Background: Bone mineral density scan (BMD) is a simple, non-invasive procedure used to assess the strength of the bones by measuring the composition of minerals mainly calcium in the bones. In this study, BMD was measured using Quantitative Computed Tomography (QCT) and Hounsfield unit (HU) in the lumbar spine and the values were correlated.
Methods: 240 participants referred for CT Abdomen and CT Lumbar spine were scanned using 64 slice Brilliance CT. Using BMD software, three different vertebral bodies from L1-L3 were taken and ROI was placed at the central portion of the trabecular bone. Two references ROI one in retro spinal muscle and one in fat tissue was also placed. To measure CT attenuation value an ROI graphic tool was drawn at the trabecular bone. The average of BMD in QCT and HU value was taken from L1-L3. Pearson Correlation Coefficient was used to correlate QCT and HU values.
Results: The mean BMD for the 21-40 age group was found to be 156.3 and 228.0 for QCT and HU respectively. Similarly, the mean BMD for 41-60 and 61-80 age groups was found to be 125.5, 173.6 and 109.1, 140.4 for QCT and HU respectively. The results showed a strong positive correlation between QCT and HU BMD (r = 0.94) with a p-value less than 0.001.
Discussion: In our present study, 64.53% (n=155) were found to have normal BMD based on the WHO diagnostic category for spine BMD in QCT. Whereas 24.58% were found to have a low bone mass (osteopenia) and 10.83% were found to have osteoporosis. The equivalent mean HU was found to be 211.98 ±31.06, 139.64 ±18.58, 87.22 ±15.92 for normal, osteopenia and osteoporosis respectively.
Conclusion: The study shows a strong correlation between QCT BMD with HU. Therefore, the CT attenuation technique can also be used to derive bone mineral density values from routine abdomen and lumbar spine MDCT for osteoporosis screening with no additional cost to the patient