Radiological assessment of a new bone densitometer - The Lunar EXPERT

Dual energy X-ray absorptiometry (DXA) is one of the most widely used techniques in the management of osteoporosis and other skeletal diseases. Although patient doses from DXA are generally low, it is still necessary to measure them to assess the risk of radiation injury. We report on a study to estimate the effective dose (ED) to patients and staff from a new DXA scanner-the Lunar EXPERT, and make a comparison with a similar study carried out on a Lunar DPX-L. The entrance surface doses were measured to be 895 mu Gy and 10.25 mu Gy for the EXPERT and DPX-L, respectively. The EXPERT maximum EDs were calculated to be 74.7 mu Sv and 44.9 mu Sv for the anteroposterior (AP) lumbar spine and the proximal femur, respectively. More than 50% reduction in ED could be achieved by using a smaller scanning width. The maximum EDs for the DPX-L were calculated to be 0.21 mu Sv and 0.15 mu Sv for the AP lumbar spine and the proximal femur, respectively. The scattered dose rates (ambient dose equivalent) were measured to be less than 2 and less than 1 mu Sv h(-1) at 50 cm and 100 cm, respectively, for the DPX-L, and the equivalent values for the EXPERT were 240 and 64 mu Sv h(-1). Although both the patient dose and scattered dose rates are quite low relative to other radiological examinations, good practice aimed at dose reduction should still be implemented. Whilst protection for the operator is not needed for the DPX-L system, it may be (depending on the size of the room) for the EXPERT system.