Gadolinium oxide nanoparticles as a multimodal contrast enhancement agent for pre-clinical proton imaging

Orthotopic tumor models in pre-clinical translational research require accurate tumor localization for effective irradiation, which is challenging due to limited tissue contrast in x-ray and proton computed tomography (xCT and pCT). This study investigates gadolinium oxide nanoparticles as a multimodal contrast agent for these imaging modalities. Proton radiographies were conducted using MiniPIX-Timepix detectors with gadolinium oxide dispersions. Simulations of pCT imaging were performed using a Monte Carlo framework with varied nanoparticle concentrations. CBCT imaging was also evaluated using a PMMA phantom. The study found significant contrast enhancement in proton radiography at 4wt% and detectability in pCT at similar levels, while xCT achieved detectability at just 0.5wt%. The findings highlight the feasibility of gadolinium oxide for enhancing proton imaging contrast, although achieving sufficient in-vivo concentrations poses a challenge. Targeting or injection strategies could address this limitation, and advanced pCT techniques like scattering pCT and PIXE may further improve tumor localization.

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