed APN, by an increase in kidney size related to the presence of hypoechoic areas associated to edema, blurred margins and reduction of the color-Doppler vascularity. Ultrasound associated with the use of color-Doppler revealed a sensibility of 76% and specificity of 75%. Color and power-Doppler have better diagnostic accuracy than basic gray scale ultrasound, in the diagnosis of focal pyelonephritis. Therefore the combined use of ultrasound and color-Doppler can obtain useful information about the diagnosis and follow-up of the disease, with an improvement in terms of cost, without significantly altering the diagnostic efficacy and reducing the amount of radiation absorbed.

[Role of cardiac magnetic resonance in cardiac involvement of Fabry disease].

PubMed

Serra, Viviana M; Barba, Miguel Angel; Torrá, Roser; Pérez De Isla, Leopoldo; López, Mónica; Calli, Andrea; Feltes, Gisela; Torras, Joan; Valverde, Victor; Zamorano, José L

2010-09-04

Fabry disease is a hereditary disorder. Clinical manifestations are multisystemic. The majority of the patients remain undiagnosed until late in life, when alterations could be irreversible. Early detection of cardiac symptoms is of major interest in Fabry's disease (FD) in order to gain access to enzyme replacement therapy. Echo-Doppler tissular imaging (TDI) has been used as a cardiologic early marker in FD. This study is intended to determine whether the cardiac magnetic resonance is as useful tool as TDI for the early detection of cardiac affectation in FD. Echocardiography, tissue Doppler and Cardio magnetic resonance was performed in 20 patients with confirmed Fabry Disease. Left ventricular hypertrophy was defined as septum and left ventricular posterior wall thickness ≥12 mm. An abnormal TDI velocity was defined as (Sa), (Ea) and/or (Aa) velocities <8 cm/s at either the septal or lateral corner. Late phase gadolinium-enhanced images sequences were obtained using magnetic resonance. Twenty patients included in the study were divided into three groups: 1. Those without left ventricular hypertrophy nor tissue Doppler impairment 2. Those without left ventricular hypertrophy and tissue Doppler impairment 3. Those with left ventricular hypertrophy and Tissue Doppler impairment. Late gadolinium enhancement was found in only one patient, who has already altered DTI and LVH. Tissue Doppler imaging (TDI) is the only diagnostic tool able to provide early detection of cardiac affectation in patients with FD. Magnetic resonance provides information of the disease severity in patients with LVH, but can not be used as an early marker of cardiac disease in patients with FD. However MRI could be of great value for diagnostic stratification. Copyright © 2009 Elsevier España, S.L. All rights reserved.

Volumetric vessel reconstruction method for absolute blood flow velocity measurement in Doppler OCT images

NASA Astrophysics Data System (ADS)

Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

2017-02-01

Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it not only relates to the properties of the laser and the scattering particles, but also relates to the geometry of both directions of the laser beam and the flow. In this paper, focusing on the analysis of cerebral hemodynamics, we presents a method to quantify the total absolute blood flow velocity in middle cerebral artery (MCA) based on volumetric vessel reconstruction from pure DOCT images. A modified region growing segmentation method is first used to localize the MCA on successive DOCT B-scan images. Vessel skeletonization, followed by an averaging gradient angle calculation method, is then carried out to obtain Doppler angles along the entire MCA. Once the Doppler angles are determined, the absolute blood flow velocity of each position on the MCA is easily found. Given a seed point position on the MCA, our approach could achieve automatic quantification of the fully distributed absolute BFV. Based on experiments conducted using a swept-source optical coherence tomography system, our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches in the rodent brain.

Modelling and characterisation of a ultrasound-actuated needle for improved visibility in ultrasound-guided regional anaesthesia and tissue biopsy.

PubMed

Kuang, Y; Hilgers, A; Sadiq, M; Cochran, S; Corner, G; Huang, Z

2016-07-01

Clear needle visualisation is recognised as an unmet need for ultrasound guided percutaneous needle procedures including regional anaesthesia and tissue biopsy. With inadequate needle visibility, these procedures may result in serious complications or a failed operation. This paper reports analysis of the modal behaviour of a previously proposed ultrasound-actuated needle configuration, which may overcome this problem by improving needle visibility in colour Doppler imaging. It uses a piezoelectric transducer to actuate longitudinal resonant modes in needles (outer diameter 0.8-1.2mm, length>65mm). The factors that affect the needle's vibration mode are identified, including the needle length, the transducer's resonance frequency and the gripping position. Their effects are investigated using finite element modelling, with the conclusions validated experimentally. The actuated needle was inserted into porcine tissue up to 30mm depth and its visibility was observed under colour Doppler imaging. The piezoelectric transducer is able to generate longitudinal vibration with peak-to-peak amplitude up to 4μm at the needle tip with an actuating voltage of 20Vpp. Actuated in longitudinal vibration modes (distal mode at 27.6kHz and transducer mode at 42.2kHz) with a drive amplitude of 12-14Vpp, a 120mm needle is delineated as a coloured line in colour Doppler images, with both needle tip and shaft visualised. The improved needle visibility is maintained while the needle is advanced into the tissue, thus allowing tracking of the needle position in real time. Moreover, the needle tip is highlighted by strong coloured artefacts around the actuated needle generated by its flexural vibration. A limitation of the technique is that the transducer mode requires needles of specific lengths so that the needle's resonance frequency matches the transducer. This may restrict the choice of needle lengths in clinical applications. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Blood flow velocity measurement by endovascular Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Sun, Cuiru; Nolte, Felix; Vuong, Barry; Cheng, Kyle H. Y.; Lee, Kenneth K. C.; Standish, Beau A.; Courtney, Brian; Marotta, Tom R.; Yang, Victor X. D.

2013-03-01

Blood flow velocity and volumetric flow measurements are important parameters for assessment of the severity of stenosis and the outcome of interventional therapy. However, feasibility of intravascular flow measurement using a rotational catheter based phase resolved Doppler optical coherence tomography (DOCT) is difficult. Motion artefacts induced by the rotating optical imaging catheter, and the radially dependent noise background of measured Doppler signals are the main challenges encountered. In this study, a custom-made data acquisition system and developed algorithms to remove non-uniform rotational distortion (NURD) induced phase shift artefact by tracking the phase shift observed on catheter sheath. The flow velocity is calculated from Doppler shift obtained by Kasai autocorrelation after motion artefact removal. Blood flow velocity profiles in porcine carotid arteries in vivo were obtained at 100 frames/s with 500 A-lines/frame and DOCT images were taken at 20 frames/s with 2500 A-lines/frame. Time-varying velocity profiles were obtained at an artery branch. Furthermore, the identification of a vein adjacent to the catheterized vessel based on the color Doppler signal was also observed. The absolute measurement of intravascular flow using a rotating fiber catheter can provide insights to different stages of interventional treatment of stenosis in carotid artery.

Pennation angle dependency in skeletal muscle tissue doppler strain in dynamic contractions.

PubMed

Lindberg, Frida; Öhberg, Fredrik; Granåsen, Gabriel; Brodin, Lars-Åke; Grönlund, Christer

2011-07-01

Tissue velocity imaging (TVI) is a Doppler based ultrasound technique that can be used to study regional deformation in skeletal muscle tissue. The aim of this study was to develop a biomechanical model to describe the TVI strain's dependency on the pennation angle. We demonstrate its impact as the subsequent strain measurement error using dynamic elbow contractions from the medial and the lateral part of biceps brachii at two different loadings; 5% and 25% of maximum voluntary contraction (MVC). The estimated pennation angles were on average about 4° in extended position and increased to a maximal of 13° in flexed elbow position. The corresponding relative angular error spread from around 7% up to around 40%. To accurately apply TVI on skeletal muscles, the error due to angle changes should be compensated for. As a suggestion, this could be done according to the presented model. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering.

PubMed

Ehn, Andreas; Zhu, Jiajian; Li, Xuesong; Kiefer, Johannes

2017-03-01

Gaining information of species, temperature, and velocity distributions in turbulent combustion and high-speed reactive flows is challenging, particularly for conducting measurements without influencing the experimental object itself. The use of optical and spectroscopic techniques, and in particular laser-based diagnostics, has shown outstanding abilities for performing non-intrusive in situ diagnostics. The development of instrumentation, such as robust lasers with high pulse energy, ultra-short pulse duration, and high repetition rate along with digitized cameras exhibiting high sensitivity, large dynamic range, and frame rates on the order of MHz, has opened up for temporally and spatially resolved volumetric measurements of extreme dynamics and complexities. The aim of this article is to present selected important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering. Applicable laser-based techniques for investigations of turbulent flows and combustion such as planar laser-induced fluorescence, Raman and Rayleigh scattering, coherent anti-Stokes Raman scattering, laser-induced grating scattering, particle image velocimetry, laser Doppler anemometry, and tomographic imaging are reviewed and described with some background physics. In addition, demands on instrumentation are further discussed to give insight in the possibilities that are offered by laser flow diagnostics.

INVASIVE AND NON-INVASIVE TECHNIQUES FOR DETECTING PORTAL HYPERTENSION AND PREDICTING VARICEAL BLEEDING IN CIRRHOSIS: A REVIEW

PubMed Central

Zardi, Enrico Maria; Di Matteo, Francesco Maria; Pacella, Claudio Maurizio; Sanyal, Arun J

2016-01-01

Portal hypertension is a severe syndrome that may derive from pre-sinusoidal, sinusoidal and post-sinusoidal causes. As a consequence, several complications (i.e., ascites, oesophageal varices) may develop. In sinusoidal portal hypertension, hepatic venous pressure gradient (HVPG) is a reliable method for defining the grade of portal pressure, establishing the effectiveness of the treatment and predicting the occurrence of complications; however, some questions exist regarding its ability to discriminate bleeding from nonbleeding varices in cirrhotic patients. Other imaging techniques (transient elastography, endoscopy, endosonography and duplex Doppler sonography) for assessing causes and complications of portal hypertensive syndrome are available and may be valuable for the management of these patients. In this review, we evaluate invasive and non-invasive techniques currently employed to obtain a clinical prediction of deadly complications, such as variceal bleeding in patients affected by sinusoidal portal hypertension, in order to create a diagnostic algorithm to manage them. Again, HVPG appears to be the reference standard to evaluate portal hypertension and monitor the response to treatment, but its ability to predict several complications and support management decisions might be further improved through the diagnostic combination with other imaging techniques. PMID:24328372

Invasive and non-invasive techniques for detecting portal hypertension and predicting variceal bleeding in cirrhosis: a review.

PubMed

Zardi, Enrico Maria; Di Matteo, Francesco Maria; Pacella, Claudio Maurizio; Sanyal, Arun J

2014-02-01

Portal hypertension is a severe syndrome that may derive from pre-sinusoidal, sinusoidal, and post-sinusoidal causes. As a consequence, several complications (i.e. ascites, oesophageal varices) may develop. In sinusoidal portal hypertension, hepatic venous pressure gradient (HVPG) is a reliable method for defining the grade of portal pressure, establishing the effectiveness of the treatment, and predicting the occurrence of complications; however, some questions exist regarding its ability to discriminate bleeding from non-bleeding varices in cirrhotic patients. Other imaging techniques (transient elastography, endoscopy, endosonography, and duplex Doppler sonography) for assessing causes and complications of portal hypertensive syndrome are available and may be valuable for the management of these patients. In this review, we evaluate invasive and non-invasive techniques currently employed to obtain a clinical prediction of deadly complications, such as variceal bleeding in patients affected by sinusoidal portal hypertension, in order to create a diagnostic algorithm to manage them. Again, HVPG appears to be the reference standard to evaluate portal hypertension and monitor the response to treatment, but its ability to predict several complications and support management decisions might be further improved through the diagnostic combination with other imaging techniques.

Imaging shear wave propagation for elastic measurement using OCT Doppler variance method

NASA Astrophysics Data System (ADS)

Zhu, Jiang; Miao, Yusi; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K. Kirk; Zhou, Qifa; Chen, Zhongping

2016-03-01

In this study, we have developed an acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) method for the visualization of the shear wave and the calculation of the shear modulus based on the OCT Doppler variance method. The vibration perpendicular to the OCT detection direction is induced by the remote acoustic radiation force (ARF) and the shear wave propagating along the OCT beam is visualized by the OCT M-scan. The homogeneous agar phantom and two-layer agar phantom are measured using the ARFOE-OCE system. The results show that the ARFOE-OCE system has the ability to measure the shear modulus beyond the OCT imaging depth. The OCT Doppler variance method, instead of the OCT Doppler phase method, is used for vibration detection without the need of high phase stability and phase wrapping correction. An M-scan instead of the B-scan for the visualization of the shear wave also simplifies the data processing.

Quantitative Doppler Analysis Using Conventional Color Flow Imaging Acquisitions.

PubMed

Karabiyik, Yucel; Ekroll, Ingvild Kinn; Eik-Nes, Sturla H; Lovstakken, Lasse

2018-05-01

Interleaved acquisitions used in conventional triplex mode result in a tradeoff between the frame rate and the quality of velocity estimates. On the other hand, workflow becomes inefficient when the user has to switch between different modes, and measurement variability is increased. This paper investigates the use of power spectral Capon estimator in quantitative Doppler analysis using data acquired with conventional color flow imaging (CFI) schemes. To preserve the number of samples used for velocity estimation, only spatial averaging was utilized, and clutter rejection was performed after spectral estimation. The resulting velocity spectra were evaluated in terms of spectral width using a recently proposed spectral envelope estimator. The spectral envelopes were also used for Doppler index calculations using in vivo and string phantom acquisitions. In vivo results demonstrated that the Capon estimator can provide spectral estimates with sufficient quality for quantitative analysis using packet-based CFI acquisitions. The calculated Doppler indices were similar to the values calculated using spectrograms estimated on a commercial ultrasound scanner.

Agile waveforms for joint SAR-GMTI processing

NASA Astrophysics Data System (ADS)

Jaroszewski, Steven; Corbeil, Allan; McMurray, Stephen; Majumder, Uttam; Bell, Mark R.; Corbeil, Jeffrey; Minardi, Michael

2016-05-01

Wideband radar waveforms that employ spread-spectrum techniques were investigated and experimentally tested. The waveforms combine bi-phase coding with a traditional LFM chirp and are applicable to joint SAR-GMTI processing. After de-spreading, the received signals can be processed to support simultaneous GMTI and high resolution SAR imaging missions by airborne radars. The spread spectrum coding techniques can provide nearly orthogonal waveforms and offer enhanced operations in some environments by distributing the transmitted energy over a large instantaneous bandwidth. The LFM component offers the desired Doppler tolerance. In this paper, the waveforms are formulated and a shift-register approach for de-spreading the received signals is described. Hardware loop-back testing has shown the feasibility of using these waveforms in experimental radar test bed.

Magnetic Doppler imaging of α2 Canum Venaticorum in all four Stokes parameters. Unveiling the hidden complexity of stellar magnetic fields

NASA Astrophysics Data System (ADS)

Kochukhov, O.; Wade, G. A.

2010-04-01

Context. Strong organized magnetic fields have been studied in the upper main sequence chemically peculiar stars for more than half a century. However, only recently have observational methods and numerical techniques become sufficiently mature to allow us to record and interpret high-resolution four Stokes parameter spectra, leading to the first assumption-free magnetic field models of these stars. Aims: Here we present a detailed magnetic Doppler imaging analysis of the spectropolarimetric observations of the prototypical magnetic Ap star α2 CVn. This is the second star for which the magnetic field topology and horizontal chemical abundance inhomogeneities have been inferred directly from phase-resolved observations of line profiles in all four Stokes parameters, free from the traditional assumption of a low-order multipolar field geometry. Methods: We interpret the rotational modulation of the circular and linear polarization profiles of the strong Fe II and Cr II lines in the spectra of α2 CVn recorded with the MuSiCoS spectropolarimeter. The surface abundance distributions of the two chemical elements and a full vector map of the stellar magnetic field are reconstructed in a self-consistent inversion using our state-of-the-art magnetic Doppler imaging code Invers10. Results: We succeeded in reproducing most of the details of the available spectropolarimetric observations of α2 CVn with a magnetic map which combines a global dipolar-like field topology with localized spots of higher field intensity. We demonstrate that these small-scale magnetic structures are inevitably required to fit the linear polarization spectra; however, their presence cannot be inferred from the Stokes I and V observations alone. We also found high-contrast surface distributions of Fe and Cr, with both elements showing abundance minima in the region of weaker and topologically simpler magnetic field. Conclusions: Our magnetic Doppler imaging analysis of α2 CVn and previous results for 53 Cam support the view that the upper main sequence stars can harbour fairly complex surface magnetic fields which resemble oblique dipoles only at the largest spatial scales. Spectra in all four Stokes parameters are absolutely essential to unveil and meaningfully characterize this field complexity in Ap stars. We therefore suggest that understanding magnetism of stars in other parts of the H-R diagram is similarly incomplete without investigation of their linear polarization spectra. Based on data obtained using the Télescope Bernard Lyot at Observatoire du Pic du Midi.

LASER BIOLOGY AND MEDICINE: Arterial pulse shape measurement using self-mixing effect in a diode laser

NASA Astrophysics Data System (ADS)

Hast, J.; Myllylä, Risto; Sorvoja, H.; Miettinen, J.

