Performance assessment of photon counting versus energy integrated CT: concordance of in vivo and phantom measurements
Photon-counting CT (PCCT) and energy-integrating CT (EICT) system offer differing image quality attributes, but it is uncertain if such attributes manifest themselves differently across phantom vs patients. This study investigated if image quality assessment with a multi-sized phantom can predict patient population trends in PCCT and EICT. Under IRB approval, 56 patients underwent clinical CT on a PCCT and four EICT scanners from two vendors (A, B). Additionally, the Mercury Phantom 3.0 (GAMMEX Sun Nuclear), representing different adult population sizes, was imaged with the same conditions and scanners. Modulation Transfer Function 10% frequency (MTF-f10), Global Noise Index (GNI), and Noise Power Spectrum average frequency (NPS-fav), peak frequency (NPS-fpeak), and 10% frequency (NPS-f10) were evaluated in both patients and Mercury Phantom (MP). The related percentage differences between PCCT and EICT images were assessed. Median differences between patients imaged with PCCT and EICT-A were 33.1%, 160.2%, 42.3%, -14.3%, and 25.2% for MTF-f10, GNI, NPS-fav, NPS-fpeak, and NPS-f10, respectively; differences between patients in PCCT and EICT-B were 11.8%, 197.6%, 35.7%, -14.0%, and 23.2%. For the same metrics, the median differences between MP imaged with PCCT and EICT-A were 256.3%, 105.5%, 48.7%, 141.8%, and 50.1%, respectively; differences between MP scanned with PCCT and EICT-B were 247.8%, 193.5%, 48.5%, 127%, and 47.5%. MP showed different values but similar trends as patient population when comparing PCCT and EICT image quality. Magnitude differences can facilitate adjustment factors to phantom data to improve representation of clinical image quality.
