Metal artifact reduction and contrast agent performance as a function of source spectral shape.

Area of Science:

• Medical Imaging Physics
• Photon Counting CT Technology
• Materials Science in Medical Imaging

Background:

• Medipix All Resolution Scanner (MARS) utilizes photon counting CT (PCCT) for advanced imaging.
• Pre-filtration is crucial for optimizing X-ray source characteristics and image quality.
• Assessing metal artifact reduction (MAR) and contrast performance (CP) is vital for clinical translation.

Purpose of the Study:

• To empirically map the X-ray source spectrum of a MARS-PCCT system with copper (Cu) and tin (Sn) pre-filters.
• To evaluate the metal artifact reduction (MAR) capabilities of these pre-filters.
• To measure the impact of pre-filtration on the contrast performance (CP) of iopromide and tantalum oxide nanoparticles (TaOxNPs).

Main Methods:

• Empirical mapping of the MARS-PCCT X-ray source with varying thicknesses of Cu and Sn filters.
• Scanning a phantom containing water, lipid, iopromide, TaOxNPs, and metal under different pre-filtration conditions.
• Quantification of MAR and CP using insert noise, signal, contrast-to-pooled-noise ratio (CPNR), and fast Fourier transform artifact metric (FFTAM).

Main Results:

• Thick Cu and Sn filters shifted the mean X-ray source energy significantly (19.2 keV and 23.4 keV, respectively).
• Thick filtration (2.1 mm Cu, 0.6 mm Sn) reduced noise by up to 74% and artifacts by up to 71%.
• Pre-filtration improved CPNR, especially for TaOxNPs (up to 61%), despite a contrast reduction for both iopromide and TaOxNPs.

Conclusions:

• Empirical source mapping with pre-filters provides critical data for photon flux distribution and detector artifacts in MARS-PCCT.
• Findings offer insights for energy binning strategies in material decomposition and guide clinical MAR development.
• Tantalum oxide nanoparticles demonstrate greater compatibility with spectral shaping compared to iopromide.