Assessment of peak kilovoltage accuracy in ten selected X-ray centers in Lagos metropolis, South-Western Nigeria: A quality control test to determine energy output accuracy of an X-ray generator

Background: Most X-ray centers recruited for this study admitted that there have been no maintenance checks on the energy output accuracy of their X-ray machines. Most centers complained of recurrent machine breakdown due to poor power supply, while others pointed out that X-ray machine age could be a contributory factor to poor image quality. Aim and Objectives: To determine peak kilovoltage (kVp) accuracy of individual X-ray unit and to compare their values with recommended standards and to further establish if machine age has a significant effect on mean kVp accuracy. Materials and Methods: One dedicated conventional X-ray unit in each of the ten diagnostic centers was used for this study denoted as D 1−D 10 . kVp was measured using a noninvasive Unfors ThinX RAD kVp meter. The kVp accuracy test was carried out by positioning the Unfors ThinX RAD kVp meter at the center of the beam axis of the patient′s couch at a focus to image distance of 100 cm. The X-ray machine technical factors were varied by selecting tube potential within the range of 50−120 kVp at a fixed tube current of 20 mA. Data analysis value was done using GraphPad Prism version 5.0 statistics software (GraphPad Software, Inc., San Diego, California, USA). Results: The kVp accuracy test for X-ray units D 1 , D 2 , D 5 , D 6 , D 7 , and D 8 were within an acceptable limit of ±5% at all selected tube potential from 50 to 120 kVp, X-ray units D 2 and D 6 showed accurate compliance at much lower kVp accuracy values. X-ray units D 3 and D 10 were above ±5% accuracy limit at all selected kVp tube potential. No statistically significant differences exist between machine age and mean kVp accuracy (P = 0.770). Conclusion: One-fourth of the total kVp accuracy results were above ±5% limit. Old X-ray machine had higher chances of failed kVp accuracy. Traces of failed test were also noticed in X-ray machines below 5 years.