Introduction: Osteoporosis is characterized by reduced bone mass, disruption of bone architecture resulting in increased bone fragility and increased fracture risk. As I have not put this sentence in the introduction part below and I havn’t put reference for this, kindly remove this sentence. Osteoporosis is diagnosed when the bone mineral density (BMD) is less than or equal to 2.5 standard deviations below that of a young adult reference population which is translated as a T-score. The most widely used technique for measurement of BMD is dual energy x-ray absorptiometry (DXA) which is non-invasive, rapid, accurate, easy to use and safe. Quantitative Computed Tomography (QCT) has advantages that it provides a true volumetric measurement of bone density and separate measurement of metabolically active trabecular and cortical bone density is possible. Aims and objectives: To determine the BMD in cortical & cancellous bones of lumbar vertebrae using QCT technique in patients ≥50 years of age and to compare the BMD of lumbar spine measured by QCT with DXA. Material and Methods: The present study is crossectional study done in 75 patients of ≥50 years of age at department of Radiodiagnosis and Imaging, BPKIHS, Dharan, Nepal. Informed consent was taken from all patients. Mid vertebral scan of L1-L4 vertebrae along with calibration phantom was done and mean BMD of trabecular, cortical bone and T-score was calculated. The DXA scan was also done in the same patient. DXA scan was analysed and results were obtained in absolute values (g/cm2), in T-score and in Z-score on the basis of WHO defined criteria. The data collected were recorded as per structured Pro forma and entered in the Excel data sheet and SPSS 16 software programme to analyze the data. The collected data was analysed using Chi square test and Pearson correlation coefficient. Results: We studied BMD of 75 subjects by both QCT and DXA. The mean age of our study subjects was 66.72 ± 11.28 (range 50 – 87) years with male: female ratio 0.56:1. The maximum numbers of patients were in age group 60-69 years, Maximum patients were with normal BMI. The mean cortical BMD by QCT was 365.40±74.54 (range 184-532), trabecular BMD was 96.01±39.25 (range 13-213), QCT T-score -3.62 ±1.42 (range -6.2-0.8) and DXA T-score was -2.31 ±1.08 (range -4.5-0.5). We found good correlation between DXA and QCT (r=0.621 and p <0.0001) to differentiate between normal and osteoporotic cases. Conclusion: We concluded that both QCT and DXA can be used to measure BMD and differentiate normal and osteoporotic patients and the difference between the two techniques is not statistically significant.
Ashok Raj Pant1*, RK Rauniyar2, Panna Lal Sah3 and Bikram Prasad Shrestha4 (Sat,) studied this question.