assessment of quantification accuracy and image quality of a full-body dual-layer spectral ct system

The performance of a recently introduced spectral computed tomography system based on a dual-layer detector has been investigated. a semi-anthropomorphic abdomen phantom for ct performance evaluation was imaged on the dual-layer spectral ct at different radiation exposure levels (ctdi vol of 10 mgy, 20 mgy and 30 mgy). the phantom was equipped with specific low-contrast and tissue-equivalent inserts including water-, adipose-, muscle-, liver-, bone-like materials and a variation in iodine concentrations. additionally, the phantom size was varied using different extension rings to simulate different patient sizes. contrast-to-noise (cnr) ratio over the range of available virtual mono-energetic images (vmi) and the quantitative accuracy of vmi hounsfield units (hu), effective-z maps and iodine concentrations have been evaluated. central and peripheral locations in the field-of-view have been examined. for all evaluated imaging tasks the results are within the calculated theoretical range of the tissue-equivalent inserts. especially at low energies, the cnr in vmis could be boosted by up to 330% with respect to conventional images using idose/spectral reconstructions at level 0. the mean bias found in effective-z maps and iodine concentrations averaged over all exposure levels and phantom sizes was 1.9% (eff. z) and 3.4% (iodine). only small variations were observed with increasing phantom size (+3%) while the bias was nearly independent of the exposure level (±0.2%). therefore, dual-layer detector based ct offers high quantitative accuracy of spectral images over the complete field-of-view without any compromise in radiation dose or diagnostic image quality.