Medical ultrasound

Primarius Dr. Günther Schamp Facharzt für Radiologie Institut für Computer- & Magnetresonanz-Tomografie.

It provides images in real-time and is portable and can be brought to the bedside. Dieser Unterschied ist zwischen Luft und z. The sound wave is partially reflected from the layers between different tissues or scattered from smaller structures.

Symptome, Ursachen, Behandlung und lindernde Maßnahmen

Ein Durchflussmesser ist ein Messgerät gemäß der grundlegenden Norm DIN Es besteht aus zwei Hauptkomponenten, dem eigentlichen Messaufnehmer, der als Durchflusssensor dient, und einem Auswerte- und Speiseteil, das auch als Transmitter oder Messumformer bezeichnet wird.

Send pulses down the 'columns' of the spreadsheet A, B, C, etc. Listen at each column for any return echoes. When an echo is heard, note how long it took for the echo to return. The longer the wait, the deeper the row 1,2,3, etc. The strength of the echo determines the brightness setting for that cell white for a strong echo, black for a weak echo, and varying shades of grey for everything in between.

When all the echoes are recorded on the sheet, we have a greyscale image. Normally, very little post processing is applied to ultrasound images. Ultrasonography sonography uses a probe containing multiple acoustic transducers to send pulses of sound into a material. Whenever a sound wave encounters a material with a different density acoustical impedance , part of the sound wave is reflected back to the probe and is detected as an echo.

The time it takes for the echo to travel back to the probe is measured and used to calculate the depth of the tissue interface causing the echo. The greater the difference between acoustic impedances, the larger the echo is. If the pulse hits gases or solids, the density difference is so great that most of the acoustic energy is reflected and it becomes impossible to see deeper. Higher frequencies have a correspondingly smaller wavelength, and can be used to make sonograms with smaller details.

Seeing deep into the body with sonography is very difficult. Some acoustic energy is lost every time an echo is formed, but most of it approximately 0. See also Acoustic attenuation for further details on modeling of acoustic attenuation and absorption. The speed of sound varies as it travels through different materials, and is dependent on the acoustical impedance of the material.

An effect of this assumption is that in a real body with non-uniform tissues, the beam becomes somewhat de-focused and image resolution is reduced. To generate a 2D -image, the ultrasonic beam is swept. A transducer may be swept mechanically by rotating or swinging. Or a 1D phased array transducer may be used to sweep the beam electronically. The received data is processed and used to construct the image. The image is then a 2D representation of the slice into the body.

Commonly a specialised probe that mechanically scans a conventional 2D-image transducer is used. However, since the mechanical scanning is slow, it is difficult to make 3D images of moving tissues. Recently, 2D phased array transducers that can sweep the beam in 3D have been developed.

These can image faster and can even be used to make live 3D images of a beating heart. Doppler ultrasonography is used to study blood flow and muscle motion. The different detected speeds are represented in color for ease of interpretation, for example leaky heart valves: Colors may alternatively be used to represent the amplitudes of the received echoes.

Several modes of ultrasound are used in medical imaging. An additional expansion or additional technique of ultrasound is biplanar ultrasound , in which the probe has two 2D planes that are perpendicular to each other, providing more efficient localization and detection.

Doppler ultrasonography employs the Doppler effect to assess whether structures usually blood [26] are moving towards or away from the probe, and its relative velocity. By calculating the frequency shift of a particular sample volume, for example flow in an artery or a jet of blood flow over a heart valve, its speed and direction can be determined and visualized.

Color Doppler is the measurement of velocity by color scale. Color Doppler images are generally combined with grayscale B-mode images to display duplex ultrasonography images. A contrast medium for medical ultrasonography is a formulation of encapsulated gaseous microbubbles [29] to increase echogenicity of blood, discovered by Dr Raymond Gramiak in [30] and named contrast-enhanced ultrasound.

This contrast medical imaging modality is clinically used throughout the world, [31] in particular for echocardiography in the United States and for ultrasound radiology in Europe and Asia.

Microbubbles-based contrast media is administrated intravenously in patient blood stream during the medical ultrasonography examination. Thanks to their size, the microbubbles remain confined in blood vessels without extravasating towards the interstitial fluid.

An ultrasound contrast media is therefore purely intravascular, making it an ideal agent to image organ microvascularization for diagnostic purposes. A typical clinical use of contrast ultrasonography is detection of a hypervascular metastatic tumor , which exhibits a contrast uptake kinetics of microbubbles concentration in blood circulation faster than healthy biological tissue surrounding the tumor.

