INTRODUCTION
Ionizing radiation has been employed in the diagnosis of various diseases and treatment since its discovery in 1895 by Wilhelm Conrad Rontgen1. There are many types of ionizing radiation available for either treatment or diagnosis worldwide. Despite wide radiation applications in medicine, it can be hazardous if not properly handled. After interaction of ionizing radiation with biological tissues through various mechanisms, the ions produced by such interactions can affect normal biological processes. Improper protection against ionizing radiation can lead to death, cancer, skin burn, cataract, infertility and genetic effects1.
The International Commission on Radiological Protection (ICRP) recommended2 a system for limiting the doses received by radiation-exposed workers. Its report addresses radiation safety practices in industrial and medical institution, control of radionuclide in the environment, protection of the public and assessment of radiation risk.
It is essential to monitor radiographers and other radiology staff as they discharge their duties to the public. This is of great importance to the radiographers in their effort to protect themselves, patients and the general public from the untoward effect of excessive radiation. It is clearly sensible for those involved in use of ionizing radiation in diagnostic radiology to have an appreciation of the possible risks involved. For radiographers, measurement of radiation doses received at periodic intervals represents a way of monitoring doses to ensure that they are within safe occupational limits.
Personnel radiation monitoring is essential to ensure that dose limits for staff is not exceeded. The dose limits for staff were published by the International Commission on Radiological Protection (ICRP) in 1977 and subsequently in the ionizing radiation regulations. A downward revision was done in 1991 by re-evaluation of data on risks. The effective annual dose limit was formerly 50mSv and the newly adopted effective annual dose limit is 20mSv averaged over five years3. The downward review of annual dose limit was to put stricter control over the use of ionizing radiation in Medicine and minimize possible hazards, especially the stochastic effects.
Film badges, thermoluminiscent dosimeters and pocket ionizing dosimeters are the recommended radiation measuring devices for use by exposed radiation workers to monitor received radiation dose4. Every worker is expected to wear his personal dosimeter always while working5. The dosimeter readings are kept as records for every staff for the purpose of evaluating their radiation history and possible risks involved. The records help in improving radiation protection practices in clinical settings. At the Washington State University, employees who have not had a radiation monitoring badge before must apply for and receive one before starting work involving radiation exposure6. Also, if the individual has worked with radiation in an institution other than Washington State University, he or she must complete and sign the release statement on radiation exposure history6. Dosimetric records are kept and are required to be disclosed when workers change jobs7. Personnel dosimetric records and monitoring are integral parts of radiography practice in Malaysia8.
This research aims at evaluating and assessing the level at which the practice of use of personnel radiation monitoring devices is being carried out in both private and public diagnostic radiology centres in Lagos State.
THEORETICAL BACKGROUND
Diagnostic radiography is the medical science of producing images of the human body, which can be used to make a diagnosis. Ionizing radiation is firmly established as an essential tool for diagnosis and therapy in medicine. The most widespread use of radiation medicine remains diagnostic radiology which involves imaging with x-rays21. A wide range of basic techniques is utilized including conventional radiography (static images captured on film loaded between intensifying screens in cassettes) and fluoroscopy (dynamic imaging with an (electronic) image intensifier.
The use of ionizing radiation for medical diagnosis is widespread throughout the world. There are significant country-to-country variations in resources and practice in medical radiology. Ionizing radiation is used increasingly in medicine principally for diagnosis with an annual global total for 1996 of about 2.5 billion examinations (78% from medical X-rays, 21% from dental x-rays and 1% from nuclear medicine). The annual average dose to the world population from all diagnostic exposures has been revised from 0.3 to 0.4mSv per caput21, 22. The average level of occupational exposures is generally similar to the global average level of natural radiation exposure. However, a few per cent of workers receive exposures several times higher than the average exposure to natural radiation. The exposure of workers is restricted by internationally recognized limits, which are set around 10 times the average exposure to natural radiation. The annual global caput effective dose due to natural sources is 2.4mSv. However, the range of individual dose is wide