Truncated-correlation photothermal coherence tomography of artificially demineralized animal bones: Two- and three-dimensional markers for mineral loss monitoring

The challenge of depth-resolved, nonionizing (hybrid-optical) detection of mineral loss in bones is addressed using truncated-correlation photothermal coherence tomography (TC-PCT). This approach has importance not only in ground-based clinical procedures, but also in microgravity space applications. Analogous to x-ray morphometric parameters, two- and three-dimensional markers have been defined and estimated for chemically demineralized goat rib bones. Cortical and trabecular regions have been analyzed independently and together using the computational slicing advantage of TC-PCT, and the results have been verified using micro-CT imaging (the gold standard). For low-demineralization levels, both modalities follow the same trend. However, for very high mineral loss that is unlikely to occur naturally, anomalies exist in both methods. Demineralization tracking has been carried out to a depth of ~3 mm below the irradiated surface. Compared with micro-CT imaging, TC-PCT offers an improved dynamic range, which is a beneficial feature while analyzing highly demineralized bones. Also, TC-PCT parameters are found to be more sensitive to trabecular and combined cortical-trabecular demineralization compared with x-ray parameters. Axial and lateral resolutions in bone imaging for the current instrumental configuration are ~25 and 100 μm, respectively.