Anatomical Factors Affecting DXA Scan Measurement of Bone Mineral Density in Lumber Spine

Abstract

Background: Dual-energy X-ray absorptiometry scan is used to measure bone mineral density. Correct measurements greatly depend on accurate selection of targeted anatomical areas of bone. Various anatomical factors including anatomical knowledge can be a potential source of error; they can falsely increase or decrease measured bone mineral density. Technician ability to recognize these factors is critical for accurate scan analysis. The aim of study was to demonstrate the prevalence of different anatomical factors affecting Dual-energy X-ray absorptiometry scan results and to analyze how they affect final clinical decision.Method: Using systematic random selection, Dual-energy X-ray absorptiometry records of lumbar spine for 50 patients were divided into two categories;the first was normal and affected by anatomical factor. The second category was divided into five groups (A1 -A5) containing a spectrum of anatomical factors that may influence bone mineral density measurements. Reports analyzed using measurements of bone mineral density, T/Z-scores from WHO based OPC. A1 and A4 were not analyzed further. A2, A3, and A5 reports were recalculated using anatomical landmarks.Results: Data from current study showed that anatomical factors affecting bone mineral density were prevalent (72%). A1 included 14 cases (28%), A2 included 8 cases (16%), A3 included 8 cases (16%), A4 and A5 included 3 cases (6%) for each. Group A2 showed a significant increase in bone mineral density. T/Z-scores (mean±SD) after reselection of ROI, were 0.44±0.19. OPC changed in three cases from A2, 3, and 5 when T/Z-score was border-line. Conclusion:Optimal DXA reports require well-trained technicians and expert clinicians who can recognize diverse anatomical factors influencing results. Effects of AF can be reduced by initiating or improving training programs of involved persons. Further studies are recommended to explore the extent to which each group of anatomical factors affects T/Z-scores.