E1203. Ultra-Low-Dose Photon-Counting CT With Spectral Shaping: How Low Can We Go in Paranasal Sinus Imaging?
  1. Jan-Peter Grunz; University Hospital Würzburg
  2. Andreas Kunz; University Hospital Würzburg
Spectral shaping can facilitate dose reduction for high-contrast imaging tasks. In this study, we compared the performance of a photon-counting (PCD-CT) and energy-integrating detector CT (EID-CT) for ultra-low-dose paranasal sinus examinations with employed tin prefiltration. The aim of our work was to define the most dose-effective scan protocols for diagnostic assessment of midface trauma, preoperative sinonasal anatomy and acute rhinosinusitis.

Materials and Methods:
Five cadaveric heads were examined with the standard-resolution scan mode of both CT systems using a tube voltage of 100 kV and tin prefiltration for seven dose-matched scan protocols (CTDIvol = 4.16 – 0.15 mGy) and two additional ultra-low-dose protocols exclusively feasible on the PCD-CT scanner (0.10 and 0.08 mGy). After applying comparable iterative reconstruction algorithms, image quality was subjectively evaluated by four radiologists. Categorical results were compared with Friedman’s ANOVA and post-hoc homogeneous subset analyses for multiple comparisons. The intraclass correlation coefficient (ICC) based on absolute agreement of single measures in a two-way random-effects model was calculated to assess interrater agreement. Image noise was quantified in standardized regions of interest to establish an additional quantitative criterion of image quality.

The most dose-effective scan protocols for diagnostic imaging of midface trauma (PCD-CT: 1.24 mGy; EID-CT: 2.05 mGy), preoperative sinonasal anatomy (PCD-CT: 0.20 mGy; EID-CT: 0.40 mGy), and acute rhinosinusitis (PCD-CT: 0.08 mGy; EID-CT: 0.15 mGy) required less radiation exposure on the PCD-CT system (p < 0.050). Ultra-low-dose PCD-CT studies (0.08 and 0.10 mGy) were considered suitable for inflammation-focused imaging, offering lower dose penalties than EID-CT studies. Interobserver agreement was excellent, indicated by an ICC value of 0.90 (95% confidence interval 0.88 – 0.93; p <0.001).

In paranasal sinus imaging with tin prefiltration, PCD-CT allows for superior dose efficiency compared to conventional EID-CT. Diagnostic assessment of rhinosinusitis with an ultra-low radiation exposure of 0.08 mGy is feasible, suggesting substantial dose reduction potential for clinical routine.