ESTIMATION OF PATIENT DOSES FOR COMMON DIAGNOSTIC X – RAY EXAMINATIONS AT FEDERAL MEDICAL CENTER, MAKURDI.
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Background of Information
This study would be carried out as part of a comprehensive project to establish a national diagnostic reference levels (NDRL) in Nigeria .Five of the most common X-ray examinations would be included. This study would consist of 200 patients who would be referred for X-ray examinations at the Federal Medical center, Makurdi. The selected X-ray examinations would be Chest (PA/AP), Chest LAT, Lumber spine AP/PA, Lumber spine LAT. Mean patient information and exposure parameters for these five radiographic examinations would be recorded at FMC.
1.2 Introduction
The need for radiation dose assessment of patients during diagnostic X-ray examinations has become imperative by the increasing knowledge of the hazards associated with ionizing radiation (Obed, et al., 2007). Patients undergoing diagnostic imaging involving ionizing radiation are subject to a wide range of exposure levels. The principal concern in radiological protection is the reduction of unnecessary exposures by requiring adequate clinical justification and optimization of patient protection as recommended by the international committee for Radiological protection (ICRP 1990). Also in the publication 60, 1990, it was stated that absorbed dose to the tissues or organs should be used for estimating the likelihood of patients to develop stochastic effect.
During a radiological examination, the irradiation of the patient should be minimized by using the best available techniques and measures should be taken to reduce as far as possible dose to other parts of the body consistent with the clinical needs of each case (Gaetano et al., 2004).
International Atomic Energy Agency (IAEA, 1996), recommended entrance skin dose (ESD) as dose descriptor for guidance levels in diagnostic radiography because it provides an indication for maximum skin dose and is useful for periodic checking of patient dose.
Patient dose measurement is an integral part of this optimization procedure. Such measurements will reveal x-ray facilities with high doses after possible dose reduction measures may be specified. Various dosimetry quantities have been suggested for the assessment of patient dose. These quantities include entrance surface dose, organ dose and effective dose. Most of the patients’ dose assessment that have been reported, in radiography, have been used on entrance surface dose measurements (Ogunseyinde et al., 2002; Ogundare et al., 2004a; Ogundare et al., 2004b, Muhogora and Nyanda 2001; Gogos et al., 2003). Entrance surface dose, however, can not be directly used to assess the risk associated with diagnostic examinations. In order to assess stochastic risk, international commission on radiological protection in 1977 (ICRP publication 26) has recommended determination of effective dose. In 1991, ICRP further recommended that patient exposures in diagnostic radiology be denoted by organ dose and effective dose.
The effective dose is given as a weighted average of the organ doses. The preferred and most complete approach for risk estimation is accurate knowledge of all patient organ doses. However, measurements or calibrations of organ doses are complex and it is often regarded as a troublesome job in diagnostic centers. This may explain why there is scanty information about organs doses of patients in diagnostic radiology.
In Nigeria, Ajayi and akinwumiju (2000) carried out a research on the measurement of entrance skin doses to patients in four common diagnostic examinations by thermo luminescence dosimetry in Nigeria, it was discovered there is variation in patients dose from hospital to hospital. Ogunseyinde et al., (2002) carried out a research financed by the international atomic energy agency (IAEA). In their work, patients’ doses in the X-ray examinations of chest posterior anterior (PA), skull PA, skull AP and skull lateral (LAT) were reported.
1.1 Relevance
Diagnostic medical X-rays constitute the largest man-made source of ionizing radiation exposure to the populati. While the determination of patient radiation dose in x-ray is common practice in Europe because of the legislation in place since 1984, (EC, 1997; EC, 1999), no such surveys are recorded in literature for Nigeria.
Nevertheless x-ray use has been constantly increasing in Nigeria tertiary health institutions. In developed countries large surveys have been carried out to determine typical patient doses in x-ray examinations. The most widely quoted is the UK survey of the early 1990s.
The importance of such surveys enables the establishment of diagnostic reference levels which aid in minimizing radiation dose to the patients and the general population in line with justification of practices and optimization of protection such that radiation doses are kept as low as reasonably achievable(ALARA principle), taking economic and social factors into account.
1.2 Aim and Objectives
Some countries in Europe have established national diagnostic reference levels (NDRLs) for common x-ray procedures as an efficient standard for optimizing radiation protection of patients. Such reference dose levels have not been established in Nigeria. This project is aimed at estimating the doses received by patients undergoing radiological examinations at FMC, Makurdi, of chest AP/PA, chest LAT, Lumber spine AP/PA, Lumber spine LAT and pelvis AP compared with the established international reference doses. The results will be useful to national and professional organizations and can be used as a baseline upon which future dose measurements may be compared.
The values of these radiographic examinations would be compared with their corresponding European guidelines. Wide variations in patient dose arising from a specific type of X-ray examination at different national places suggests that significant reductions in patient dose would be possible without affecting image quality.
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