Comparison Study of a-Se/CMOS Detector and Commercial Alternatives for High-Resolution X-Ray Imaging of Soil Structure

Abstract

Computed tomography (CT) serves as a noninvasive technique for pinpointing specific areas within objects, facilitating the examination of soil distributions and localized flow processes within soil pore networks. CT scanning yields cross-sectional sequences that unveil insights into the internal structure of pore networks, which is crucial for understanding root–soil interactions. In this investigation, we explore the potential of employing a high-resolution amorphous selenium (a-Se) direct conversion detector coupled with complementary metal–oxide–semiconductor (CMOS) readouts for micro-CT scanning of soil matrices. This approach aims to visualize the aggregation status and pore network connectivity within intact soil. In addition, we compare the capabilities of the a-Se/CMOS detector with other commercially available detectors evaluating performance in terms of spatial resolution, noise levels, and overall imaging quality. The integration of a-Se’s intrinsic high spatial resolution with small-pixel CMOS readouts enables detailed visualization of soil aggregates in plant samples. By varying X-ray energy and soil thickness, we achieved a spatial resolution of $\leq$ 25 $\mu$m and a noise-limited performance of eight photons/pixel at 20 keV. Although thick soil presents challenges due to high X-ray attenuation, finer details are discernible in thinner samples, underscoring the importance of careful selection of soil thickness and container material.