The aim of imaging is to provide detailed and reliable pictorial information about structures within the body with the minimum risk and discomfort. Most imaging is now highly computerized and has largely replaced exploratory surgery in establishing the presence and extent of disease. Recent techniques are also able to indicate how well a tissue or an organ is functioning.
The first techniques used for imaging the body were based on X-rays, a form of high-energy radiation that is able to pass through body tissues. Some X-rays require particular substances, called contrast media, to improve the visibility of certain structures.
Over the last 40–50 years, many new techniques have been introduced, most of which involve the use of computers that control the imaging equipment and are able to create images of the body in three dimensions.
This section begins by explaining the basic imaging methods that use X-rays, which include ordinary and contrast X-rays and CT scanning. Other imaging techniques are then covered, such as MRI and ultrasound scanning, which do not involve the use of radiation, and different types of radionuclide scanning.
Viewing structures or organs in the body is often important for screening, diagnosis, or monitoring disease. Structures that are easily accessible, such as the ears, may be viewed directly using basic viewing instruments; those deeper inside the body are usually viewed indirectly, using complex optical instruments called endoscopes to transmit images on to a monitor screen.
Some viewing techniques may be used as part of a routine examination. For example, your doctor can look at your ears, eyes, and throat simply and quickly in his or her surgery. Each of the instruments used is designed to view a particular part of the body. For example, an otoscope is used to look at the ears and an ophthalmoscope to look at the eyes. The first article covers these basic viewing techniques.
To view other organs deeper within the body, your doctor may arrange for an endoscopic investigation. Endoscopy is discussed in the second article. An endoscope is a viewing device that enables body cavities or internal organs to be inspected. Most endoscopes are flexible or rigid tube-like instruments but there is also a new type (called a wireless capsule endoscope) that essentially consists of a camera in a pill-sized, self-contained capsule. Each type of endoscope is designed to view a particular part of the body.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.