Imaging properties of Fe3O4@Au and Fe3O4@Bi hybrid nanocomposites as contrast agents in spectral X-ray computed tomography: A Monte Carlo simulation study

Objective(s): In this paper, we evaluated some imaging properties of Fe3O4@Au and Fe3O4@Bi hybrid nanocomposites as contrast agents in spectral CT. For this purpose, we simulated a spectral CT scanner with photon-counting detectors (PCDs) in 6 energy bins by a Monte Carlo simulator. Materials and Methods: A cylindrical phantom was designed with a diameter of 8 cm and a height of 10 cm. Fe3O4@Au and Fe3O4@Bi hybrid nanocomposites were designed as a core-shell with a diameter of 80 nm. Simulation results were utilized to reconstruct cross-sectional images through the filtered back-projection (FBP) algorithm in MATLAB software. Signal intensity and contrast to noise ratio (CNR) of tested contrast agents were calculated in spectral CT images. Results: The results indicated a comparable image quality for Fe3O4@Au and Fe3O4@Bi hybrid nanocomposites at different energy bins. However, in the energy range of 80 to 120 keV (bin 4 and 5), the difference in signal intensity and CNR between these two nanocomposites increased. The maximum signal intensity and CNR for Fe3O4@Au and Fe3O4@Bi were acquired at the highest concentration. The maximum signal intensity for Fe3O4@Au was 144±10 (HU) in the 4th energy bin and for Fe3O4@Bi 162±19 (HU) in the 5th energy bin. Besides, the maximum CNRs of 74±6 and 67.5±9 for Fe3O4@Au in bin 4, while for Fe3O4@Bi in bin 5 were obtained respectively. Conclusion: Based on our results, Fe3O4@Au and Fe3O4@Bi hybrid nanocomposites have provided promising results as contrast agents in spectral CT. Fe3O4@Bi nanocomposites are recommended due to their lower price and availability.