ASSESSMENT OF RADIATION DOSE CREEP FROM COMPUTED RADIOGRAPHY UNITS OF DIAGNOSTIC CENTRES IN ABUJA, NIGERIA

The use of computed radiography (CR) in the X-ray imaging systems is displacing the conventional film screen system due to obvious advantages of the former. However, the wide dynamic range of the CR system has created a lacuna for unintentional overexposure of patients called dose creep. The aim of this study is to assess radiation dose creep from some computed radiography units and also assess the knowledge of radiographers about dose creep and exposure index (EI) with a view to creating awareness on the phenomenon of dose creep. In this cross-sectional and retrospective study, 2156 exposure indices were analysed. A survey questionnaire of 50 radiographers were also analysed. The exposure indices were grouped into three, viz; under exposure, optimum exposure and over exposure, based on the manufacturers recommended range (MRR) of EI. The radiographers were assessed on their knowledge of dose creep, EI and application of the MRR of exposure index. AGFA CR30-XM skull X-ray exams demonstrated the highest amount of dose creep (overexposure) rates of 56.3%. The overall distribution of the EI values in the CR units revealed that 9.9% of the data were associated with dose creep. This indicates that the probability of dose creep in the X-ray exams was 0.099. Only 37.9% (818) of the exposure indices were in the MRR. There was no significant variation of dose creep according to gender. Most of the radiographers, 92% (46) did not know the meaning of dose creep with respect to computed radiography while 58% (29) of them did not know the meaning of exposure index. None of the radiographers compared the exposure index of their X-ray images with the MRR as a means of optimizing patient dose. All X-ray examinations demonstrated a proportion of dose creep from the CR units. Radiographers were not complying with the manufacturers recommended range of exposure index. And the radiographers had poor knowledge of dose creep and exposure index with respect to computed radiography. Computed radiography is recommended for diagnostic centres due to obvious dose saving potentials and radiographers require adequate knowledge of computed radiography physics.