INTRODUCTION
A homogeneous x-ray beam can be defined as a beam that contains photon of only one energy as compared to heterogeneous x-ray beam containing several photons of energies1. When a homogeneous x-ray beam passes through a medium, its intensity falls exponentially with the distance covered. Raising the tube current will increase the intensity of the X-ray beam and no change in the homogeneity of the X-ray beam. Increasing the beam filtration will reduce the intensity of the X-ray beam and increase the homogeneity of the X-ray beam 1.
Reducing the tube voltage will decrease the homogeneity and intensity of the X-ray beam. Using a target material with a higher atomic number will increase the intensity and increase the homogeneity therefore producing good diagnostic images 1. Other factors that affect x-ray beam homogeneity are mA, kVp, target material, distance and half value thickness (HVT) which is that thickness of a specified material which will reduce the intensity of a beam of x-radiation to half its original value1.
A beam is more penetrative or of higher quality if it has a higher half value layer. The effective photon energy of a heterogeneous x-ray beam is equal to the photon energy of homogeneous x-ray beam which has the same half value layer as the heterogeneous beam in question.
The need for frequent quality assurance test, and repairs (in case of total breakdown) are well known: lack of such services leads to underutilization of expensive medical equipment, thereby making health-care services in any country less cost-effective 2. The problems of quality control, preventive maintenance in Enugu is on the increase; this is the case because the demand for modern medical equipment in the health-care sector has increased in recent years, but this has not been accompanied by a commensurate increase in qualified personnel in medical electronics to provide the needed services. Using service engineers from foreign suppliers to overcome this problem is not a viable option; this is because the service is not available under short notice, and when available it is prohibitively expensive. Therefore, local medical centers in Enugu have continued to rely on the scarce services provided by the qualified local personnel in medical electronics.
Quality assurance test of x-ray equipment in Enugu are further worsened by the general lack of skill, personnel, and suitable tools in carrying out the test. This, coupled with the chronic shortage of personnel in medical electronics and financial resources, has exacerbated the problem by lowering the possibilities for follow up actions based on the results of quality control procedures.
The benefits of using high-quality X-ray images in diagnosing disease and in the guidance of therapeutic procedures are well known. X-rays are used in the diagnosis of many diseases and disorders, and they help clinicians confirm or rule out a diagnosis. The risk to individuals from the radiation used in diagnostic X-rays is small compared to the benefits which accurate diagnosis and treatment can provide 2. Unfortunately, due to the rapid increase in the number of X-ray units in Enugu, many users of X-ray equipment do not understand the basic principles of radiation protection, thus maximizing the associated radiation risks to patients. The benefits of diagnostic X-rays are drastically reduced when the equipment is operated without adequate quality control and maintenance. In most cases, such equipment has higher radiation risks because of an increased dose in a single exposure and repeated exposure attributed to low image quality. 3, 4
The provision of high quality health care services is the goal of all medical outfits. In the case of diagnostic radiological facilities 3 patient selection, the conduct of examination and the interpretation of the result can all have an impact on the achievement of these goals. It has been increasingly recognized that quality assurance program directed at equipment and operator performance can be of great value in improving the diagnostic information content, reducing radiation exposure, reducing medical cost and improving departmental management. This quality assurance program contributes to the provision of high quality health care. 4
Despites the emphasis on the need for quality assurance test, it is still been given poor attention in many radiology departments due to some limiting factors which includes (i) lack of tools or equipment needed for this test (ii) poor attention and low interest, on the part of Head of Radiology Department (iii) lack of knowhow, due to no practical exposure during the academic training. The impetus for this research came as a result of the concern that the recent increase in the acquisition of X-ray machines in Enugu with limited technical knowhow and tools to maintain and assessment of such equipment can severely undermine the anticipated health benefits from diagnostic X-ray examinations.
Quality control is important in nations that use or intend to use objective assessment of radiological images and international image quality guidelines to unify X-ray-imaging practices nationally and internationally. 5,6 The aim of this work is to report on the current status of homogeneity of X-ray beam in x-ray producing machines in Enugu metropolis.