Photon Counting CT of the Head: Retrospective Analysis of Image Quality and Dose in Comparison to Energy Integrating Detector CT

RATIONALE AND OBJECTIVES: Non-contrast computed tomography (CT) of the head (NCCT) is one of the most frequently performed CT examination in emergency settings. Photon-counting detector CT (PCD-CT) promises reduced radiation dose and improved image quality, yet systematic data for NCCT - particularly under varying acquisition parameters - remain scarce. MATERIALS AND METHODS: In this retrospective study, patients undergoing NCCT with PCD-CT at 120 and 140 kVp and varying radiation doses were compared with patients scanned on a modern energy-integrating detector (EID-CT) system. Each PCD-CT subgroup was evaluated separately and compared with the EID-CT group using both quantitative and qualitative analyses. Quantitative assessment employed 16 regions of interest (ROIs), for qualitative analysis images were rated by four radiologists using five-point Likert scales. RESULTS: In total, 428 patients were included. On PCD-CT, virtual monoenergetic images (VMI) 65 keV at 120 kVp demonstrated the best quantitative image parameters. At comparable radiation dose noise was lower for EID-CT in several cortical regions (p ≤ 0.01). Contrast was higher for EID-CT at most brain locations (p < 0.05), except in the inferior caudate head and thalamus. In contrast, subjective image quality assessment showed higher ratings for PCD-CT regarding noise (4.60 ± 0.61 vs. 3.94 ± 0.93; p < 0.001) and overall image quality (4.43 ± 0.63 vs. 4.08 ± 0.93; p = 0.02), with substantial interreader reliability. CONCLUSION: PCD-CT achieved comparable radiation dose and superior subjective image quality compared to a modern EID-CT for NCCT, although some objective quantitative parameters favored EID-CT. Further optimization of reconstruction algorithms, particularly polyenergetic reconstructions, may unlock the full potential of PCD-CT for routine neuroimaging.