Design of fixed and mobile PET/CT facilities - the similarities and the challenges

Design of PET/CT facilities present particular challenges for Radiation Protection. The high energy gamma ray emitted from the radionuclides used, the prolonged uptake period with patients within the facility and the relatively high dose rates from those patients result in some shielding being required and a careful consideration of the layout within each unit. This paper will present the approach used for the design of a fixed facility and will present staff dose data demonstrating that the design has resulted in low staff doses. The approach used to design mobile facilities will then be described, and a consideration of the doses received on this type of unit will also be given. The fixed facility was installed into a wooden clad building and was extremely small. The building was shared with other non radiation workers. Walls were constructed from dense concrete blocks and the layout arranged to prevent a direct line of site between the patient and workers at any point apart from the scan room where a lead glass window was used. For the mobile facility lead was used as the shielding material. The basic approach was to maximise the distance between operators and resting patients. Because of weight restrictions and limitation on the dose rate at the scanner defined by the scanner manufacturer, a higher dose constraint had to be adopted for staff on the unit. Additional complications include the mobility of the unit which can be parked adjacent to buildings with a variety of construction materials. Results of whole body monitoring for staff in the fixed facility over 5 years will be presented with the results from the mobile units over the last year. These will demonstrate the difficulties in keeping doses as low as reasonably achievable in the mobile scenario and the importance of designing the facility with staff dose in mind from the outset. (author)