24 World Health • 48th Yeor, No. 3, Moy-June 1995 Protection against radiation in medicine Cesar F. Arias &Jorge J. Skvarca

The protection of patients is the area in which the greatest reductions in human exposure to radiation can be made - by improving the quality of equipment and practices and raising the standard of justification for procedures.

Radiology in paediatrics ca lls far special protection procedures for the young patients. the probability of cancer grows with the dose of radiation absorbed. he discovery of X-rays by Whenever radiation is used for Rontgen in 1895 and radioactiv­ The risk of radiation any purpose, people working with it, Tity by Becquerel in 1896 opened as well as some members of the up the field for using ionizing radia­ Human beings are naturally exposed public, are unavoidably exposed to tion in science and technology. This to the radioactive substances of the small doses of radiation under proved to be a valuable tool for earth, and to cosmic radiation. normal circumstances. In the case research on the structure of matter, Globally, the average dose per of medical use, the patient is delib­ and its applications in medicine have person is about 2 millisieverts (mSv) erately exposed to radiation in order been explored since the beginning of per year, which is about 10 times the to obtain the necessary diagnostic the century. Ionizing radiation is dose received from a simpleX-ray information or for treatment. In now used for medical purposes in examination. addition, accidents can occur in three areas: diagnostic radiology, When X-rays and radioactivity which people receive high doses. radiotherapy, and nuclear medicine. first came into use, little was known Throughout the world, there are about the effects of ionizing radiation about 800 000 X-ray units being used on health. It was the acute effects, Protection against radiation for diagnostic radiology; 4000 cobalt such as skin erythema, cataracts and radioactive sources and 1800 accel­ reduced production of blood cells The Second International Congress erators being used for radiotherapy; that were recognized first. These of Radiology, held in Paris in 1928, and 13 000 nuclear medicine clinics only occur when tissues receive recommended the establishment of using unsealed radioactive sources doses of radiation several thousand an international organization to study for diagnosis and therapy. times as large as those received by an the question of protection against The growing complexity of average person in a year from natural radiation. This was the origin of the radiation medicine can be seen in the radiation. The carcinogenic effects International Commission on use of such devices as computerized were discovered later, and some Radiological Protection (ICRP) . The tomography in diagnostic radiology, information on them was gathered ICRP has produced about 70 publica­ linear accelerators in radiotherapy, from studies on patients who had tions and its recommendations have and positron emission tomography in been treated with radiation and been followed by most countries, as nuclear medicine. This has led to the workers painting radium on the dials well as by various international need for maintenance and quality of watches. After the bombing of organizations such as WHO and the control of equipment, using highly Hiroshima and Nagasaki, large-scale International Atomic Energy Agency specialized personnel. epidemiological studies showed that (IAEA). World Health • 48th Year, No. 3, Moy-J une 1995 25

able, are set as follows: occupa­ ment and procedures. tional exposure should not exceed The protection of patients is now 20 mSv per year and no member receiving particular attention, as it is of the public should receive more the area in which the greatest reduc­ than 1 mSv per year. The risk of tions in human exposure to radiation accidents must be considered. can be made. The global collective • All exposure should be kept as dose received by patients from diag­ low as reasonably achievable. nostic radiology is 5000 times Protection against radiation is a greater than the dose received by the matter of professional culture, world's population from nuclear and national regulatory authori­ power production. A significant part ties work to promote appropriate of that dose could be avoided without attitudes as well as compliance loss of health benefits by improving A radiation protection specialist checks with the rules. To provide them the quality of equipment and prac­ equipment to ensure that it meets safety with the necessary information tices and raising the standard of requirements. for doing this, the International justification for procedures. To In 1990 the Commission pub­ Basic Safety Standards for prevent accidents where radiation is lished ICRP Publication 60, which Protection Against Ionizing used for medical purposes, safety provided an update on radiobiology Radiation and for the Safety of measures have to be adopted in the and the current conceptual frame­ Radiation Sources were prepared design, installation, use, repair and work for radiation protection. The jointly by FAO, IAEA, ILO, the eventual disposal of equipment. • following points from this publica­ Nuclear Energy Agency (NEA) tion give an indication of its basic of OECD, the Pan American philosophy. Health Organization (PAHO) and Mr Cesar F. Arias is Chairman of the Advisory • Every exposure to radiation may WHO. WHO also works with Council on Radiological Applications and a former member of the ICRP Committee 3 on have detrimental effects on countries to improve standards Protection in Medicine. His address is Pampa human health, since the carcino­ through training and consultation 2669- 5A, {CP 1428}, Buenos Aires, genic effect of radiation cannot be on the procurement and use of Argentina. Mr )orge). Skvarca is Chief of the Department of Medical Devices at the completely avoided. equipment. Argentinian Ministry of Health. His address is • No practice involving exposures P.O. Box 3268, Correo Central 1000, Buenos Aires. to radiation should be adopted Medical establishments are the most unless it produces sufficient numerous and widespread source of benefit to the exposed individuals radiation in any country, and because or to society to offset the radia­ their activities are mainly beneficial, tion detriment it causes. the risks involved are often ignored. Radiation expert This makes the promotion of proper • Dose limits, defined as a level of In the same year that radioactivi ty dose above which the conse­ protection a difficult task. In the case was discovered - 1 896- one of quences for the individual would of a patient's exposure, the risks and the leading sc ientists in med ica l be widely regarded as unaccept- the benefits apply to the same person, radiation physics and radiation and must be carefully weighed protection, Rolf Maximilian Sievert, against each was born in Sweden He entered other by the the med ical physics field in 1920 physician respon­ and is known for his theoretica l sible. Dosage calculations of the dose distribution must be limited around radium tubes (Sievert integral), for the design of to what is strictly dosemeters (Sievert chambers), and necessary; limits for his research in radiation have not been set protecti on. because they Sievert was for many yea rs depend on the chairman of the International possible benefits, Commiss ion on Radiological but reference Protection (IC RP), and the in itiator levels are being and chai rm an of th e United Nations suggested for use Scientific Committee on the Effects in radiology and of Atomic Radi ation (UNSCEAR) nuclear medicine He retired in 1965 and was honoured after his death by having as a means of the unit for "dose equivalent" na med judging the after him as the Sievert (Sv) A radiographer views the patient from inside her protected control booth. quality of equip-