Polyenergetic known-component CT reconstruction with unknown material compositions and unknown x-ray spectra

Abstract

Metal artifacts can cause substantial image quality issues in computed tomography. This is particularly true in interventional imaging where surgical tools or metal implants are in the field-of-view. Moreover, the region-of-interest is often near such devices which is exactly where image quality degradations are largest. Previous work on known-component reconstruction (KCR) has shown the incorporation of a physical model (e.g. shape, material composition, etc.) of the metal component into the reconstruction algorithm can significantly reduce artifacts even near the edge of a metal component. However, for such approaches to be effective, they must have an accurate model of the component that include energy-dependent properties of both the metal device and the CT scanner, placing a burden on system characterization and component material knowledge. In this work, we propose a modified KCR approach that adopts a mixed forward model with a polyenergetic model for the component and a monoenergetic model for the background anatomy. This new approach called Poly-KCR jointly estimates a spectral transfer function associated with known components in addition to the background attenuation values. Thus, this approach eliminates both the need to know component material composition a prior as well as the requirement for an energy-dependent characterization of the CT scanner. We demonstrate the efficacy of this novel approach and illustrate its improved performance over traditional and model-based iterative reconstruction methods in both simulation studies and in physical data including an implanted cadaver sample.

Improving Structure Delineation for Radiation Therapy Planning Using Dual-Energy CT

“…The study sets are subsequently utilized for calculating treatment plans, from which dose volume histogram (DVH) statistics are obtained to quantify the plan’s effectiveness relative to the prescription, with the goal of adequately covering the targets while maximally sparing OARs. Hence, RT planning depends on the quality of the planning images, which may lack in image contrast and functional information due to the limitations of poly-energetic CT ( 1 ).…”

Known‐component 3D image reconstruction for improved intraoperative imaging in spine surgery: A clinical pilot study

“…As in previous work, to ease the computational load, the registration parameters were solved prior to estimation of the spectral coefficients and reconstruction of the background anatomy, as illustrated in Fig. .…”

“…An edgepreserving roughness penalty was chosen for R l à ð Þ using a Huber function of pairwise voxel differences over a first-order neighborhood with a penalty strength adjusted by the parameter b. 41 As in previous work, 35 to ease the computational load, the registration parameters were solved prior to estimation of the spectral coefficients and reconstruction of the background anatomy, as illustrated in Fig. 2.…”

“…29 KC-Recon has been subsequently extended to support deformable or approximate KC models, [30][31][32][33] integration of a polyenergetic forward model, 34 and estimation of the energy-dependent properties of the component via a spectral transfer function (STF). 35 In simulation and phantom studies, KC-Recon demonstrated combined benefits of metal artifact reduction, improved noise-resolution characteristics, and the potential for strong dose reduction. The studies below report a modification of the KC-Recon algorithm to better account for components with more than one material type and translate the method for the first time to clinical studies of patients receiving spine surgery.…”

Dual‐energy CT imaging of nasopharyngeal cancer cells using multifunctional gold nanoparticles

“…At ∼100 keV, the same linear attenuation coefficients can be measured for bone and iodine when monoenergetic X‐ray is applied. The information obtained at energy levels close to 50 keV permits the decomposition of these two materials [7]. Since medical X‐ray imaging tubes generate a polyenergetic spectrum, DECT can be specified as the use of attenuation measurements obtained from various energy spectra [8].…”