Multiscale dual energy micro-CT for imaging using iodinated and gold nanoparticles

Abstract

Dual energy (DE) micro-CT shows great potential to provide accurate tissue composition by utilizing the energy dependence of x-ray attenuation in different materials. This is especially well-suited for pre-clinical imaging using nanoparticle-based contrast agents in situations where quantitative material decomposition helps probe processes which are otherwise limited by poor soft tissue contrast. We have previously proposed optimal in vivo DE micro-CT methods for imaging using iodinated and gold nanoparticles. However, in vivo studies are limited in spatial resolution due to constraints in sampling time and radiation dose. Ex vivo dual energy imaging can provide much higher resolution and can serve as a validation of in vivo studies. Our study proposes multiscale in vivo and ex vivo DE micro-CT of the same subjects using two in-house developed micro-CT systems. We use a dual source micro-CT system to scan a mouse that has been injected with both iodinated and gold nanoparticles for in vivo DE scanning at 63 micron resolution. The same mouse is then scanned ex vivo with DE on a separate single source micro-CT system at a spatial resolution of 22 microns. We perform reconstructions using filtered back projection followed by noise reduction via joint bilateral filtration. A dynamic flat field correction method has been applied on the ex vivo micro-CT data to correct for image artifacts. A DE post-reconstruction decomposition is used to create iodine and gold material maps which are used to measure accumulation of contrast agent within the body. We evaluate challenges associated with each imaging methodology. Our results compare image quality and material maps. Overall, our methods represent a substantial tool for multiscale DE micro-CT imaging using wellcharacterized contrast agents and serving various applications in biological research.