Reduced Iodinated Contrast Media Administration in Coronary CT Angiography on a Clinical Photon-Counting Detector CT System

Abstract

PurposeThe aim of this study was to evaluate strategies to reduce contrast media volumes for coronary computed tomography (CT) angiography on a clinical first-generation dual-source photon-counting detector (PCD)-CT system using a dynamic circulation phantom.Materials and MethodsCoronary CT angiograph is an established method for the assessment of coronary artery disease that relies on the administration of iodinated contrast media. Reduction of contrast media volumes while maintaining diagnostic image quality is desirable. In this study, a dynamic phantom containing a 3-dimensional-printed model of the thoracic aorta and coronary arteries was evaluated using a clinical contrast injection protocol with stepwise reduced contrast agent concentrations (100%, 75%, 50%, 40%, 30%, and 20% contrast media content of the same 50 mL bolus, resulting in iodine delivery rates of 1.5, 1.1, 0.7, 0.6, 0.4 and 0.3 gl/s) on a first-generation, dual-source PCD-CT. Polychromatic images (T3D) and virtual monoenergetic images were reconstructed in the range of 40 to 70 keV in 5-keV steps. Attenuation and noise were measured in the coronary arteries and background material and the contrast-to-noise ratio (CNR) were calculated. Attenuation of 350 HU and a CNR of the reference protocol at 70 keV were regarded as sufficient for simulation of diagnostic purposes. Vessel sharpness and noise power spectra were analyzed for the aforementioned reconstructions.ResultsThe standard clinical contrast protocol (bolus with 100% contrast) yielded diagnostic coronary artery attenuation for all tested reconstructions (>398 HU). A 50% reduction in contrast media concentration demonstrated sufficient attenuation of the coronary arteries at 40 to 55 keV (>366 HU). Virtual monoenergetic image reconstructions of 40 to 45 and 40 keV allowed satisfactory attenuation of the coronary arteries for contrast concentrations of 40% and 30% of the original protocol. A reduction of contrast agent concentration to 20% of the initial concentration provided insufficient attenuation in the target vessels for all reconstructions. The highest CNR was found for virtual monoenergetic reconstructions at 40 keV for all contrast media injection protocols, yielding a sufficient CNR at a 50% reduction of contrast agent concentration.ConclusionsUsing virtual monoenergetic image reconstructions at 40 keV on a dual-source PCD-CT system, contrast media concentration could be reduced by 50% to obtain diagnostic attenuation and objective image quality for coronary CT angiography in a dynamic vessel phantom. These initial feasibility study results have to be validated in clinical studies.

Standardization and Quantitative Imaging With Photon-Counting Detector CT

“…Just as in DECT, VMIs can be generated from PCD-CT 23,26,71,110,111 . In addition to tube potential and tube current, PCD-CT systems require the selection of additional acquisition parameters, such as energy thresholds, which can further complicate clinical workflow.…”

New Horizons in Vascular Imaging With Photon-Counting Detector CT

“…19 Improvements in image quality with a higher CNR provide the ground for lowering the radiation dose and/or reduction of the amount of administered iodinated contrast media. 20,21 Emrich et al 22 showed in a phantom study that with use of virtual monoenergetic reconstructions at 40 keV, a sufficient CNR at a 50% reduction of contrast media dosage can be achieved. In a prospective study with 100 patients, Higashigaito et al 23 showed that the improved CNR of CT angiography with PCD-CT allows considerable contrast media reduction.…”

First Experience With a Whole-Body Spectral Photon-Counting CT Clinical Prototype

“…At low-energy, that is, 40 keV, VMI enables an increase in CT attenuation of iodine and more generally of tissue with high photoelectric absorption. This improves contrast-to-noise ratios of enhanced lesions or vessels 55,56 and decreases the iodine load for a satisfactory level of vessel opacification 57–59 . At higher energy than 70 keV, VMI enables a reduction of beam-hardening like-artifacts, thus improving the visualization of tissues surrounding high-attenuating tissues, iodinated vessels, 60 or metallic structures such as stents or prostheses 61,62 .…”

“…This improves contrast-tonoise ratios of enhanced lesions or vessels 55,56 and decreases the iodine load for a satisfactory level of vessel opacification. [57][58][59] At higher energy than 70 keV, VMI enables a reduction of beam-hardening likeartifacts, thus improving the visualization of tissues surrounding high-attenuating tissues, iodinated vessels, 60 or metallic structures such as stents or prostheses. 61,62 In our experience, the advantages of using VMI with SPCCT rely in the combination of all the technical benefits, that is, an improved spatial resolution, an improved discrimination between photoelectric and Compton effects, as well as a greater dose efficiency and weighting of the low-energy photons.…”