APPLICATION OF DIAGNOSTIC REFERENCE LEVELS FOR RADIOLOGICAL PROCEDURES AT SELECTED TEACHING HOSPITALS IN NORTH EASTERN NIGERIA

​​​​​​Background of the Study

Diagnostic reference level (DRL) is defined as an investigation level used as a tool to aid optimization of protection in the medical exposures of patients for diagnostic and interventional procedures (International Commission on Radiological Protection (ICRP), 2017). Established DRLs are used to identify unusually high radiation doses for radiological examinations (Donald et al., 2012; Jeska et al., 2014). They are suggested action levels above which a facility should review its methods and determine if acceptable image quality can be achieved at lower doses (Wallace, 2010). Diagnostic reference levels is an optimization tool to ensure patients are adequately protected and it is deemed to be an important mechanism for the management of patient dose to ensure it is within the medical purpose of x-ray examination (Carroll, 2014). In the recommendation of international commission of Radiological protection (ICRP, Report 103), the principle for setting DRLs are enumerated, the local, regional and national objectives is clearly defined, including the degree of the specification of clinical and technical conditions for medical imaging task. The selected value of the DRL is based on the relevant regional, national and local data, the quantity used for the DRLs can be obtained in practical way ( ICRP,2017).The use of diagnostic reference levels has been supported by national and international advisory bodies (Donald et al., 2012). These and other organizations have provided guidelines on measuring radiation dose and setting diagnostic reference levels (ICRP, 2011).The concept of investigation levels for diagnostic medical exposures was first proposed by the International Commission of Radiological protection (ICRP) in its 1990 recommendations, and further developed into diagnostic reference levels (DRL) in 1996 in ICRP publication (Hart et al.,2012). The numerical values of diagnostic reference levels are advisory however; implementation of the DRLs concept may be required by regulatory and professional bodies(Wallace, 2010).Diagnostic reference levels (DRLs) are optimization tools used as special type of dose constraints above which doses must be reviewed and considered above acceptable levels, especially if acceptable image quality can be achieved at lower doses.(Muhammed et al., 2016).Optimizing the protection of patients, and maintaining appropriate good practice is a priority for all diagnostic radiological examinations (Muhammed et al., 2016). Many studies carried out to measure entrance surface dose (ESD) in different countries and their results were compared with dose levels recommended by relevant organizations. Also, organizations such as the National Radiological Protection Board (NRPB) and International Atomic Energy Agency (IAEA) recommended the use of dose constraints or investigation levels to provide guidance for medical exposures (IAEA, 2012). In the United States, Greece, Brazil and Bangladesh, investigations showed that patients dose from common x-ray examinations were below the reference levels set by International Commission on Radiological Protection (ICRP publication 60, 1991). In contrast, in China and Tanzania researchers reported that the average ESDs were comparatively high for x-ray examinations (Gholami et al., 2015)

The radiation protection system for patients referred for medical exposures in diagnostic radiology is governed by principles of justification, optimization and dose limit ( ICRP, 2017). The consideration of DRLsgives you an idea of the radiation doses received for standard size patients (Roshan et al., 2011). Diagnostic radiological examination is justified if the benefits to the individual patients from the medical diagnosis are obtained with good quality image. (Jeska et al., 2014).Once medical exposure is justified it means, that the radiological examination must be carried out with the equipment and exposure parameters that ensure doses to patients as low as reasonably practicable consistent with intended diagnostic purpose (Wallace, 2010). The medical field over the years has benefited enormously from the use of x-ray radiation with various new developments associated with diagnosis and therapy(Jeska et al., 2014).Radiation can be a major risk in radiology and the growing use and increasing complexity of radiologic examination have been accompanied by public health concerns resulting from radiation exposure to both patients and personnel (Axiesson, 2011).It is known that of all man made sources of radiation, diagnostic x-rays contribute the largest part to the collective population dose, and are the most encountered radiation in diagnostic radiology leading to injurious somatic and genetic effects on human beings (UNSCEAR, 2012).