2002-11-01

The self-mixing effect in a diode laser and the Doppler technique are used for quantitative measurements of the cardiovascular pulses from radial arteries of human individuals. 738 cardiovascular pulses from 10 healthy volunteers were studied. The Doppler spectrograms reconstructed from the Doppler signal, which is measured from the radial displacement of the radial artery, are compared to the first derivative of the blood pressure signals measured from the middle finger by the Penaz technique. The mean correlation coefficient between the Doppler spectrograms and the first derivative of the blood pressure signals was 0.84, with a standard deviation of 0.05. Pulses with the correlation coefficient less than 0.7 were neglected in the study. Percentage of successfully detected pulses was 95.7%. It is shown that cardiovascular pulse shape from the radial artery can be measured noninvasively by using the self-mixing interferometry.

Modeling the Performance of Direct-Detection Doppler Lidar Systems in Real Atmospheres

NASA Technical Reports Server (NTRS)

McGill, Matthew J.; Hart, William D.; McKay, Jack A.; Spinhirne, James D.

1999-01-01

Previous modeling of the performance of spaceborne direct-detection Doppler lidar systems has assumed extremely idealized atmospheric models. Here we develop a technique for modeling the performance of these systems in a more realistic atmosphere, based on actual airborne lidar observations. The resulting atmospheric model contains cloud and aerosol variability that is absent in other simulations of spaceborne Doppler lidar instruments. To produce a realistic simulation of daytime performance, we include solar radiance values that are based on actual measurements and are allowed to vary as the viewing scene changes. Simulations are performed for two types of direct-detection Doppler lidar systems: the double-edge and the multi-channel techniques. Both systems were optimized to measure winds from Rayleigh backscatter at 355 nm. Simulations show that the measurement uncertainty during daytime is degraded by only about 10-20% compared to nighttime performance, provided a proper solar filter is included in the instrument design.

Modeling the performance of direct-detection Doppler lidar systems including cloud and solar background variability.

PubMed

McGill, M J; Hart, W D; McKay, J A; Spinhirne, J D

1999-10-20

Previous modeling of the performance of spaceborne direct-detection Doppler lidar systems assumed extremely idealized atmospheric models. Here we develop a technique for modeling the performance of these systems in a more realistic atmosphere, based on actual airborne lidar observations. The resulting atmospheric model contains cloud and aerosol variability that is absent in other simulations of spaceborne Doppler lidar instruments. To produce a realistic simulation of daytime performance, we include solar radiance values that are based on actual measurements and are allowed to vary as the viewing scene changes. Simulations are performed for two types of direct-detection Doppler lidar system: the double-edge and the multichannel techniques. Both systems were optimized to measure winds from Rayleigh backscatter at 355 nm. Simulations show that the measurement uncertainty during daytime is degraded by only approximately 10-20% compared with nighttime performance, provided that a proper solar filter is included in the instrument design.

ImSyn: photonic image synthesis applied to synthetic aperture radar, microscopy, and ultrasound imaging

NASA Astrophysics Data System (ADS)

Turpin, Terry M.; Lafuse, James L.

1993-02-01

ImSynTM is an image synthesis technology, developed and patented by Essex Corporation. ImSynTM can provide compact, low cost, and low power solutions to some of the most difficult image synthesis problems existing today. The inherent simplicity of ImSynTM enables the manufacture of low cost and reliable photonic systems for imaging applications ranging from airborne reconnaissance to doctor's office ultrasound. The initial application of ImSynTM technology has been to SAR processing; however, it has a wide range of applications such as: image correlation, image compression, acoustic imaging, x-ray tomographic (CAT, PET, SPECT), magnetic resonance imaging (MRI), microscopy, range- doppler mapping (extended TDOA/FDOA). This paper describes ImSynTM in terms of synthetic aperture microscopy and then shows how the technology can be extended to ultrasound and synthetic aperture radar. The synthetic aperture microscope (SAM) enables high resolution three dimensional microscopy with greater dynamic range than real aperture microscopes. SAM produces complex image data, enabling the use of coherent image processing techniques. Most importantly SAM produces the image data in a form that is easily manipulated by a digital image processing workstation.

Enhanced spectral domain optical coherence tomography for pathological and functional studies

NASA Astrophysics Data System (ADS)

Yuan, Zhijia

Optical coherence tomography (OCT) is a novel technique that enables noninvasive or minimally invasive, cross-sectional imaging of biological tissue at sub-10mum spatial resolution and up to 2-3mm imaging depth. Numerous technological advances have emerged in recent years that have shown great potential to develop OCT into a powerful imaging and diagnostic tools. In particular, the implementation of Fourier-domain OCT (FDOCT) is a major step forward that leads to greatly improved imaging rate and image fidelity of OCT. This dissertation summarizes the work that focuses on enhancing the performances and functionalities of spectral radar based FDOCT (SDOCT) for pathological and functional applications. More specifically, chapters 1-4 emphasize on the development of SDOCT and its utility in pathological studies, including cancer diagnosis. The principle of SDOCT is first briefly outlined, followed by the design of our bench-top SDOCT systems with emphasis on spectral linear interpolation, calibration and system dispersion compensation. For ultrahigh-resolution SDOCT, time-lapse image registration and frame averaging is introduced to effectively reduce speckle noise and uncover subcellular details, showing great promise for enhancing the diagnosis of carcinoma in situ. To overcome the image depth limitation of OCT, a dual-modal imaging method combing SDOCT with high-frequency ultrasound is proposed and examined in animal cancer models to enhance the sensitivity and staging capabilities for bladder cancer diagnosis. Chapters 5-7 summarize the work on developing Doppler SDOCT for functional studies. Digital-frequency-ramping OCT (DFR-OCT) is developed in the study, which has demonstrated the ability to significantly improve the signal-to-noise ratio and thus sensitivity for retrieving subsurface blood flow imaging. New DFR algorithms and imaging processing methods are discussed to further enhance cortical CBF imaging. Applications of DFR-OCT for brain functional studies are presented and laser speckle imaging is combined to enable quantitative cerebral blood flow (CBF) imaging at high spatiotemporal resolutions. An angiography-enhanced Doppler optical coherence tomography (aDFR-OCT) was also demonstrated to enable quantitative imaging of capillary changes for brain functional studies. Lastly, future work on technological development and potential biomedical applications is briefly outlined.

In vivo endoscopic Doppler optical coherence tomography imaging of mouse colon

NASA Astrophysics Data System (ADS)

Welge, Weston A.; Barton, Jennifer K.

2016-03-01

Colorectal cancer remains the second deadliest cancer in the United States, despite the high sensitivity and specificity of colonoscopy and sigmoidoscopy. While these standard imaging procedures can accurately detect medium and large polyps, some studies have shown miss rates up to 25% for polyps less than 5 mm in diameter. An imaging modality capable of detecting small lesions could potentially improve patient outcomes. Optical coherence tomography (OCT) has been shown to be a powerful imaging modality for adenoma detection in a mouse model of colorectal cancer. While previous work has focused on analyzing the structural OCT images based on thickening of the mucosa and changes in light attenuation in depth, imaging the microvasculature of the colon may enable earlier detection of polyps. The structure and function of vessels grown to support tumor growth are markedly different from healthy vessels. Doppler OCT is capable of imaging microvessels in vivo. We developed a method of processing raw fringe data from a commercial swept-source OCT system using a lab-built miniature endoscope to extract microvessels. This method can be used to measure vessel count and density and to measure flow velocities. This may improve early detection and aid in the development of new chemopreventive and chemotherapeutic drugs. We present, to the best of our knowledge, the first endoscopic Doppler OCT images of in vivo mouse colon.

Relationship between the blood perfusion values determined by laser speckle imaging and laser Doppler imaging in normal skin and port wine stains.

PubMed

Chen, Defu; Ren, Jie; Wang, Ying; Zhao, Hongyou; Li, Buhong; Gu, Ying

2016-03-01

Laser Doppler imaging (LDI) and laser speckle imaging (LSI) are two major optical techniques aiming at non-invasively imaging the skin blood perfusion. However, the relationship between perfusion values determined by LDI and LSI has not been fully explored. 8 healthy volunteers and 13 PWS patients were recruited. The perfusions in normal skin on the forearm of 8 healthy volunteers were simultaneously measured by both LDI and LSI during post-occlusive reactive hyperemia (PORH). Furthermore, the perfusions of port wine stains (PWS) lesions and contralateral normal skin of 10 PWS patients were also determined. In addition, the perfusions for PWS lesions from 3 PWS patients were successively monitored at 0, 10 and 20min during vascular-targeted photodynamic therapy (V-PDT). The average perfusion values determined by LSI were compared with those of LDI for each subject. In the normal skin during PORH, power function provided better fits of perfusion values than linear function: powers for individual subjects go from 1.312 to 1.942 (R(2)=0.8967-0.9951). There was a linear relationship between perfusion values determined by LDI and LSI in PWS and contralateral normal skin (R(2)=0.7308-0.9623), and in PWS during V-PDT (R(2)=0.8037-0.9968). The perfusion values determined by LDI and LSI correlate closely in normal skin and PWS over a broad range of skin perfusion. However, it still suggests that perfusion range and characteristics of the measured skin should be carefully considered if LDI and LSI measures are compared. Copyright © 2015 Elsevier B.V. All rights reserved.

Multimodal ultrasonographic assessment of leiomyosarcoma of the femoral vein in a patient misdiagnosed as having deep vein thrombosis: A case report.

PubMed

Zhang, Mei; Yan, Feng; Huang, Bin; Wu, Zhoupeng; Wen, Xiaorong

2017-11-01

Primary leiomyosarcoma (LMS) of the vein is a rare tumor that arises from the smooth muscle cells of the vessel wall and has an extremely poor prognosis. This tumor can occur in vessels such as the inferior vena cava, great saphenous vein, femoral vein, iliac vein, popliteal vein, and renal vein; the inferior vena cava is the most common site. LMS of the femoral vein can result in edema and pain in the lower extremity; therefore, it is not easy to be differentiated from deep vein thrombosis (DVT). Moreover, virtually no studies have described the ultrasonographic features of LMS of the vein in detail. We present a case of a 55-year-old woman with LMS of the left femoral vein that was misdiagnosed as having deep vein thrombosis (DVT) on initial ultrasonographic examination. The patient began to experience edema and pain in her left leg seven months previously. She was diagnosed as having DVT on initial ultrasonographic examination, but the DVT treatment that she had received for 7 months failed to improve the status of her left lower limb. She subsequently underwent re-examination by means of a multimodal ultrasonographic imaging approach (regular B-mode imaging, color Doppler imaging, pulsed-wave Doppler imaging, contrast-enhanced ultrasonography), which confirmed a diagnosis of LMS. This patient was treated successfully with surgery. This case demonstrates that use of multiple ultrasonographic imaging techniques can be helpful to diagnose LMS accurately. Detection of vasculature in a dilated vein filled with a heterogeneous hypoechoic substance on ultrasonography is a sign of a tumor. The pitfall of misdiagnosing this tumor as DVT is a useful reminder.

Multimodal ultrasonographic assessment of leiomyosarcoma of the femoral vein in a patient misdiagnosed as having deep vein thrombosis

PubMed Central

Zhang, Mei; Yan, Feng; Huang, Bin; Wu, Zhoupeng; Wen, Xiaorong

2017-01-01

Abstract Rationale: Primary leiomyosarcoma (LMS) of the vein is a rare tumor that arises from the smooth muscle cells of the vessel wall and has an extremely poor prognosis. This tumor can occur in vessels such as the inferior vena cava, great saphenous vein, femoral vein, iliac vein, popliteal vein, and renal vein; the inferior vena cava is the most common site. LMS of the femoral vein can result in edema and pain in the lower extremity; therefore, it is not easy to be differentiated from deep vein thrombosis (DVT). Moreover, virtually no studies have described the ultrasonographic features of LMS of the vein in detail. Patient concerns: We present a case of a 55-year-old woman with LMS of the left femoral vein that was misdiagnosed as having deep vein thrombosis (DVT) on initial ultrasonographic examination. The patient began to experience edema and pain in her left leg seven months previously. She was diagnosed as having DVT on initial ultrasonographic examination, but the DVT treatment that she had received for 7 months failed to improve the status of her left lower limb. Diagnoses: She subsequently underwent re-examination by means of a multimodal ultrasonographic imaging approach (regular B-mode imaging, color Doppler imaging, pulsed-wave Doppler imaging, contrast-enhanced ultrasonography), which confirmed a diagnosis of LMS. Interventions: This patient was treated successfully with surgery. Outcomes: This case demonstrates that use of multiple ultrasonographic imaging techniques can be helpful to diagnose LMS accurately. Detection of vasculature in a dilated vein filled with a heterogeneous hypoechoic substance on ultrasonography is a sign of a tumor. Lessons: The pitfall of misdiagnosing this tumor as DVT is a useful reminder. PMID:29145269

Relationship of spaced antenna and Doppler techniques for velocity measurements (keynote paper), part 3

NASA Technical Reports Server (NTRS)

Vincent, R. A.

1984-01-01

The Doppler, spaced-antenna and interferometric methods of measuring wind velocities all use the same basic information, the Doppler shifts imposed on backscattered radio waves, but they process it in different ways. The Doppler technique is most commonly used at VHF since the narrow radar beams are readily available. However, the spaced antenna (SA) method has been successfully used with the SOUSY and Adelaide radars. At MF/HF the spaced antenna method is widely used since the large antenna arrays (diameter 1 km) required to generate narrow beams are expensive to construct. Where such arrays of this size are available then the Doppler method has been successfully used (e.g., Adelaide and Brisbane). In principle, the factors which influence the choice of beam pointing angle, the optimum antenna spacing will be the same whether operation is at MF or VHF. Many of the parameters which govern the efficient use of wind measuring systems have been discussed at previous MST workshops. Some of the points raised by these workshops are summarized.

Discharge measurements at gaging stations

USGS Publications Warehouse

Turnipseed, D. Phil; Sauer, Vernon B.

2010-01-01

The techniques and standards for making discharge measurements at streamflow gaging stations are described in this publication. The vertical axis rotating-element current meter, principally the Price current meter, has been traditionally used for most measurements of discharge; however, advancements in acoustic technology have led to important developments in the use of acoustic Doppler current profilers, acoustic Doppler velocimeters, and other emerging technologies for the measurement of discharge. These new instruments, based on acoustic Doppler theory, have the advantage of no moving parts, and in the case of the acoustic Doppler current profiler, quickly and easily provide three-dimensional stream-velocity profile data through much of the vertical water column. For much of the discussion of acoustic Doppler current profiler moving-boat methodology, the reader is referred to U.S. Geological Survey Techniques and Methods 3-A22 (Mueller and Wagner, 2009). Personal digital assistants (PDAs), electronic field notebooks, and other personal computers provide fast and efficient data-collection methods that are more error-free than traditional hand methods. The use of portable weirs and flumes, floats, volumetric tanks, indirect methods, and tracers in measuring discharge are briefly described.

Analysing simple motions using the Doppler effect—‘seeing’ sound

NASA Astrophysics Data System (ADS)

Stonawski, Tamás; Gálik, Tamás

2017-01-01

The Doppler effect has seen widespread use in the past hundred years. It is used for medical imaging, for measuring speed, temperature, direction, etc, and it makes the spatial relations of motion easy to map. The Doppler effect also allows GPS receivers to measure the speed of a vehicle significantly more accurately than dashboard speedometers. Its diverse applications have prompted us to revisit the simple motions from kinematics with the help of everyday objects in our experiments.

Power Doppler ultrasound of rheumatoid synovitis: quantification of vascular signal and analysis of interobserver variability.

PubMed

Kamishima, Tamotsu; Tanimura, Kazuhide; Henmi, Mihoko; Narita, Akihiro; Sakamoto, Fumihiko; Terae, Satoshi; Shirato, Hiroki

2009-05-01

The objective of this study was to assess interobserver uncertainties in power Doppler (PD) examination of the fingers of patients with rheumatoid arthritis (RA), by separating the source of the discrepancy into (1) acquisition of the images and (2) criteria for assessment of the images. Twenty patients who had been diagnosed with RA were enrolled in this study. Ultrasound examinations were performed by one inexperienced and two experienced sonographers. Interobserver variation was measured using a conventional semiquantitative image grading scale. Interobserver variation of the quantitative PD (QPD) index (the summation of the colored pixels in a region of interest) was also assessed. The agreement was higher between the two experienced sonographers (kappa value of 0.8) than between experienced and inexperienced sonographers (kappa value, 0.6-0.7) in the semiquantitative image grading scale. Results suggest that the difference in the assessment on the image grading scale was due more to the difference in the acquisition of the images than to variations in the grading criteria between sonographers. An excellent relationship was noted between the image grading scale and the QPD index for Doppler signal with a Spearman's coefficient of rank correlation of 0.83 (P < 0.0001). Interobserver discrepancies in the image grading and QPD index methods were due more to the difference in the acquisition of the image than to the grading criteria used. The QPD index seems to be as reliable as the image grading scale with reasonable interobserver agreement between experienced sonographers.

Preamputation evaluation of lower-limb skeletal muscle perfusion with H(2) (15)O positron emission tomography.

PubMed

Scremin, Oscar U; Figoni, Stephen F; Norman, Keith; Scremin, A M Erika; Kunkel, Charles F; Opava-Rutter, Dorene; Schmitter, Eric D; Bert, Alberto; Mandelkern, Mark

2010-06-01

To establish whether muscle blood flow (MBF) measurements with O-water positron emission tomography could reliably identify patients with critical limb ischemia and detect and quantify a distal deficit in skeletal MBF in these cases. O-water positron emission tomography scans were performed at rest or during unloaded ankle plantar and dorsiflexion exercise of the diseased leg in 17 subjects with leg ischemia or on a randomly selected leg of 18 age-matched healthy control subjects. TcPO2 was evaluated with Novametrix monitors and perfusion of skin topically heated to 44 degrees C and adjacent nonheated areas with a Moor Instruments laser Doppler imaging scanner. The enhancement of MBF induced by exercise was significantly lower in ischemic than in normal legs, and the sensitivity and specificity of this phenomenon were similar to those of laser Doppler imaging or TcPO2 in identifying ischemia subjects. In addition, the exercise MBF deficit was predominant at the distal-leg levels, indicating the ability of the technique to help determine the correct level of amputation. Skeletal MBF of legs with severe ischemia can be detected accurately with O-water positron emission tomography and could add valuable information about viability of skeletal muscle in the residual limb when deciding the level of an amputation.

