Dual energy CT reconstruction using the constrained one step spectral image reconstruction algorithm.

Area of Science:

• Medical Imaging
• Computational Imaging
• Materials Science

Background:

• The constrained one-step spectral CT image reconstruction (cOSSCIR) method estimates basis material maps from spectral CT data.
• It utilizes a polyenergetic x-ray transmission model and convex constraints for stable inversion.
• cOSSCIR is applicable to dual-energy CT systems, including fast/slow kV switching and dual-source scanners.

Purpose of the Study:

• To investigate cOSSCIR's application to dual-kV spectral CT data.
• To evaluate cOSSCIR with both registered and unregistered spectral acquisitions (slow and fast kV switching).
• This study marks the first demonstration of cOSSCIR for dual-kV reconstruction.

Main Methods:

• Developed an integrating detector model for dual-kV data reconstruction.
• Validated the detector model using inverse crime simulations with a pelvic phantom.
• Applied cOSSCIR to physical phantom experiments with bone, adipose, and liver tissue analogs.
• Compared cOSSCIR with conventional image-domain decomposition methods.

Main Results:

• Simulations successfully recovered material basis maps, highlighting challenges with unregistered data.
• Experimental reconstructions showed <6.5% error in bone, adipose, and liver basis maps for both registered/unregistered protocols.
• Virtual mono-energetic images at 50 keV had <4% error, with decomposition vectors closely matching ground truth.
• Preliminary iodine quantification yielded an average concentration of 9.2 mg/mL.

Conclusions:

• cOSSCIR accurately recovers material basis maps from dual-kV data, irrespective of registration or imaging protocol.
• Material decomposition quantification favorably compares to image-domain approaches.
• Results suggest cOSSCIR's potential for iodine quantification via two-material decomposition.