Effect of Varying HVL Values on the Dose Output of Plain X-Ray Machines at a Fixed kV of 80, a Regulatory Perspective

Background: HVL in diagnostic X-ray machines is an important property for defining the penetration ability of an X-ray beam into the human body and, hence, the beam hardness. Materials and Methods: The study utilized the findings of the radiation safety inspections conducted between 2022 and 2023 to investigate the variation of the Half-value layer (HVL) with dose output, taking 64 X-ray machines based on a set criterion. Results: A total of 26 X-ray machines failed the HVL test, while 38 passed the HVL test. Of the 38 that passed the test, 14 had very high and extremely high HVLs and produced doses below the lower limit of the permissible range of 0.025 - 0.08 mGy/mAs. The corrective action for 26 machines that generally failed the HVL test was to minimize the filtration by removing the filter plates. However, this had to be done only after a conclusive investigation to check the accuracy of tube current (mA), timer (s), and tube potential (kVp) parameters. Conclusion: Therefore, the regulatory body recommends that HVL tests be part of the acceptance and commissioning tests for the new machines in Uganda and be done routinely for the machines in use, as specified in the quality control program for each X-ray machine.