A new method for blood velocity measurements using ultrasound FMCW signals.

PubMed

Kunita, Masanori; Sudo, Masamitsu; Inoue, Shinya; Akahane, Mutsuhiro

2010-05-01

The low peak power of frequency-modulated continuous wave (FMCW) radar makes it attractive for various applications, including vehicle collision warning systems and airborne radio altimeters. This paper describes a new ultrasound Doppler measurement system that measures blood flow velocity based on principles similar to those of FMCW radar. We propose a sinusoidal wave for FM modulation and introduce a new demodulation technique for obtaining Doppler information with high SNR and range resolution. Doppler signals are demodulated with a reference FMCW signal to adjust delay times so that they are equal to propagation times between the transmitter and the receiver. Analytical results suggest that Doppler signals can be obtained from a selected position, as with a sample volume in pulse wave Doppler systems, and that the resulting SNR is nearly identical to that obtained with continuous wave (CW) Doppler systems. Additionally, clutter power is less than that of CW Doppler systems. The analytical results were verified by experiments involving electronic circuits and Doppler ultrasound phantoms.

Power M-mode Doppler (PMD) for observing cerebral blood flow and tracking emboli.

PubMed

Moehring, Mark A; Spencer, Merrill P

2002-01-01

Difficulties in location of transcranial ultrasound (US) windows and blood flow in cerebral vessels, and unambiguous detection of microemboli, have limited expansion of transcranial Doppler US. We developed a new transcranial Doppler modality, power M-mode Doppler (PMD), for addressing these issues. A 2-MHz digital Doppler (Spencer Technologies TCD100M) having 33 sample gates placed with 2-mm spacing was configured to display Doppler signal power, colored red and blue for directionality, in an M-mode format. The spectrogram from a user-selected depth was displayed simultaneously. This system was then explored on healthy subjects and patients presenting with varying cerebrovascular pathology. PMD facilitated window location and alignment of the US beam to view blood flow from multiple vessels simultaneously, without sound or spectral clues. Microemboli appeared as characteristic sloping high-power tracks in the PMD image. Power M-mode Doppler is a new paradigm facilitating vessel location, diagnosis, monitoring and microembolus detection.

[Venous Doppler color echography: importance and inconveniences].

PubMed

Laroche, J P; Dauzat, M; Muller, G; Janbon, C

1993-01-01

Color Doppler is a technique which performs a real-time opacification of the vascular system with blue indicating reverse flow and red indicating forward flow (directional color coding). In venous pathology, the use of color Doppler improves significantly the anatomical evaluation of the inferior vena cava, the iliac vein, the deep femoral vein, and the sural system. Color Doppler facilitates the study of deep venous thrombosis (providing useful information to differentiate ancient from most recent thrombus) and also the study of post-thrombotic conditions (assessment of reverse flow, repermeation phenomena). Finally, color Doppler produces a better insight for the study of varicose veins, especially with regard to mapping, identification of communicante veins, and study of the external saphenous vein.

Vascularization of liver tumors - preliminary results with Coded Harmonic Angio (CHA), phase inversion imaging, 3D power Doppler and contrast medium-enhanced B-flow with second generation contrast agent (Optison).

PubMed

Jung, E M; Kubale, R; Jungius, K-P; Jung, W; Lenhart, M; Clevert, D-A

2006-01-01

To investigate the dynamic value of contrast medium-enhanced ultrasonography with Optison for appraisal of the vascularization of hepatic tumors using harmonic imaging, 3D-/power Doppler and B-flow. 60 patients with a mean age of 56 years (range 35-76 years) with 93 liver tumors, including histopathologically proven hepatocellular carcinoma (HCC) [15 cases with 20 lesions], liver metastases of colorectal tumors [17 cases with 33 lesions], metastases of breast cancer [10 cases with 21 lesions] and hemangiomas [10 cases with 19 lesions] were prospectively investigated by means of multislice CT as well as native and contrast medium-enhanced ultrasound using a multifrequency transducer (2.5-4 MHz, Logig 9, GE). B scan was performed with additional color and power Doppler, followed by a bolus injection of 0.5 ml Optison. Tumor vascularization was evaluated with coded harmonic angio (CHA), pulse inversion imaging with power Doppler, 3D power Doppler and in the late phase (>5 min) with B-flow. In 15 cases with HCC, i.a. DSA was performed in addition. The results were also correlated with MRT and histological findings. Compared to spiral-CT/MRT, only 72/93 (77%) of the lesions could be detected in the B scan, 75/93 (81%) with CHA and 93/93 (100%) in the pulse inversion mode. Tumor vascularization was detectable in 43/93 (46%) of lesions with native power Doppler, in 75/93 (81%) of lesions after administering contrast medium in the CHA mode, in 81/93 (87%) of lesions in the pulse inversion mode with power Doppler and in 77/93 (83%) of lesions with contrast-enhanced B-flow. Early arterial and capillary perfusion was best detected with CHA, particularly in 20/20 (100%) of the HCC lesions, allowing a 3D reconstruction. 3D power Doppler was especially useful in investigating the tumor margins. Up to 20 min after contrast medium injection, B-flow was capable of detecting increased metastatic tumor vascularization in 42/54 (78%) of cases and intratumoral perfusion in 17/20 (85%) of HCC cases. All 19 hemangiomas were correctly classified by phase inversion imaging. Contrast medium-enhanced ultrasound investigation of liver tumors with Optison allowed reliable detection of tumor foci and, in most cases, appraisal of tumor vascularization. The time available for evaluation of tumor margin vascularization was substantially longer in B-flow.

Magnetic Resonance and Computed Tomography Imaging for the Evaluation of Pulmonary Hypertension

PubMed Central

Freed, Benjamin H.; Collins, Jeremy D.; François, Christopher J.; Barker, Alex J.; Cuttica, Michael J.; Chesler, Naomi C.; Markl, Michael; Shah, Sanjiv J.

2016-01-01

Imaging plays a central role in the diagnosis and management of all forms of pulmonary hypertension (PH). While Doppler echocardiography is essential for the evaluation of PH, its ability to optimally evaluate the right ventricle (RV) and pulmonary vasculature is limited by its 2D planar capabilities. Magnetic resonance imaging (MRI) and computed tomography (CT) are capable of determining the etiology and pathophysiology of PH, and can be very useful in the management of these patients. Exciting new techniques such as RV tissue characterization with T1 mapping, 4D flow of the RV and pulmonary arteries, and CT lung perfusion imaging are paving the way for a new era of imaging in PH. These imaging modalities complement echocardiography and invasive hemodynamic testing, and may be useful as surrogate endpoints for early-phase PH clinical trials. Here we discuss the role of MRI and CT in the diagnosis and management of PH, including current uses and novel research applications, and we discuss the role of value-based imaging in PH. PMID:27282439

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

NASA Astrophysics Data System (ADS)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; Chilson, Phillip B.; Wharton, Sonia

2016-12-01

Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w'2) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w'2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w'2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w'2. After the autocovariance technique is applied, values of w'2 from the Doppler lidars are generally in close agreement (R2 ≈ 0.95 - 0.98) with those calculated from sonic anemometer measurements.

Left atrial strain: a new parameter for assessment of left ventricular filling pressure.

PubMed

Cameli, Matteo; Mandoli, Giulia Elena; Loiacono, Ferdinando; Dini, Frank Lloyd; Henein, Michael; Mondillo, Sergio

2016-01-01

In order to obtain accurate diagnosis, treatment and prognostication in many cardiac conditions, there is a need for assessment of left ventricular (LV) filling pressure. While systole depends on ejection function of LV, diastole and its disturbances influence filling function and pressures. The commonest condition that represents the latter is heart failure with preserved ejection fraction in which LV ejection is maintained, but diastole is disturbed and hence filling pressures are raised. Significant diastolic dysfunction results in raised LV end-diastolic pressure, mean left atrial (LA) pressure and pulmonary capillary wedge pressure, all referred to as LV filling pressures. Left and right heart catheterization has traditionally been used as the gold standard investigation for assessing these pressures. More recently, Doppler echocardiography has taken over such application because of its noninvasive nature and for being patient friendly. A number of indices are used to achieve accurate assessment of filling pressures including: LV pulsed-wave filling velocities (E/A ratio, E wave deceleration time), pulmonary venous flow (S wave and D wave), tissue Doppler imaging (E' wave and E/E' ratio) and LA volume index. LA longitudinal strain derived from speckle tracking echocardiography (STE) is also sensitive in estimating intracavitary pressures. It is angle-independent, thus overcomes Doppler limitations and provides highly reproducible measures of LA deformation. This review examines the application of various Doppler echocardiographic techniques in assessing LV filling pressures, in particular the emerging role of STE in assessing LA pressures in various conditions, e.g., HF, arterial hypertension and atrial fibrillation.

Intravascular ultrasound in coronary atherosclerosis: a new approach to clinical assessment.

PubMed

Liebson, P R; Klein, L W

1992-06-01

Intravascular ultrasound evaluation of the coronary arteries by means of a selective coronary catheter attached to an ultrasound unit has afforded precise depiction of coronary lumen diameter and area at the level of the catheter tip. The arterial wall at this level can be evaluated for lipid, fibrous tissue, calcification, wall dissections, and intraluminal thrombi. The technique has the advantage over coronary angioscopy and angiography in that it does not require infusions or injections to allow visualization, and it has the ability to depict the inside of the arterial wall. The current disadvantages include the inability to visualize the vessel segments distal to the catheter tip. Three-dimensional reconstruction techniques allow depiction of the segment of the artery traversed by the catheter tip. The use of Doppler ultrasound imaging provides information on coronary flow velocities through coronary obstructions. Intravascular ultrasound images may provide information that complements the coronary arteriogram and may have an impact on patient care and clinical investigation strategies.

Positron transport in solids and the interaction of positrons with surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, Yuan.

1991-01-01

In studying positron transport in solids, a two-stream model is proposed to account for the epithermal positrons. Thus positron implantation, thermalization, and diffusion processes are completely modeled. Experimentally, positron mobility in thermally grown SiO[sub 2] is measured in a sandwiched structure by using the Doppler broadening technique. Positron drift motion and the electric field configuration in a Si surface buried under overlayers are measured with the positron annihilation [gamma]-ray centroid shift technique. These studies are not only important in measuring positron transport and other properties in complicated systems, they are also of practical significance for material characterizations. In studying positronmore » interactions with surfaces, a multiple-encounter picture is proposed of thermal positrons participating in the surface escape processes. Positron trapping into the surface image potential is also studied, considering the long-range nature of the image potential. Experimentally, the positron annihilation induced Auger electron spectroscopy (PAES) is used to study an ionic insulator surface KCl(100).« less

Doppler Global Velocimeter Development for the Large Wind Tunnels at Ames Research Center

NASA Technical Reports Server (NTRS)

Reinath, Michael S.

1997-01-01

Development of an optical, laser-based flow-field measurement technique for large wind tunnels is described. The technique uses laser sheet illumination and charged coupled device detectors to rapidly measure flow-field velocity distributions over large planar regions of the flow. Sample measurements are presented that illustrate the capability of the technique. An analysis of measurement uncertainty, which focuses on the random component of uncertainty, shows that precision uncertainty is not dependent on the measured velocity magnitude. For a single-image measurement, the analysis predicts a precision uncertainty of +/-5 m/s. When multiple images are averaged, this uncertainty is shown to decrease. For an average of 100 images, for example, the analysis shows that a precision uncertainty of +/-0.5 m/s can be expected. Sample applications show that vectors aligned with an orthogonal coordinate system are difficult to measure directly. An algebraic transformation is presented which converts measured vectors to the desired orthogonal components. Uncertainty propagation is then used to show how the uncertainty propagates from the direct measurements to the orthogonal components. For a typical forward-scatter viewing geometry, the propagation analysis predicts precision uncertainties of +/-4, +/-7, and +/-6 m/s, respectively, for the U, V, and W components at 68% confidence.

Interferometric Dynamic Measurement: Techniques Based on High-Speed Imaging or a Single Photodetector

PubMed Central

Fu, Yu; Pedrini, Giancarlo

2014-01-01

In recent years, optical interferometry-based techniques have been widely used to perform noncontact measurement of dynamic deformation in different industrial areas. In these applications, various physical quantities need to be measured in any instant and the Nyquist sampling theorem has to be satisfied along the time axis on each measurement point. Two types of techniques were developed for such measurements: one is based on high-speed cameras and the other uses a single photodetector. The limitation of the measurement range along the time axis in camera-based technology is mainly due to the low capturing rate, while the photodetector-based technology can only do the measurement on a single point. In this paper, several aspects of these two technologies are discussed. For the camera-based interferometry, the discussion includes the introduction of the carrier, the processing of the recorded images, the phase extraction algorithms in various domains, and how to increase the temporal measurement range by using multiwavelength techniques. For the detector-based interferometry, the discussion mainly focuses on the single-point and multipoint laser Doppler vibrometers and their applications for measurement under extreme conditions. The results show the effort done by researchers for the improvement of the measurement capabilities using interferometry-based techniques to cover the requirements needed for the industrial applications. PMID:24963503

Tissue viability imaging: microvascular response to vasoactive drugs induced by iontophoresis.

PubMed

Henricson, Joakim; Nilsson, Anders; Tesselaar, Erik; Nilsson, Gert; Sjöberg, Folke

2009-09-01

When one is studying the physiology of the cutaneous microcirculation there is a need for relevant non-invasive and versatile techniques. In this study we used a new optical device, the tissue viability imager (TiVi), to map changes in cutaneous microvascular concentrations of red blood cells during iontophoresis of vasoactive substances (noradrenaline (NA) and phenylephrine (Phe) for vasoconstriction and acetylcholine (ACh) and sodium nitroprusside (SNP) for vasodilatation). We aimed to present data both individually and pooled, using a four-variable logistic dose response model that is commonly used in similar in vitro vascular studies. The accuracy of the TiVi was also investigated by calculating the coefficient of variation and comparing it with similar tests previously done using laser Doppler imaging. Tests were also performed using the TiVi and LDPI simultaneously to further compare the two methods. Results showed that the TiVi is capable of quantifying vascular responses to iontophorised noradrenaline and phenylephrine without the need to increase background flow first. Fitting the TiVi data to the dose response model resulted in ED(50)-values with narrow confidence intervals and acceptable r(2) values. Mean ED(50)-values for the TiVi did not differ significantly from similar values obtained using laser Doppler. Results further seem to suggest that when the blood perfusion increases during vasodilatation in skin the initial phase relies mainly on an increase in red blood cell concentration whereas the further perfusion increase is due to an increase in red blood cell velocity.

Comparative analysis of renal flow using contrast power Doppler and gray-scale ultrasound

NASA Astrophysics Data System (ADS)

Sehgal, Chandra M.; Arger, Peter H.; Bovee, Kenneth C.; Pugh, Charles; Kirchhofer, Justin I.

1997-05-01

Our previous studies have shown that renal perfusion can be visualized by imaging the transit of a contrast agent through the parenchyma of the organ using gray scale (GS) and power Doppler (PD) ultrasound.However, the relative merits and the sensitivities of the two imaging methods are not known. This study compares the effectiveness of the two modes in visualizing kidney perfusion at the clinical dose of contrast agents. GS and PD images of the dog kidneys were recorded using a clinical ultrasound scanner at 4-7 MHz. A fixed longitudinal plane of the kidney was imaged by mounting the transducer on the animal with a specially designed holder. A dose of 0.1 m1/kg of Echogen was injected intravenously and GS and PD images were recorded simultaneously on two separate time-encoded video tapes during the passage of the contrast agent through the kidneys. The enhancement of GS and PD images was assessed qualitatively by three radiologists. The quantitative assessment was made by measuring the regional and global enhancements of digitized B-scan and PS images. Regional measurements were made by comparing brightness of the post contrast images with that of a pre-contrast reference image pixel by pixel. Student t-test was used to determine the statistical significance of the change. The regions representing statistically significant differences were encoded on the image in color with brightness proportional to the magnitude of change. The regions with no significant change were represented in GS. This generated a series of new images, referred to as StatMap, with color representing regions of perfusion. Changes in power Doppler images were visually detectable with high confidence in all five dogs by al three radiologists. There was no perceptible changes in B-scans. Computer analysis of PD images yielded characteristic indicator dilution curves in all five dogs with an initial rise time of 2-5 sec and a peak at 7-20 sec. The enhancement in PD lasted for 97-400 seconds. The peak to pre-injection Doppler power ratio was 2.41 +/- 0.85. There were not detectable changes in gray scale images except in one dog which exhibited a small change. The StatMap images of PD exhibited perfusion over the entire kidney, whereas the GS images showed perfusion to be sparsely distributed.

