INTRODUCTION
X-radiation (composed of X-rays) is a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. Radiations can be conveniently categorized into charged particulate radiations (fast electrons and heavy particles) and uncharged radiations (electromagnetic radiations and neutrons). Radiation can also be classified as ionizing or non-ionizing. Ionizing radiation is further classified into directly ionizing and indirectly ionizing (IAEA, 2005).
X-ray which is the radiation of interest in this research is an electromagnetic and uncharged radiation. It was discovered by a German professor of Physics Wilhelm Conrad Rontgen on 8 November, 1895 while he was working with a cathode ray generator (Gail, 2012). When electrons are accelerated to energies in excess of 5 keV and are directed on to a target surface, xrays are emitted. The emitted radiation originates principally from rapid deceleration of the electrons when they interact with the nucleus of the target atoms. These x-trays are referred to as bremsstrahlung. The second sets of x-rays are characteristic in nature and are produced when the fast beam of electrons from the cathode displaces the electrons in the K-orbits of the target atoms.
All X-rays exhibit the following properties (Andy, 2008):
Fluorescence: visible lights are produced by phosphors;
Photographic effects: a photographic film can be forged when exposed to x-rays
Penetration: X-rays have the ability to penetrate opaque substances
Ionization and Excitation: The ability of x-ray to raise an electron to a higher energy level in an atom or eject it completely from the atom forms the basis for most of its properties.
Chemical changes: X-rays can effect chemical changes when they pass through substances.
Biological effects: Biological effects of x-rays on living tissues can be directly or indirectly. In direct effect the x-ray energy ionizes a biological macromolecule essential for survival and reproduction of the cell. In indirect effects, the x-ray energy ionizes water molecule to produce hydrogen (H*) and hydroxyl (OH*) free radicals respectivelywhich further produce hydrogen peroxide (H2O2) and hydroperoxyl radical (HO2*) which are poisonous to the cell (Gail, 2012). The cell may be killed or its reproduction may cease consequently.
Diagnostic X-rays (primarily from CT scans due to the large dose used) increase the risk of developmental problems and cancer in those exposed (Hall & Brenner, 2008). X-rays are classified as a carcinogen by both the World Health Organization’s International Agency for Research on Cancer and the U.S. government (Roobottom, Mitchell & Morgan, 2010). It is estimated that 0.4% of current cancers in the United States are due to computed tomography (CT scans) performed in the past and that this may increase to as high as 1.5-2% with 2007 rates of CT usage.
Experimental and epidemiological data currently do not support the proposition that there is a threshold dose of radiation below which there is no increased risk of cancer (Upton, 2003). However, this is under increasing doubt. It is estimated that the additional radiation will increase a person’s cumulative risk of getting cancer by age 75 by 0.6–1.8%. The amount of absorbed radiation depends upon the type of X-ray test and the body part involved. CT and fluoroscopy entail higher doses of radiation than do plain X-rays.
To place the increased risk in perspective, a plain chest X-ray will expose a person to the same amount from background radiation that people are exposed to (depending upon location) every day over 10 days, while exposure from a dental X-ray is approximately equivalent to 1 day of environmental background radiation. Each such X-ray would add less than 1 per 1,000,000 to the lifetime cancer risk. An abdominal or chest CT would be the equivalent to 2–3 years of background radiation to the whole body, or 4–5 years to the abdomen or chest, increasing the lifetime cancer risk between 1 per 1,000 to 1 per 10,000. This is compared to the roughly 40% chance of a US citizen developing cancer during their lifetime (National Cancer Institute, 2010). For instance, the effective dose to the torso from a CT scan of the chest is about 5 mSv, and the absorbed dose is about 14 mGy. A head CT scan (1.5mSv, 64mGy) that is performed once with and once without contrast agent, would be equivalent to 40 years of background radiation to the head. Accurate estimation of effective doses due to CT is difficult with the estimation uncertainty range of about ±19% to ±32% for adult head scans depending upon the method used (Gregory, Bibbo and Pattison, 2008; Shrimptom, et al, 2003).
The risk of radiation is greater to a fetus, so in pregnant patients, the benefits of the investigation (X-ray) should be balanced with the potential hazards to the fetus. In the US, there are an estimated 62 million CT scans performed annually, including more than 4 million on children. Avoiding unnecessary X-rays (especially CT scans) reduces radiation dose and any associated cancer risk Donnelly, 2005).
Medical X-rays are a significant source of man-made radiation exposure. In 1987, they accounted for 58% of exposure from man-made sources in the United States. Since man-made sources accounted for only 18% of the total radiation exposure, most of which came from natural sources (82%), medical X-rays only accounted for 10% of total American radiation exposure; medical procedures as a whole (including nuclear medicine) accounted for 14% of total radiation exposure. By 2006, however, medical procedures in the United States were contributing much more ionizing radiation than was the case in the early 1980s. In 2006, medical exposure constituted nearly half of the total radiation exposure of the U.S. population from all sources. The increase is traceable to the growth in the use of medical imaging procedures, in particular computed tomography (CT), and to the growth in the use of nuclear medicine (US National Research Council, 2006).
Generally, an exposure to x-rays whether high dosed or low dosed poses serious health risks and dangers; exposures to ionizing radiations are on the increase and becoming highly irresistible in medicine especially as most diagnostic and screening procedures depends on them. Against this background, this study tries to investigate into safety measures considered in the design and building of medical imaging centres.
The issue of safety in the utilization of radiation sources in medicine and industries has not been given adequate attention in most radiological centers found all over the world despite the efforts of national and international law enforcement agencies such as Nigerian Nuclear Regulatory Authority (NNRA) and International Atomic Energy Agency (IAEA), respectively (Adejumoet al,2012).
In Nigeria, Okejiet al, (2010) assessed radiographs taken in some teaching and specialist hospitals in South-East to evaluate the levels of x-ray beam collimation on the radiographs.It was reported that 52% and 59% of the radiographs taken in the teaching and specialist hospitals, respectively, were poorly collimated.This normally leads to greater exposure of staff and patients. Unfortunately, only about 60% of Nigerian employers and employees in x-ray diagnostic centers have good knowledge of hazards associated with radiation exposure (Aweda and Awosanya, 2007).
The environmental monitoring and quality control tests carried out by Oluwafisoyeet al, (2009) at an x-ray facility in a Nigerian hospital showed dose rates of 4µSv/h and 5µSv/h at the reception and outside the entrance door respectively.
Exposure to x-rays sometimes occur incidentally without direct exposure to imaging devices and X-ray equipment, this has been associated with poor design and construction of X-ray centres.
This research is basically aimed at assessing safety measures in the design and building of X-ray centres in Port Harcourt.
This study will specifically investigate into the following areas;
The research questions guiding this study includes;
This study will extend and limit itself to the assessment and evaluation of safety measures, rules, regulations, and principles that governs the design and construction of imaging facilities and evaluate how strictly they are adhered to.
The issue of radiation safety have been relegated to the background, imaging practitioners have carried out routine radiological diagnosis without due regards to safety; medical facilities have been designed just to promote business interest with little or no regard safety issues surrounding the use of imaging equipment and general imaging practice. This study will serve as a wakeup call emphasizing safety, as it concerns imaging practitioners.
This research will benefit scholars and academicians as it will serve as a reference and basis for other studies.
Those particularly involved in Medical Imaging Practice and Policy making will particularly benefit as this study will reignite in them the need to strengthen imaging policies and practice principles.