Phototherapy irradiation cabinets normally rely on one timer or dose meter in order to control the ultraviolet (UV) exposure of patients. Faults may occur in the electronic control, or the operator may set the prescribed dose incorrectly. If this happens, a patient will receive an exposure different from that intended, which in the case of overexposure may result in severe burning resulting in hospitalisation.
Some phototherapy equipment has secondary devices (e.g. mechanical timer) for controlling the dose in case the primary system fails. We have designed and built a secondary dose meter that sounds an alarm if an overdose is about to occur. The unique feature of our device is that it measures the irradiance level within the cabinet and uses this value in combination with the dose set by the operator, to calculate the alarm time. Using the measured irradiance value in this manner ensures that the calculated exposure time compensates for variations in UV output as the lamps age.
Allan W, Diffey BL. A device for minimising the risk of overexposure of patients undergoing phototherapy. Photodermatology, Photoimmunology & Photomedicine 2002; 18: 199-201.
Bill Allan, Sunderland Unit, Sunderland. Tel: +44 (0)191-569-9035.
Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, NE4 6BE, UK.
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