The invasive monitoring of the microcirculatory cerebral blood flow by laser Doppler flowmetry has been proposed as means for the detection and prevention of cerebral ischemia in comatose patients. However, the use of this technique is not widespread, nor has it proven to influence the patient's outcome. Recent reports selected ...

This paper reviews the development and use of laser-Doppler perfusion monitors and imagers over the past two decades. The enormous interest in microvascular blood perfusion coupled with the 'ease of use' of the technique has led to 1500+ publications citing its use. However, useful results can only be achieved with ...

There are many analogies between cold-induced vasodilatation (CIV) and vasomotion (VM), but the demonstration of any relationship between these two microvascular homeostatic reactions is to date lacking. In a group of seven controls and seven patients with Raynaud phenomenon in the vasomotor stage of the disease, we studied, by means ...

Ultrasound systems can be used to investigate blood flow by use of the Doppler effect. The flow information may be displayed as either a real-time sonogram or a two-dimensional colour image. Estimates of maximum velocity using commercial systems are in error by typically 10-100 per cent; this is associated with ...

Ultrasound and the Doppler effect are used to measure blood velocity non-invasively in order to diagnose blood vessel disease. Intrusive lesions on arterial walls give rise to an alteration of the time-varying blood velocity waveform and local blood flow disturbance which are detected and measured using the envelope and width ...

Continuous monitoring of cardiac output in neonates would be of considerable benefit but, as yet, there is no practical method to achieve this aim. We have now evaluated the feasibility of using an intra-aortic Doppler probe. We introduced a pulsed Doppler probe of 0.46 mm diameter via the umbilical artery ...

The utility of laser Doppler flowmetry (LDF) is limited by the requirement for placement of the LDF probe directly on the bone surface. A system of implantable and detachable fibres was developed so that repeated non-anaesthetized measurements could be made. Using a specially designed flow chamber and a flow medium ...

OBJECTIVES: A feasibility study to evaluate whether analysis techniques adapted from X-ray angiography can be used to analyze the transient enhancement of prostate blood flow patterns in color Doppler maps as obtained after administering ultrasound contrast agents. METHODS: Injections of ultrasound contrast agents were given to dogs and humans, and ...

BACKGROUND AND AIM OF THE STUDY: Steady and pulsatile flow models used to assess the hydrodynamic aspects of prosthetic heart valves are generally made of Plexiglas and Lucite tubing. They often allow continuous-wave and pulsed-wave Doppler ultrasound velocity measurements to be made parallel to the flow, but cannot be used ...

Ways to measure blood perfusion using ultrasound techniques such as continuous-wave Doppler, pulsed Doppler, colour Doppler and power Doppler will be reviewed. From a certain standpoint, blood perfusion may be defined as the difference between arterial inflow and arterial outflow from a considered volume, i.e. capillary flow. The low velocities ...

OBJECTIVE: The purpose of this study was to determine the effect of tooth morphotype on intraindividual and interindividual variations of baseline data as well as on temporal variations between testing intervals in the assessment of pulpal blood-flow by means of laser Doppler flowmetry. STUDY DESIGN: In 14 volunteers, maxillary incisors, ...

The tissue matrix in the human body is continuously in motion driven by forces generated by the circulatory and respiratory systems. The linear velocities recorded can be as high as 300 microm/s. The question raised: is the motion of tissue matrix generating an error signal in laser-Doppler (LD) recordings that ...

Current clinical Doppler ultrasound systems could only measure the flow vector parallel to the ultrasound beam axis, and the knowledge of the Doppler angle (beam-to-flow angle) is needed to calculate the real flow velocity. Currently, the Doppler angle is determined visually by manually aligning a vessel axis marker along the ...

For a better understanding of the relationship between the Doppler power and erythrocyte aggregation of whole blood under steady flow in a conduit, the effects of Doppler angle, fibrinogen concentration, and hematocrit were investigated in a mock flow loop. The results show that, at a mean shear rate of 102 ...

The Doppler backscatter properties of a blood-mimickig fluid (BMF) were studied to evaluate its suitability for use in a Doppler flow test object. Measurements were performed using a flow rig with C-flex tubing and BMF flow produced by a roller pump or a gear pump. A SciMed Doppler system was ...

PURPOSE: This study determined whether the portable Advance Laser Flowmeter Model 21, a clinical instrument, would indicate significant values when pulpal blood flow was present or absent; whether the analog output of the flowmeter was time-linked to the heart rate; and whether labial and lingual crown surfaces produced different flow ...

OBJECTIVE: To assess the ability of colour/pulsed Doppler ultrasound to detect failed physiologic change of the spiral arteries in pregnancies complicated by pre-eclampsia. DESIGN: Prospective matched-pairs case controlled study. SETTING: Tertiary referral teaching hospital. SAMPLE: Sixteen women with severe pre-eclampsia and 16 normotensive controls. METHODS: Colour/pulsed Doppler assessment of blood ...