Multibeam single frequency synthetic aperture radar processor for imaging separate range swaths

NASA Technical Reports Server (NTRS)

Jain, A. (Inventor)

1982-01-01

A single-frequency multibeam synthetic aperture radar for large swath imaging is disclosed. Each beam illuminates a separate ""footprint'' (i.e., range and azimuth interval). The distinct azimuth intervals for the separate beams produce a distinct Doppler frequency spectrum for each beam. After range correlation of raw data, an optical processor develops image data for the different beams by spatially separating the beams to place each beam of different Doppler frequency spectrum in a different location in the frequency plane as well as the imaging plane of the optical processor. Selection of a beam for imaging may be made in the frequency plane by adjusting the position of an aperture, or in the image plane by adjusting the position of a slit. The raw data may also be processed in digital form in an analogous manner.

Observations of barium ion jets in the magnetosphere using Doppler imaging systems and very sensitive imaging systems using imaging photon detectors

NASA Technical Reports Server (NTRS)

Rees, D.; Conboy, J.; Heinz, W.; Heppner, J. P.

1985-01-01

Observations of four shaped charge releases from rockets launched from Alaska are described. Results demonstrate that imaging and Doppler imaging instruments, based on exploiting the imaging photon detector, provide additional insight into the motion and development of low intensity targets such as the fast ion jets produced by shaped charge releases. It is possible to trace the motion of fast ion jets to very great distances, of the order of 50,000 km, outward along the Earth's magnetic field, when the conditions are suitable for the outward (upward) motion and/or acceleration of such ion jets. It is shown that ion jets, which fade below the lower sensitivity threshold of previous instruments, do not always disappear. There is no evidence of an abrupt field-aligned shear-type acceleration.

Comparison of laser Doppler and laser speckle contrast imaging using a concurrent processing system

NASA Astrophysics Data System (ADS)

Sun, Shen; Hayes-Gill, Barrie R.; He, Diwei; Zhu, Yiqun; Huynh, Nam T.; Morgan, Stephen P.

2016-08-01

Full field laser Doppler imaging (LDI) and single exposure laser speckle contrast imaging (LSCI) are directly compared using a novel instrument which can concurrently image blood flow using both LDI and LSCI signal processing. Incorporating a commercial CMOS camera chip and a field programmable gate array (FPGA) the flow images of LDI and the contrast maps of LSCI are simultaneously processed by utilizing the same detected optical signals. The comparison was carried out by imaging a rotating diffuser. LDI has a linear response to the velocity. In contrast, LSCI is exposure time dependent and does not provide a linear response in the presence of static speckle. It is also demonstrated that the relationship between LDI and LSCI can be related through a power law which depends on the exposure time of LSCI.

Relevance of tissue Doppler in the quantification of stress echocardiography for the detection of myocardial ischemia in clinical practice

PubMed Central

Sicari, Rosa

2005-01-01

In the present article we review the main published data on the application of Tissue Doppler Imaging (TDI) to stress echocardiography for the detection of myocardial ischemia. TDI has been applied to stress echocardiography in order to overcome the limitations of visual analysis for myocardial ischemia. The introduction of a new technology for clinical routine use should pass through the different phases of scientific assessment from feasibility studies to large multicenter studies, from efficacy to effectiveness studies. Nonetheless the pro-technology bias plays a major role in medicine and expensive and sophisticated techniques are accepted before their real usefulness and incremental value to the available ones is assessed. Apparently, TDI is not exempted by this approach : its applications are not substantiated by strong and sound results. Nonetheless, conventional stress echocardiography for myocardial ischemia detection is heavily criticized on the basis of its subjectivity. Stress echocardiography has a long lasting history and the evidence collected over 20 years positioned it as an established tool for the detection and prognostication of coronary artery disease. The quantitative assessment of myocardial ischemia remains a scientific challenge and a clinical goal but time has not come for these newer ultrasonographic techniques which should be restricted to research laboratories. PMID:15679889

Calculation of the diameter of the central retinal artery from noninvasive measurements in humans.

PubMed

Dorner, Guido T; Polska, Elzbieta; Garhöfer, Gerhard; Zawinka, Claudia; Frank, Barbara; Schmetterer, Leopold

2002-12-01

The aim of the present study was to calculate the diameter of the central retinal artery from results as obtained with non-invasive techniques in healthy young subjects. Twenty-four healthy male subjects participated in this study. Total retinal blood flow was calculated from combined bi-directional laser Doppler velocimetry and measurement of retinal venous diameters using the Zeiss retinal vessel analyzer. Using these techniques red blood cell velocity and vessel diameters of all visible veins entering the optic nerve head were measured and total retinal blood flow was calculated. Blood flow velocity in the central retinal artery was measured with color Doppler imaging. Form these outcome parameters the diameter of the central retinal artery was calculated for each subject individually. In the present study cohort the mean retinal blood flow was 38.1 +/- 9.1 microl/min and the mean flow velocity in the central retinal artery was 6.3 +/- 1.2 cm/s. From these data we calculated a mean diameter of the central retinal artery of 163 +/- 17 microm. Our results are in good agreement with data obtained from in vitro studies. The data of the present study also indicate that one needs to be careful to interpret velocity data from the central retinal artery in terms of retinal blood flow.

Coherent Doppler lidar for automated space vehicle rendezvous, stationkeeping and capture

NASA Technical Reports Server (NTRS)

Bilbro, James A.

1991-01-01

The inherent spatial resolution of laser radar makes ladar or lidar an attractive candidate for Automated Rendezvous and Capture application. Previous applications were based on incoherent lidar techniques, requiring retro-reflectors on the target vehicle. Technology improvements (reduced size, no cryogenic cooling requirement) have greatly enhanced the construction of coherent lidar systems. Coherent lidar permits the acquisition of non-cooperative targets at ranges that are limited by the detection capability rather than by the signal-to-noise ratio (SNR) requirements. The sensor can provide translational state information (range, velocity, and angle) by direct measurement and, when used with any array detector, also can provide attitude information by Doppler imaging techniques. Identification of the target is accomplished by scanning with a high pulse repetition frequency (dependent on the SNR). The system performance is independent of range and should not be constrained by sun angle. An initial effort to characterize a multi-element detection system has resulted in a system that is expected to work to a minimum range of 1 meter. The system size, weight and power requirements are dependent on the operating range; 10 km range requires a diameter of 3 centimeters with overall size at 3 x 3 x 15 to 30 cm, while 100 km range requires a 30 cm diameter.

SAR imaging - Seeing the unseen

NASA Technical Reports Server (NTRS)

Kobrick, M.

1982-01-01

The functional abilities and operations of synthetic aperture radar (SAR) are described. SAR employs long wavelength radio waves in bursts, imaging a target by 'listening' to the small frequency changes that result from the Doppler shift due to the relative motion of the imaging craft and the motions of the target. The time delay of the signal return allows a determination of the location of the target, leading to the build up of a two-dimensional image. The uses of both Doppler shifts and time delay enable detailed imagery which is independent of distance. The synthetic aperture part of the name of SAR derives from the beaming of multiple pulses, which result in a picture that is effectively the same as using a large antenna. Mechanisms contributing to the fineness of SAR images are outlined.

Left ventricular to left atrial communication secondary to a paraaortic abscess: color flow Doppler documentation.

PubMed

Fisher, E A; Estioko, M R; Stern, E H; Goldman, M E

1987-07-01

Aortic root abscess occurs frequently in aortic prosthetic valve infective endocarditis. The present echocardiographic report documents a ruptured abscess that led to a direct communication between the left ventricular outflow tract and the left atrium confirmed by real-time (color flow) Doppler imaging.

Fluorescence endoscopic imaging for evaluation of gastric mucosal blood flow: a preliminary study

NASA Astrophysics Data System (ADS)

Bocquillon, Nicolas; Mordon, Serge R.; Mathieu, D.; Maunoury, Vincent; Marechal, Xavier-Marie; Neviere, Remi; Wattel, Francis; Chopin, Claude

1999-02-01

Microcirculatory disorders of the gastrointestinal tract appear to be a major compound of the multiple organ dysfunction syndrome secondary to sepsis or septic shock. A better analysis of mucosal hypoperfusion in critically ill patients with sepsis may be helpful for the comprehension of this high mortality-associated syndrome. Fluorescence endoscopy has been recognized as a non-invasive method for both spatial and temporal evaluation of gastrointestinal mucosal perfusion. We performed this imaging technique during routine gastric endoscopy in patients with sepsis criteria. The study included gastric observation and appearance time of gastric fluorescence after an intravenous 10% sodium - fluorescein bolus. Qualitative analysis of high fluorescence areas was compared with mucosal blood flow measurements by laser - Doppler flowmetry. We concluded that the fluorescence endoscopic imaging in critically ill patients with sepsis may reveal spacial and temporal differences in the mucosal microcirculation distribution.

Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Jenkins, Michael W.; Peterson, Lindsy; Gu, Shi; Gargesha, Madhusudhana; Wilson, David L.; Watanabe, Michiko; Rollins, Andrew M.

2010-11-01

Hemodynamics is thought to play a major role in heart development, yet tools to quantitatively assess hemodynamics in the embryo are sorely lacking. The especially challenging analysis of hemodynamics in the early embryo requires new technology. Small changes in blood flow could indicate when anomalies are initiated even before structural changes can be detected. Furthermore, small changes in the early embryo that affect blood flow could lead to profound abnormalities at later stages. We present a demonstration of 4-D Doppler optical coherence tomography (OCT) imaging of structure and flow, and present several new hemodynamic measurements on embryonic avian hearts at early stages prior to the formation of the four chambers. Using 4-D data, pulsed Doppler measurements could accurately be attained in the inflow and outflow of the heart tube. Also, by employing an en-face slice from the 4-D Doppler image set, measurements of stroke volume and cardiac output are obtained without the need to determine absolute velocity. Finally, an image plane orthogonal to the blood flow is used to determine shear stress by calculating the velocity gradient normal to the endocardium. Hemodynamic measurements will be crucial to identifying genetic and environmental factors that lead to congenital heart defects.

Quantitative imaging of red blood cell velocity invivo using optical coherence Doppler tomography

NASA Astrophysics Data System (ADS)

Ren, Hugang; Du, Congwu; Park, Kicheon; Volkow, Nora D.; Pan, Yingtian

2012-06-01

We present particle counting ultrahigh-resolution optical Doppler tomography (pc-μODT) that enables accurate imaging of red blood cell velocities (νRBC) of cerebrovascular networks by detecting the Doppler phase transients induced by the passage of a RBC through a capillary. We apply pc-μODT to image the response of capillary νRBC to mild hypercapnia in mouse cortex. The results show that νRBC in normocapnia (νN = 0.72 ± 0.15 mm/s) increased 36.1% ± 5.3% (νH = 0.98 ± 0.29 mm/s) in response to hypercapnia. Due to uncorrected angle effect and low hematocrit (e.g., ˜10%), νRBC directly measured by μODT were markedly underestimated (νN ≈ 0.27 ± 0.03 mm/s, νH ≈ 0.37± 0.05 mm/s). Nevertheless, the measured νRBC increase (35.3%) matched that (36.1% ± 5.3%) by pc-μODT.

Noninvasive Doppler Tissue Measurement of Pulmonary Artery Compliance in Children with Pulmonary Hypertension

PubMed Central

Dyer, Karrie; Lanning, Craig; Das, Bibhuti; Lee, Po-Feng; Ivy, D. Dunbar; Valdes-Cruz, Lilliam; Shandas, Robin

2007-01-01

Background We have shown previously that input impedance of the pulmonary vasculature provides a comprehensive characterization of right ventricular afterload by including compliance. However, impedance-based compliance assessment requires invasive measurements. Here, we develop and validate a noninvasive method to measure pulmonary artery (PA) compliance using ultrasound color M-mode (CMM) Doppler tissue imaging (DTI). Methods Dynamic compliance (Cdyn) of the PA was obtained from CMM DTI and continuous wave Doppler measurement of the tricuspid regurgitant velocity. Cdyn was calculated as: [(Ds − Dd)/(Dd × Ps)] × 104; where Ds = systolic diameter, Dd = diastolic diameter, and Ps = systolic pressure. The method was validated both in vitro and in 13 patients in the catheterization laboratory, and then tested on 27 pediatric patients with pulmonary hypertension, with comparison with 10 age-matched control subjects. Cdyn was also measured in an additional 13 patients undergoing reactivity studies. Results Instantaneous diameter measured using CMM DTI agreed well with intravascular ultrasound measurements in the in vitro models. Clinically, Cdyn calculated by CMM DTI agreed with Cdyn calculated using invasive techniques (23.4 ± 16.8 vs 29.1 ± 20.6%/100 mm Hg; P = not significant). Patients with pulmonary hypertension had significantly lower peak wall velocity values and lower Cdyn values than control subjects (P < .01). Cdyn values followed an exponentially decaying relationship with PA pressure, indicating the nonlinear stress–strain behavior of these arteries. Reactivity in Cdyn agreed with reactivity measured using impedance techniques. Conclusion The Cdyn method provides a noninvasive means of assessing PA compliance and should be useful as an additional measure of vascular reactivity subsequent to pulmonary vascular resistance in patients with pulmonary hypertension. PMID:16581479

Noninvasive Doppler tissue measurement of pulmonary artery compliance in children with pulmonary hypertension.

PubMed

Dyer, Karrie; Lanning, Craig; Das, Bibhuti; Lee, Po-Feng; Ivy, D Dunbar; Valdes-Cruz, Lilliam; Shandas, Robin

2006-04-01

We have shown previously that input impedance of the pulmonary vasculature provides a comprehensive characterization of right ventricular afterload by including compliance. However, impedance-based compliance assessment requires invasive measurements. Here, we develop and validate a noninvasive method to measure pulmonary artery (PA) compliance using ultrasound color M-mode (CMM) Doppler tissue imaging (DTI). Dynamic compliance (C(dyn)) of the PA was obtained from CMM DTI and continuous wave Doppler measurement of the tricuspid regurgitant velocity. C(dyn) was calculated as: [(D(s) - D(d))/(D(d) x P(s))] x 10(4); where D(s) = systolic diameter, D(d) = diastolic diameter, and P(s) = systolic pressure. The method was validated both in vitro and in 13 patients in the catheterization laboratory, and then tested on 27 pediatric patients with pulmonary hypertension, with comparison with 10 age-matched control subjects. C(dyn) was also measured in an additional 13 patients undergoing reactivity studies. Instantaneous diameter measured using CMM DTI agreed well with intravascular ultrasound measurements in the in vitro models. Clinically, C(dyn) calculated by CMM DTI agreed with C(dyn) calculated using invasive techniques (23.4 +/- 16.8 vs 29.1 +/- 20.6%/100 mm Hg; P = not significant). Patients with pulmonary hypertension had significantly lower peak wall velocity values and lower C(dyn) values than control subjects (P < .01). C(dyn) values followed an exponentially decaying relationship with PA pressure, indicating the nonlinear stress-strain behavior of these arteries. Reactivity in C(dyn) agreed with reactivity measured using impedance techniques. The C(dyn) method provides a noninvasive means of assessing PA compliance and should be useful as an additional measure of vascular reactivity subsequent to pulmonary vascular resistance in patients with pulmonary hypertension.

Techniques in Broadband Interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erskine, D J

2004-01-04

This is a compilation of my patents issued from 1997 to 2002, generally describing interferometer techniques that modify the coherence properties of broad-bandwidth light and other waves, with applications to Doppler velocimetry, range finding, imaging and spectroscopy. Patents are tedious to read in their original form. In an effort to improve their readability I have embedded the Figures throughout the manuscript, put the Figure captions underneath the Figures, and added section headings. Otherwise I have resisted the temptation to modify the words, though I found many places which could use healthy editing. There may be minor differences with the officialmore » versions issued by the US Patent and Trademark Office, particularly in the claims sections. In my shock physics work I measured the velocities of targets impacted by flyer plates by illuminating them with laser light and analyzing the reflected light with an interferometer. Small wavelength changes caused by the target motion (Doppler effect) were converted into fringe shifts by the interferometer. Lasers having long coherence lengths were required for the illumination. While lasers are certainly bright sources, and their collimated beams are convenient to work with, they are expensive. Particularly if one needs to illuminate a wide surface area, then large amounts of power are needed. Orders of magnitude more power per dollar can be obtained from a simple flashlamp, or for that matter, a 50 cent light bulb. Yet these inexpensive sources cannot practically be used for Doppler velocimetry because their coherence length is extremely short, i.e. their bandwidth is much too wide. Hence the motivation for patents 1 & 2 is a method (White Light Velocimetry) for allowing use of these powerful but incoherent lamps for interferometry. The coherence of the illumination is modified by passing it through a preparatory interferometer.« less

Synchronized epiaortic two-dimensional and color Doppler echocardiographic guidance enables routine ascending aortic cannulation in type A acute aortic dissection.

PubMed

Inoue, Yoshito; Takahashi, Ryuichi; Ueda, Toshihiko; Yozu, Ryohei

2011-02-01

Preference for arterial inflow during surgery for type A acute aortic dissection remains controversial. Antegrade central perfusion prevents malperfusion and retrograde embolism, and the ascending aorta provides arterial access for rapid establishment of systemic perfusion, especially if there is hemodynamic instability. It has not been used routinely, however, because of the disruption caused to the aorta. We evaluated the safety and efficacy of routine cannulation of the dissected aorta for the repair of type A dissection. Surgical results were analyzed for 83 consecutive patients with type A acute aortic dissection between 2002 and 2009. They were treated surgically by prosthetic graft replacement under hypothermic circulatory arrest. The ascending aorta was routinely cannulated using the Seldinger technique with epiaortic echocardiographic guidance; antegrade systemic perfusion was evaluated by color Doppler ultrasound. Systemic antegrade perfusion via the dissected ascending aorta was performed safely in all cases. There was no malperfusion or thromboembolism as a result of ascending aortic cannulation. Epiaortic 2-dimensional and color Doppler imaging provided real-time monitoring adequate for the placement and for proper systemic perfusion. There were 5 in-hospital deaths (5/83=6.0%) and 8 strokes (preoperative 6/83=7.2%, postoperative 2/83=2.4%). A total of 78 patients (78/83=94%) were discharged and have been followed up without major adverse cardiac events for a mean duration of 31.8 months. Ascending aortic cannulation is a simple and safe technique that provides a rapid and reliable route of antegrade central systemic perfusion in type A aortic dissection. Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

The complex of optical methods for study of gas-liquid jets

NASA Astrophysics Data System (ADS)

Poplavski, S. V.; Boiko, V. M.

