Ultrasound

Ultrasound of the embryo

Medical ultrasound, or sonography, is a diagnostic imaging technique based on the application of ultrasound. It is used to create an image of internal body structures such as muscles, joints, blood vessels, and internal organs for possible pathology or lesions. The practice of examining pregnant women using ultrasound is called obstetric ultrasound, and is widely used.

Overview

Ultrasound is a high-frequency sound wave that is beyond the range of human hearing. It's utilized in various fields of medicine, and is subdivided into anatomical and functional ultrasound. Its applications range from diagnostic to therapeutic.

Diagnostic Ultrasound

Diagnostic ultrasound is a non-invasive method of imaging the internal structures of the body. It utilizes a transducer or probe that emits sound waves in the megahertz (MHz) range, which is above the human hearing threshold. These sound waves bounce off tissues and organs, and their echoes are detected by the transducer. The time taken by the echoes to return allows the calculation of the distance of the tissue or organ from the probe, creating a two-dimensional image of the internal structures.

Some probes can be placed internally through the gastrointestinal tract, vagina, or blood vessels to improve the image quality. Sterile probes can also be used during surgeries to provide real-time imaging of the surgical field.

Anatomical ultrasound generates images of internal organs or structures, while functional ultrasound utilizes movement, velocity, and physical properties of tissues to create information maps. These maps assist physicians in visualizing changes or differences in function within a structure or organ.

Therapeutic Ultrasound

Therapeutic ultrasound, unlike its diagnostic counterpart, doesn't produce images. It utilizes high-intensity sound waves to interact with body tissues. This interaction can result in various modifications such as tissue movement, heating, blood clot dissolution, or targeted drug delivery. The beams can also destroy diseased or abnormal tissues such as tumors.

Ultrasound Procedure

During an ultrasound examination, a gel is applied to the skin to prevent air pockets, which can block the sound waves, from forming between the transducer and the skin. The transducer is then moved over the area of interest to capture images.

Applications of Ultrasound

Diagnostic ultrasound has a wide range of applications. It's used extensively in obstetrics and gynecology to monitor the development of the fetus. Other areas of use include cardiology, vascular medicine, gastroenterology, urology, neurology, and ophthalmology. It's also used for guiding needles for biopsies and catheter placement.

Functional ultrasound applications such as Doppler ultrasound and elastography provide additional information about blood flow and tissue stiffness, respectively. Doppler ultrasound is used to measure blood flow and detect blockages in the blood vessels. Elastography allows for the differentiation of tumors from healthy tissues by measuring tissue stiffness.

Therapeutic ultrasound is used for targeted tissue heating and destruction, for instance in High-Intensity Focused Ultrasound (HIFU) therapy. It's used in various treatment procedures, including the treatment of uterine fibroids and prostate tissue, and alleviation of pain from bone metastases.

Risks

Diagnostic ultrasound is generally regarded as safe and does not produce ionizing radiation like that produced by x-rays. Still, ultrasound is capable of producing some biological effects in the body under specific settings and conditions. For this reason, the FDA requires that diagnostic ultrasound devices operate within acceptable limits. The FDA, as well as many professional societies, discourage the casual use of ultrasound (e.g. for keepsake videos) and recommend that it be used only when there is a true medical need.

See Also

• Obstetric ultrasound
• Doppler ultrasound
• Elastography
• High Intensity Focused Ultrasound

References

• "Medical Ultrasound". RadiologyInfo.org. Retrieved 2023-05-18.
• "Diagnostic Ultrasound". MedlinePlus. Retrieved 2023-05-18.
• "Therapeutic Ultrasound". American Institute of Ultrasound in Medicine. Retrieved 2023-05-18.
• "High-Intensity Focused Ultrasound". Mayo Clinic.

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