Joint Optimization of Collimator and Reconstruction Parameters in X-Ray Fluorescence Computed Tomography Using...

Area of Science:

• Medical Imaging
• Biomedical Engineering
• X-ray Fluorescence Computed Tomography (XFCT)

Background:

• X-ray Fluorescence Computed Tomography (XFCT) is crucial for imaging low concentrations of high atomic number (Z) elements in small animal models.
• Optimizing collimator design and image reconstruction is key to enhancing XFCT performance.

Purpose of the Study:

• To jointly optimize collimator design and image reconstruction algorithms for XFCT.
• To evaluate single pinhole (SPH) and multi-pinhole (MPH) collimator designs for imaging high-Z elements.

Main Methods:

• Evaluated SPH and MPH collimators (5, 7, 9 pinholes) made of lead, stainless steel, and brass.
• Modeled a digital phantom with gold nanoparticles and simulated K-shell XFCT using a 125 kVp, Sn-filtered spectrum.
• Employed Maximum-Likelihood Expectation-Maximization (ML-EM) for image reconstruction and channelized Hotelling observer (CHO) for image quality assessment via AUC.

Main Results:

• Multi-pinhole (MPH) collimators outperformed single pinhole (SPH) collimators.
• A stainless steel focusing type MPH with 7 pinholes, combined with 20 iterations of ML-EM, achieved the highest Area Under the Curve (AUC).
• Consistently high AUCs were observed with focusing type MPH designs featuring 7 pinholes.

Conclusions:

• Optimized combinations of collimator design and image reconstruction parameters significantly improve XFCT performance.
• Focusing type 7-pinhole MPH collimators offer superior image quality for detecting low concentrations of high-Z elements in XFCT.