Dual-energy X-ray absorptiometry for histologic bone sections.

Abstract

In fundamental osteoporosis research precise and accurate assessment of the mineral quantity in histological bone sections is of particular importance when studying the local effects of implants releasing bone modulating agents. A potentially useful technique to estimate the bone mineral density (BMD) is dual-energy X-ray absorptiometry (DXA). A highly collimated (0.13 mm) Hologic 2000 with a line spacing and point resolution of 0.13 mm was used. The mineral content was measured in regions of 3.1 mm(2). A ceramic hydroxyapatite (CHA) phantom was developed as a reference standard. The phantom was made of a single-phase hydroxyapatite starting powder by compressing and sintering at 1000 degrees Celsius. The true density was 3.14 + or - 0.001 g/cm(3). The calcium/phosphorus ratio was close to the theoretical one of 1.67. The mean precision error expressed as the coefficient of variation (CV) of the mineral density (MD) measurements of the phantoms with thicknesses of 1, 2, and 3 mm was 0.2%. Embedded undecalcified alveolar bone sections of dogs (0.0015-1 mm in thickness) were scanned simultaneously with a phantom 1 mm in thickness. The precision error (CV) of the BMD measurements calculated by DXA for sections > or = 0.1 mm and with a BMD > or = 0.14 g/cm(2) was 0.81%. There was a linear relationship between the BMD calculated by DXA and the estimated BMD in the histological bone sections by means of the true density of the phantom. It is concluded that DXA using a standard CHA phantom is a precise and accurate method to measure MD changes as small as 1% in histological bone areas of 3.1 mm(2) provided that the loss or gain in BMD is > or = 0.14 g/cm(2).