Medical ultrasonography (sonography) is an ultrasound-based diagnostic imaging technique used to visualize internal organs, their size, structure and their pathological lesions. A baby in its mothers womb, viewed in a sonogram Ultrasound is sound with a frequency greater than the upper limit of human hearing, approximately 20 kilohertz. ... Medical imaging is the process by which physicians evaluate an area of the subjects body that is not normally visible. ... A lesion is a non-specific term referring to abnormal tissue in the body. ...

Uses

Ultrasonography (sonography) is widely utilized in medicine. It is possible to perform diagnosis or therapeutic procedures with the guidance of ultrasonography (for instance biopsies or drainage of fluid collections). Typically uses a hand-held probe (often called a scan head) that is placed directly on and moved over the patient: a water-based gel ensures good coupling between the patient and scan head. Medicine on the Web NLM (National Library of Medicine, contains resources for patients and healthcare professionals) Virtual Hospital (digital health sciences library by the University of Iowa) Online Medical Dictionary Collection of links to free medical resources Category: ‪Medicine‬ ... Diagnosis (from the Greek words dia = by and gnosis = knowledge) is the process of identifying a disease by its signs, symptoms and results of various diagnostic procedures. ... Look up Therapy on Wiktionary, the free dictionary Therapy (in Greek: θεραπεία) or treatment is the attempted remediation of a health problem, usually following a diagnosis. ... A biopsy (in Greek: bios = life and opsy = look/appearance) is a medical test involving the removal of cells or tissues for examination. ...

Medical ultrasonography is used in, for example:

• Cardiology; see echocardiography
• Endocrinology
• Gastroenterology
• Gynaecology; see gynecologic ultrasonography
• Obstetrics; see obstetric ultrasonography
• Ophthalmology; see A-scan ultrasonography, B-scan ultrasonography
• Urology
• Intravascular ultrasound

Cardiology is the branch of medicine dealing with disorders of the heart and blood vessels. ... An echocardiogram. ... Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones. ... Gastroenterology or gastrology is the medical specialty concerned with the field of digestive diseases. ... The shamefulness associated with the examination of female genitalia has long inhibited the science of gynaecology. ... Gynecologic ultrasonography or Gyn sonography refers to the application of medical ultrasonography to the female pelvic organs, specifically the uterus, the ovaries, the Fallopian tubes, as well as the bladder, the Pouch of Douglas, and any findings in the pelvis of relevance outsite of pregnancy. ... Obstetrics (from the Latin obstare, to stand by) is the surgical specialty dealing with the care of a woman and her offspring during pregnancy, childbirth and the puerperium (the period shortly after birth). ... Obstetric ultrasonograph of a fetus at 16 weeks. ... An optical refractor in use. ... A-scan ultrasound biometry, commonly referred to as an A-scan, is routine type of diagnostic test used in ophthalmology. ... B-scan ultrasonography, or B-scan, is a diagnostic test used in ophthalmology to produce a two-dimensional, cross-sectional view of the eye and the orbit. ... Urology is the field of surgery that focuses on the urinary tracts of males and females, and of the male reproductive system. ... Intravascular ultrasound (IVUS) is an medical imaging methodology using (a) specially designed long thin complex manufactured catheters attached to (b) computerized ultrasound equipment. ...

Instrumentation

Ultrasonography (sonography) uses a probe containing one or more acoustic transducers to send pulses of sound into a material. Whenever a sound wave encounters a material with a different acoustical impedence, part of the sound wave is reflected, which the probe detects 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 impedences, the larger the echo is. The difference between gases and solids is so great that most of the acoustic energy is reflected, and so imaging of objects beyond that region is not possible. Night writing was a system of code that used symbols of twelve dots (2 wide and 6 high) designed by Charles Barbier in response to Napoleons demand for a code that soldiers could use to communicate silently and without light at night. ... A transducer is a device that converts one type of energy to another, or responds to a physical parameter. ... Echo may refer to: Echo (mythology), a nymph from Greek mythology. ...

The speed of sound is different in different materials, and is dependent on the acoustical impedance of the material. Part of the acoustic energy is lost every time an echo is formed. The acoustic impedance Z (or sound impedance) is the ratio of sound pressure p to particle velocity v in a medium or acoustic component. ...

Sound in the range of hearing and ultrasound can be focused. The echoes received by a stationary probe will result in a single dimensional signal showing peaks for every major material change.

