Noninvasive imaging of small living insects using high-speed phase-contrast CT

Noninvasive visualization of intact, living insects marks an important methodological advance for research in entomology, ecology, and environmental science. In this study, we investigated the safety and imaging efficacy of high-speed phase-contrast CT (PCCT) for visualizing living Trichorhina tomentosa (TT). TT is a widely distributed group of small insect organisms in natural environments. Using TT as a model organism for live imaging studies holds broad biological significance, as it offers valuable real-time insights into fundamental entomological functions, species-specific ecological adaptations, and organism-environment interactions under realistic conditions. A high-speed PCCT system that integrated a fast-acquisition detector, a rapid-rotation sample stage, and a quick-action shutter was employed. The image acquisition speed of the detector was set to 2400 fps, and the sample stage rotated at a speed of 720°/s. The shutter operated with high efficiency, achieving full opening or closing in 3 ms. Each CT scan, which consisted of 600 projections of TT, was completed in 250 ms, covering a 180° rotation. Initial projection data underwent phase retrieval (PR) via the phase-attenuation duality method to extract quantitative phase information. Tissue visibility was quantitatively assessed using the signal-to-noise ratio (SNR). The absorbed irradiation dose (AID) in one CT scan ranged from 371 to 380 mGy. The TT specimens remained viable and in good condition throughout a week of post-imaging monitoring, underscoring both the high safety profile and physiological compatibility of the PCCT system. The anatomical structures of the TT body were clearly visualized, allowing for reliable dimensional measurements. Our findings demonstrate that the high-speed PCCT system holds considerable potential for the noninvasive in vivo visualization of small living insects possessing radiation tolerance that meets or exceeds currently applied dose levels.