Quantitative perfusion imaging from non-contrast micro-ct for pulmonary embolism evaluation in preclinical models

Objective.Pulmonary embolism (PE) has a high mortality rate, making early diagnosis critical for patient survival. While computed tomography (CT) pulmonary angiography effectively aids diagnosis and embolus localization, patients with iodine allergies and kidney disease experience delayed diagnosis and/or adverse effects. This exploratory preclinical study qualitatively describes PE-induced hemodynamic changes observable in CT perfusion imaging (CT-P), a computationally derived surrogate for perfusion imaging derived from non-contrast four-dimensional CT (4DCT), in a small pilot cohort.Approach. Two laboratory mice were imaged with a micro-4DCT scanner before and after the introduction of a synthetic PE, created using radiopaque alginate beads to enable embolus localization in 4DCT images. CT-P images were computed by segmenting the right and left lungs at the maximum inhale/exhale phase and quantifying the local tissue displacements using deformable image registration. Pre- and post-embolism CT-P heterogeneity was compared as a function of proximity to the embolism in the axial, coronal, and sagittal planes. CT-ventilation (CT-V) images were also computed using the Integrated Jacobian method to investigate co-localized ventilation-perfusion changes.Main results.In this two-animal pilot study, pre- and post-embolism imaging enabled observations not feasible in human studies. CT-P was observed to increase locally at the embolism site but decreased distally within the same lobe. Other lobes within the affected lung showed reduced perfusion, while the contralateral lung showed a compensatory increase mirroring the embolism location. Local perfusion variance near the embolism appeared greater in the unaffected regions. A lobe-wise CT-V/CT-P mismatch of 12.79% and 13.60% was observed pre- and post-embolization.Significance.As a hypothesis-generating preclinical study, these results demonstrate the methodological potential of CT-P to capture embolism-associated hemodynamic changes, motivating future studies with larger sample sizes.