Scanning Posture Of Sitting And Supine Dxa Measurement Study Of The Impact Of Bilateral Forearm Bone Density Results

ObjectiveTo analyze the quality control of the dual energy X-ray absorptiometry(DXA) in our center.Material and resultsThe DXA scanner was GE Lunar Prodigy. In eachday clinical practice, a phantom scan was performed and passed, the results were entered into the QC software package of the DXA scanner; GE Lunar aluminum spine phantom was scanned also everyday, then the Shewhart charts was used to monitor the machine's stability. The same operator scanned and analysed the data.ResultsThe QA test was completed everyday before the patient's BMD was scanned by the machine during the study period. From January7,2010to November12,2010, BMDs and the fat results of the QA phantom were closed to the base line. The same results were in the normal tissue and lean results.From November1,2009to November12,2010, the average BMD of GE-Lunar spine phantom was1.196g/cm2, there was no significant drift or shift in calibration during the study period.ConclusionThe performance of DXA quality control in our center was well established and appropriate. Purpose:To evaluate the BMD measurement precision of the bilateral forearm obtained by DXA in both the sitting and supine positions, and to compare whether there were differences at BMD, BMC and Area of the bilateral forearm, at the same time to determine the association between BMD of bilateral forearms and that of the spine and femur, respectively. Subjects and methods:BMD of30right-handed healthy Chinese volunteers was measured with GE Lunar Prodigy at the bilateral forearms in both sitting and supine positions as well as at lumbar spine and the right femur. All subjects received repeated measurements in the same day (re-positioning), and the average of repeated BMD results was used for analysis.Results:(1) The BMD precision errors of the bilateral forearm in the sitting and supine positions varied from0.99%to2.55%, the BMC precision errors varied from1.44-2.11%, and the Area precision varied from1.15-2.73%;(2) The BMD and BMC values were higher in dominance forearm, no matter in sitting or in supine position (p<0.05). There were no differences between the Area in the dominance and non-dominant forearms in the both two positions;(3) There were significant differences at both the1/3radius level and in the total radius between forearm BMD on the same side in the sitting position and those in the supine position (p<0.05). The BMD values obtained in the supine position were lower than those in the routine sitting position. There were significant differences at both the1/3radius level and in the total radius between forearm BMC on the same side in the sitting position and those in the supine position (p<0.05). The BMC values obtained in the supine position were lower than those in the routine sitting position. There were no differences between the Area in the same side of the two positions;(4) The bilateral forearm BMDs of the ultradistal (UD) radius in the both two different scanning positions were significantly associated with lumbar spine\femoral neck\Ward's\Troch\Total BMD, respectively. The total radius and the total forearm BMD in the different positions was associated with the BMD of the femoral neck\Troch\Total.Conclusions:There was left-right difference in bilateral forearms BMDs either in sitting or supine position. A change in body scanning position from sitting to supine will significantly influence foreann BMD results.