Radiology: Volume 257: Number 2-November 2010
Matthew J. Budoff, MD Yasmin S. Hamirani, MD Yanlin L. Gao, MD Hussain Ismaeel, MD Ferdinand R. Flores, BS Janis Child, BS Sivi Carson, BS James N. Nee, BS Songshou Mao, BS
Purpose: To create standard thoracic bone mineral density (BMD) values for patients undergoing cardiac computed tomogra¬phy (CT) by using thoracic quantitative CT and to compare these BMDs (in a subpopulation) with those obtained by using lumbar spine quantitative CT.
Materials and methods: The institutional review board approved this HIPAA-compliant study. A total of 9585 asymptomatic subjects (mean age, 56 years; age range, 30-90 years) who underwent coronary artery calcium scanning, including 4131 women, were examined. Patients with vertebral deformities or fractures were excluded. Six hundred forty-four subjects (322 of whom were female) also underwent lumbar quantitative CT. The mean thoracic vertebral BMDs for both sexes were reported separately in a subgroup of subjects aged 30 years and in 29 age-based subgroups in 2-year intervals from ages 30 to 90 years. The formulas used to calculate the female T score (Tf) and the male T score (Tm) on the basis of thoracic quantitative CT measurements were as follows: Tf = (BMDim - 222)/36, and Tm = (BMDim - 215)/33, where BMDim is the individual mean BMD. Comparisons between thoracic quantitative CT and lumbar quantitative CT mea¬surements, as well as analyses of intraobserver, interob¬server, and interscan variability, were performed.
Results: The young-subgroup mean BMD was 221.9 mg/mL ± 36.2 (standard deviation) for the female subjects and 215.2 mg/mL ± 33.2 for the male subjects. The mean thoracic BMDs for the female and male subjects were found to be 20.7% higher and 17.0% higher, respectively, than the values measured with lumbar quantitative CT (P < .001 for both comparisons). A significant positive association between the thoracic and lumbar quantita¬tive CT measurements (r > 0.85, P < .001) was found. Intraobserver, interobserver, and interscan variabilities in thoracic quantitative CT measurements were 2.5%, 2.6%, and 2.8%, respectively.
Conclusion: There was a significant association between the mean thoracic and lumbar BMDs. Therefore, standard derived measurements (young-subgroup BMD ± standard deviation) based on these data can be used with thoracic CT images to estimate the bone mineral status.