Ultraviolet germicidal irradiation of the inner bore of a CT gantry

Mahesh, Mahadevappa; Siewerdsen, Jeffrey H.

PURPOSE: To investigate the feasibility and practicality of ultraviolet (UV) germicidal irradiation of the inner bore of a computed tomography (CT) gantry as a means of viral decontamination. METHOD: A UV lamp (PADNUT 38 W, 253 nm UV‐C light tube) and UV‐C dosimeter (GENERAL UV‐C Digital Light Meter No. UV512C) were used to measure irradiance throughout the inner bore of a CT scanner gantry. Irradiance (units μW/cm(2)) was related to the time required to achieve 6‐log viral kill (10(−6) survival fraction). RESULTS: A warm‐up time of ~120 s was required for the lamp to reach stable irradiance. Irradiance at the scan plane (z = 0 cm) of the CT scanner was 580.9 μW/cm(2), reducing to ~350 μW/cm(2) at z = ±20 cm toward the front or back of the gantry. The angular distribution of irradiation was uniform within 10% coefficient of variation. A conservative estimate suggests at least 6‐log kill (survival fraction ≤ 10(−6)) of viral RNA within ±20 cm of the scan plane with an irradiation time of 120 s from cold start. More conservatively, running the lamp for 180 s (3 min) or 300 s (5 min) from cold start is estimated to yield survival fraction <<10(−7) survival fraction within ±20 cm of the scan plane. CONCLUSION: Ultraviolet irradiation of the inner bore of the CT gantry can be achieved with a simple UV‐C lamp attached to the CT couch. Such practice could augment manual wipe‐down procedures, improve safety for CT technologists or housekeeping staff, and could potentially reduce turnover time between scanning sessions.