2017-10-01

A set of optical methods for studying the dispersion and dynamics of liquids in high-speed gas jets was realized. Four optical methods were used: shadow imaging, PIV method, Laser Doppler Anemometer (LDA), a method for recording the dispersity of a spray by angular scattering of light. With the example of a supersonic coaxial jet with a central fluid supply, a technique is developed that makes it possible to obtain not only the sum of the data by four methods but new critical data on the structure of the two-phase flow, such as the concentration distributions of the spray.

Doppler velocity measurements from large and small arteries of mice

PubMed Central

Reddy, Anilkumar K.; Madala, Sridhar; Entman, Mark L.; Michael, Lloyd H.; Taffet, George E.

2011-01-01

With the growth of genetic engineering, mice have become increasingly common as models of human diseases, and this has stimulated the development of techniques to assess the murine cardiovascular system. Our group has developed nonimaging and dedicated Doppler techniques for measuring blood velocity in the large and small peripheral arteries of anesthetized mice. We translated technology originally designed for human vessels for use in smaller mouse vessels at higher heart rates by using higher ultrasonic frequencies, smaller transducers, and higher-speed signal processing. With these methods one can measure cardiac filling and ejection velocities, velocity pulse arrival times for determining pulse wave velocity, peripheral blood velocity and vessel wall motion waveforms, jet velocities for the calculation of the pressure drop across stenoses, and left main coronary velocity for the estimation of coronary flow reserve. These noninvasive methods are convenient and easy to apply, but care must be taken in interpreting measurements due to Doppler sample volume size and angle of incidence. Doppler methods have been used to characterize and evaluate numerous cardiovascular phenotypes in mice and have been particularly useful in evaluating the cardiac and vascular remodeling that occur following transverse aortic constriction. Although duplex ultrasonic echo-Doppler instruments are being applied to mice, dedicated Doppler systems are more suitable for some applications. The magnitudes and waveforms of blood velocities from both cardiac and peripheral sites are similar in mice and humans, such that much of what is learned using Doppler technology in mice may be translated back to humans. PMID:21572013

Measurements in the Turbulent Boundary Layer at Constant Pressure in Subsonic and Supersonic Flow. Part 2: Laser-Doppler Velocity Measurements

NASA Technical Reports Server (NTRS)

Dimotakis, P. E.; Collins, D. J.; Lang, D. B.

1979-01-01

A description of both the mean and the fluctuating components of the flow, and of the Reynolds stress as observed using a dual forward scattering laser-Doppler velocimeter is presented. A detailed description of the instrument and of the data analysis techniques were included in order to fully document the data. A detailed comparison was made between the laser-Doppler results and those presented in Part 1, and an assessment was made of the ability of the laser-Doppler velocimeter to measure the details of the flows involved.

Ultracool Dwarfs and their companions

NASA Astrophysics Data System (ADS)

Blake, Cullen H.

This thesis explores new techniques for making precise measurements of low-mass stars and brown dwarfs, collectively known as Ultracool Dwarfs (UCDs). These new techniques are directly applicable to the search for extrasolar planets and efforts to test theoretical models of stellar structure and evolution at the bottom of the main sequence. The first three chapters of this thesis describe the development and application of a new technique for making radial velocity measurements of UCDs at near infrared (NIR) wavelengths. The first chapter describes a pilot study that demonstrates a significant improvement over previous work on Doppler measurements in the NIR. Using this technique we have carried out a Doppler survey of 65 L dwarfs. The second chapter describes the discovery of a new spectroscopic binary that may be one of the most important for constraining theoretical models of UCDs. The third chapter describes the Doppler survey in detail and presents measurements of a new spectroscopic binary system that is an excellent candidate for a giant planetary companion to a mid-L dwarf. This chapter also includes a discussion of the of the rotation, space motions, and binarity of the L dwarfs in the survey sample. The fourth chapter describes efforts to obtain precise photometric measurements of UCDs with the Peters Automated Infrared Imaging Telescope (PAIRITEL). Using software scheduling and data reduction systems designed in part by the author, PAIRITEL gathered more than 10 6 seconds of observations of a sample of 20 UCDs. We investigate the limitations to ground-based infrared photometry and characterize the ability of a system like PAIRITEL to detect transits of UCDs by Earth-like planets. The fifth chapter explores the potential impact of future synoptic surveys on studies of UCDs. Surveys like Pan-STARRS and LSST will obtain a small number of high-quality observations of a large number of UCDs. Using data from the Sloan Digital Sky Survey, we demonstrate that such data can be used to reliably detect low-mass eclipsing binary stars. We present the discovery of a double- lined eclipsing binary system that allows us to directly measure the masses and radii of two M dwarfs.

Assessment of Remote Sensing Technologies for Location of Hydrogen and Helium Leaks

NASA Technical Reports Server (NTRS)

Sellar, R. Glenn; Sohn, Yongho; Mathur, Varun; Reardon, Peter

2001-01-01

In Phase 1 of this project, a hierarchy of techniques for H2 and He leak location was developed. A total of twelve specific remote sensing techniques were evaluated; the results are summarized. A basic diffusion model was also developed to predict the concentration and distribution of H2 or He resulting from a leak. The objectives of Phase 2 of the project consisted of the following four tasks: Advance Rayleigh Doppler technique from TRL 1 to TRL 2; Plan to advance Rayleigh Doppler technique from TRL 2 to TRL 3; Advance researchers and resources for further advancement; Extend diffusion model.

a Virtual Trip to the Schwarzschild-De Sitter Black Hole

NASA Astrophysics Data System (ADS)

Bakala, Pavel; Hledík, Stanislav; Stuchlík, Zdenĕk; Truparová, Kamila; Čermák, Petr

2008-09-01

We developed realistic fully general relativistic computer code for simulation of optical projection in a strong, spherically symmetric gravitational field. Standard theoretical analysis of optical projection for an observer in the vicinity of a Schwarzschild black hole is extended to black hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de Sitter (SdS) spacetimes. Influence of the cosmological constant is investigated for static observers and observers radially free-falling from static radius. Simulation includes effects of gravitational lensing, multiple images, Doppler and gravitational frequency shift, as well as the amplification of intensity. The code generates images of static observers sky and a movie simulations for radially free-falling observers. Techniques of parallel programming are applied to get high performance and fast run of the simulation code.

Laser based imaging of time depending microscopic scenes with strong light emission

NASA Astrophysics Data System (ADS)

Hahlweg, Cornelius; Wilhelm, Eugen; Rothe, Hendrik

2011-10-01

Investigating volume scatterometry methods based on short range LIDAR devices for non-static objects we achieved interesting results aside the intended micro-LIDAR: the high speed camera recording of the illuminated scene of an exploding wire -intended for Doppler LIDAR tests - delivered a very effective method of observing details of objects with extremely strong light emission. As a side effect a schlieren movie is gathered without any special effort. The fact that microscopic features of short time processes with high emission and material flow might be imaged without endangering valuable equipment makes this technique at least as interesting as the intended one. So we decided to present our results - including latest video and photo material - instead of a more theoretical paper on our progress concerning the primary goal.

Left ventricular longitudinal myocardial function in overt hypothyroidism: a tissue Doppler echocardiographic study.

PubMed

Tiryakioglu, Selma Kenar; Tiryakioglu, Osman; Ari, Hasan; Basel, Mehmet Cem; Ozkan, Hakan; Bozat, Tahsin

2010-05-01

The aim of this study was to assess left ventricular (LV) myocardial regional function in overt hypothyroidism by use of tissue Doppler imaging and to compare the results to the hormonal profile and standard Doppler echocardiographic examination. Hypothyroidic (Group 1, n = 25) and euthyroidic patients (Group 2, n = 25) underwent transthorasic echocardiography, strain and strain rate imaging. Standard echocardiography showed that patients with overt hypothyroidism had significantly longer isovolumic contraction time (IVCT) (P < 0.05), deceleration time (DT) (P = 0.014) and isovolumic relaxation time (IVRT) (P = 0.022). Tissue Doppler imaging showed that the mean peak systolic strain (SI) (16.47 + or - 1.45 vs. 20.63 + or - 1.51, P < 0.001), the mean peak systolic strain rate (SSR) (1.05 + or - 0.13 vs. 1.47 + or - 0.11, P < 0.001), the mean peak early diastolic strain rate (ESr) (1.72 + or - 0.38 vs. 2.03 + or - 0.25, P < 0.05) and the mean peak late diastolic strain rate (ASr) (1.22 + or - 0.31 vs. 1.46 + or - 0.32, P < 0.05) were significantly lower in Group 1 compared to Group 2. For all patients, the systolic strain and systolic strain rate parameters negatively correlated with thyroid stimulating hormone levels and positively correlated with the levels of free triiodothyronine (fT(3)) and free tetraiodothyronine (fT(4)). These results indicate that overt hypothyroidism is associated with early impairment in LV longitudinal myocardial function, and that tissue Doppler echocardiography is useful for the grading of disease and detection of early impairment. (ECHOCARDIOGRAPHY 2010;27:505-511).

Improved performance of a digital phase-locked loop combined with a frequency/frequency-rate estimator

NASA Technical Reports Server (NTRS)

Mileant, A.; Simon, M.

1986-01-01

When a digital phase-locked loop with a long loop update time tracks a signal with high Doppler, the demodualtion losses due to frequency mismatch can become very significant. One way of reducing these Doppler-related losses is to compensate for the Doppler effect using some kind of frequency-rate estimator. The performance of the fixed-window least-squares estimator and the Kalman filter is investigated; several Doppler compensating techniques are proposed. It is shown that the variance of the frequency estimator can be made as small as desired, and with this, the Doppler effect can be effectively compensated. The remaining demodulation losses due to phase jitter in the loop can be less than 0.1 dB.

Comparison of perioperative outcomes between endoscope-assisted technique and handheld acoustic Doppler for perforator identification in fasciocutaneous flaps.

PubMed

Huang, Jen-Wu; Huang, Chih-Sheng; Shih, Yu-Chung; Perng, Cherng-Kang; Lin, Yi-Ying; Wu, Szu-Hsien

2018-06-01

The endoscopic technique has been utilized to harvest muscle flaps and detect perforators of fasciocutaneous flaps. This study aimed to compare the perioperative outcomes between the endoscope-assisted technique and handheld acoustic Doppler for perforator identification in fasciocutaneous flaps.This retrospective case-control study included patients who underwent fasciocutaneous flap reconstruction for traumatic soft tissue defects. In the case group, perforator identification was assisted by the endoscope-assisted technique. In the control group, age- and sex-matched patients received handheld acoustic Doppler to detect perforators. Perioperative outcomes, flap characteristics, and postoperative complications were compared.There were 12 patients in the case group and 12 in the control group. Compared with the control group, the case group had a significantly shorter length of donor-site wounds (9 cm vs 12 cm, P = .023) and a significantly smaller proportion of patients receiving skin grafting at the donor sites (0% vs 41.7%, P = .037). The case group had a longer operative time, but the difference was not statistically significant (180 minutes vs 150 minutes, P = .367). The amount of blood loss, the time length of postoperative drainage, and complications did not significantly differ between the 2 groups.The endoscope-assisted technique for perforator identification of fasciocutaneous flaps provided less donor-site morbidity and a significantly shorter length of donor-site wounds than the conventional handheld acoustic Doppler, which suggests that this technique could be a valuable alternative when a precise design is indicated.

Planetary Radar Imaging with the Deep-Space Network's 34 Meter Uplink Array

NASA Technical Reports Server (NTRS)

Vilnrotter, V.; Tsao, P.; Lee, D.; Cornish, T.; Jao, J.; Slade, M.

2011-01-01

A coherent uplink array consisting of up to three 34-meter antennas of NASA's Deep Space Network has been developed for the primary purpose of increasing EIRP at the spacecraft. Greater EIRP ensures greater reach, higher uplink data rates for command and configuration control, as well as improved search and recovery capabilities during spacecraft emergencies. It has been conjectured that Doppler-delay radar imaging of lunar targets can be extended to planetary imaging, where the long baseline of the uplink array can provide greater resolution than a single antenna, as well as potentially higher EIRP. However, due to the well known R-4 loss in radar links, imaging of distant planets is a very challenging endeavor, requiring accurate phasing of the Uplink Array antennas, cryogenically cooled low-noise receiver amplifiers, and sophisticated processing of the received data to extract the weak echoes characteristic of planetary radar. This article describes experiments currently under way to image the planets Mercury and Venus, highlights improvements in equipment and techniques, and presents planetary images obtained to date with two 34 meter antennas configured as a coherently phased Uplink Array.

Planetary Radar Imaging with the Deep-Space Network's 34 Meter Uplink Array

NASA Technical Reports Server (NTRS)

Vilnrotter, Victor; Tsao, P.; Lee, D.; Cornish, T.; Jao, J.; Slade, M.

2011-01-01

A coherent Uplink Array consisting of two or three 34-meter antennas of NASA's Deep Space Network has been developed for the primary purpose of increasing EIRP at the spacecraft. Greater EIRP ensures greater reach, higher uplink data rates for command and configuration control, as well as improved search and recovery capabilities during spacecraft emergencies. It has been conjectured that Doppler-delay radar imaging of lunar targets can be extended to planetary imaging, where the long baseline of the uplink array can provide greater resolution than a single antenna, as well as potentially higher EIRP. However, due to the well known R4 loss in radar links, imaging of distant planets is a very challenging endeavor, requiring accurate phasing of the Uplink Array antennas, cryogenically cooled low-noise receiver amplifiers, and sophisticated processing of the received data to extract the weak echoes characteristic of planetary radar. This article describes experiments currently under way to image the planets Mercury and Venus, highlights improvements in equipment and techniques, and presents planetary images obtained to date with two 34 meter antennas configured as a coherently phased Uplink Array.

Grey-scale and colour Doppler ultrasound versus magnetic resonance imaging for the prenatal diagnosis of placenta accreta.

PubMed

Rezk, Mohamed Abd-Allah; Shawky, Mohamed

2016-01-01

To assess the effectiveness of grey-scale and colour Doppler ultrasound (US) versus magnetic resonance imaging (MRI) for the prenatal diagnosis of placenta accreta. A prospective observational study including a total of 74 patients with placenta previa and previous uterine scar (n = 74). Grey-scale and colour Doppler US was done followed by MRI by different observers to diagnose adherent placenta. Test validity of US and MRI were calculated. Maternal morbidity and mortality were also assessed. A total of 53 patients confirmed to have placenta accreta at operation. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of US was 94.34, 91.67, 96.15 and 88% compared to 96.08, 87.50, 94.23 and 91.3% for MRI, respectively. The most relevant US sign was turbulent blood flow by colour Doppler, while dark intra-placental band was the most sensitive MRI sign. Venous thromboembolism (1.3%), bladder injury (29.7%), ureteric injury (18.9%), postoperative fever (10.8%), admission to ICU (50%) and re-operation (31.1%). Placenta accreta can be successfully diagnosed by grey-scale and colour Doppler US. MRI would be more likely suggested for either posteriorly or laterally situated placenta previa in order to exclude placental invasion.

Boundary Layer Measurements in a Supersonic Wind Tunnel Using Doppler Global Velocimetry

NASA Technical Reports Server (NTRS)

Meyers, James F.; Lee, Joseph W.; Cavone, Angelo A.

2010-01-01

A modified Doppler Global Velocimeter (DGV) was developed to measure the velocity within the boundary layer above a flat plate in a supersonic flow. Classic laser velocimetry (LV) approaches could not be used since the model surface was composed of a glass-ceramic insulator in support of heat-transfer measurements. Since surface flare limited the use of external LV techniques and windows placed in the model would change the heat transfer characteristics of the flat plate, a novel approach was developed. The input laser beam was divided into nine equal power beams and each transmitted through optical fibers to a small cavity within the model. The beams were then directed through 1.6-mm diameter orifices to form a series of orthogonal beams emitted from the model and aligned with the tunnel centerline to approximate a laser light sheet. Scattered light from 0.1-micron diameter water condensation ice crystals was collected by four 5-mm diameter lenses and transmitted by their respective optical fiber bundles to terminate at the image plane of a standard two-camera DGV receiver. Flow measurements were made over a range from 0.5-mm above the surface to the freestream at Mach 3.51 in steady state and heat pulse injected flows. This technique provides a unique option for measuring boundary layers in supersonic flows where seeding the flow is problematic or where the experimental apparatus does not provide the optical access required by other techniques.

