Objectives: To evaluate the value of virtual monoenergetic images (VMI) from photon-counting detector CT (PCD-CT) for discriminability of severe lung injury and atelectasis in polytraumatized patients. Materials & Methods: Contrast-enhanced PCD-CT examinations of 20 polytraumatized patients with severe thoracic trauma were included in this retrospective study. Spectral PCD-CT data were reconstructed using a noise-optimized virtual monoenergetic imaging (VMI) algorithm with calculated VMIs ranging from 40 to 120 keV at 10 keV increments. Injury-to-atelectasis contrast-to-noise ratio (CNR) was calculated and compared at each energy level based on CT number measurements in severely injured as well as atelectatic lung areas. Three radiologists assessed subjective discriminability, noise perception, and overall image quality. Results: CT values for atelectasis decreased as photon energy increased from 40 keV to 120 keV (mean Hounsfield units (HU): 69 at 40 keV; 342 at 120 keV), whereas CT values for severe lung injury remained near-constant from 40 keV to 120 keV (mean HU: 42 at 40 keV; 44 at 120 keV) with significant differences at each keV level (p < 0.001). The optimal injury-to-atelectasis CNR was observed at 40 keV in comparison with the remaining energy levels (p < 0.001) except for 50 keV (p > 0.05). In line with this, VMIs at 40 keV were rated best regarding subjective discriminability. VMIs at 60–70 keV, however, provided the highest subjective observer parameters regarding subjective image noise as well as image quality. Conclusions: Discriminability between severely injured and atelectatic lung areas after thoracic trauma can be substantially improved by virtual monoenergetic imaging from PCD-CT with superior contrast and visual discriminability at 40–50 keV.

Liquid biomarkers are essential in trauma cases and critical care and offer valuable insights into the extent of injury, prognostic predictions, and treatment guidance. They can help assess the severity of organ damage (OD), assist in treatment decisions and forecast patient outcomes. Notably, small extracellular vesicles, particularly those involved in splenic trauma, have been overlooked. Here, we reanalyzed our data and explored whether monocyte-derived small EVs are correlated with AAST score (American Association for the Surgery of Trauma) scoring and are sensitive enough to distinguish the severity of splenic trauma in our explorative study. There was a correlation between monocyte-derived small extracellular vesicles (EVs) and the AAST score (r_Sp = 0.82, p < 0.001). Specifically, we observed that blood-borne small EVs originating from monocytes (CD9⁺CD14⁺ sEVs) were directly correlated with AAST scores. These EVs were found to be significantly elevated in patients with complex spleen injuries (AAST I–IV with hemodynamic instability and need for operative management) in an incremental manner; these patients were typically classified as AAST grade II or higher, which frequently included accompanying solid organ injuries. Our initial discovery shows great promise and warrants further exploration. This could pave a novel future path for a new critical care management approach for splenic injuries. There may also be synergistic effects when combined with extended focused assessment with sonography in trauma (E-FAST) sonography, particularly in triage scenarios, where resource constraints prevent immediate access to a CT scan.