What is the nature of X-radiation?

X-radiation is counted among ionising radiation and does not differ from gamma radiation in its physical nature. In contrast to nuclear radiation, which is generated in radioactive substances (radionuclides) and is emitted for so long until even the "last" radionuclide has decayed, no X-radiation is generated any more after the X-ray device has been switched off. X-radiation is generated when energetic electrons are slowed down at the anode of an X-ray tube. The higher the abutted tube voltage which the electrons are accelerated with, the more permeating is the very short-wave radiation.

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How does X-radiation work?

For higher doses (above 200 mSv) it has been proved that X-radiation can cause virulent diseases or damage in the unborn child in the womb. The probability for these effects depends on the dose. Also for lower doses damage cannot be excluded entirely. Even lowest doses bear a – small – risk. Different tissues and organs vary in their radio-sensitivity, and the radio-sensitivity decreases considerably with advancing years.

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Since when have X-ray devices been applied in the medical field?

The X-ray device known for more than one hundred years is among the instruments most frequently applied in medicine. Since then, X-ray diagnostic procedures have permanently been developed further. For most types of examination, the radiation exposure of patients has considerably been reduced. In the last decades, in particular the development of sensitive film/foil systems, modern image intensifiers and digital systems contributed to the reduction of radiation exposure.

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Does X-radiation accumulate in the body?

Some people's opinion that X-radiation would accumulate in the body is not correct. If during an X-ray examination the radiation penetrates the human body, part of the radiation is absorbed in the tissue and can result in biological changes in the cells. Damaged cells, however, can also be repaired or removed by the body. For most X-ray examinations, progress in X-ray technology during the past 30 years has led to a considerable decrease in the doses taken up with each single image. The doses received in many types of X-ray examination can be compared with those taken up by man due to natural radiation sources.

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How many X-ray examinations are annually carried out in Germany?

In Germany, about more than 130 million X-ray examinations are carried out per year today. For current information please refer to X-ray diagnostics: Frequency and radiation exposure.

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Which level of radiation dose occurs in X-ray examinations?

Depending on the type of examination and the special conditions, radiation exposure in X-ray examinations varies from patient to patient. Therefore only rough reference values can be given here. In the case of examinations of limbs, teeth and thorax, the doses are very low and amount to less than one millisievert. Slightly higher dose values, e. g. in the range of one to several millisievert, occur in X-ray images of the spinal column, the pelvis, the veins, the abdomen or computer tomographies (CT examinations) of the head. Radiation exposure is the highest for examinations of the gastrointestinal tract, the arteries and for CT examinations of thorax and abdomen, the values being in the range of about five to max. thirty millisievert. Compared to this, natural radiation exposure which we are permanently exposed to in Germany, is between 2 and 3 mSv on average, in extreme cases 10 mSv.

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Whereby does the physician decide if X-radiation shall be applied?

Responsibility for the radiation exposure of patients is with the competent physician who decides – after having considered benefit and risk – about the X-ray application in diagnosis and therapy. Such exposure is only justified if the radiation risk is very low compared with the diagnostic or therapeutic benefit. The dose should be kept as low as can be reconciled with the medical purpose.

Most types of examination in X-ray diagnostics and in nuclear-medical diagnostics are standardised. In many thousand applications benefit could be achieved which justified them. Each of these types of examination has to be optimised according to radiation protection principles. An application of dose limit values could restrict the diagnostic benefit. Therefore it is currently recommended on an international level not to apply dose limit values to medical exposures. Nonetheless are physicians obliged to perform each examination in such a way that the radiation exposure for the patient is as low as possible. The Federal Office for Radiation Protection has published "diagnostic reference values" as target values which should not be exceeded in standard examinations in patients with normal weight.

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What can a patient do to keep radiation exposure low?

• Let your physician explain and justify the necessity of the planned X-ray examination to you!
• Inform your physician if similar examinations have been carried out with you recently!
• Present your X-ray passport to your physician and have examinations entered there!
• Bring along previously made X-ray images or have them requested!
• Before they undergo an X-ray examination, women should tell if they are or think they are pregnant since in case of pregnancy X-ray examinations should only be performed in exceptional cases which are especially justified.
• Mind that radiation protection is ensured for the not examined body parts (lead apron!).

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What is an X-ray passport and where can you get it?

The purpose of the X-ray passport is that attending physicians and in particular physicians carrying out examinations can see prior to an X-ray examination which X-ray examinations have been performed recently. The X-ray passport serves as "mnemonic" for patients and simplifies communication with the physician, since laypersons are frequently not able to name the X-ray examinations already carried out in them correctly.

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How useful is the early diagnosis of breast cancer with the help of mammography?

For women, breast cancer is the most frequent type of cancer and occurs in Germany in about 10 % of all women. If detected in due time in the early stage, this serious disease can, however, be cured in more than 90 % of the cases. In addition to a review of the medical history, visual examination and palpation, three imaging procedures are used to diagnose breast cancer:

• X-ray mammography
• sonography – i. e. ultrasound examinations
• magnetic resonance imaging.

With mammography it is possible to recognise tumours at an early stage, when the patient is not yet in a position to palpate it; chances for healing are still very good at this stage. Ultrasound and magnetic resonance imaging (MRI) are used as an important supplementary examination.

What is to be recommended?

In case a patient finds a lump in her breast, she should contact a physician. In this case mammography should be carried out as a first step of imaging diagnostics. For women without palpable or other suspect diagnostic findings the possibility and benefit of screening and early diagnosis examinations are currently being investigated scientifically.

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