A new formulation for the Doppler signal generation process in pulsatile flow has been developed enabling easier identification and quantification of the mechanisms involved in spectral broadening and the development of a simple estimation formula for the measured rms spectral width. The accuracy of the estimation formula was tested by ...

Doppler Monte Carlo (DMC) simulations of the transport of light through turbid media, e.g., tissue, can be used to predict or to interpret measurements of the blood perfusion of tissue by laser-Doppler perfusion flowmetry. We describe the physical and mathematical background of Doppler Monte Carlo calculations, and present some comparisons ...

This study presents and tests the clinical validity of a hemodynamic grading system that depends on noninvasive transcranial Doppler ultrasonographic parameters. The suggested transcranial Doppler-based grading system was compared with the Spetzler-Martin anatomic grading for prognosticative validity and clinical dependability. We concluded the following: (1) The pulsatility index was shown ...

RATIONALE AND OBJECTIVES: The ability to create short boluses in targeted arteries with rapid rise times is limited by the transport of bubbles from the venous to arterial portion of the circulation. Acoustic interruption of contrast agent in arteries may create the short boluses necessary for simple wash-in/wash-out measures of ...

PURPOSE: Determination of aortic blood flow (ABF) using esophageal Doppler has been proposed as a low invasive hemodynamic monitoring method. The esophageal echo-Doppler Dynemo 3000 (Sometec Inc., Paris, France) system, recently available on the market, is an original device measuring simultaneously, and at the same anatomic level, aortic diameter, and ...

An enhanced high-resolution laser Doppler imaging (EHR-LDI) technique intended for visualization of separate microvessels was evaluated by use of in vitro flow models. In EHR-LDI, a laser beam focused to a half-power diameter less than 40 microm successively scans the tissue under study in steps of 25 microm. Spatial blood ...

OBJECTIVE: We evaluated the ability of power Doppler sonography to show increased soft-tissue blood flow in patients with reflex sympathetic dystrophy of the lower extremity. SUBJECTS AND METHODS: Power Doppler sonography was performed in 30 patients with reflex sympathetic dystrophy of the lower extremity and in 26 asymptomatic control subjects. ...

PURPOSE: We believed that a totally noninvasive video urodynamic system could be invented based on the concept of Doppler ultrasonography. To develop this system we measured flow velocity in an experimental urethra using 4 materials, including natural urine. MATERIALS AND METHODS: A cellulose tube was inserted into a standoff pad ...

The laser-Doppler method is frequently used in clinical experiments for blood perfusion measurement. A multichannel laser-Doppler probe was constructed, and calibrated and evaluated using a flow model and real examination of healthy subjects. Results obtained on a three-capillary flow model suggest that the probe can be used to obtain information ...

OBJECT: This study was designed to investigate the incidence of early abnormalities in the cerebral circulation after head injury by relating the results of the initial computerized tomography (CT) scan with transcranial Doppler (TCD) ultrasound readings to see if the side of injury and the outcome can be predicted by ...

This paper deals with theoretical aspects of blood flow and the ultrasonic Doppler spectrum. Blood flow in the vessel can be considered as a pipe flow with a circular cross-section. Blood flow is, in general, complex and pulsatile. Navier-Stokes and the continuity equations are the governing equations for the blood ...

PURPOSE: To show that extending Doppler imaging into the high-frequency domain could allow detection and characterization of blood flow in small arterioles and capillaries. METHODS: A 40-MHz continuous wave Doppler system and a 60-MHz pulsed-wave Doppler system were constructed, tested, and used to examine the ciliary body region in two ...

While ultrasound has been well accepted as an accurate test for the diagnosis of both femoral and popliteal deep venous thrombosis (DVT), its role in the detection of calf DVT has been less clear. There have been variable results between studies in the accuracy of colour Doppler or compression sonographic ...

A new fiber-optic catheter for in vivo blood-flow measurements has been developed. The catheter is designed to measure blood flow in both the forward (toward the catheter tip) and reverse (away from the catheter tip) flow directions. It consists of two multimode optical fibers with core diameter of 50 microns ...

Whereas previous studies have shown that ultrasonic backscatter and Doppler power from blood are affected by flow turbulence, turbulence level has only been inferred from the flow Reynolds number and not directly measured. In this study, both ultrasonic Doppler power and flow turbulence intensity were measured in situ to quantify ...

For several decades, cranial windows have been used to investigate questions relating to cerebral blood flow and its regulation. In general, these techniques have utilized either 'open' cranial windows for the direct observation of the intracranial vasculature, or 'closed' cranial windows in which the skull and dura are removed and ...

