Medical ultrasonography
Medical ultrasonography is an ultrasound-based imaging diagnostic technique used to visualize internal organs, their size, structure and their pathological lesions.
Ultrasonography is widely utilized in medicine, primarily in gastroenterology, cardiology, gynaecology and obstetrics, urology and endocrinology. It is possible to perform diagnosis or therapeutic procedures with the guidance of ultrasonography (for instance biopsies).
Strengths of ultrasound imaging:
- 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; examinations can be performed at the bedside.
Weaknesses of ultrasound imaging:
- Ultrasound cannot penetrate bone and performs poorly when there is air between the scanner and the organ of interest. For example, overlying gas in the gastrointestinal tract often makes ultrasound scanning of the pancreas difficult.
- 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.
History
Medical ultrasonography was invented in 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 for 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. Hertz was familiar with using ultrasonic reflectoscopes for nondestructive materials testing, and together they developed the idea of using this method in medicine.
The first successful measurement of heart activity was made on October 29, 1953 using a device lent 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). The first obstetric measurements were made in Scotland.
Doppler ultrasonography
Ultrasonography can be enhanced with Doppler measurements, which employ the Doppler effect to assess whether structures (e.g. blood) are moving towards or away from the probe. By calculating the frequency shift of a particular organ, e.g. the jet of blood flow over a heart valve, its velocity and direction can be determined and visualised. This is particularily useful in echocardiography (ultrasonography of the heart) and essential in determining reverse blood flow in the liver vasculature in portal hypertension.
Applied ultrasonography
See feature articles:
External Links
- Web Site Directory (http://www.xraylinks.com) of radiological sites
- About the discovery of medical ultrasonography (http://www.ob-ultrasound.net/ingehertz.html)
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