Development of anatomically variable digital Wistar rat phantoms for small animal imaging research.

BACKGROUND: Digital phantoms are valuable tools for evaluating small animal imaging systems. They can help optimize imaging parameters before live studies, supporting efforts to reduce animal use and refine experimental protocols. Wistar rats are widely used in preclinical imaging research due to their well-characterized biology and relevance to human disease. PURPOSE: This study develops a series of anatomically variable digital Wistar rat phantoms to support small animal imaging research. METHODS: We constructed 10 computational Wistar rat phantoms (six males, four females) with weights ranging from 188 to 474 g using high-resolution (200 µm) co-registered micro-CT and MRI data to generate detailed 3D anatomical models. The segmented organs and bones, including 35 distinct anatomical tissues, were fitted with smooth polygon mesh surfaces, ensuring flexibility for modeling motion, anatomical variation, and seamless voxelization at any resolution. To demonstrate the utility of the phantoms, we conducted a photon-counting CT (PCCT) simulation using a 279 g female model. The phantom was voxelized into material maps representing soft tissue, iodine contrast, and bone. Simulated PCCT projections were reconstructed using both analytical and iterative methods to compare image quality and accuracy of material decomposition. RESULTS: Measured body sizes and organ masses confirm that the computational phantoms capture inter-subject anatomical variation. Iterative reconstruction outperformed analytical reconstruction in the PCCT simulation, reducing noise and improving material decomposition accuracy. Root mean square error (RMSE) across the water, iodine, and calcium maps decreased from 0.17 g/mL, 2.07 mg/mL, and 11.49 mg/mL to 0.02, 0.21, and 1.98, respectively. CONCLUSIONS: The resulting anatomically variable digital phantoms will provide a valuable resource for preclinical imaging research, enabling the evaluation of imaging systems, optimization of imaging protocols, and validation of reconstruction algorithms across a representative range of anatomies. The demonstrated PCCT study highlights the potential of these phantoms for advancing virtual pre-clinical imaging trials.

Duke Scholars

Author Alexandra Badea Radiology

Author Cristian Tudorel Badea Radiology

Author G. Allan Johnson Radiology

Author William Paul Segars Radiology