Evaluation of Bone Mineral Density using Quantitative Computed Tomography in Pre- and Post-menopausal Women: A Retrospective Cross-sectional Study

Introduction: Osteoporosis is increasingly becoming a public health concern especially in the ageing population. Fractures related to osteoporosis are an important cause for pain and disability. Most common methods used for measuring Bone Mineral Density (BMD) include Dual-energy X-ray Absorptiometry (DXA) and Quantitative Computed Tomography (QCT). There is a substantial increase in the number of patients undergoing a primary Computed Tomography (CT) study of the abdomen for various clinical reasons. Use of QCT for measurement of BMD helps to identify the high risk patients for osteoporotic fractures. This also reduces the need for any additional imaging, radiation exposure, cost or patient time. Aim: To compare the BMD values between pre-menopausal and post-menopausal females using QCT. Materials and Methods: This was a retrospective crosssectional study. A total of 40 patients with 20 patients each in premenopausal and post-menopausal group who had undergone routine abdominal CT for various clinical indications unrelated to bone disorders were evaluated. Regions of Interest (ROIs) were measured on the axial images at T12 through L5 vertebrae at three locations, one over the trabecular part of vertebrae, one on the posterior paraspinal muscles and the third ROI over the subcutaneous fat. BMD was calculated by using phantom less QCT software of the Philips CT workstation. Both t-score and BMD values were automatically generated by the software. The thresholds for spinal trabecular BMD were <120 mg/cc for osteopenia (equivalent to a DXA T-score of -1.0 SD) and <80 mg/cc for osteoporosis (equivalent to a DXA T-score of -2.5 SD). Descriptive statistics were used to describe clinical demographics using range, means and Standard Deviation (mean±SD). Student’s t-test was used to analyse comparisons between the study groups. Results: For pre-menopausal women (n=20) in the age group of 30-45 years, the mean BMD observed was 157.01±27.36 mg/cc. For post-menopausal women (n=20) in the age group of >45 years, the mean BMD observed was 129.77±48.92 mg/cc. The mean t-score values for pre-menopausal and post-menopausal women were -0.67±0.88 and -1.57±1.58, respectively. Comparison of t-score (p<0.05) and BMD (p