BACKGROUND AND PURPOSE: Oscillating flow or systolic spikes are typical Doppler-sonographic flow signals found in the presence of cerebral circulatory arrest, which if irreversible, results in brain death. The Neurosonology Research Group (NSRG) of the World Federation of Neurology (WFN) created a Task Force Group in order to evaluate the ...

BACKGROUND: A new Doppler flowmeter using a special transducer forming two ultrasound beams to insonate vessels was developed. This low-cost flowmeter allows the flow to be measured independently of the angle of insonation. METHODS: Sixty-five flow determinations were made in the carotid arteries of five pigs. The flowmeter measured the ...

Ultrasound pulsed transducers are very important for blood flow measurement and imaging. Ultrasound pulsed transducers are broadband transducers which require relatively heavy external damping to achieve a good axial resolution and an adequately wide bandwidth. In this work, using a simple RLC circuit model, broadband transducers were constructed and tested. ...

PURPOSE: To investigate through the use of cerebral Doppler technology whether emboli are a more common cause of nonarteritic anterior ischemic optic neuropathy (NAION) than previously recognized. METHODS: Eleven patients with a recent (<121 days) history of nonarteritic anterior ischemic optic neuropathy and 10 age-matched controls (event > 121 days) ...

Pulse wave Doppler techniques promise the ability to make more effective measurements of dynamic cardiovascular functions. Quantitative measurement of blood flow can be achieved by using the pulse wave Doppler system. This paper discusses the design parameters of the pulse wave Doppler blood flowmeter (PW Doppler) with respect to the ...

Documentation and measurement of intraoperative cerebral blood flow during various neurosurgical procedures is not only valuable but also very informative. There are various methods by which qualitative and quantitative measurement of blood flow have been developed over the years. The use of perivascular ultrasonic flow more recently is fast gaining ...

Compared to conventional color Doppler ultrasound imaging, the new color Doppler modality "color Doppler energy" (CDE) has improved the possibility of visualizing blood vessels having low blood-flow velocities, but appears to be influenced by the settings of the ultrasound instrument and motion artefacts. The aim of this methodological study was ...

In pediatric neurosonography, conventional color Doppler imaging has been the primary adjunct to routine gray-scale imaging. Power Doppler sonography is a relatively recent development that does not have the limitations of conventional color Doppler ultrasound. The power Doppler technique measures the energy of moving red blood cells instead of the ...

Burn injury causes vascular thrombosis and occlusion by thermal damage to the vascular network in the dermis. In this study, fibre optic confocal imaging (FOCI) and laser doppler flowmetry were used to detect changes in vascular morphology and local dermal blood flux over 4 h, in three defined zones after ...

The aim of this study was to demonstrate coronary sinus blood flow in the human fetus by color Doppler imaging and pulsed wave Doppler sonography and to determine the feasibility of using Doppler ultrasound for routine investigation. Visualization of the coronary sinus blood flow by color Doppler imaging was attempted ...

In two mid-trimester fetuses with microcephaly, transvaginal sonography revealed aberrant findings, including large subarachnoid spaces and a rudimentary shape of the lateral ventricles. In one of these fetuses, power Doppler ultrasound demonstrated a discrepancy in the size of the signals generated by the intracranial arteries branching from the internal carotids ...

OBJECTIVE: Color Doppler imaging (CD) has had a great impact on ultrasonography (US). This technique depicts local flow by encoding an estimate of the mean Doppler frequency shift at a particular position in color. However, the choice of the mean frequency shift as the parameter for representing flow in color ...

This study assessed within- and between-day variability of human superior mesenteric artery blood flow (SMABF) using transcutaneous Doppler ultrasound. Two groups of healthy volunteers were studied after fasting overnight; six subjects were studied for one visit of 90 min duration (group 1) and six other subjects attended the laboratory for ...

OBJECTIVES: To describe the use of laser Doppler velocimetry for measurement of vaginal blood flow and report the effects of estrogen compared with estrogen-androgen treatment in post-menopausal women. DESIGN: Literature review of pelvic blood flow studies and sexual function. Findings from a prospective, randomized, parallel study. SETTING: Normal human volunteers ...

Many of the changes resulting from arterial disease can be measured, using Doppler ultrasound for measurement of blood velocity and B-scan imaging for measurement of tissue structure and composition. Wall thickness, the degree of arterial narrowing and plaque volume can be measured using B-scan imaging, and 3D ultrasound can be ...

Doppler sonography has been used in breast tumours mainly for differential diagnostic purposes. Since angiogenesis appears to be related to the patient's prognosis, Doppler sonography may also have prognostic implications. CW Doppler was initially used, but is now obsolete. Contemporary studies are carried out using colour Doppler. Quantification of colour ...

The trend for treatment of deep second degree burns and third degree burns is toward early excision and skin grafting. The ability to predict burn depth accurately as early as possible is important for early excision and skin grafting. This study, prospectively evaluated the ability of laser Doppler flow measurements, ...