Fast kV-switching and dual-layer flat-panel detector enabled cone-beam CT joint spectral imaging

Area of Science:

• Medical Imaging Physics
• Cone-Beam Computed Tomography (CBCT)
• Dual-Energy Spectral Imaging

Background:

• Cone-beam CT (CBCT) spectral imaging faces challenges in accurate material discrimination due to limited energy separation from single technologies (fast kV-switching or dual-layer flat-panel detectors).
• X-ray scatter in cone-beam scans further complicates material decomposition without correction.
• Existing methods struggle with unpaired signal levels in effective low- and high-energy projections.

Purpose of the Study:

• To develop and evaluate a source-detector joint multi-energy spectral imaging solution for CBCT, combining fast kV-switching (FKS) and dual-layer flat-panel detector (DL-FPD) technologies.
• To conduct a feasibility study on the first tabletop CBCT system with integrated joint spectral imaging capabilities.
• To improve the accuracy and robustness of material discrimination in CBCT spectral imaging.

Main Methods:

• A novel CBCT system was developed, integrating fast kV-switching (FKS) for rapid kVp alternation and a dual-layer flat-panel detector (DL-FPD) for distinct energy level detection.
• Noise performance was analyzed using Cramér-Rao lower bound (CRLB) calculations for FKS, DL-FPD, and the joint solution.
• A dual-domain projection completion scheme compensated for FKS angular mismatch, followed by maximum-likelihood material decomposition and virtual monochromatic image (VMI) reconstruction.

Main Results:

• Numerical simulations indicated significant improvements in energy separation and reduced noise levels with the joint spectral imaging solution.
• Physics experiments demonstrated superior performance: contrast-to-noise ratios (CNRs) for water and iodine basis images improved by up to 62.8% compared to single technologies.
• For head phantom scans, the joint solution reduced streaking artifacts and decreased VMI standard deviation by up to 19.5% compared to FKS and DL-FPD alone.

Conclusions:

• The feasibility of a joint spectral imaging solution for CBCT using FKS and DL-FPD was successfully demonstrated.
• The developed tabletop CBCT system exhibits enhanced CNR and effective artifact reduction, validating the combined approach.
• This joint spectral imaging strategy offers a promising advancement for improved material discrimination and image quality in CBCT applications.