The use of clinical CT for baseline bone density assessment

Many patients having an abnormal initial bone densitometry study have had a previous abdominal/pelvic computed tomography (CT) for other clinical reasons. This study evaluates if a nondedicated quantitative CT (QCT) abdominal/pelvic CT scan could be used as reliable baseline data for subsequent dedicated bone density studies.

Twenty-six patients (13 men, 13 women) undergoing clinically-indicated non-i.v. and i.v. contrast abdominal/pelvic CT had dedicated QCT performed immediately following scans of the L1, L2, and L3 vertebral bodies. QCT was then performed on all three scans. A repeated measures analysis of variance model was used to analyze the data in order to compare noncontrast clinical CT with QCT and noncontrast clinical with contrast clinical CT.

The mean bone mineral density for the noncontrast clinical study was 98.51 (mg/cc) versus 90.56 (mg/cc) for QCT (p = 0.0003; 95% confidence interval: 3.90 to 13.71). There was no significant difference (p = 0.085) between QCT performed from non-i.v. and i.v. contrast clinical CT scans.

Bone densitometry can be performed from either non-i.v. or i.v. contrast clinical CT scans if a conversion factor is applied. This can be determined by utilizing a formula Daverage = -7.83 + (0.99 x NCaverage), where Daverage and NCaverage are the abbreviations of "dedicated" and "noncontrast clinical" BMD averaged over vertebral bodies L1-L3, respectively.