To generate a 2D-image, the probe is swivelled, either mechanically or electronically through a phased array of acoustic transducers. The data is analyzed by computer and used to construct the image. In a similar way, 3D images can be generated by computer using a specialised probe. Dimension (from Latin measured out) is, in essence, the number of degrees of freedom available for movement in a space. ... // Description A giant phased-array radar in Alaska In telecommunication, a phased array is a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction... The rewrite of this article is being devised at Talk:3D computer graphics/Temp. ...

Some sonographic machines can produce colour images, of sorts. From the amount of energy in each echo, the difference in acoustic impedence can be calculated and a colour is then assigned accordingly.

The frequencies used for medical imaging are generally in the range of 1 to 10 MHz. Higher frequencies have a correspondingly lower wavelength, and so images can have a greater resolution. However, the attenuation of the sound wave is increased at higher frequencies, so in order to better penetration of deeper tissues, a lower frequency (3-5MHz) may be used.

Doppler sonography

Ultrasonography can be enhanced with Doppler measurements, which employ the Doppler effect to assess whether structures (usually blood) are moving towards or away from the probe, and its relative velocity. By calculating the frequency shift of a particular sample volume, for example a jet of blood flow over a heart valve, its speed and direction can be determined and visualised. This is particularly useful in cardiovascular studies (ultrasonography of the vasculature and heart) and essential in many areas such as determining reverse blood flow in the liver vasculature in portal hypertension. The Doppler information is displayed graphically using spectral Doppler, or as an image using colour Doppler or power Doppler. It is often presented audibly using stereo speakers: this produces a very distinctive, although synthetic, sound. Sound waves emanating from an ambulance moving to the right. ... In medicine, portal hypertension is hypertension (high blood pressure) in the portal vein and its branches. ...

Strengths and weaknesses

Strengths of sonography

• It images muscle and soft tissue very well and is particularly useful for delineating the interfaces between solid and fluid-filled spaces.
• It renders "live" images, where the operator can dynamically select the most useful section for diagnosing and documenting changes, often enabling rapid diagnoses.
• It shows the structure as well as some aspects of the function of organs.
• It has no known long-term side effects and rarely causes any discomfort to the patient.
• Equipment is widely available and comparatively flexible.
• Small, easily carried scanners are available; examinations can be performed at the bedside.
• Relatively inexpensive compared to other modes of investigation (e.g. DEXA, computed X-ray tomography or magnetic resonance imaging).

A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... In medicine, the term soft tissue refers to tissues that connect, support, or surround other structures and organs of the body. ... Dual energy X-ray absorptiometry (DXA, previously DEXA) is a means of measuring bone mineral density (BMD). ...

Weaknesses of ultrasound imaging

• Classical ultrasound devices have trouble penetrating bone but current research on ultrasound bone imaging will make it possible with dedicated devices in the future.
• Ultrasound performs very poorly when there is a gas between the scan head and the organ of interest, due to the extreme differences in acoustical impedence. For example, overlying gas in the gastrointestinal tract often makes ultrasound scanning of the pancreas difficult, and lung imaging is not possible (apart from demarcating pleural effusions).
• Even in the absence of bone or air, the depth penetration of ultrasound is limited, making it difficult to image structures that are far removed from the body surface, especially in obese patients.
• The method is operator-dependent. A high level of skill and experience is needed to acquire good-quality images and make accurate diagnoses.

Grays illustration of a human femur, a typically recognized bone. ... The pancreas is a retroperitoneal organ that serves two functions: exocrine - it produces pancreatic juice containing digestive enzymes endocrine - it produces several important hormones // Anatomy The pancreas is a retroperitoneal organ located posterior to the stomach on the posterior abdominal wall. ...

History

United States

Ultrasonic energy was first applied to the human body for medical purposes by Dr. George D. Ludwig at the Naval Medical Research Institute, Bethesda, Maryland in the late 1940s. For more on the history of medical ultasonography in the United States see: ^[1] also [http://www.obgyn.net/us/us.asp?page=/us/news_articles/ultrasound_history/asp-history-toc

The] first demonstration of color Doppler by Geoff Stevenson, MD, who was also involved in the early developments and medical use of Doppler shifted ultrasonic energy. See: [http://www.obgyn.net/displayarticle.asp?page=/us/feature/doppler_history/history_ultrasound

Sweden

Medical] ultrasonography was used 1953 at Lund University by cardiologist Inge Edler and Carl Hellmuth Hertz, the son of Gustav Ludwig Hertz, who was a graduate student at the department of nuclear physics. 1953 (MCMLIII) is a common year starting on Thursday. ... Lund University Lund University (Swedish: Lunds universitet) is a university in Lund in southernmost Sweden. ... Cardiology is the branch of medicine dealing with disorders of the heart and blood vessels. ... Carl Hellmuth Hertz (1920-1990) was the son of Gustav Ludwig Hertz. ... Gustav Ludwig Hertz (July 22, 1887, Hamburg – October 30, 1975, Berlin) was a German physicist, and a nephew of Heinrich Rudolf Hertz. ... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ...

