This is a set of precision scans acquired on the same day. On the top,  BMD = 0.790 g/sq cm and T = -1.0 in the Radius 33%. On the bottom, BMD = 0.693 g/sq cm,  T = -2.1 in the Radius 33%. The images appear to be well acquired. Observe the white oval in the upper left corner of the image on the left. This is air from the slot in the forearm positioner.

The point typing image indicates that the identification of bone is identical between both scans. Tissue point-typing demonstrates the problem, not only the patient’s arm, but the board are being measured as the soft tissue baseline. These different measurements in the respective BMD calculations result in the BMD difference observed from the reports.

Given the difference in densities between the positioner slot and the positioner, the software identified just the slot as air on the left. The scan on the right had consistent density outside the arm, consequently, that entire region was classified as air. This slot artifact only occurs when the slot covers the entire width of the first swipes at the very beginning or end. The recommendation is to always check the point-typing of forearm scans.