A Clinically Driven Task-Based Comparison of Photon Counting and Conventional Energy Integrating CT for Soft Tissue, Vascular, and High-Resolution Tasks

Photon-counting CT (PCCT) detectors are the next step in advancing CT system development and will replace the current energy-integrating detectors (EIDs) in CT systems in the near future. In this context, the performance of PCCT was compared to EID CT for three clinically relevant tasks: 1) abdominal soft tissue imaging, where differentiating low contrast features is important; 2) vascular imaging, where iodine detectability is critical; and 3) high-resolution skeletal and lung imaging. A multitiered phantom was imaged on an investigational clinical PCCT system (Siemens Healthineers) across different doses using three imaging modes: macro and ultrahigh resolution (UHR) PCCT modes and EID CT. Images were reconstructed using filtered backprojection and soft tissue (B30f), vascular (B46f), or high-resolution (B70f; U70f for UHR) kernels. Noise power spectra, task transfer functions, and detectability index were evaluated. For a soft tissue task, PCCT modes showed comparable noise and resolution with improved contrast-to-noise ratio. For a vascular task, PCCT modes showed lower noise and improved iodine detectability. For a high resolution task, macro mode showed lower noise and comparable resolution while UHR mode showed higher noise but improved spatial resolution for both air and bone. PCCT offers competitive advantages to EID CT for clinical tasks.