Finally, applications in quantitative perfusion [33] relative measurement of blood flow [34] emerge for identifying early patient response to an anti-cancerous drug treatment methodology and clinical study by Dr Nathalie Lassau in [35] , enabling to determine the best oncological therapeutic options. In oncological practice of medical contrast ultrasonography, clinicians use the method of parametric imaging of vascular signatures [37] invented by Dr Nicolas Rognin in This method is based on medical computational science [39] [40] to analyze a time sequence of ultrasound contrast images, a digital video recorded in real-time during patient examination.

Two consecutive signal processing steps are applied to each pixel of the tumor:. Once signal processing in each pixel completed, a color spatial map of the parameter is displayed on a computer monitor , summarizing all vascular information of the tumor in a single image called parametric image see last figure of press article [41] as clinical examples.

This parametric image is interpreted by clinicians based on predominant colorization of the tumor: In the first case suspicion of malignant tumor , the clinician typically prescribes a biopsy to confirm the diagnostic or a CT scan examination as a second opinion.

In the second case quasi-certain of benign tumor , only a follow-up is needed with a contrast ultrasonography examination a few months later. The main clinical benefits are to avoid a systematic biopsy risky invasive procedure of benign tumors or a CT scan examination exposing the patient to X-ray radiation.

The parametric imaging of vascular signatures method proved to be effective in humans for characterization of tumors in the liver.

The future of contrast ultrasonography is in molecular imaging with potential clinical applications expected in cancer screening to detect malignant tumors at their earliest stage of appearance. Molecular ultrasonography or ultrasound molecular imaging uses targeted microbubbles originally designed by Dr Alexander Klibanov in ; [44] [45] such targeted microbubbles specifically bind or adhere to tumoral microvessels by targeting biomolecular cancer expression overexpression of certain biomolecules occurs during neo-angiogenesis [46] [47] or inflammation [48] processes in malignant tumors.

As a result, a few minutes after their injection in blood circulation, the targeted microbubbles accumulate in the malignant tumor; facilitating its localization in a unique ultrasound contrast image. In , the very first exploratory clinical trial in humans for prostate cancer was completed at Amsterdam in the Netherlands by Dr Hessel Wijkstra. In molecular ultrasonography, the technique of acoustic radiation force also used for shear wave elastography is applied in order to literally push the targeted microbubbles towards microvessels wall; firstly demonstrated by Dr Paul Dayton in At the stage of scientific preclinical research, the technique of acoustic radiation force was implemented as a prototype in clinical ultrasound systems and validated in vivo in 2D [51] and 3D [52] [53] imaging modes.

Ultrasound is also used for elastography, which is a relatively new imaging modality that maps the elastic properties of soft tissue.

For example, cancerous tumors will often be harder than the surrounding tissue, and diseased livers are stiffer than healthy ones. There are many ultrasound elastography techniques. Interventional ultrasonography involves biopsy , emptying fluids, intrauterine Blood transfusion Hemolytic disease of the newborn. Compression ultrasonography is when the probe is pressed against the skin. This can bring the target structure closer to the probe, increasing spatial resolution of it.

Comparison of the shape of the target structure before and after compression can aid in diagnosis. It used in ultrasonography of deep venous thrombosis , wherein absence of vein compressibility is a strong indicator of thrombosis. Results are not reliable when the patient is symptomless and must be checked, for example in high risk postoperative patients mainly in orthopedic patients.

A normal appendix without and with compression. Absence of comprehensibility indicates appendicitis. Compression is used in this ultrasonograph to get closer to the abdominal aorta , making the superior mesenteric vein and the inferior vena cava look rather flat. As with all imaging modalities, ultrasonography has its list of positive and negative attributes.

Ultrasonography is generally considered safe imaging, [63] with the World Health Organizations saying: Diagnostic ultrasound studies of the fetus are generally considered to be safe during pregnancy. This diagnostic procedure should be performed only when there is a valid medical indication, and the lowest possible ultrasonic exposure setting should be used to gain the necessary diagnostic information under the "as low as reasonably practicable" or ALARP principle.

However, medical ultrasonography should not be performed without a medical indication to perform it. To do otherwise would be to perform unnecessary health care to patients, which bring unwarranted costs and may lead to other testing. Overuse of ultrasonography is sometimes as routine as screening for deep vein thrombosis after orthopedic surgeries in patients who are not at heightened risk for having that condition.

