Merfat Algethami, Anton Blencowe, Bryce Feltis and Moshi Geso
Background: Investigation of the contrast enhancement effects on the CT images of the conventional iodinated contrast media (CM) or bismuth sulfide nanoparticles (Bi2S3 NPs) with increasing x-ray tube potentials.
Materials and methods: A phantom was filled with iodinated CM or Bi2S3 NP solutions at concentrations ranging from 0 to 65 mM and the phantom was scanned with a CT scanner using tube potentials of 80, 100, 120 and 140 kVp at a fixed current of 200 mA. The CT contrast enhancement and contrast-to-noise ratios (CNR) of all scanned images were calculated.
Results: This study demonstrated that greater image contrast was observed with Bi2S3 NPs compared to the iodinated CM at all concentrations and energies (80-140 kVp) tested. For example, at a concentration of 65 mM and tube potential of 140 kVp, a CNR enhancement of three to four times was observed for Bi2S3 NPs compared to iodinated CM. Even at a conventional tube potential of 80 KVp, one to two-fold increase in CNR was noted for Bi2S3 NPs. Results are also demonstrated that CNR increased with increasing concentration of Bi2S3 NPs at a fixed tube potential.
Conclusion: These results highlight the effects of the different physical densities and atomic numbers of the two elements (I versus Bi), and their role in enhancing the probability of Compton scattering (CS) and photoelectric effects (PEs). As tube potential was increased, the CT numbers for both Bi2S3 NPs and iodinated CM decreased, consistent with a decrease in the probability of CS and PEs with increasing beam energy. However, the rate of decrease for iodinated CM was larger than Bi2S3 NPs. A good correlation was observed between the experimental results and the theoretical spectra based on linear attenuation coefficients .
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