Twelve hour reproducibility of choroidal blood flow parameters in healthy subjects

PubMed Central

Polska, E; Polak, K; Luksch, A; Fuchsjager-Mayrl, G; Petternel, V; Findl, O; Schmetterer, L

2004-01-01

Aims/background: To investigate the reproducibility and potential diurnal variation of choroidal blood flow parameters in healthy subjects over a period of 12 hours. Methods: The choroidal blood flow parameters of 16 healthy non-smoking subjects were measured at five time points during the day (8:00, 11:00, 14:00, 17:00, and 20:00). Outcome parameters were pulsatile ocular blood flow as assessed by pneumotonometry, fundus pulsation amplitude as assessed by laser interferometry, blood velocities in the opthalmic and posterior ciliary arteries as assessed by colour Doppler imaging, and choroidal blood flow, volume, and velocity as assessed by fundus camera based laser Doppler flowmetry. The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. Results: None of the techniques used found a diurnal variation in choroidal blood flow. Coefficients of variation were within 2.9% and 13.6% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 11.2% to 58.8%. Conclusions: These data indicate that in healthy subjects the selected techniques provide adequate reproducibility to be used in clinical studies. Variability may, however, be considerably higher in older subjects or subjects with ocular disease. The higher individual differences in flow parameter readings limit the use of the techniques in clinical practice. To overcome problems with measurement validity, a clinical trial should include as many choroidal blood flow outcome parameters as possible to check for consistency. PMID:15031172

Twelve hour reproducibility of choroidal blood flow parameters in healthy subjects.

PubMed

Polska, E; Polak, K; Luksch, A; Fuchsjager-Mayrl, G; Petternel, V; Findl, O; Schmetterer, L

2004-04-01

To investigate the reproducibility and potential diurnal variation of choroidal blood flow parameters in healthy subjects over a period of 12 hours. The choroidal blood flow parameters of 16 healthy non-smoking subjects were measured at five time points during the day (8:00, 11:00, 14:00, 17:00, and 20:00). Outcome parameters were pulsatile ocular blood flow as assessed by pneumotonometry, fundus pulsation amplitude as assessed by laser interferometry, blood velocities in the opthalmic and posterior ciliary arteries as assessed by colour Doppler imaging, and choroidal blood flow, volume, and velocity as assessed by fundus camera based laser Doppler flowmetry. The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. None of the techniques used found a diurnal variation in choroidal blood flow. Coefficients of variation were within 2.9% and 13.6% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 11.2% to 58.8%. These data indicate that in healthy subjects the selected techniques provide adequate reproducibility to be used in clinical studies. Variability may, however, be considerably higher in older subjects or subjects with ocular disease. The higher individual differences in flow parameter readings limit the use of the techniques in clinical practice. To overcome problems with measurement validity, a clinical trial should include as many choroidal blood flow outcome parameters as possible to check for consistency.

Integration of a laser doppler vibrometer and adaptive optics system for acoustic-optical detection in the presence of random water wave distortions

NASA Astrophysics Data System (ADS)

Land, Phillip; Robinson, Dennis; Roeder, James; Cook, Dean; Majumdar, Arun K.

2016-05-01

A new technique has been developed for improving the Signal-to-Noise Ratio (SNR) of underwater acoustic signals measured above the water's surface. This technique uses a Laser Doppler Vibrometer (LDV) and an Adaptive Optics (AO) system (consisting of a fast steering mirror, deformable mirror, and Shack-Hartmann Wavefront Sensor) for mitigating the effect of surface water distortions encountered while remotely recording underwater acoustic signals. The LDV is used to perform non-contact vibration measurements of a surface via a two beam laser interferometer. We have demonstrated the feasibility of this technique to overcome water distortions artificially generated on the surface of the water in a laboratory tank. In this setup, the LDV beam penetrates the surface of the water and travels down to be reflected off a submerged acoustic transducer. The reflected or returned beam is then recorded by the LDV as a vibration wave measurement. The LDV extracts the acoustic wave information while the AO mitigates the water surface distortions, increasing the overall SNR. The AO system records the Strehl ratio, which is a measure of the quality of optical image formation. In a perfect optical system the Strehl ratio is unity, however realistic systems with imperfections have Strehl ratios below one. The operation of the AO control system in open-loop and closed-loop configurations demonstrates the utility of the AO-based LDV for many applications.

Real-Time Color-Doppler Guidance of HIFU for the Selective Avoidance or Occlusion of Blood Vessels

NASA Astrophysics Data System (ADS)

Rabkin, Brian A.; Zderic, Vesna; Vaezy, Shahram

2005-03-01

High-intensity focused ultrasound (HIFU) has been shown to effectively occlude blood vessels deep within tissue. The objective of the current study was to synchronize HIFU and color-Doppler ultrasound (US) for the real-time visualization of flow within blood vessels during HIFU treatment. The excitation of the HIFU was synchronized with the color-Doppler imager by collecting the excitation pulses of one of the elements of either a curved array intracavitary (C 9-5) or an intraoperative (CL 10-5) imaging probe. The collected excitation pulse was converted into a TTL-high pulse, which was delayed and gated to time the excitation duration and location of the HIFU pulse with respect to each imaging frame. The single pulse was used to drive a 3.2 MHz concave HIFU transducer (focal length of 3.5 cm, f-number 1) while the US imager was not collecting RF signals from the treatment region of the US image. The feasibility of the system was demonstrated in vivo by the selective ablation of tissue adjacent to, or the occlusion of, large vessels (including the femoral artery) both transcutaneously and interoperatively in the rabbit and pig. For the occlusion of vessels, the HIFU focus was placed immediately distal (with respect to the transducer) to the vessel at a depth of 2-2.5 cm. HIFU was applied at in situ intensities of 1000-2000 W/cm2, at a duty cycle of 50-75%, and a HIFU pulse repetition frequency (set by the US image frame rate) of 6-18 Hz. During each HIFU exposure, the HIFU pulse resulted in color interference bands running vertically within the color-Doppler window. Through the synchronization of the US imager with the HIFU excitation, the location and duration of the interference bands were set outside the treatment region within each image frame. This provided the operator with a clear view of the HIFU treatment site during therapy. Gross assessment showed necrosis of the tissue surrounding the HIFU treated vessel and occlusion of vessels up to 4 mm in diameter after a 30 s HIFU exposure. We have developed a method of synchronizing pulsed HIFU with color-Doppler US imaging for the real-time visualization of flow within blood vessels during HIFU therapy. This provides a means of guiding HIFU therapy for the detection and occlusion of deep vessels, or the selective ablation of tissue surrounding the vessels without vascular occlusion.

Functional optical coherence tomography: principles and progress

NASA Astrophysics Data System (ADS)

Kim, Jina; Brown, William; Maher, Jason R.; Levinson, Howard; Wax, Adam

2015-05-01

In the past decade, several functional extensions of optical coherence tomography (OCT) have emerged, and this review highlights key advances in instrumentation, theoretical analysis, signal processing and clinical application of these extensions. We review five principal extensions: Doppler OCT (DOCT), polarization-sensitive OCT (PS-OCT), optical coherence elastography (OCE), spectroscopic OCT (SOCT), and molecular imaging OCT. The former three have been further developed with studies in both ex vivo and in vivo human tissues. This review emphasizes the newer techniques of SOCT and molecular imaging OCT, which show excellent potential for clinical application but have yet to be well reviewed in the literature. SOCT elucidates tissue characteristics, such as oxygenation and carcinogenesis, by detecting wavelength-dependent absorption and scattering of light in tissues. While SOCT measures endogenous biochemical distributions, molecular imaging OCT detects exogenous molecular contrast agents. These newer advances in functional OCT broaden the potential clinical application of OCT by providing novel ways to understand tissue activity that cannot be accomplished by other current imaging methodologies.

Functional Optical Coherence Tomography: Principles and Progress

PubMed Central

Kim, Jina; Brown, William; Maher, Jason R.; Levinson, Howard; Wax, Adam

2015-01-01

In the past decade, several functional extensions of optical coherence tomography (OCT) have emerged, and this review highlights key advances in instrumentation, theoretical analysis, signal processing and clinical application of these extensions. We review five principal extensions: Doppler OCT (DOCT), polarization-sensitive OCT (PS-OCT), optical coherence elastography (OCE), spectroscopic OCT (SOCT), and molecular imaging OCT. The former three have been further developed with studies in both ex vivo and in vivo human tissues. This review emphasizes the newer techniques of SOCT and molecular imaging OCT, which show excellent potential for clinical application but have yet to be well reviewed in the literature. SOCT elucidates tissue characteristics, such as oxygenation and carcinogenesis, by detecting wavelength-dependent absorption and scattering of light in tissues. While SOCT measures endogenous biochemical distributions, molecular imaging OCT detects exogenous molecular contrast agents. These newer advances in functional OCT broaden the potential clinical application of OCT by providing novel ways to understand tissue activity that cannot be accomplished by other current imaging methodologies. PMID:25951836

Fixed Delay Interferometry for Doppler Extrasolar Planet Detection

NASA Astrophysics Data System (ADS)

Ge, Jian

2002-06-01

We present a new technique based on fixed delay interferometry for high-throughput, high-precision, and multiobject Doppler radial velocity (RV) surveys for extrasolar planets. The Doppler measurements are conducted by monitoring the stellar fringe phase shifts of the interferometer instead of absorption-line centroid shifts as in state-of-the-art echelle spectroscopy. High Doppler sensitivity is achieved through optimizing the optical delay in the interferometer and reducing photon noise by measuring multiple fringes over a broad band. This broadband operation is performed by coupling the interferometer with a low- to medium-resolution postdisperser. The resulting fringing spectra over the bandpass are recorded on a two-dimensional detector, with fringes sampled in the slit spatial direction and the spectrum sampled in the dispersion direction. The resulting total Doppler sensitivity is, in theory, independent of the dispersing power of the postdisperser, which allows for the development of new-generation RV machines with much reduced size, high stability, and low cost compared to echelles. This technique has the potential to improve RV survey efficiency by 2-3 orders of magnitude over the cross-dispersed echelle spectroscopy approach, which would allow a full-sky RV survey of hundreds of thousands of stars for planets, brown dwarfs, and stellar companions once the instrument is operated as a multiobject instrument and is optimized for high throughput. The simple interferometer response potentially allows this technique to be operated at other wavelengths independent of popular iodine reference sources, being actively used in most of the current echelles for Doppler planet searches, to search for planets around early-type stars, white dwarfs, and M, L, and T dwarfs for the first time. The high throughput of this instrument could also allow investigation of extragalactic objects for RV variations at high precision.

[The use of intraoperative Doppler ultrasound in endoscopic transsphenoidal surgery].

PubMed

Sharipov, O I; Kutin, M A; Kalinin, P L; Fomichev, D V; Lukshin, V A; Kurnosov, A B

2016-01-01

Doppler ultrasound (DUS) has been widely used in neurosurgical practice to diagnose various cerebrovascular diseases. This technique is used in transsphenoidal surgery to identify the localization of intracranial arteries when making an approach or during tumor resection. To identify the cavernous segment of the internal carotid artery (ICA) and/or basilar artery during endoscopic transsphenoidal surgery, we used a combined device on the basis of a click line curette («Karl Storz») and a 16 MHz Doppler probe (Lassamed). The technique was used in 51 patients during both standard transsphenoidal surgery (23 cases) and transsphenoidal tumor resection through an extended approach (28 cases). Doppler ultrasound was used in different situations: to determine a trajectory of the endonasal transsphenoidal approach in the absence of the normal anatomical landmarks (16 cases), to define the limits of safe resection of a tumor located in the laterosellar region (7), and to implement an extended transsphenoidal endoscopic approach (28). Intraoperative Doppler ultrasound enabled identification of the cavernous segment of the internal carotid artery in 45 cases and the basilar artery in 2 cases; a blood vessel was not found in 4 cases. Injury to the cavernous segment of the internal carotid artery was observed only in 1 case. The use of the described combined device in transsphenoidal surgery turned Doppler ultrasound into an important and useful technique for visualization of the ICA within the tumor stroma as well as in the case of the changed skull base anatomy. Its use facilitates manipulations in a deep and narrow wound and enables inspection of the entire surface of the operative field in various planes, thereby surgery becomes safer due to the possibility of maximum investigation of the operative field.

Measurement of precipitation induced FUV emission and Geocoronal Lyman Alpha from the IMI mission

NASA Technical Reports Server (NTRS)

Mende, Stephen B.; Fuselier, S. A.; Rairden, R. L.

1995-01-01

This final report describes the activities of the Lockheed Martin Palo Alto Research Laboratory in studying the measurement of ion and electron precipitation induced Far Ultra-Violet (FUV) emissions and Geocoronal Lyman Alpha for the NASA Inner Magnetospheric Imager (IMI) mission. this study examined promising techniques that may allow combining several FUV instruments that would separately measure proton aurora, electron aurora, and geocoronal Lyman alpha into a single instrument operated on a spinning spacecraft. The study consisted of two parts. First, the geocoronal Lyman alpha, proton aurora, and electron aurora emissions were modeled to determine instrument requirements. Second, several promising techniques were investigated to determine if they were suitable for use in an IMI-type mission. Among the techniques investigated were the Hydrogen gas cell for eliminating cold geocoronal Lyman alpha emissions, and a coded aperture spectrometer with sufficient resolution to separate Doppler shifted Lyman alpha components.

Optical multi-point measurements of the acoustic particle velocity with frequency modulated Doppler global velocimetry.

PubMed

Fischer, Andreas; König, Jörg; Haufe, Daniel; Schlüssler, Raimund; Büttner, Lars; Czarske, Jürgen

2013-08-01

To reduce the noise of machines such as aircraft engines, the development and propagation of sound has to be investigated. Since the applicability of microphones is limited due to their intrusiveness, contactless measurement techniques are required. For this reason, the present study describes an optical method based on the Doppler effect and its application for acoustic particle velocity (APV) measurements. While former APV measurements with Doppler techniques are point measurements, the applied system is capable of simultaneous measurements at multiple points. In its current state, the system provides linear array measurements of one component of the APV demonstrated by multi-tone experiments with tones up to 17 kHz for the first time.

Radar Imaging of Asteroids

NASA Astrophysics Data System (ADS)

Ostro, S. J.

1996-09-01

Measurements of the distribution of echo power in time delay (range) and Doppler frequency (line-of-sight velocity) can synthesize images of near-Earth and main-belt asteroids (NEAs and MBAs) that traverse the detectability windows of groundbased radar telescopes. Under ideal circumstances, current radar waveforms can achieve decameter surface resolution. The number of useful pixels obtainable in an imaging data set is of the same order as the signal-to-noise ratio, SNR, of an optimally filtered, weighted sum of all the data. (SNR increases as the square root of the integration time.) The upgraded Arecibo telescope which is about to become operational, should be able to achieve single-date SNRs {\\underline>} (20,100) for an average of (35,5) MBAs per year and single-date SNRs {\\underline>} (20,100,1000) for an average of (10,6,2) of the currently catalogued NEAs per year; optical surveying of the NEA population could increase the frequency of opportunities by an order of magnitude. The strongest imaging opportunities predicted for Arecibo between now and the end of 1997 include (the peak SNR/date is in parentheses): 9 Metis (110), 27 Euterpe (170), 80 Sappho (100), 139 Juewa (140), 144 Vibilia (140), 253 Mathilde (100), 2102 Tantalus (570), 3671 Dionysus (170), 3908 1980PA (4400), 4179 Toutatis (16000), 4197 1982TA (1200), 1991VK (700), and 1994PC1 (7400). A delay-Doppler image projects the echo power distribution onto the target's apparent equatorial plane. One cannot know a priori whether one or two (or more) points on the asteroid contributed power to a given pixel, so accurate interpretation of delay-Doppler images requires modeling (Hudson, 1993, Remote Sensing Rev. 8, 195-203). Inversion of an imaging sequence with enough orientational coverage can remove "north/south" ambiguities and can provide estimates of the target's three-dimensional shape, spin state, radar scattering properties, and delay-Doppler trajectory (e.g., Ostro et al. 1995, Science 270, 80-83; Hudson and Ostro 1995, Science 270, 84-86).

Power and color Doppler ultrasound settings for inflammatory flow: impact on scoring of disease activity in patients with rheumatoid arthritis.

PubMed

Torp-Pedersen, Søren; Christensen, Robin; Szkudlarek, Marcin; Ellegaard, Karen; D'Agostino, Maria Antonietta; Iagnocco, Annamaria; Naredo, Esperanza; Balint, Peter; Wakefield, Richard J; Torp-Pedersen, Arendse; Terslev, Lene

2015-02-01

To determine how settings for power and color Doppler ultrasound sensitivity vary on different high- and intermediate-range ultrasound machines and to evaluate the impact of these changes on Doppler scoring of inflamed joints. Six different types of ultrasound machines were used. On each machine, the factory setting for superficial musculoskeletal scanning was used unchanged for both color and power Doppler modalities. The settings were then adjusted for increased Doppler sensitivity, and these settings were designated study settings. Eleven patients with rheumatoid arthritis (RA) with wrist involvement were scanned on the 6 machines, each with 4 settings, generating 264 Doppler images for scoring and color quantification. Doppler sensitivity was measured with a quantitative assessment of Doppler activity: color fraction. Higher color fraction indicated higher sensitivity. Power Doppler was more sensitive on half of the machines, whereas color Doppler was more sensitive on the other half, using both factory settings and study settings. There was an average increase in Doppler sensitivity, despite modality, of 78% when study settings were applied. Over the 6 machines, 2 Doppler modalities, and 2 settings, the grades for each of 7 of the patients varied between 0 and 3, while the grades for each of the other 4 patients varied between 0 and 2. The effect of using different machines, Doppler modalities, and settings has a considerable influence on the quantification of inflammation by ultrasound in RA patients, and this must be taken into account in multicenter studies. Copyright © 2015 by the American College of Rheumatology.

