PRECISION AND ACCURACY OF COMPUTED DIGITAL ABSORPTIOMETRY FOR ASSESSMENT OF BONE-DENSITY OF THE HAND

Widespread osteoporosis testing and diagnosis are currently limited du e to the high capital cost and reduced portability of many existing bo ne densitometry techniques. In this study we evaluated an inexpensive, low radiation, X-ray-based technique for assessing bone density of th e middle phalanx. The technique, termed computed digital absorptiometr y (CDA), is similar to radiographic absorptiometry (RA), using a singl e-energy X-ray source, an aluminum alloy step-wedge, and a charge-coup led device (CCD) detector system to automatically compute bone mineral content (BMC, g) and bone mineral density (BMD, g/cm(2)) in the middl e phalanx of the third finger. The potential advantage of CDA over cur rent RA techniques is that by using a filmless detector system, no off -site processing of radiographs is required and bone density results a re obtained immediately after the test. Using human cadaveric specimen s we determined the accuracy and short-term precision of CDA as well a s its correlation with other hand and forearm bone densitometry method s. We obtained 26 cadaveric forearms (50% female, mean age 78 years, r ange 52-96 years). BMC and BMD of the middle phalanx of the third fing er were determined using CDA and using RA. We assessed forearm BMC and BMD using single-energy and dual-energy X-ray absorptiometry (SXA and DXA). Precision of CDA was assessed by measuring ten of the specimens five times each with repositioning between measurements. Finally, the middle phalanx was dissected and incinerated to determine ash weight. BMC estimates from CDA and from RA were strongly correlated with ash weight (r = 0.89), p < 0.001 and r = 0.93, p < 0.001, respectively). T he mean coefficients of variation using CDA were 1.36% and 0.70% for p halanx BMC and BMD, respectively. BMC and BMD measured by CDA were str ongly correlated with hand and forearm bone mineral measurements perfo rmed by SXA, DXA and RA (r = 0.74-0.91). These results indicate that C DA accurately and precisely predicts BMC of the middle phalanx. Thus, with further clinical verification, this technique may prove to be a u seful tool for the widespread testing and assessment of osteoporotic f racture risk.