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

Abstract

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.

3D Dental Subsurface Imaging Using Enhanced Truncated Correlation-Photothermal Coherence Tomography

“…Building on the high sensitivity of 808 nm TPLI to dental caries, we present here the first application of the recently developed enhanced Truncated Correlation-Photothermal Coherence Tomography (eTC-PCT) 26 thermophotonics-based 3D imaging technology to dental imaging. This technology is an evolution of the original TC-PCT method 27 , which has been shown to be capable of monitoring bone mineral loss 28,29 . The eTC-PCT modality has enabled significantly higher depth-profiling capabilities with industrial materials 26,30,31 compared to the original TC-PCT and to today’s state-of-the-art dynamic photothermal imaging technologies, namely lock-in thermography and photothermal radar.…”

Matched-Filter Thermography

“…A significant breakthrough was achieved in the field by Tabatabaei and Mandelis' introduction of thermal coherence tomography (TCT) [22,26], which used the binary phase coding pulse compression technique (i.e., a narrow-band phase encoding technique) to optimize the thermal-waves' matched-filter responses in order to resolve overlaying absorbers in a diffusive field. Application of matched-filtering in a thermography system using pulsed excitation was first demonstrated by Kaiplavil and Mandelis [40] in 2011 and was later optimized to yield a highly depth-resolved thermal-wave tomographic imaging modality, termed truncated-correlation photothermal coherence tomography (TC-PCT) [41][42][43][44]. Some other fundamental advancements in the field of TWR include: incorporation of Barker [45] and Golay [46,47] code pulse compression techniques and performance optimization using spectral shaping [48].…”

Pulsed inductive thermal wave radar (PI-TWR) using cross correlation matched filtering in eddy current thermography

“…Mulaveesala highlights the Hilbert transform-based time domain phase analysis scheme introduced for testing and evaluation of sub-surface defects in a mild steel sample [30]. Also, Mandelis et al proposed truncated-correlation photothermal coherence tomography (TC-PCT) based on Hilbert transform and matched-filtering, which enabled three-dimensional visualization of subsurface features [31][32][33]. However, the variable eddy current excitation signals and advanced radar processing methods have not been used in eddy current thermography to solve the discrepancy between dynamic range and depth resolution or to improve the defect detectability.…”