Cross-correlation Doppler global velocimetry (CC-DGV)

NASA Astrophysics Data System (ADS)

Cadel, Daniel R.; Lowe, K. Todd

2015-08-01

A flow velocimetry method, cross-correlation Doppler global velocimetry (CC-DGV), is presented as a robust, simplified, and high dynamic range implementation of the Doppler global/planar Doppler velocimetry technique. A sweep of several gigahertz of the vapor absorption spectrum is used for each velocity sample, with signals acquired from both Doppler-shifted scattered light within the flow and a non-Doppler shifted reference beam. Cross-correlation of these signals yields the Doppler shift between them, averaged over the duration of the scan. With presently available equipment, velocities from 0 ms-1 to over 3000 ms-1 can notionally be measured simultaneously, making the technique ideal for high speed flows. The processing routine is shown to be robust against large changes in the vapor pressure of the iodine cell, benefiting performance of the system in facilities where ambient conditions cannot be easily regulated. Validation of the system was performed with measurements of a model wind turbine blade boundary layer made in a 1.83 m by 1.83 m subsonic wind tunnel for which laser Doppler velocimetry (LDV) measurements were acquired alongside the CC-DGV results. CC-DGV uncertainties of ±1.30 ms-1, ±0.64 ms-1, and ±1.11 ms-1 were determined for the orthogonal stream-wise, transverse-horizontal, and transverse-vertical velocity components, and root-mean-square deviations of 2.77 ms-1 and 1.34 ms-1 from the LDV validation results were observed for Reynolds numbers of 1.5 million and 2 million, respectively. Volumetric mean velocity measurements are also presented for a supersonic jet, with velocity uncertainties of ±4.48 ms-1, ±16.93 ms-1, and ±0.50 ms-1 for the orthogonal components, and self-validation done by collapsing the data with a physical scaling.

Language Lateralization in Children Using Functional Transcranial Doppler Sonography

ERIC Educational Resources Information Center

Haag, Anja; Moeller, Nicola; Knake, Susanne; Hermsen, Anke; Oertel, Wolfgang H.; Rosenow, Felix; Hamer, Hajo M.

2010-01-01

Aim: Language lateralization with functional transcranial Doppler sonography (fTCD) and lexical word generation has been shown to have high concordance with the Wada test and functional magnetic resonance imaging in adults. We evaluated a nonlexical paradigm to determine language dominance in children. Method: In 23 right-handed children (12…

Propofol Induction's Effect on Cardiac Function

ClinicalTrials.gov

2015-03-31

This Study Was Focused to Evaluate Feasibility of Doppler Tissue Monitoring During the Induction Anesthesia,; and Evaluate Routine Propofol Induction's Effect on Myocardial Tissue Motion, Using Non-invasive Doppler Tissue and 2D Speckle Tracking Imaging.; This is the First Study, to Our Knowledge, Which Has Evaluated the Possible Impact of Propofol Induction on LV Function.

Analysis of Supergranule Sizes and Velocities Using Solar Dynamics Observatory (SDO)/Helioseismic Magnetic Imager (HMI) and Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) Dopplergrams

NASA Technical Reports Server (NTRS)

Williams, Peter E.; Pesnell, W. Dean; Beck, John G.; Lee, Shannon

2013-01-01

Co-temporal Doppler images from Solar and Heliospheric Observatory (SOHO)/ Michelson Doppler Imager (MDI) and Solar Dynamics Observatory (SDO)/Helioseismic Magnetic Imager (HMI) have been analyzed to extract quantitative information about global properties of the spatial and temporal characteristics of solar supergranulation. Preliminary comparisons show that supergranules appear to be smaller and have stronger horizontal velocity flows within HMI data than was measured with MDI. There appears to be no difference in their evolutionary timescales. Supergranule sizes and velocities were analyzed over a ten-day time period at a 15-minute cadence. While the averages of the time-series retain the aforementioned differences, fluctuations of these parameters first observed in MDI data were seen in both MDI and HMI time-series, exhibiting a strong cross-correlation. This verifies that these fluctuations are not instrumental, but are solar in origin. The observed discrepancies between the averaged values from the two sets of data are a consequence of instrument resolution. The lower spatial resolution of MDI results in larger observed structures with lower velocities than is seen in HMI. While these results offer a further constraint on the physical nature of supergranules, they also provide a level of calibration between the two instruments.

Predictors of transient left ventricular dysfunction following transcatheter patent ductus arteriosus closure in pediatric age.

PubMed

Agha, Hala Mounir; Hamza, Hala S; Kotby, Alyaa; Ganzoury, Mona E L; Soliman, Nanies

2017-10-01

To evaluate the left ventricular function before and after transcatheter percutaneous patent ductus arteriosus (PDA) closure, and to identify the predictors of myocardial dysfunction post-PDA closure if present. Transcatheter PDA closure; conventional, Doppler, and tissue Doppler imaging; and speckle tracking echocardiography. To determine the feasibility and reliability of tissue Doppler and myocardial deformation imaging for evaluating myocardial function in children undergoing transcatheter PDA closure. Forty-two children diagnosed with hemodynamically significant PDA underwent percutaneous PDA closure. Conventional, Doppler, and tissue Doppler imaging, and speckle-derived strain rate echocardiography were performed at preclosure and at 48 hours, 1 month, and 6 months postclosure. Tissue Doppler velocities of the lateral and septal mitral valve annuli were obtained. Global and regional longitudinal peak systolic strain values were determined using two-dimensional speckle tracking echocardiography. The median age of the patients was 2 years and body weight was 15 kg, with the mean PDA diameter of 3.11 ± 0.99 mm. M-mode measurements (left ventricular end diastolic diameter, left atrium diameter to aortic annulus ratio, ejection fraction, and shortening fraction) reduced significantly early after PDA closure ( p  < 0.001). After 1 month, left ventricular end diastolic diameter and left atrium diameter to aortic annulus ratio continued to decrease, while ejection fraction and fractional shortening improved significantly. All tissue Doppler velocities showed a significant decrease at 48 hours with significant prolongation of global myocardial function ( p  < 0.001) and then were normalized within 1 month postclosure. Similarly, global longitudinal strain significantly decreased at 48 hours postclosure ( p  < 0.001), which also recovered at 1 month follow-up. Preclosure global longitudinal strain showed a good correlation with the postclosure prolongation of the myocardial performance index. Transcatheter PDA closure causes a significant decrease in left ventricular performance early after PDA closure, which recovers completely within 1 month. Preclosure global longitudinal strain can be a predictor of postclosure myocardial dysfunction.

[Spiral CT angiography in practice].

PubMed

Pavcec, Zlatko; Zokalj, Ivan; Rumboldt, Zoran; Pal, Andrej; Saghir, Hussein; Ozretić, David; Latin, Branko; Perhoć, Zeljka; Marotti, Miljenko

2005-01-01

Incidence of vascular diseases and development of new radiologic techniques in the last three decades has given strong impuls for introduction of non-invasive vascular diagnostic methods. Thanks to the introduction of Doppler ultrasound, new types of computed tomography (CT) and magnetic resonance (MR) scanners, non-invasive vascular diagnostic methods are replacing conventional invasive (catheter) angiographic methods. Computed tomographic angiography (CTA) is a noninvasive vascular diagnostic method based on continuous scanning with CT scanner during intravenous application of contrast material. Performing of CTA is possible after introduction of spiral CT technique whose characteristics are short imaging time and volumetric data acquisition. The main goal of this article, based on our experiences, is to review the role of CTA, performed on single-slice CT scanner, in managment of patients with vascular pathology.

Remote sensing of mesospheric winds with the High-Resolution Doppler Imager

NASA Technical Reports Server (NTRS)

Hays, Paul B.; Abreu, V. J.; Burrage, M. D.; Gell, D. A.; Grassi, H. J.; Marshall, A. R.; Morton, Y. T.; Ortland, D. A.; Skinner, W. R.; Wu, D. L.

1992-01-01

Observations of the winds in the upper atmosphere obtained with the High-Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) are discussed. This instrument is a very stable high-resolution triple-etalon Fabry-Perot interferometer, which is used to observe the slight Doppler shifts of absorption and emission lines in the O2 Atmospheric bands induced by atmospheric motions. Preliminary observations indicate that the winds in the mesosphere and lower thermosphere are a mixture of migrating and non-migrating tides, and planetary-scale waves. The mean meridional winds are dominated by the 1,1 diurnal tide which is easily extracted from the daily zonal means of the satellite observations. The daily mean zonal winds are a mixture of the diurnal tide and a zonal flow which is consistent with theoretical expectations.

Feasibility study: real-time 3-D ultrasound imaging of the brain.

PubMed

Smith, Stephen W; Chu, Kengyeh; Idriss, Salim F; Ivancevich, Nikolas M; Light, Edward D; Wolf, Patrick D

2004-10-01

We tested the feasibility of real-time, 3-D ultrasound (US) imaging in the brain. The 3-D scanner uses a matrix phased-array transducer of 512 transmit channels and 256 receive channels operating at 2.5 MHz with a 15-mm diameter footprint. The real-time system scans a 65 degrees pyramid, producing up to 30 volumetric scans per second, and features up to five image planes as well as 3-D rendering, 3-D pulsed-wave and color Doppler. In a human subject, the real-time 3-D scans produced simultaneous transcranial horizontal (axial), coronal and sagittal image planes and real-time volume-rendered images of the gross anatomy of the brain. In a transcranial sheep model, we obtained real-time 3-D color flow Doppler scans and perfusion images using bolus injection of contrast agents into the internal carotid artery.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debnath, Mithu; Iungo, Giacomo Valerio; Brewer, W. Alan

During the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign, which was carried out at the Boulder Atmospheric Observatory (BAO) in spring 2015, multiple-Doppler scanning strategies were carried out with scanning wind lidars and Ka-band radars. Specifically, step–stare measurements were collected simultaneously with three scanning Doppler lidars, while two scanning Ka-band radars carried out simultaneous range height indicator (RHI) scans. The XPIA experiment provided the unique opportunity to compare directly virtual-tower measurements performed simultaneously with Ka-band radars and Doppler wind lidars. Furthermore, multiple-Doppler measurements were assessed against sonic anemometer data acquired from the meteorological tower (met-tower) present at the BAOmore » site and a lidar wind profiler. As a result, this survey shows that – despite the different technologies, measurement volumes and sampling periods used for the lidar and radar measurements – a very good accuracy is achieved for both remote-sensing techniques for probing horizontal wind speed and wind direction with the virtual-tower scanning technique.« less

Is Doppler tissue velocity during early left ventricular filling preload independent?

NASA Technical Reports Server (NTRS)

Yalcin, F.; Kaftan, A.; Muderrisoglu, H.; Korkmaz, M. E.; Flachskampf, F.; Garcia, M.; Thomas, J. D.

2002-01-01

BACKGROUND: Transmitral Doppler flow indices are used to evaluate diastolic function. Recently, velocities measured by Doppler tissue imaging have been used as an index of left ventricular relaxation. OBJECTIVE: To determine whether Doppler tissue velocities are influenced by alterations in preload. METHODS: Left ventricular preload was altered in 17 patients (all men, mean (SD) age, 49 (8) years) during echocardiographic measurements of left ventricular end diastolic volume, maximum left atrial area, peak early Doppler filling velocity, and left ventricular myocardial velocities during early filling. Preload altering manoeuvres included Trendelenberg (stage 1), reverse Trendelenberg (stage 2), and amyl nitrate (stage 3). Systolic blood pressure was measured at each stage. RESULTS: In comparison with baseline, left ventricular end diastolic volume (p = 0.001), left atrial area (p = 0.003), peak early mitral Doppler filling velocity (p = 0.01), and systolic blood pressures (p = 0.001) were all changed by preload altering manoeuvres. Only left ventricular myocardial velocity during early filling remained unchanged by these manoeuvres. CONCLUSIONS: In contrast to standard transmitral Doppler filling indices, Doppler tissue early diastolic velocities are not significantly affected by physiological manoeuvres that alter preload. Thus Doppler tissue velocities during early left ventricular diastole may provide a better index of diastolic function in cardiac patients by providing a preload independent assessment of left ventricular filling.

An airport wind shear detection and warning system using Doppler radar: A feasibility study

NASA Technical Reports Server (NTRS)

Mccarthy, J.; Blick, E. F.; Elmore, K. L.

1981-01-01

A feasibility study was conducted to determine whether ground based Doppler radar could measure the wind along the path of an approaching aircraft with sufficient accuracy to predict aircraft performance. Forty-three PAR approaches were conducted, with 16 examined in detail. In each, Doppler derived longitudinal winds were compared to aircraft measured winds; in approximately 75 percent of the cases, the Doppler and aircraft winds were in acceptable agreement. In the remaining cases, errors may have been due to a lack of Doppler resolution, a lack of co-location of the two sampling volumes, the presence of eddy or vortex like disturbances within the pulse volume, or the presence of point targets in antenna side lobes. It was further concluded that shrouding techniques would have reduced the side lobe problem. A ground based Doppler radar operating in the optically clear air, provides the appropriate longitudinal winds along an aircraft's intended flight path.

Flow Quantification by Nuclear Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Vu, Anthony Tienhuan

1994-01-01

In this dissertation, a robust method for the measurement and visualization of flow field in laminar, complex and turbulent flows by Nuclear Magnetic Resonance Imaging utilizing flow induced Adiabatic Fast Passage (AFP) principle will be presented. This dissertation focuses on the application of AFP in spatially resolvable size vessels. We first review two main flow effects in NMR: time-of-flight and phase dispersion. The discussion of NMR flow imaging application - flow measurements and NMR angiography will be given. The theoretical framework of adiabatic passage will be discussed in order to explain the principle of flow-induced adiabatic passage tagging for flow imaging applications. From a knowledge of the basic flow-induced adiabatic passage principle, we propose a multi-zone AFP excitation scheme to deal with flow in a curved tube, branches and constrictions, i.e. complex and turbulent flow regimes. The technique provides a quick and simple way to acquire flow profiles simultaneously at several locations and arbitrary orientations inside the field-of-view. The flow profile is the time-averaged evolution of the labeled flowing material. Results obtained using a carotid bifurcation and circular jet phantoms are similar to the previous experimental studies employing laser Doppler Anemometry, and other flow visualization techniques. In addition, the preliminary results obtained with a human volunteer support the feasibility of the technique for in vivo flow quantification. Finally, a quantitative comparison of flow measurement of the new proposed techniques with the more established Phase Contrast MRA was performed. The results show excellent correlation between the two methods and with the standard volumetric flow rate measurement indicating that the flow measurements obtained using this technique are reliable and accurate under various flow regimes.

Hybrid space-airborne bistatic SAR geometric resolutions

NASA Astrophysics Data System (ADS)

Moccia, Antonio; Renga, Alfredo

2009-09-01

Performance analysis of Bistatic Synthetic Aperture Radar (SAR) characterized by arbitrary geometric configurations is usually complex and time-consuming since system impulse response has to be evaluated by bistatic SAR processing. This approach does not allow derivation of general equations regulating the behaviour of image resolutions with varying the observation geometry. It is well known that for an arbitrary configuration of bistatic SAR there are not perpendicular range and azimuth directions, but the capability to produce an image is not prevented as it depends only on the possibility to generate image pixels from time delay and Doppler measurements. However, even if separately range and Doppler resolutions are good, bistatic SAR geometries can exist in which imaging capabilities are very poor when range and Doppler directions become locally parallel. The present paper aims to derive analytical tools for calculating the geometric resolutions of arbitrary configuration of bistatic SAR. The method has been applied to a hybrid bistatic Synthetic Aperture Radar formed by a spaceborne illuminator and a receiving-only airborne forward-looking Synthetic Aperture Radar (F-SAR). It can take advantage of the spaceborne illuminator to dodge the limitations of monostatic FSAR. Basic modeling and best illumination conditions have been detailed in the paper.

Ultrasonography with color Doppler and power Doppler in the diagnosis of periapical lesions

PubMed Central

Goel, Sumit; Nagendrareddy, Suma Gundareddy; Raju, Manthena Srinivasa; Krishnojirao, Dayashankara Rao Jingade; Rastogi, Rajul; Mohan, Ravi Prakash Sasankoti; Gupta, Swati

2011-01-01

Aim: To evaluate the efficacy of ultrasonography (USG) with color Doppler and power Doppler applications over conventional radiography in the diagnosis of periapical lesions. Materials and Methods: Thirty patients having inflammatory periapical lesions of the maxillary or mandibular anterior teeth and requiring endodontic surgery were selected for inclusion in this study. All patients consented to participate in the study. We used conventional periapical radiographs as well as USG with color Doppler and power Doppler for the diagnosis of these lesions. Their diagnostic performances were compared against histopathologic examination. All data were compared and statistically analyzed. Results: USG examination with color Doppler and power Doppler identified 29 (19 cysts and 10 granulomas) of 30 periapical lesions accurately, with a sensitivity of 100% for cysts and 90.91% for granulomas and a specificity of 90.91% for cysts and 100% for granulomas. In comparison, conventional intraoral radiography identified only 21 lesions (sensitivity of 78.9% for cysts and 45.4% for granulomas and specificity of 45.4% for cysts and 78.9% for granulomas). There was definite correlation between the echotexture of the lesions and the histopathological features except in one case. Conclusions: USG imaging with color Doppler and power Doppler is superior to conventional intraoral radiographic methods for diagnosing the nature of periapical lesions in the anterior jaws. This study reveals the potential of USG examination in the study of other jaw lesions. PMID:22223940

Superharmonic microbubble Doppler effect in ultrasound therapy

NASA Astrophysics Data System (ADS)

Pouliopoulos, Antonios N.; Choi, James J.

