Spectral performance evaluation of a second-generation spectral detector CT

Abstract

AbstractObjectiveTo characterize a second-generation wide-detector dual-layer spectral computed tomography system for material quantification accuracy, acquisition parameter and patient size dependencies, and tissue characterization capabilities.MethodsA phantom with multiple tissue-mimicking and material inserts was scanned with a dual-layer spectral detector CT using different tube voltages, collimation widths, radiation dose levels, and size configurations. Accuracy of iodine density maps and virtual monoenergetic images (MonoE) were investigated. Additionally, differences between conventional and MonoE 70 keV images were calculated to evaluate acquisition parameter and patient size dependencies. To demonstrate material quantification and differentiation, liver-mimicking inserts with adipose and iron were analyzed with a two-base decomposition utilizing MonoE 50 and 150 keV, and root mean square error (RMSE) for adipose and iron content was reported.ResultsSpectral accuracy was high for the measured inserts across a wide range of MonoE levels. MonoE 70 keV demonstrated reduced dependence compared to conventional image for phantom size (3 vs. 29 HU) and acquisition parameters, particularly tube voltage (5 vs. 43 HU) and noise-dose (9 vs. 11 HU). Iodine density quantification was successful with errors ranging from 0.25 to 0.5 mg/mL. Similarly, inserts with different amounts of adipose and iron were easily differentiated, and the small deviation in values within inserts corresponded to a RMSE of 1.78 ± 0.37% and 0.87 ± 0.37 mg/mL for adipose and iron content, respectively.ConclusionThe second-generation dual-layer CT enables acquisition of quantitatively accurate spectral data without compromises from differences in patient size and acquisition parameters.Key Points-With second-generation wide-detector dual-layer computed tomography, spectral quantification is further improved.-Spectral performance is independent of acquisition parameters such as tube voltage (100 kVp versus 120 kVp) and z-coverage (10 versus 80 mm).-Spectral performance is not significantly impacted by patient habitus.