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. Hertz was familiar with using ultrasonic reflectoscopes for nondestructive materials testing, and together they developed the idea of using this method in medicine. This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ... In nondestructive testing, tests are carried out in such a way as to not disturb the specimen’s structural or surface integrity. ...

The first successful measurement of heart activity was made on October 29, 1953 using a device borrowed from the ship construction company Kockums in Malmö. On December 16 the same year, the method was used to generate an echo-encephalogram (ultrasonic probe of the brain). Edler and Hertz published their findings in 1954. October 29 is the 302nd day of the year (303rd in leap years) in the Gregorian Calendar, with 63 days remaining. ... 1953 (MCMLIII) is a common year starting on Thursday. ... Kockums in Malmö, 1970 Foto: PÃ¥l-Nils Nilsson. ... Malmö â–¶(?) IPA: [málmø:] is a town and municipality in the southernmost Swedish province of SkÃ¥ne. ... December 16 is the 350th day of the year (351st in leap years) in the Gregorian Calendar. ... Comparative brain sizes In the anatomy of animals, the brain, or encephalon (Greek for in the head), is the higher, supervisory center of the nervous system. ... 1954 (MCMLIV) was a common year starting on Friday of the Gregorian calendar. ...

Scotland

Parallel developments in Glasgow, Scotland (coincidentally also a major shipbuilding centre) by Professor Ian Donald and colleagues at the Glasgow Royal Maternity Hospital (GRMH) led to the first diagnostic applications of the technique. Donald was an obstetrician with a self-confessed "childish interest in machines, electronic and otherwise", who, having treated the wife of one of the company's directors, was invited to visit the Research Department of marine boilermakers Babcock & Wilcox at Renfrew, where he used their industrial ultrasound equipment to conduct experiments on various morbid anatomical specimens and assess their ultrasonic characteristics. Together with the medical physicist Tom Brown and fellow obstetrican Dr John MacVicar, Donald refined the equipment to enable differentiation of pathology in live volunteer patients. These findings were reported in The Lancet on 7th June 1958 as "Investigation of Abdominal Masses by Pulsed Ultrasound" - possibly one of the most important papers ever published in the field of diagnostic medical imaging. Glasgow (or Glaschu in Gaelic) is Scotlands largest city and unitary council, situated on the River Clyde in the countrys west central lowlands. ... Transport in Scotland Timeline of Scottish history Caledonia List of not fully sovereign nations Subdivisions of Scotland National parks (Scotland) Traditional music of Scotland Flower of Scotland Wars of Scottish Independence National Trust for Scotland Historic houses in Scotland Castles in Scotland Museums in Scotland Abbeys and priories in Scotland... Obstetrics (from the Latin obstare, to stand by) is the surgical specialty dealing with the care of a woman and her offspring during pregnancy, childbirth and the puerperium (the period shortly after birth). ... Renfrew (Rinn Friù in Scottish Gaelic) is a small town and former royal burgh in the Renfrewshire region of Scotland (see main article on the town of Renfrew, Scotland). ... The Lancet is a British medical journal, published weekly by the Lancet Publishing Group, part of Reed Elsevier. ... Medical imaging is the process by which physicians evaluate an area of the subjects body that is not normally visible. ...

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 foetus. With the opening of the new Queen Mother's Hospital on Yorkhill in 1964, 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 fetal 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. Yorkhill is a district in the Scottish city of Glasgow. ...

References

• Donald I, MacVicar J, Brown TG. Investigation of abdominal masses by pulsed ultrasound. Lancet 1958;1(7032):1188-95. PMID 13550965
• Edler I, Hertz CH. The use of ultrasonic reflectoscope for the continuous recording of movements of heart walls. Kungl Fzsiogr Sallsk i Lund Forhandl. 1954;24:5. Reproduced in Clin Physiol Funct Imaging 2004;24:118-36. PMID 15165281.
• S. A. Kana (2003). Introduction to physics in modern medicine, Tsylor & Francis. ISBN 0-415-30171-8.

1. ^  History of the AIUM.   URL accessed on November 15, 2005.

The Lancet is a British medical journal, published weekly by the Lancet Publishing Group, part of Reed Elsevier. ... November 15 is the 319th day of the year (320th in leap years) in the Gregorian Calendar, with 46 days remaining. ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ...

External links

• Web Site Directory of radiological sites
• About the discovery of medical ultrasonography