BMD measurements of the spine derived from sagittal reformations of contrast-enhanced MDCT without dedicated software

Abstract

Purpose: To assess QCT equivalent BMD of the lumbar spine in sagittal reformations of routine abdominal contrast-enhanced MDCT with simple PACS measurement tools and to apply this method to MDCT datasets for differentiating patients with and without osteoporotic vertebral fractures.

Materials and methods: Eight postmenopausal women (65±5 years) underwent standard QCT to assess BMD of L1-L3. Afterwards routine abdominal contrast-enhanced MDCT images of these women were obtained and apparent BMD of L1-L3 was measured using the sagittal reformations. The MDCT-to-QCT conversion equation for BMD was calculated with linear regression analysis. The conversion equation was applied to vertebral BMD datasets (L1-L3) of 75 postmenopausal women (66±4 years). Seventeen of the 75 patients had osteoporotic vertebral fractures.

Results: BMD values of contrast-enhanced MDCT were on average 56 mg/ml higher than those of standard QCT. A correlation coefficient of r=0.94 (p<0.05) was calculated for the BMD values of MDCT and standard QCT with the conversion equation BMDQCT=0.69×BMDMDCT-11 mg/ml. Accordingly converted BMD values of patients with vertebral fractures were significantly lower than those of patients without vertebral fractures (69 mg/ml vs. 85 mg/ml; p<0.05). Using ROC analysis to differentiate patients with and without vertebral fractures, AUC=0.72 was obtained for converted BMD values (p<0.05). Short- and long-term reproducibility errors for BMD measurements in the sagittal reformations amounted 2.09% and 7.70%, respectively.

Conclusion: BMD measurements of the spine could be computed in sagittal reformations of routine abdominal contrast-enhanced MDCT with minimal technical and time effort. Using the conversion equation, the acquired BMD data could differentiate patients with and without osteoporotic vertebral fractures.