Compare Densitometers

The GS-800™ calibrated densitometer, Mac, 100-240 V, is used for protein and nucleic acid densitometric imaging applications. The densitometer features automated calibration, scanning white light 400-750 nm illumination, dynamic range from 0 to 0.3 OD, a 30 x 40 cm imaging platen, 12-bit data collection, and resolution down to 36.3 micrometers. This system includes Quantity 1 software for Macintosh. Dimensions: 62.6 x 47.3 x 19.3 cm.
In clinical practice, decisions must be made about how to convert to new technologies. To address the issue,  2separate studies were conducted. They evaluated the relationship between results of lumbar spine measurements using 2 dual photon absorptiometry  instruments and one dual energy X-ray  instrument with the same subjects (47 volunteers), and also in 55 patients who were measured on the DPA1 and DXA machines. Second, they measured the lumbar spine and the proximal femur in 3 groups of  twelve  female volunteers 3 tmes on one instrument within 1 week. They purposely simulated a busy clinic setting with different technologists, older radioactive sources, and a heterogeneous patient group. The comparison study indicated a significant difference between the mean bone density values reported by the machines, however the results were highly correlated (R ² = 0.89–0.96). The short-term precision errors (coefficients of variation) differed among the instruments, ranging from 1.3% (DXA of the spine) to 5.1% (DPA1 of the spine), and in the femoral neck, 2.3% and 2.4% (DXA and DPA1, respectively) versus 3.5% by DPA2. This study emphasizes the differences between instruments, the potential for greater error in busy clinic environments, and the apparent superiority of dual energy X-ray absorptiometry under these less than ideal conditions.