Multi‐energy computed tomography and material quantification: Current barriers and opportunities for advancement

Abstract

Computed tomography (CT) technology has rapidly evolved since its introduction in the 1970s. It is a highly important diagnostic tool for clinicians as demonstrated by the significant increase in utilization over several decades. However, much of the effort to develop and advance CT applications has been focused on improving visual sensitivity and reducing radiation dose. In comparison to these areas, improvements in quantitative CT have lagged behind. While this could be a consequence of the technological limitations of conventional CT, advanced dual-energy CT (DECT) and photoncounting detector CT (PCD-CT) offer new opportunities for quantitation. Routine use of DECT is becoming more widely available and PCD-CT is rapidly developing. This review covers efforts to address an unmet need for improved quantitative imaging to better characterize disease, identify biomarkers, and evaluate therapeutic response, with an emphasis on multi-energy CT applications. The review will primarily discuss applications that have utilized quantitative metrics using both conventional and DECT, such as bone mineral density measurement, evaluation of renal lesions, and diagnosis of fatty liver disease. Other topics that will be discussed include efforts to improve quantitative CT volumetry and radiomics. Finally, we will address the use of quantitative CT to enhance image-guided techniques for surgery, radiotherapy and interventions and provide unique opportunities for development of new contrast agents.

Virtual monoenergetic images from dual-energy CT: systematic assessment of task-based image quality performance

“…In the last decade, beneficial applications of dual-energy CT (DECT) have been shown for different body regions (1)(2)(3)(4)(5)(6)(7)(8). DECT offers the generation of so called virtual monoenergetic images (VMI) which can be used to increase CT attenuation of iodinated structures, to improve CT attenuation stability or to reduce metal artifacts (9)(10)(11).…”

Simultaneous dual‐contrast imaging using energy‐integrating detector multi‐energy CT: An in vivo feasibility study

“…24 First, compared to the tungsten cluster con-trast medium, we used gadolinium-based material as the second contrast medium, which is widely used in magnetic resonance imaging and some special applications in CT imaging, 26 while the biological properties of tungsten as a potential CT contrast agent are still not well understood. 27 The larger difference in Kedge energies between iodine (33.2 keV) and tungsten (69.5 keV) than iodine and gadolinium (50.2 keV) may lead to better noise properties in material decomposition of iodine and tungsten. Second, the material decomposition in the iodine/tungsten study was performed directly on a commercial software with twomaterial decomposition where the tungsten and water were assigned into a single basis material map, which led to only a qualitative analysis in that study.…”

“…However, there are two major differences between our study and the iodine/tungsten study 24 . First, compared to the tungsten cluster contrast medium, we used gadolinium‐based material as the second contrast medium, which is widely used in magnetic resonance imaging and some special applications in CT imaging, 26 while the biological properties of tungsten as a potential CT contrast agent are still not well understood 27 . The larger difference in K‐edge energies between iodine (33.2 keV) and tungsten (69.5 keV) than iodine and gadolinium (50.2 keV) may lead to better noise properties in material decomposition of iodine and tungsten.…”

Multi-Energy and Fast-Convergence Iterative Reconstruction Algorithm for Organic Material Identification Using X-ray Computed Tomography

“…Different from the medical applications of dual and multiple-energy CT, which produce more precise images necessary for a better diagnostic [ 13 , 14 ], the forensic use of dual and multiple CT permits the simultaneous determination of the effective atomic number Z eff and density of controlled material, accurately differentiating explosives from the other organic materials in the luggage. In this regard, it is worth mentioning that densities or effective atomic numbers alone cannot differentiate explosives; this can only be achieved if they are simultaneously used [ 6 , 15 ].…”