Model-based dual-energy tomographic image reconstruction of objects containing known metal components

Area of Science:

• Orthopedic imaging
• Medical physics
• Biomedical engineering

Background:

• Dual-energy (DE) decomposition is used in orthopedic imaging for bone composition analysis and contrast enhancement.
• Assessing fracture healing through callus mineralization is a key application, but metal implants cause significant artifacts.
• Existing methods struggle to accurately measure bone density in the presence of internal fixation hardware.

Purpose of the Study:

• To develop and validate a novel algorithm for mitigating metal artifacts in dual-energy imaging.
• To enable accurate bone mineral density measurements during fracture healing assessment in the presence of implants.
• To improve the reliability of longitudinal assessments of fracture repair.

Main Methods:

• A novel algorithm combining simultaneous reconstruction-decomposition was developed, integrating model-based material decomposition (MBMD) with the known-component (KC) reconstruction framework.
• The algorithm was applied to simulated dual-energy (DE) data from a multisource cone-beam CT (CBCT) system with non-coinciding energy projections.
• Validation was performed using a digital extremity phantom with varying calcium-water mixtures and titanium implants, comparing results to MBMD without KC.

Main Results:

• The proposed algorithm effectively suppressed metal artifacts in reconstructed images.
• Estimated calcium concentrations closely matched those of an implant-free phantom in most regions.
• The KC-augmented MBMD method showed significantly lower errors (1.5-5x for simple, 3-5x for complex implants) in calcium density estimates compared to conventional MBMD.

Conclusions:

• The developed algorithm successfully mitigates metal artifacts in dual-energy imaging of bone.
• Accurate bone mineral density measurements are achievable even with the presence of metallic implants.
• This method holds promise for improved longitudinal monitoring of fracture healing using multisource CBCT systems.