Similarly, although there is no evidence ultrasound could be harmful for the fetus, medical authorities typically strongly discourage the promotion, selling, or leasing of ultrasound equipment for making "keepsake fetal videos". Diagnostic and therapeutic ultrasound equipment is regulated in the USA by the Food and Drug Administration , and worldwide by other national regulatory agencies. The FDA limits acoustic output using several metrics; generally, other agencies accept the FDA-established guidelines.

The primary regulated metrics are Mechanical Index MI , a metric associated with the cavitation bio-effect, and Thermal Index TI a metric associated with the tissue heating bio-effect. The FDA requires that the machine not exceed established limits, which are reasonably conservative so as to maintain diagnostic ultrasound as a safe imaging modality.

This requires self-regulation on the part of the manufacturer in terms of the machine's calibration. Ultrasound-based pre-natal care and sex screening technologies were launched in India in the s.

With concerns about its misuse for sex-selective abortion , the Government of India passed the Pre-natal Diagnostic Techniques Act PNDT in to regulate legal and illegal uses of ultrasound equipment. Thereafter, in , the American acoustical physicist Floyd Firestone devised the first ultrasonic echo imaging device, the Supersonic Reflectoscope, to detect internal flaws in metal castings. In , the Austrian neurologist Karl Theo Dussik was in collaboration with his brother, Friedreich, a physicist, likely, the first person to ultrasonically echo image the human body, outlining thereby the ventricles of a human brain.

In his book "L'investigation vasculaire par ultrasonographie Doppler" Ed Masson, [26] Dr Claude Franceschi laid down the Doppler Ultrasound fundamentals of the hemodynamics semiotics, which are still in use in current Doppler arterial and venous Duplex Ultrasound investigations.

These findings were reported in The Lancet on 7 June [86] as "Investigation of Abdominal Masses by Pulsed Ultrasound" — possibly one of the most important papers ever published in the field of diagnostic medical imaging.

At GRMH, Professor Donald and Dr James Willocks then refined their techniques to obstetric applications including fetal head measurement to assess the size and growth of the fetus. With the opening of the new Queen Mother's Hospital in Yorkhill in , it became possible to improve these methods even further.

Dr Stuart Campbell 's pioneering work on fetal cephalometry led to it acquiring long-term status as the definitive method of study of foetal growth. As the technical quality of the scans was further developed, it soon became possible to study pregnancy from start to finish and diagnose its many complications such as multiple pregnancy, fetal abnormality and placenta praevia.

Diagnostic ultrasound has since been imported into practically every other area of medicine. Medical ultrasonography was used in at Lund University by cardiologist Inge Edler and Gustav Ludwig Hertz 's son Carl Hellmuth Hertz , who was then a graduate student at the University's department of nuclear physics. Edler had asked Hertz if it was possible to use radar to look into the body, but Hertz said this was impossible.

However, he said, it might be possible to use ultrasonography. Daraus wird präzise und zuverlässig der Durchfluss in Flüssigkeiten, Gasen und Dampf bestimmt. Messgut wird durch bewegliche Messkammerwände verdrängt für Flüssigkeiten und Gase geeignet. Volumenzähler mit beweglichen Kammerwänden Verdrängungszähler sind.

Die bei Abwasserbehandlungsanlagen vorhandenen Venturi-Rinnen haben fast immer rechteckige Querschnitte. Neue Entwicklungen der magnetisch-induktiven Durchflussmesser für Teilfüllung durch eingebaute Teilmengenerfassung, Leerrohrdetektion und deren Messgenauigkeit ermöglichen heute den Einsatz bei solchen Anwendungen.

Es entfallen somit für den Anwender aufwendige Überleitungen von Freispiegelströmung in Druckrohrströmung und zurück. Sie wurde April in Brüssel beschlossen und muss bis Ende Oktober in den Mitgliedstaaten ratifiziert sein. Nationale Ausnahmen sind jedoch möglich, verbieten aber alternative Regelungen. Es gab verschiedene Novellierungen mit unterschiedlichen Klassifizierungen für die Messgenauigkeit und Anforderungen bezüglich der Selbstkontrolle.

Die neuen Ausgaben aus dem Jahre sind aber fast deckungsgleich mit der MI Ansichten Lesen Bearbeiten Quelltext bearbeiten Versionsgeschichte. Navigation Hauptseite Themenportale Zufälliger Artikel. In anderen Sprachen Links hinzufügen. Diese Seite wurde zuletzt am Dezember um Behandelt werden alle Patienten bis ins hohe Alter auf ärztliche Empfehlung. Über die Stimulationsmatte kombiniert es wohltuende Wärme und sanfte dynamische Tiefenwellen zu einem Gesamtpaket.

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