Comparison of low-energy virtual monoenergetic images between photon-counting CT and energy-integrating detectors CT: A phantom study

Joël Greffier; Sebastian Faby; Maxime Pastor; Julien Frandon; Julien Erath; Jean Paul Beregi; Djamel Dabli

doi:10.1016/j.diii.2024.02.009

Comparison of low-energy virtual monoenergetic images between photon-counting CT and energy-integrating detectors CT: A phantom study

Diagn Interv Imaging. 2024 Feb 29:S2211-5684(24)00044-5. doi: 10.1016/j.diii.2024.02.009. Online ahead of print.

Authors

Joël Greffier¹, Sebastian Faby², Maxime Pastor³, Julien Frandon³, Julien Erath², Jean Paul Beregi³, Djamel Dabli³

Affiliations

¹ IMAGINE UR UM 103, Montpellier University, Department of Medical Imaging, Nîmes University Hospital, 30029 Nîmes, France. Electronic address: joel.greffier@chu-nimes.fr.
² Department of Computed Tomography, Siemens Healthineers AG, 91301 Forchheim, Germany.
³ IMAGINE UR UM 103, Montpellier University, Department of Medical Imaging, Nîmes University Hospital, 30029 Nîmes, France.

PMID: 38429207
DOI: 10.1016/j.diii.2024.02.009

Abstract

Purpose: The purpose of this study was to assess image quality and dose level using a photon-counting CT (PCCT) scanner by comparison with a dual-source CT (DSCT) scanner on virtual monoenergetic images (VMIs) at low energy levels.

Materials and methods: A phantom was scanned using a DSCT and a PCCT with a volume CT dose index of 11 mGy, and additionally at 6 mGy and 1.8 mGy for PCCT. Noise power spectrum and task-based transfer function were evaluated from 40 to 70 keV on VMIs to assess noise magnitude and noise texture (f_av) and spatial resolution on two iodine inserts (f₅₀), respectively. A detectability index (d') was computed to assess the detection of two contrast-enhanced lesions according to the energy level used.

Results: For all energy levels, noise magnitude values were lower with PCCT than with DSCT at 11 and 6 mGy, but greater at 1.8 mGy. f_av values were higher with PCCT than with DSCT at 11 mGy (8.6 ± 1.5 [standard deviation [SD]%), similar at 6 mGy (1.6 ± 1.5 [SD]%) and lower at 1.8 mGy (-17.8 ± 2.2 [SD]%). For both inserts, f₅₀ values were higher with PCCT than DSCT at 11- and 6 mGy for all keV levels, except at 6 mGy and 40 keV. d' values were higher with PCCT than with DSCT at 11- and 6 mGy for all keV and both simulated lesions. Similar d' values to those of the DSCT at 11 mGy, were obtained at 2.25 mGy for iodine insert at 2 mg/mL and at 0.96 mGy for iodine insert at 4 mg/mL at 40 keV.

Conclusion: Compared to DSCT, PCCT reduces noise magnitude and improves noise texture, spatial resolution and detectability on VMIs for all low-keV levels.

Keywords: Dual-energy; Iterative reconstruction; Multidetector computed tomography; Photon counting CT; Task-based image quality assessment.