What is X-ray?
X-ray radiation is the basis of X-ray diagnostics. It was discovered in 1895 by Wilhelm Röntgen, a German physicist.
X-rays are produced by applying a large voltage between two electric poles (anode and cathode). The resulting energy is partially emitted in the form of X-rays. This penetrates tissue, attenuating to varying degrees depending on its density, and can then be collected and made visible. Dense tissue (such as bone) attenuates the penetrating radiation more than soft tissue (such as muscle or lung tissue) and therefore appears bright on the images.
X-rays are ionizing radiation, which means that they can alter matter they pass through by knocking negative particles (electrons) out of the shell of atoms or molecules. In this way, X-rays can cause damage to genetic material (DNA) when they penetrate tissue. This DNA damage can be harmful to health in the long term and lead to cancer, for example.
In the past, the X-ray image was recorded in analog form on a special film. In the meantime, low-radiation digital X-rays (digital radiography, DR) using computers have become established almost everywhere. The images obtained in this way can be digitally post-processed.
X-ray is an imaging technique that is used as standard in many areas of medicine. Important forms of examination are:
Conventional X-ray.
This is the “simplest” type of X-ray examination. It is used, for example, to diagnose bone fractures, but also diseases of the chest (such as pneumonia, enlargement of the heart muscle in the case of cardiac insufficiency, bulging of the aorta) or abdominal cavity (such as intestinal obstruction, gallstones).
Contrast X-ray
Sometimes it is useful for diagnosis to highlight certain structures (especially soft tissue) more strongly, i.e., to contrast them. Contrast medium is used for this purpose. The contrast medium appears quite bright on the X-ray image. It can be administered to a patient in various ways – for example, as an injection into a vein or artery, as a drinking solution by mouth, or as an intestinal enema into the rectum. The contrast medium allows good imaging of, for example, the blood vessels (angiography) or the excretory function of the kidney (excretory urography). The gastrointestinal tract can also be examined well in this way, for example, for the presence of polyps, stenoses or outpouchings.
Digital subtraction angiography (DSA)
During the exposures it is very important that the patient does not move!
Special X-ray examinations
There are a variety of special X-ray procedures. Two types are mentioned here as examples:
- DVT X-ray (Digital Volume Tomography): Similar to computed tomography, but has much lower radiation exposure. Used primarily in dentistry and ENT medicine. Also allows three-dimensional images to be taken (3D X-ray).
- OPG X-ray (orthopantomography): Used by dentists to visualize teeth and jaws. The X-ray tube rotates in a semicircle around the head and a “panoramic image” is obtained.
When is X-ray performed?
This examination method is used to diagnose many different injuries and diseases. Some examples are:
- Bone fracture (Fracture): Radiography is very well suited for the diagnosis of bone fractures and has become the method of choice here.
- Osteoporosis (bone loss) by means of DEXA (densitometry; radiography with a low radiation dose).
- Diseases and injuries of the blood vessels by means of angiography (vascular X-ray)
- Breast cancer by means of mammography (chest X-ray)
- Diseases and injuries of the chest organs (such as lungs, heart): Can be well visualized with a chest x-ray.
X-rays at the dentist
X-rays of teeth and jaws are an important examination method for the dentist: The hard teeth and the jaw bone can be visualized particularly well.
When should x-rays not be taken? (Contraindications)
Due to the potentially harmful effect of X-rays on health, there must be a valid medical reason for each application (the so-called “justifying indication”). This means “that the health benefit of the application on humans outweighs the radiation risk”. Other procedures with comparable health benefits, which are associated with no or lower radiation exposure, must be taken into account in the weighing process” (Section 23 of the X-ray Ordinance). In the case of children and pregnant women, special care must be taken to determine whether the examination is necessary. However, there is no absolute contraindication – i.e. situations in which X-rays must not be taken under any circumstances.
What do you do during an X-ray?
The examination can then be documented by the radiologist on a special X-ray passport. This is to avoid unnecessary repetitions of the examination (and thus unnecessary radiation exposure).
Fasting for the examination
If the stomach and intestines or gall bladder and bile ducts are to be x-rayed, you must be fasting, i.e. you must not eat or drink anything for some time beforehand. Sometimes you also have to do a bowel cleanse the day before, i.e. take a laxative. You will receive more detailed instructions from your doctor in advance.
What are the risks of X-rays?
Possible risks associated with the examination primarily concern the contrast medium (if one is used) and radiation exposure.
Contrast medium
Often the contrast medium contains iodine. Therefore, caution must be exercised in people with thyroid disease (hyperthyroidism or hypothyroidism) and prophylactic medication may need to be administered. Similar considerations apply to patients with impaired renal function (renal insufficiency).
When injecting an iodine-containing contrast medium into the vascular system, a feeling of heat and a bitter taste in the mouth may occur temporarily.
Very rarely, the contrast medium used may cause allergic reactions (redness, itching, nausea, etc.) and even allergic shock with cardiovascular arrest. In the case of a mild allergic reaction, anti-allergic medication usually helps.
Radiation exposure
Acute side effects of radiation (such as reddening of the skin) are very rare. A greater danger comes from the long-term consequences of radiation exposure. However, it is difficult to specify exact limits above which X-rays are harmful – the transitions are fluid. However, the radiation dose during a simple X-ray examination is low. For example, the radiation dose of a lung x-ray is roughly equivalent to the radiation dose of a transatlantic flight. Each additional X-ray, of course, increases the body’s radiation exposure. Therefore, before each X-ray examination, the doctor weighs its benefits. However, one should keep in mind that even with many X-rays taken within a short period of time, the health risk of an undetected disease is usually much greater.
X-ray & pregnancy
What do I have to watch out for after the X-ray?
If you have been given a water-soluble contrast medium in a blood vessel before the examination, you should drink plenty afterwards. In this way, the contrast medium is excreted more quickly via the kidneys and intestines. Beyond that, there are no special things to take care of after the X-ray.
