Polychromatic Cone-Beam X-Ray Fluorescence Computed Tomography of Gold Nanoparticle-Loaded Objects
B Jones1, N Manohar3*, A Karellas2, S Cho3, (1) Univ. of Colorado School of Medicine, AURORA, CO, (2) University of Massachusetts Medical School, Worcester, MA, (3) Georgia Institute of Technology, Atlanta, GATH-A-213CD-3 Thursday 8:00:00 AM - 9:55:00 AM Room: 213CD
Purpose: To determine the spatial distribution and amount of gold nanoparticles (GNPs) within small-animal-sized objects using polychromatic cone-beam x-ray fluorescence computed tomography (XFCT) under realistic constraints on x-ray dose, scan time, and image resolution.
Methods: 6-mm-diameter cylindrical tubes containing saline solution and 0.5-2.0 wt. % of GNPs were inserted into a cylindrical polymethyl methacrylate (PMMA) phantom, 3 cm in diameter and 5 cm in height. The phantom was irradiated by a cone-beam of polychromatic 105 kVp x-rays filtered by 0.9 mm of tin. Energy-sensitive cadmium telluride detectors behind a 2.5 mm diameter lead pinhole collimator collected the spectrum of emitted gold K-shell fluorescence and Compton scattered photons at an angle of 90º relative to the beam central axis as the phantom was rotated to a series of 60 projection angles in 6º steps. Sinograms of gold fluorescence photon signals were constructed by extracting the gold fluorescence peak height from the Compton background, and the image of GNP location and concentration was reconstructed using a maximum likelihood iterative reconstruction algorithm.
Results: Using the measured sinograms, XFCT images of GNP-loaded objects were successfully reconstructed, accurately determining both the GNP location and concentration. The x-ray dose delivered during the XFCT scanning was measured using the AAPM TG-61 protocol, and it was determined that, using an array detector, it would be possible to acquire these images in one hour with a tissue dose of approximately 20 cGy.
Conclusions: With a few easily achievable modifications, the current benchtop setup would be capable of producing useful XFCT images of small animals injected with GNPs with the total scanning time and a tissue dose comparable to other modalities currently available for routine pre-clinical in-vivo imaging such as micro-CT.
Supported in part by NIH/NCI grant 1R01CA155446