Empirical quantification of bone mineral and organic phase attenuation coefficients using CT imaging and controlled thermal processing.

Abstract

Accurate quantification of bone mineral, organic, and water phases is critical for evaluating bone quality, assessing fracture risk, and diagnosing skeletal diseases. Dual-energy computed tomography (DECT) holds promise for decomposing these phases but fundamentally relies on precise linear attenuation coefficients (LACs) for each phase. Existing surrogate-based imaging methods-typically assuming fixed phase attenuation coefficients-fail to reflect the compositional heterogeneity of native bone, leading to systematic errors in decomposition. This study presents a novel empirical framework for determining the average LACs of bone mineral and organic phases using 28 standardized cylindrical bovine bone specimens. The method integrates high-resolution CT imaging with a controlled drying-ashing protocol to isolate phase-specific masses and volumes. In conjunction with a linear mixture attenuation model, specimen-wise average LACs for the bone, mineral, and organic phases were characterized at selected energy levels. Results showed the following: 1) Average LACs had wide variability across the specimens, e.g., ranging from 1.16 to 2.38 cm^-1 for mineral phase and 0.004-0.085 cm^-1 for organic phase at 45 kV, highlighting the limitations of using fixed surrogate-based values. 2) Bone density correlated more strongly with organic density than with mineral density, emphasizing the importance of accurately quantifying the organic phase for bone quality and health assessment. 3) Bone LACs were strongly correlated with mineral LACs but not with organic LACs, underscoring the inability of single-energy CT to capture meaningful information from the organic phase. The proposed empirical framework demonstrates the feasibility of characterizing phase-specific LACs in real bone tissue and may support physiologically accurate DECT modeling, advancing personalized, composition-based bone diagnostics.