X-ray is the most frequently used ionizing radiation for diagnostic imaging and it plays a significant role in effective health care delivery both in developed and developing countries (Olowookere et al., 2012). Several studies reported the need to establish diagnostic reference levels in Nigeria (Olowookere et al., 2012; Sharifat et al., 2010). DRLs permit individuals and institutions performing radiological procedures to compare the radiation dose in their center with other established work so as to check their performance. (Sharifat et al.,2010). X-ray is said to be the major contributor to the collective effective dose of the general public (Johnson and Brennan, 2012). The need for radiation dose assessment for the patient during diagnostic x-ray examinations has been highlighted with the increasing knowledge of hazard of ionizing radiation (Johnson and Brennan, 2012). Because of the deleterious effects of x-rays, it is necessary to protect patients undergoing diagnostic and therapeutic procedures. The aim of any diagnostic radiological x-ray examination is to produce images of sufficient and optimum quality with doses justified and optimized. The assessment of dose includes the contributions from primary beams, scattered and leakage radiation(Nzotta and Udeh, 2013)

The Australian radiation protection and Nuclear safety Agency(ARPANSA), (2014) suggested that the DRLs is the 75th percentile (Third quartile) of the spread of mean doses of common protocols as recorded from data submitted to the National diagnostic reference service (ARPANSA, 2014). A local facility reference levels (FRLs) is defined as the mean value of the spread of doses for common protocols surveyed at the Local Radiology facility (Abdullahiet al., 2015). The major objective of DRLs is to help avoid excessive radiation dose to the patient that does not contribute additional clinical information to diagnostic Radiology task (ARPANSA, 2014). DRL should be selected by professional medical bodies‟ often in conjunction with health and radiation protection authorities and their values would be specific to a country or a region. DRL are a guide to encourage good clinical practice (Donald et al., 2010). Diagnostic reference levels are a quality assurance and quality improvement tool for controlling radiation dose (Donald et al., 2010). They are intended to be a reasonable indication of dose for average size patients and to provide guidance on what is achievable with current good practice rather than optimum performance (Donald et al., 2012). The objective of the study is to establish DRLs for radiology procedures in major referral centers in North eastern Nigeria.

Statement of the Problem

Increasing concerns over radiation doses received by patients and the associated radiation risks have become a major issue in recent years. (Rehani, 2015). Reducing radiation dose in radiological examination is of utmost importance particularly in the light of continued increase in the number of new modalities and examinations performed annually (NCRP, 2010). In Nigeria, in spite of the large number of x-ray examinations carried out yearly, the dose information available is grossly inadequate. In addition, there are no evidence of published data indicating the establishment of diagnostic reference levels for radiologic examination in Nigeria (Micheal et al., 2016). The need for optimization of patient protection through implementation of measures to keep doses to patients undergoing radiology examination within acceptable ranges for the clinical purpose of each examination has been a topic of global recognition (Institute of Physics and Engineering in Medicine (IPEM) , 2015).Diagnostic Reference Levels (DRLs), which is the recommended tool in achieving optimization of doses, is yet to be set or unavailable for radiology procedures in Nigeria (Olarinoye and Sharifat, 2008; Olowookere, 2012; Nworgu and Bamidele,2010). Absence of DRLs could result to unsafe practice which poses detrimental effects on patients as a result of increase in patient‟s dose and consequent radiation risks. Without DRLs the hospitals, clinics and diagnostic centers cannot measure their performance. The regulatory and professional bodies saddled with the responsibility of licensing, monitoring and authorizing the practice and dispensing of radiation doses to patients will have no idea of DRL values in our region. Practices are presently referenced to United Kingdom radiological practice standards, European commission (EC) and Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). More so, IPEM (2004) recommends that every country and or facility should have or set its DRLs, because practices and advancement in technology varies from one country to another and hence one country’s DRL cannot be a good representation of another. To the best of researcher‟s knowledge and based on literature search, there are no documented DRLs or radiation dose assessments for radiological procedures in any facility in North Eastern Nigeria. Identifying situations where the level of patient dose is usually highcannot be determined without dose assessment. The relationship between dose values and anthropometric/technical parameters has not been assessed in teaching hospitals in North eastern Nigeria, hence they are not yet known.