Comparison of True and Virtual Non-contrast Venous Attenuation Markers for Anemia Detection in Photon-Counting Detector CT Stroke Imaging

Abstract

Background: Anemia is common among patients with acute ischemic stroke (AIS) and is associated with poorer outcomes, including higher mortality and less favorable recovery. CT-based blood attenuation measurements have been investigated as a noninvasive imaging marker of hemoglobin levels. Objectives: This study evaluates the diagnostic performance of photon-counting detector CT (PCD-CT) for anemia detection using both true non-contrast (TNC) and virtual non-contrast (VNC) images in patients with AIS. Methods: This single-center, retrospective study included 45 AIS patients from a previously investigated cohort who underwent both unenhanced head CT and CT angiography of the supra-aortic vessels on the same PCD-CT system, enabling a vessel-matched comparison of TNC and VNC attenuation measurements in intracranial venous structures. Attenuation measurements were obtained from predefined venous structures, including the great cerebral vein (VCM), superior sagittal sinus (SSS), sigmoid sinus, confluence of sinuses, and internal jugular vein. Hemoglobin levels were classified according to WHO criteria, and correlation, regression, and ROC analyses were performed. Thresholds were selected exploratorily using the Youden index. Results: Forty-five AIS patients were included (20 females, 25 males; mean age 72.2 years), of whom 16 (35.6%) were anemic. TNC measurements in the VCM showed the strongest association with hemoglobin levels (r = 0.75, R2 = 0.56, P < 0.001) and the highest intracranial diagnostic performance for anemia detection (AUC = 0.87; threshold ≤ 42 HU; sensitivity 81.3%; specificity 75.9%). VCM-VNC measurements showed a weaker but significant association with hemoglobin levels (r = 0.51, R2 = 0.26, P < 0.001) and lower diagnostic performance (AUC = 0.72; threshold ≤ 36 HU; sensitivity 87.5%; specificity 62.1%). Among intracranial VNC markers, the sigmoid sinus showed the highest diagnostic performance (AUC = 0.84; threshold ≤ 32.5 HU; sensitivity 81.3%; specificity 79.3%). In the pragmatic non-vessel-matched comparison, internal jugular VNC showed AUC values similar to those of VCM-TNC (0.869 vs. 0.865; DeLong P = 0.485). Conclusions: Attenuation measurements from TNC and VNC PCD-CT images were associated with hemoglobin levels in AIS patients. TNC, particularly in the great cerebral vein, remained the most robust marker in vessel-matched intracranial comparisons. Internal jugular VNC may offer a pragmatic, screening-oriented marker in stroke workflows; however, this non-vessel-matched comparison conflates modality and anatomical-location effects. Prospective validation with time-matched laboratory data is required before clinical implementation.