X-rays are a type of high energy radiation. The rays pass easily through fluids and soft tissues of the body. However, dense tissue such as bone will block some of the x-rays. The denser the tissue, the less x-rays pass through.
A film, similar to a photographic film, is placed behind the part of the body being x-rayed. The x-ray machine fires a short burst of x-rays through part of your body. The x-rays hit the film which is then developed. The more x-rays that hit the film, the blacker it develops. So, dense parts of the body that block many of the x-rays show up white (such as bones). Hollow or air filled parts of the body show up black (such as parts of the lung). Soft tissues such as muscle and body organs show up as various shades of grey, depending on how dense they are. The developed film is studied by an x-ray doctor (radiologist) who sends a report to the doctor who requested the test.
An ordinary x-ray test is painless. You cannot see or feel x-rays. You should stay still when the x-ray beam is 'fired' as otherwise the picture may be blurred.
An ordinary x-ray is a quick, easy and cheap test. It may be all that is needed to diagnose or assess various problems.
There is very little risk with having one x-ray test. However, with repeated tests there is a risk that the x-rays may damage some cells in the body, possibly leading to cancer in the future. The dose of x-ray radiation is always kept to the minimum needed to get a good picture of the particular body part being checked. (Also, radiographers who take the x-ray pictures always wear lead aprons or go behind a protective screen when the x-rays are fired to avoid repeated exposure to x-rays.)
X-ray machines are used to screen objects non-invasively. Luggage at airports is examined for possible bombs and weapons. These machines are very low dose and safe to be around.
Other notable uses of X-rays include:
· X-ray crystallography in which the pattern produced by the diffraction of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice (most notably used by Rosalind Franklin to discover the double helix structure of DNA).
· X-ray astronomy, which is an observational branch of astronomy, which deals with the study of X-ray emission from celestial objects.
· X-ray microscopic analysis, which uses electromagnetic radiation in the soft X-ray band to produce images of very small objects.
· X-ray fluorescence, a technique in which X-rays are generated within a specimen and detected. The outgoing energy of the X-ray can be used to identify the composition of the sample.
· Paintings are often X-rayed to reveal the underdrawing or alterations in the course of painting, or by later restorers. Many pigments such as lead white show well in X-ray photographs.
IV. Find the sentences containing:
a) the main idea of the text;
b) specifying information (risks with having x-ray tests; use of x-ray technology in health care; x-ray equipment; medical electronics; x-ray in our life).
V. Say which facts presented in the text you’ve already been familiar with.