Effects of patient size, geometry, and simulated aortic calcification and bowel gas on quantitative CT bone mineral determination

The authors investigate the impact of changes in patient size and geometry and simulated bowel gas and aortic calcification on quantitative computed tomographic (CT) findings. Multiple scans of the CIRS torso phantom in three size configurations showed that mean bone mineral determinations (BMD), did not significantly vary with phantom size. Variations in patient cross-sectional geometry at constant volume were assessed with use of a custom-manufactured body phantom constructed with three elliptical ratios: 1:1 (round), 1.3:1, and 1.6:1 (flattened ellipse). Measured BMD values of a 50 mg/cm2 mineral plug decreased significantly (59.0, 58.1, 57.0 mg/cm2) with increasing elliptical ratio. Bowel gas was simulated by drilling various holes into the body phantom. No significant differences in BMD were noted. A simulated aortic calcification similarly caused no significant difference. The authors' results indicate that quantitative CT is relatively insensitive to changes in cross-sectional size, aortic calcification, and bowel gas, whereas changes in patient geometry have a slight effect