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

Abstract

Dual-energy (DE) decomposition has been adopted in orthopedic imaging to measure bone composition and visualize intraarticular contrast enhancement. One of the potential applications involves monitoring of callus mineralization for longitudinal assessment of fracture healing. However, fracture repair usually involves internal fixation hardware that can generate significant artifacts in reconstructed images. To address this challenge, we develop a novel algorithm that combines simultaneous reconstruction-decomposition using a previously reported method for model-based material decomposition (MBMD) augmented by the known-component (KC) reconstruction framework to mitigate metal artifacts. We apply the proposed algorithm to simulated DE data representative of a dedicated extremity cone-beam CT (CBCT) employing an x-ray unit with three vertically arranged sources. The scanner generates DE data with non-coinciding high- and low-energy projection rays when the central source is operated at high tube potential and the peripheral sources at low potential. The proposed algorithm was validated using a digital extremity phantom containing varying concentrations of Ca-water mixtures and Ti implants. Decomposition accuracy was compared to MBMD without the KC model. The proposed method suppressed metal artifacts and yielded estimated Ca concentrations that approached the reconstructions of an implant-free phantom for most mixture regions. In the vicinity of simple components, the errors of Ca density estimates obtained by incorporating KC in MBMD were ∼1.5–5× lower than the errors of conventional MBMD; for cases with complex implants, the errors were ∼3–5× lower. In conclusion, the proposed method can achieve accurate bone mineral density measurements in the presence of metal implants using non-coinciding DE projections acquired on a multisource CBCT system.

Computed Tomography

“…132 Among these, MBMD has the potential to achieve improved resolution-noise tradeoff compared with analytical methods and the ability to incorporate prior knowledge, for example, models of metal hardware present in the FOV, enabling DE imaging around orthopedic hardware. 132…”

“…129 The formation of material concentration images in DE-CBCT has been reported using all major categories of computational approaches known from DECT: pre-reconstruction projection-domain decomposition, 126 postreconstruction image-domain decomposition, 131 and direct iterative 1-step model-based material decomposition (MBMD). 132 Among these, MBMD has the potential to achieve improved resolution-noise tradeoff compared with analytical methods and the ability to incorporate prior knowledge, for example, models of metal hardware present in the FOV, enabling DE imaging around orthopedic hardware. 132…”

“…Application of DE-CBCT to BMD evaluation has recently been reported in dental imaging 134 . In musculoskeletal imaging, a simulation study assuming perfect scatter correction found an accurate assessment of BMD by DE-CBCT 132 ; with low-error measurements even in the vicinity of metal hardware when a previous model of the hardware was included in the MBMD. However, accurate scatter correction will likely be essential for robust BMD estimation using DE-CBCT 126 …”

Feasibility of bone marrow edema detection using dual‐energy cone‐beam computed tomography

“…The interest in the application of this technique in detecting BME is motivated by the advantages of DE CT compared to MRI in emergency medicine and longitudinal disease monitoring, including faster examination times and less stringent contraindications for patients with metal. 9,10 This work investigates whether the BME imaging capability of DE CT can be translated onto the emerging cone-beam CT (CBCT) systems for musculoskeletal (MSK) imaging 12-16-f or example, the dedicated extremity CBCT [17][18][19] or robotic x-ray devices such as Multitom Rax (Siemens Healthineers, Forchheim, Germany). 15,[20][21][22][23] MSK CBCT offers advanced 3D imaging capabilities for orthopedic settings that traditionally relied on 2D radiography, including novel diagnostic features like weight-bearing scans [24][25][26] and high-resolution evaluation of fine bone detail (e.g., trabecular bone 27 or subtle fractures).…”

Quantitative dual-energy imaging of bone marrow edema using multi-source cone-beam CT with model-based decomposition

“…Here, we investigate the feasibility of DE BME detections on a recently introduced extremity CBCT scanner 4 (Fig. 1A) with a unique three-source x-ray unit 5,6 that enables fast DE acquisition in a single gantry rotation by applying different potentials to the central versus the peripheral x-ray sources 7 . However, compared to the conventional dual-source CT, the x-ray sources on this CBCT device are arranged axially, resulting in suboptimal geometric sampling in energy channels associated with the peripheral sources (Fig.…”