Evaluation and Designation of Controlled and Supervised areas

Abstract

In surgical theatres, portable C‐arm fluoroscopy equipment is used to provide real-time X- ray guidance to assist staff performing various procedures. Many hospital workers are exposed to some level of ionising radiation while performing or assisting with these routine patient procedures. Many studies have been published regarding the radiation exposure of surgeons or assistant surgeons due to their proximity to the radiation source in the operating room. However, there is a paucity of published literature on the exposure levels for staff who stand two or more metres away from the X-ray source. This study aims to evaluate the extent of the required controlled and supervised areas for orthopaedic surgical procedures in University Hospital Galway (UHG). This will be based on the typical workload for these procedures in UHG, with the dose rate at various points from the isocentre either measured or calculated using the inverse square law. The scatter radiations from a PMMA phantom when exposed to X-rays were measured at various locations and heights around a Ziehm Solo and GE OEC 9800 C-arm for different projections. A Fluke 451P survey meter was used to measure the scattered radiation expected in an operating theatre during surgery, with the relevant parameters for each set of measurements recorded. The results indicated that the scattered radiation exposure is reduced by increasing the distance between the patient and staff. The results also showed that at 1.5 metres from the Ziehm Solo C-arm with the tube over the table, the dose rates, when combined with the UHG workload, would allow it to be designated as a controlled area. Within this area, lead aprons and thyroid shields are to be worn by staff. For the same equipment with the tube under the table and for the GE OEC 9800 with the tube over the table, at 1.5 metres and greater from the isocentre, the scattered dose received was sufficiently low to designate this as a supervised area. In practice, the advice to wear lead protective aprons once inside the theatre doors would still be required to ensure optimal radiation protection and ensure staff doses are kept ALARA. However, due to the low levels of scattered radiation at the periphery of the theatre, an occasional urgent and necessary short visit by an unprotected staff member to the newly designated supervised areas during a procedure would not be a cause of concern from a radiation protection perspective or necessitate an incident investigation.