Assessment of quantification accuracy and image quality of a full-body dual-layer spectral CT system

作者：Ehn Sebastian; Sellerer Thorsten; Muenzel Daniela; Fingerle Alexander A.; Kopp Felix; Duda Manuela; Mei Kai; Renger Bernhard; Herzen Julia; Dangelmaier Julia; Schwaiger Benedikt J.; Sauter Andreas; Riederer Isabelle; Renz Martin; Braren Rickmer; Rummeny Ernst J.; Pfeiffer Franz; Noeel Peter B.

来源：Journal of Applied Clinical Medical Physics, 2018, 19(1): 204-217.

DOI：10.1002/acm2.12243

• dual-energy CT
• effective atomic number
• iodine quantification
• spectral CT
• virtual mono-energetic imaging

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 (CTDIvol 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.

• 出版日期2018-1