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 diseas es. Although patient doses from DXA are generally low, it is still nec essary to measure them to assess the risk of radiation injury. We repo rt on a study to estimate the effective dose (ED) to patients and staf f 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 dos es were measured to be 895 mu Gy and 10.25 mu Gy for the EXPERT and DP X-L, respectively. The EXPERT maximum EDs were calculated to be 74.7 m u 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 a chieved 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 s pine and the proximal femur, respectively. The scattered dose rates (a mbient 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 th e equivalent values for the EXPERT were 240 and 64 mu Sv h(-1). Althou gh both the patient dose and scattered dose rates are quite low relati ve to other radiological examinations, good practice aimed at dose red uction 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.