Dual-energy micro-CT imaging for differentiation of iodine- and gold-based nanoparticles

Abstract

Spectral CT imaging is expected to play a major role in the diagnostic arena as it provides material decomposition on an elemental basis. One fascinating possibility is the ability to discriminate multiple contrast agents targeting different biological sites. We investigate the feasibility of dual energy micro-CT for discrimination of iodine (I) and gold (Au) contrast agents when simultaneously present in the body. Simulations and experiments were performed to measure the CT enhancement for I and Au over a range of voltages from 40-to-150 kVp using a dual source micro-CT system. The selected voltages for dual energy micro-CT imaging of Au and I were 40 kVp and 80 kVp. On a massconcentration basis, the relative average enhancement of Au to I was 2.75 at 40 kVp and 1.58 at 80 kVp. We have demonstrated the method in a preclinical model of colon cancer to differentiate vascular architecture and extravasation. The concentration maps of Au and I allow quantitative measure of the bio-distribution of both agents. In conclusion, dual energy micro-CT can be used to discriminate probes containing I and Au with immediate impact in pre-clinical research.

In vivocharacterization of tumor vasculature using iodine and gold nanoparticles and dual energy micro-CT

“…For this reason, the optimal sensitivity matrix was calibrated using low to intermediate concentrations of I and Au (0, 2, 4, 6 mg/mL) which were presumed to be least affected by beam hardening. In practice, calibrating the sensitivities with higher concentrations yields uniformly lower sensitivities for I and Au at 40 and 80 kVp as documented in (Badea et al , 2011). As a consequence of the choice to optimize the sensitivity matrix for low to intermediate concentrations, the sensitivity matrix derived here is better conditioned than the sensitivity matrix previously derived, improving the accuracy in separating I and Au, particularly near the limits of detectability of the two materials.…”

“…In a recent study we performed both simulations and experimental validation in phantoms to determine the optimal scanning energies for the separation of Au and I using our micro-CT system (Badea et al , 2011). Our work has shown that micro-CT imaging at 40 and 80 kVp provides the best decomposition results in terms of accuracy and contrast.…”

Spectral Hounsfield units: a new radiological concept

“…Multi-energy CT offers better characterisation of materials, image reconstruction optimisation, and experimental iodine-, bismuthand gold-labelled nanoparticle contrast agents for tagging of disease processes in vivo e.g. fibrin [7], macrophages [8] and colon cancer [9].…”

Lung imaging in rodents using dual energy micro-CT

“…For the dual source micro-CT system, 40 kVp is the lowest voltage allowed by the micro-CT system’s x-ray generator. This voltage provides minimum enhancement, while values in the range of 70 or 80 kVp provide maximum enhancement when imaging iodine solutions[17]. Bilateral filtering was also applied.…”