Modern technological advances have enabled the human body to be visualized and investigated in a wide variety of ways. Imaging creates pictures of internal organs and structures, which may be displayed as digital images on a monitor or recorded on photographic film. Viewing techniques use specialized devices, including endoscopes, to look directly at internal structures of the body.
Imaging and viewing techniques are often used to confirm a diagnosis or to make one if other tests are not conclusive. These techniques may also be used to screen for some disorders and to monitor the progress of a disease or treatment. Most imaging techniques, and some complex viewing techniques, are carried out in hospital.
Since German physicist Wilhelm Röntgen’s discovery in 1895 that X-rays can be used to create “shadow pictures” of bones inside the body, X-rays have been used in medical imaging. Simple X-rays are still used today, mainly to image the skeleton although they are also used to image other parts of the body, for example, the chest in the diagnosis of diseases such as pneumonia. X-ray images may be captured directly on to photographic film or by a special detector plate, which produces a signal that is converted by computer into a digital image that is displayed on a monitor.
CT (computerized tomography) scanning is a technique that uses X-rays to produce detailed images not only of hard tissues such as bones but also of soft tissues. CT scanning typically produces cross-sectional images (“slices”) through the body. Liquids called contrast media can be introduced into hollow or fluid-filled body structures, such as blood vessels or the digestive tract, to enable them to be seen clearly using X-rays. Radionuclide scanning detects the radiation emitted by radioactive substances introduced into the body, allowing doctors to assess cell activity in body tissues.
Other medical imaging techniques include MRI (magnetic resonance imaging), which uses radio waves and magnets to produce clear, very detailed images, and ultrasound scanning, which uses sound waves. Neither of these techniques uses radiation.
Depending on the problem, a direct view of part of the body sometimes provides more useful information than a picture created by an imaging technique. Structures near the surface of the body, such as the eardrum, can be viewed directly using simple instruments. Endoscopes are used to look deeper inside the body.
Endoscopes are typically either rigid or flexible and are introduced into the body through a natural opening or through a small incision. They have a light to illuminate the area being viewed; a camera on the end to transmit images to a monitor, or a lens and fibre-optic system for direct visual inspection; and a channel to allow instruments to be passed along inside the endoscope. Flexible and rigid endoscopes may be used not only to examine internal structures but also to remove small samples of tissue for examination and perform various surgical operations. A newer type of endoscope, known as a wireless capsule endoscope, is a self-contained pill-sized device containing a camera, light source, and transmitter. It is swallowed and transmits images as it passes along the digestive tract but cannot be used to take samples or perform surgical procedures.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.