35-19 X-ray Phantom for Micro-CT Analysis of Frozen Sediments

Session: Ice sheets, glaciers, and landscapes, oh my! (Posters)

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Abstract:

Thanks to recent developments in micro-computed tomography (micro-CT), it has gained popularity in characterizing mineral inclusions and sedimentary structures in ice cores, permafrost and subglacial materials. However, grain-scale quantitative analysis is complicated by micro-scale effects on X-ray attenuation reflected in reconstructed images. Within a single scan, compositional heterogeneity and geometrical variability leads to attenuation artifacts, such as edge effects and beam hardening and overlapping attenuation domains. In addition, quantitative attempts across scans are highly dependent on CT calibration and homogeneity of the sample pool. CT phantoms are used routinely in the medical field to quantitatively extract information from whole-body scans for quality control and accuracy in diagnosis. This project aims to develop and analyze CT phantoms containing known mineral phases to evaluate micro-CT calibration, segmentation methodology, and mineral composition identification within and across scans. Cylindrical epoxy phantoms, mimicking sediment-laden ice cores, were constructed with 9 materials spanning a range of X-ray attenuation coefficients: apatite, anorthite, calcite, quartz, halite, organic matter, Styrofoam, epoxy and air bubbles. Materials were inserted into a 0.8 cm diameter cylindrical tube with Styrofoam mesh to introduce pore space, characteristic of frozen sediment. We scanned three phantoms using micro-CT (Bruker SkyScan 1173) and assessed their quality using histogram-based thresholding, edge detection, and segmentation analysis. Our evaluation of artifacts in the scans indicates that attenuation overlap dominates small-scale grain edges, causing saturation and bleeding across boundaries. Therefore, small size, low attenuation minerals like quartz become indistinguishable from the ice/epoxy matrix, and higher attenuation minerals like apatite lose edge resolution that complicates grain boundary and shape identification. These results highlight the challenges of quantitative analysis for micro-CT analysis of ice cores. To date, our research shows the importance of 1. Closely matching the range of attenuation coefficients between the study sample and phantom, 2. Ensuring sufficient porosity for edge detection, 3. Optimizing beam characteristics using the phantom. This highlights the significance to develop environment-specific phantoms.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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