In vitro and in vivo spiral CT to determine bone mineral density: Initial experience in patients at risk for osteoporosis

PURPOSE: To evaluate, both experimentally and in vivo, if nondedicated standard spiral computed tomography (CT) may be used to obtain reliable bone mineral density (BMD) data. MATERIALS AND METHODS: Twenty lumbar spine specimens from human cadavers were examined with standard quantitative CT and spiral CT. In addition, 50 patients with a history of lymphoma and chemotherapy were examined. These patients underwent long-term follow-up CT to rule out tumor recurrence. Quantitative CT was performed before contrast medium administration to assess potential posttherapeutic osteoporosis. In addition, fracture status of the spine was determined. Mean BMD values and SDs were calculated, and relationships between measurements obtained with quantitative CT and spiral CT were assessed with linear regression analysis and two-tailed tests of significance (t test). A linear fit was used to calculate quantitative CT data from spiral CT values. RESULTS: For the specimens, a coefficient of determination (r(2) = 0.99, P < .001) was found between BMD measurements obtained with quantitative CT and those obtained with spiral CT. Mean BMD in specimens was 63.6 mg/mL +/- 36.6 with quantitative CT and 74.4 mg/mL +/- 38.2 with spiral CT. Mean BMD in patients was 105.0 mg/mL +/- 34.6 with quantitative CT and 139.5 mg/mL +/- 42.7 with contrast medium-enhanced spiral CT. A coefficient of determination (r(2) = 0.91, P < .001) was obtained between these measurements. Mean BMD from L1 through L3 vertebrae was calculated, and spiral CT data were multiplied by 0.77 to yield quantitative CT data. Differences in BMD were significant (P < .05) for patients with (n = 9) and those without fractures (n = 41), as determined with spiral CT and quantitative CT. CONCLUSION: Correlations between BMD data obtained with spiral CT and standard quantitative CT were highly significant. By using a conversion factor, BMD measurements can be determined with routine abdominal spiral CT scans. (C) RSNA, 2004.