LAUSR

Purpose Multi-slice computed tomography (CT) is one of the fastest and most efficient medical imaging techniques due to its multiple beam projections providing high-quality scans of cross-sectional images of the different organs and tissues of the body. Although multi-slice CTs provide great benefits in diagnostic medicine, its high intensity x-rays and secondary radiation pose potential harm to radiological personnel and the general public. Thus, radiation protection survey evaluation of the facility is warranted. In this study, scattered radiation levels produced by selected multi-slice CT facilities were evaluated and their shielding adequacy were also assessed. Methods Scattered radiation measurements of 256-, 128-, and two 16-slice CT machines were conducted using a survey meter. The machines were all set at axial mode with pitch equal to 1. Doses were measured from 16-cm and 32-cm polymethylmethacrylate (PMMA) for head and abdominal phantoms, respectively. Dose maps were generated at distances of 1, 1.5 and 2 m from the isocenter at 45° angle increments. Shielding adequacy measurements were performed at designated points inside the control room and main door of the machine rooms with calculated shielding design goal and occupancy factor ratio (P/T) of 0.1 and 0.16 respectively. Percent ratio of P/T with the calculated average weekly dose of the facilities were also evaluated. Results Scattered radiation dose maps exhibited inverse relationship of dose values with distance but not isotropically. The highest values obtained were 191  μ Sv and 152  μ Sv for the two 16-slice CT used for head phantom which were operational for longer periods of time (22.5 s and 29 s respectively). Moreover, dose values of 155  μ Sv for 128-slice (2.9 s) and 112.2  μ Sv for 256-slice (3.37 s) used on abdominal phantom were also rendered as the highest. Percent ratios obtained ranged only from 0.35% to 7.38% thus making the shielding of the facilities adequate. Conclusions The scattered radiation measurements and shielding adequacy calculations conducted have shown that the standard procedure and design goals of the selected facilities are adequate and safe to both radiological personnel and the general public.