Accuracy of dual-energy computed tomography for the measurement of iodine concentration using cardiac CT protocols: validation in a phantom model

Abstract

Purpose To assess the accuracy of dual-energy CT (DECT) for the quantification of iodine concentrations in a thoracic phantom across various cardiac DECT protocols and simulated patient sizes. Materials and methods Experiments were performed on first- and second-generation dual-source CT (DSCT) systems in DECT mode using various cardiac DECT protocols. An anthropomorphic thoracic phantom was equipped with tubular inserts containing known iodine concentrations (0–20 mg/mL) in the cardiac chamber and up to two fat-equivalent rings to simulate different patient sizes. DECT-derived iodine concentrations were measured using dedicated software and compared to true concentrations. General linear regression models were used to identify predictors of measurement accuracy Results Correlation between measured and true iodine concentrations (n=72) across CT systems and protocols was excellent (R=0.994–0.997, P< 0.0001). Mean measurement errors were 3.0 ± 7.0 % and −2.9 ± 3.8 % for first- and second-generation DSCT, respectively. This error increased with simulated patient size. The second-generation DSCT showed the most stable measurements across a wide range of iodine concentrations and simulated patient sizes. Conclusion Overall, DECT provides accurate measurements of iodine concentrations across cardiac CT protocols, strengthening the case for DECT-derived blood volume estimates as a surrogate of myocardial blood supply.

Beyond Stenosis Detection

“…Because iodine concentration is a surrogate for myocardial perfusion, the myocardial blood pool can be quantified based on the per-voxel amount of iodine. 47 Dedicated software typically generates a color-coded iodine distribution map overlay on top of a virtual noncontrasted image (Fig. 4).…”

“…Quantitative evaluation was recently performed on a phantom study showing high accuracy for myocardial iodine quantification. 47 Radiation doses for prospective ECG-triggered or retrospectively ECG-triggered acquisition are equivalent to those of single-energy cardiac CT acquisition. 34 …”

Dual-energy computed tomography for detection of coronary artery disease

“…By harnessing the unique features of DECT to allow for differentiation of iodine attenuation characteristics when it is exposed to low- and high-energy photon levels, DECT allows for the mapping of iodine distribution in the myocardium as a quantitative, albeit surrogate, marker for perfusion and blood volume based on the per-voxel amount of the iodine tracer. [21,22] Typically color-coded maps of iodine distribution are generated and superimposed on the virtual non-contrast CT data,[23] rendering the perfusion defects easier to appreciate by visual assessment. Indeed, a recent study by Koonce et al .…”

“…using a phantom model demonstrated the (semi)quantitative evaluation of perfusion on static single-phase DECT imaging to exhibit a higher accuracy when compared to standard visual grading. [21] For the routine qualitative assessment, myocardial attenuation of the ischemic area is compared to that of a normal remote territory. A drawback of this approach, however, is the necessity of a normally perfused area to act as a reference standard; hence, balanced ischemia may go undetected when utilizing qualitative DECT imaging.…”

Cardiac CT for myocardial ischaemia detection and characterization—comparative analysis

“…77 This makes quantification of myocardial blood pool from iodine concentration possible with DE FP CT . 78 Dual source CT scanners make use of independent tube regulation, while single source CT scanners are able to produce DE images through rapid tube current switching. 79 Cardiac applications, however, have mostly been assessed using dual source CT, with synchronized acquisitions at both energy levels.…”