Intermanufacturer Comparison of Dual-Energy CT Iodine Quantification and Monochromatic Attenuation: A Phantom Study

Abstract

Purpose To determine the accuracy of dual-energy computed tomographic (CT) quantitation in a phantom system comparing fast kilovolt peak-switching, dual-source, split-filter, sequential-scanning, and dual-layer detector systems. Materials and Methods A large elliptical phantom containing iodine (2, 5, and 15 mg/mL), simulated contrast material-enhanced blood, and soft-tissue inserts with known elemental compositions was scanned three to five times with seven dual-energy CT systems and a total of 10 kilovolt peak settings. Monochromatic images (50, 70, and 140 keV) and iodine concentration images were created. Mean iodine concentration and monochromatic attenuation for each insert and reconstruction energy level were recorded. Measurement bias was assessed by using the sum of the mean signed errors measured across relevant inserts for each monochromatic energy level and iodine concentration. Iodine and monochromatic errors were assessed by using the root sum of the squared error of all measurements. Results At least one acquisition paradigm per scanner had iodine biases (range, -2.6 to 1.5 mg/mL) with significant differences from zero. There were no significant differences in iodine error (range, 0.44-1.70 mg/mL) among the top five acquisition paradigms (one fast kilovolt peak switching, three dual source, and one sequential scanning). Monochromatic bias was smallest for 70 keV (-12.7 to 15.8 HU) and largest for 50 keV (-80.6 to 35.2 HU). There were no significant differences in monochromatic error (range, 11.4-52.0 HU) among the top three acquisition paradigms (one dual source and two fast kilovolt peak switching). The lowest accuracy for both measures was with a split-filter system. Conclusion Iodine and monochromatic accuracy varies among systems, but dual-source and fast kilovolt-switching generally provided the most accurate results in a large phantom. RSNA, 2017 Online supplemental material is available for this article.

Cone‐beam CT‐derived relative stopping power map generation via deep learning for proton radiotherapy

“…This finding is consistent with other authors who found inferior performance of the Twinbeam system for virtual monoenergetic and virtual noncontrast imaging. 50,51 Using images with reduced stopping power uncertainty could allow for reduced margins when designing treatment plans, possibly opening pathways to dose escalation and increased organ-at-risk sparing. 52 If dose could be calculated on daily CBCT using the proposed method, the margins typically added for setup uncertainties could be reduced since the patient would not be moved between "simulation" and treatment.…”

Principles and applications of multienergy CT: Report of AAPM Task Group 291

“…142 Furthermore, CT numbers from virtual monoenergetic images are accurate to within 10 HU across different CT scanner models from different CT scanner manufacturers. 143 These desirable properties reduce variations in the calculation of SPR values.…”

Development of a dual‐energy computed tomography quality control program: Characterization of scanner response and definition of relevant parameters for a fast‐kVp switching dual‐energy computed tomography system

“…In our study, we found that across all 10 DECT scanners, iodine quantification errors were reported to be within 5%–10%, corresponding to ±0.3 and ±1.5 mg/mL for the 2 and 15 mg/mL inserts, respectively. This low error and the low dependence on the technique parameters investigated, suggest that iodine density maps may be used in a quantitative manner for clinically relevant iodine concentrations regardless of the technique parameters used …”

“…Iodine quantification error was also shown to increase with increasing phantom size; however, this effect has been disputed by other studies . Evaluation of the CT number stability for monoenergetic reconstructions has shown dependence on phantom size, as well as greater inaccuracies for dense materials in low keV reconstructions . This effect may be due to suboptimal correction of beam hardening effects for these energies.…”