Quantitative computed tomography of spine: comparison of three-dimensional and two-dimensional imaging approaches in clinical practice.

Abstract

Quantitative computed tomography (QCT), a widely utilized technique for determining bone mineral density (BMD) at various skeletal sites, may yield less precise measurements if there are operator measurement errors and other technical variables. Two-dimensional (2D)and three-dimensional (3D)QCT scans of the lumbar spine of 21 women were compared in order to investigate the effects of potential operator variability on the precision of BMD measurements and to examine resulting differences of these imaging approaches in clinical practice. No significant difference was found (p > 0.05) in precision between the 2D and 3D QCT BMD measurements owing to operator measurement errors on the CT scans. The variability in BMD values within numerous small regions of interest (ROIs)( approximately 75 mm (2) ) of cancellous bone within a single vertebra was 10.1%, larger than the 2D or 3D BMD variability measured in typical regions ( approximately 250 mm (2)) by an order of magnitude. 3D BMD values in this population, which represented a wide range of clinical values, were found to be significantly greater than 2D BMD values by an average of 5.6% (p = 0.00024) relative to the 2D QCT values. Our findings suggest technical measurement error does not have a significant effect on precision of BMD measurements obtained with either QCT method. Several factors, however, including the incorporation of focal regions of higher density bone mass within the 3D QCT ROI may account for the higher BMD values compared with those for 2D QCT.