2016-08-01

The introduction of microbubbles in focused ultrasound therapies has enabled a diverse range of non-invasive technologies: sonoporation to deliver drugs into cells, sonothrombolysis to dissolve blood clots, and blood-brain barrier opening to deliver drugs into the brain. Current methods for passively monitoring the microbubble dynamics responsible for these therapeutic effects can identify the cavitation position by passive acoustic mapping and cavitation mode by spectral analysis. Here, we introduce a new feature that can be monitored: microbubble effective velocity. Previous studies have shown that echoes from short imaging pulses had a Doppler shift that was produced by the movement of microbubbles. Therapeutic pulses are longer (>1 000 cycles) and thus produce a larger alteration of microbubble distribution due to primary and secondary acoustic radiation force effects which cannot be monitored using pulse-echo techniques. In our experiments, we captured and analyzed the Doppler shift during long therapeutic pulses using a passive cavitation detector. A population of microbubbles (5  ×  104-5  ×  107 microbubbles ml-1) was embedded in a vessel (inner diameter: 4 mm) and sonicated using a 0.5 MHz focused ultrasound transducer (peak-rarefactional pressure: 75-366 kPa, pulse length: 50 000 cycles or 100 ms) within a water tank. Microbubble acoustic emissions were captured with a coaxially aligned 7.5 MHz passive cavitation detector and spectrally analyzed to measure the Doppler shift for multiple harmonics above the 10th harmonic (i.e. superharmonics). A Doppler shift was observed on the order of tens of kHz with respect to the primary superharmonic peak and is due to the axial movement of the microbubbles. The position, amplitude and width of the Doppler peaks depended on the acoustic pressure and the microbubble concentration. Higher pressures increased the effective velocity of the microbubbles up to 3 m s-1, prior to the onset of broadband emissions, which is an indicator for high magnitude inertial cavitation. Although the microbubble redistribution was shown to persist for the entire sonication period in dense populations, it was constrained to the first few milliseconds in lower concentrations. In conclusion, superharmonic microbubble Doppler effects can provide a quantitative measure of effective velocities of a sonicated microbubble population and could be used for monitoring ultrasound therapy in real-time.

Superharmonic microbubble Doppler effect in ultrasound therapy

PubMed Central

Pouliopoulos, Antonios N; Choi, James J

2016-01-01

Abstract The introduction of microbubbles in focused ultrasound therapies has enabled a diverse range of non-invasive technologies: sonoporation to deliver drugs into cells, sonothrombolysis to dissolve blood clots, and blood-brain barrier opening to deliver drugs into the brain. Current methods for passively monitoring the microbubble dynamics responsible for these therapeutic effects can identify the cavitation position by passive acoustic mapping and cavitation mode by spectral analysis. Here, we introduce a new feature that can be monitored: microbubble effective velocity. Previous studies have shown that echoes from short imaging pulses had a Doppler shift that was produced by the movement of microbubbles. Therapeutic pulses are longer (>1 000 cycles) and thus produce a larger alteration of microbubble distribution due to primary and secondary acoustic radiation force effects which cannot be monitored using pulse-echo techniques. In our experiments, we captured and analyzed the Doppler shift during long therapeutic pulses using a passive cavitation detector. A population of microbubbles (5  ×  104–5  ×  107 microbubbles ml−1) was embedded in a vessel (inner diameter: 4 mm) and sonicated using a 0.5 MHz focused ultrasound transducer (peak-rarefactional pressure: 75–366 kPa, pulse length: 50 000 cycles or 100 ms) within a water tank. Microbubble acoustic emissions were captured with a coaxially aligned 7.5 MHz passive cavitation detector and spectrally analyzed to measure the Doppler shift for multiple harmonics above the 10th harmonic (i.e. superharmonics). A Doppler shift was observed on the order of tens of kHz with respect to the primary superharmonic peak and is due to the axial movement of the microbubbles. The position, amplitude and width of the Doppler peaks depended on the acoustic pressure and the microbubble concentration. Higher pressures increased the effective velocity of the microbubbles up to 3 m s−1, prior to the onset of broadband emissions, which is an indicator for high magnitude inertial cavitation. Although the microbubble redistribution was shown to persist for the entire sonication period in dense populations, it was constrained to the first few milliseconds in lower concentrations. In conclusion, superharmonic microbubble Doppler effects can provide a quantitative measure of effective velocities of a sonicated microbubble population and could be used for monitoring ultrasound therapy in real-time. PMID:27469394

Performance assessment techniques for Doppler radar physiological sensors.

PubMed

Hafner, Noah; Lubecke, Victor

2009-01-01

This paper presents a technique for assessing the performance of continuous wave Doppler radar systems for physiological sensing. The technique includes an artificial target for testing physiological sensing radar systems with motion analogous to human heart movement and software algorithms leveraging the capabilities of this target to simply test radar system performance. The mechanical target provides simple to complex patterns of motion that are stable and repeatable. Details of radar system performance can be assessed and the effects of configuration changes that might not appear with a human target can be observed when using this mechanical target.

M2K Planet Search: Spectroscopic Screening and Transit Photometry

NASA Astrophysics Data System (ADS)

Mann, Andrew; Gaidos, E.; Fischer, D.; Lepine, S.

2010-10-01

The M2K project is a search for planets orbiting nearby early M and late K dwarf drawn from the SUPERBLINK catalog. M and K dwarfs are highly attractive targets for finding low-mass and habitable planets because (1) close-in planets are more likely to orbit within their habitable zone, (2) planets orbiting them induce a larger Doppler signal and have deeper transits than similar planets around F, G, and early K type stars, (3) planet formation models predict they hold an abundance of super-Earth sized planets, and (4) they represent the vast majority of the stars close enough for direct imaging techniques. In spite of this, only 10% of late K and early M dwarfs are being monitored by current Doppler surveys. As part of the M2K project we have obtained low-resolution spectra for more than 2000 of our sample of 10,000 M and K dwarfs. We vet our sample by screening these stars for high metallicity and low chromospheric activity. We search for transits on targets showing high RMS Doppler signal and photometry candidates provided by SuperWASP project. By using "snapshot” photometry have been able to achieve sub-millimag photometry on numerous transit targets in the same night. With further follow-up observations we will be able to detect planets smaller than 10 Earth masses.

Analysis of achilles tendon vascularity with second-generation contrast-enhanced ultrasound.

PubMed

Genovese, Eugenio; Ronga, Mario; Recaldini, Chiara; Fontana, Federico; Callegari, Leonardo; Maffulli, Nicola; Fugazzola, Carlo

2011-01-01

To compare morphological, power Doppler, and contrast-enhanced ultrasound (CEUS) features of the Achilles tendon between asymptomatic athletes and athletes who had undergone surgical repair of a previous rupture. Twenty-four athletes were divided in two groups (A and B). Group A included 14 patients with a median age of 32 years (range 27 to 47 years) who had undergone surgical repair for unilateral Achilles tendon rupture. Group B (control group) included 10 subjects with a median age of 34 years (range 27 to 40 years) with no previous or present history of tendinopathy. All patients were evaluated with ultrasound, power Doppler, and CEUS with second-generation contrast agent. We studied the uninjured Achilles tendon in athletes of group A and either the left or the right Achilles tendon of the athletes in group B. CEUS showed a significantly greater ability to detect a greater number of vascular spots within the uninjured tendon of group A compared to group B (<0.05). In athletes who had suffered a tear of an Achilles tendon, CEUS detected small vessels that were not identified by power Doppler ultrasound in the uninjured contralateral Achilles tendon. CEUS is useful to evaluate vascularity not detected by other imaging techniques. Vascularity in the uninjured tendon seems to be increased in patients who had a previous rupture. Copyright © 2011 Wiley Periodicals, Inc.

In vivo endoscopic Doppler optical coherence tomography imaging of the colon

PubMed Central

Welge, Weston A.; Barton, Jennifer K.

2017-01-01

Background and Objective Colorectal cancer remains the second deadliest cancer in the United States. Several screening methods exist, however detection of small polyps remains a challenge. Optical coherence tomography has been demonstrated to be capable of detecting lesions as small as 1 mm in the mouse colon, but detection is based on measuring a doubling of the mucosa thickness. The colon microvasculature may be an attractive biomarker of early tumor development because tumor vessels are characterized by irregular structure and dysfunction. Our goal was to develop an endoscopic method of detecting and segmenting colon vessels using Doppler optical coherence tomography to enable future studies for improving early detection and development of novel chemopreventive agents. Method We conducted in vivo colon imaging in an azoxymethane (AOM)-treated mouse model of colorectal cancer using a miniature endoscope and a swept-source OCT system at 1040 nm with a 16 kHz sweep rate. We applied the Kasai autocorrelation algorithm to laterally oversampled OCT B-scans to resolve vascular flow in the mucosa and submucosa. Vessels were segmented by applying a series of image processing steps: (1) intensity thresholding, (2) two-dimensional matched filtering, and (3) histogram segmentation. Results We observed differences in the vessels sizes and spatial distribution in a mature adenoma compared to surrounding undiseased tissue and compared the results with histology. We also imaged flow in four young mice (2 AOM-treated and 2 control) showing no significant differences, which is expected so early after carcinogen exposure. We also present flow images of adenoma in a living mouse and a euthanized mouse to demonstrate that no flow is detected after euthanasia. Conclusion We present, to the best of our knowledge, the first Doppler OCT images of in vivo mouse colon collected with a fiber-based endoscope. We also describe a fast and robust image processing method for segmenting vessels in the colon. These results suggest that Doppler OCT is a promising imaging modality for vascular imaging in the colon that requires no exogenous contrast agents. PMID:27546786

A new method for the noninvasive determination of abdominal muscle feedforward activity based on tissue velocity information from tissue Doppler imaging.

PubMed

Mannion, A F; Pulkovski, N; Schenk, P; Hodges, P W; Gerber, H; Loupas, T; Gorelick, M; Sprott, H

2008-04-01

Rapid arm movements elicit anticipatory activation of the deep-lying abdominal muscles; this appears modified in back pain, but the invasive technique used for its assessment [fine-wire electromyography (EMG)] has precluded its widespread investigation. We examined whether tissue-velocity changes recorded with ultrasound (M-mode) tissue Doppler imaging (TDI) provided a viable noninvasive alternative. Fourteen healthy subjects rapidly flexed, extended, and abducted the shoulder; recordings were made of medial deltoid (MD) surface EMG and of fine-wire EMG and TDI tissue-velocity changes of the contralateral transversus abdominis, obliquus internus, and obliquus externus. Muscle onsets were determined by blinded visual analysis of EMG and TDI data. TDI could not distinguish between the relative activation of the three muscles, so in subsequent analyses only the onset of the earliest abdominal muscle activity was used. The latter occurred <50 ms after the onset of medial deltoid EMG (i.e., was feedforward) and correlated with the corresponding EMG onsets (r = 0.47, P < 0.0001). The mean difference between methods was 20 ms and was likely explained by electromechanical delay; limits of agreement were wide (-40 to +80 ms) but no greater than those typical of repeated measurements using either technique. The between-day standard error of measurement of the TDI onsets (examined in 16 further subjects) was 16 ms. TDI yielded reliable and valid measures of the earliest onset of feedforward activity within the anterolateral abdominal muscle group. The method can be used to assess muscle dysfunction in large groups of back-pain patients and may also be suitable for the noninvasive analysis of other deep-lying or small/thin muscles.

Does accessory pathway significantly alter left ventricular twist/torsion? A study in Wolff-Parkinson-White syndrome by velocity vector imaging.

PubMed

Aminian, Farimah; Esmaeilzadeh, Maryam; Moladoust, Hassan; Maleki, Majid; Shahrzad, Soraya; Emkanjoo, Zahra; Sadeghpour, Anita

2014-08-01

The aim of this study was to determine the impact of manifest accessory pathway on left ventricle (LV) twist physiology in Wolff-Parkinson-White (WPW) patients. Although this issue was addressed in 1 study based on speckle tracking method, there was no comparative study with a different technique. We planned to use velocity vector imaging (VVI) to find out how much an accessory pathway can affect LV twist mechanics. Thirty patients were enrolled regarding inclusion and exclusion criteria. Two serial comprehensive transthoracic echocardiography evaluations were performed before and after radiofrequency catheter ablation (RFCA) within 24 hours. Stored cine loops were analyzed using VVI technique and LV twist and related parameters were extracted. Comparing pre- and post-RFCA data, no significant changes were observed in LV systolic and diastolic dimensions, LV ejection fraction (LVEF), and Doppler and tissue Doppler-related parameters. VVI study revealed remarkable rise in peak LV apical rotation (10.3º ± 3.0º to 13.8º ± 3.6º, P < 0.001) and basal rotation (-6.0 ± 1.8º to -7.7 ± 1.8º, P < 0.001) after RFCA. Subsequently LV twist showed a surge from 14.7º ± 3.9º to 20.2º ± 4.4º (P < 0.001). LV untwisting rate changed significantly from -96 ± 67 to -149.0 ± 47.5°/sec (P < 0.001) and apical-basal rotation delay showed a remarkable decline after RFCA (106 ± 81 vs. 42.8 ± 26.0 msec, P < 0.001). Accessory pathways have a major impact on LV twist mechanics. © 2013, Wiley Periodicals, Inc.

Evaluation of microvascular anastomosis using real-time ultrahigh resolution Fourier domain Doppler optical coherence tomography

PubMed Central

Huang, Yong; Tong, Dedi; Zhu, Shan; Wu, Lehao; Mao, Qi; Ibrahim, Zuhaib; Lee, WP Andrew; Brandacher, Gerald; Kang, Jin U.

2014-01-01

Background Evolution and improvements in microsurgical techniques and tools have paved the way for super-microsurgical anastomoses with vessel diameters often approaching below 0.8 mm in the clinical realm and even smaller (0.2–0.3 mm) in murine models. Several imaging and monitoring devices have been introduced for post-operative monitoring but intra-operative guidance, assessment and predictability have remained limited to binocular optical microscope and surgeon’s experience. We present a high-resolution real time 3D imaging modality for intra-operative evaluation of luminal narrowing, thrombus formation and flow alterations. Methods An imaging modality that provides immediate, in-depth high resolution 3D structure view and flow information of the anastomosed site called phase resolved Doppler optical coherence tomography (PRDOCT) was developed. 22 mouse femoral artery anastomoses and 17 mouse venous anastomoses were performed and evaluated with PRDOCT. Flow status, vessel inner lumen 3D structure, and early thrombus detection were analyzed based on PRDOCT imaging results. Initial PRDOCT based predictions were correlated with actual long term surgical outcomes. Eventually four cases of mouse orthotopic limb transplantation were carried out and PRDOCT predicted long term patency were confirmed by actual results. Results PRDOCT was able to provide high-resolution 3D visualization of the vessel flow status and vessel inner lumen. The assessments based on PRDOCT visualization shows a 92% sensitivity and 90% specificity for arterial anastomoses and 90% sensitivity and 86% specificity for venous anastomoses. Conclusions PRDOCT is an effective evaluation tool for microvascular anastomosis. It can predict the long term vessel patency with high sensitivity and specificity. PMID:25811583

Medical application of artificial immune recognition system (AIRS): diagnosis of atherosclerosis from carotid artery Doppler signals.

PubMed

Latifoğlu, Fatma; Kodaz, Halife; Kara, Sadik; Güneş, Salih

2007-08-01

This study was conducted to distinguish between atherosclerosis and healthy subjects. Hence, we have employed the maximum envelope of the carotid artery Doppler sonograms derived from Fast Fourier Transformation-Welch method and Artificial Immune Recognition System (AIRS). The fuzzy appearance of the carotid artery Doppler signals makes physicians suspicious about the existence of diseases and sometimes causes false diagnosis. Our technique gets around this problem using AIRS to decide and assist the physician to make the final judgment in confidence. AIRS has reached 99.29% classification accuracy using 10-fold cross validation. Results show that the proposed method classified Doppler signals successfully.

Optical frequency standards for gravitational wave detection using satellite velocimetry

NASA Astrophysics Data System (ADS)

Vutha, Amar

2015-04-01

Satellite Doppler velocimetry, building on the work of Kaufmann and Estabrook and Wahlquist, is a complementary technique to interferometric methods of gravitational wave detection. This method is based on the fact that the gravitational wave amplitude appears in the apparent Doppler shift of photons propagating from an emitter to a receiver. This apparent Doppler shift can be resolved provided that a frequency standard, capable of quickly averaging down to a high stability, is available. We present a design for a space-capable optical atomic frequency standard, and analyze the sensitivity of satellite Doppler velocimetry for gravitational wave astronomy in the milli-hertz frequency band.

[The role of ultrasonography in the investigation of male infertility].

PubMed

Fejes, Zsuzsanna; Pásztor, Norbert; Karczagi, Lilla; Brzózka, Ádám; Király, István; Morvay, Zita; Palkó, András

2018-05-01

Unintended childlessness affects approximately 9-15% of couples in the reproductive age. It is known that a remarkable proportion of infertility is caused by the disorders of the male reproductive functions. Diagnostic imaging methods and especially ultrasonography play a crucial role in the infertility work-up, the ultrasound examination has become the method of choice for imaging in diseases affecting the testis. With the development of high resolution transducers and technology using colour Doppler, pulsed Doppler, share wave elastography and strain elastography, it is now possible to make accurate diagnoses. However, the place of the new imaging methods in the algorithm of infertility check-up should be clearly defined. Orv Hetil. 2018; 159(21): 815-822.