Photon-counting detector CT with iodine quantification: improved distinction between bland and neoplastic portal vein thrombosis.

Abstract

Neoplastic portal vein thrombosis (PVT) is a critical prognostic factor in hepatocellular carcinoma (HCC); however, differentiation from bland PVT remains challenging using conventional imaging criteria. Photon-counting detector CT (PCD-CT) enables quantitative iodine density (ID) assessment in every contrast-enhanced acquisition. This study evaluated the diagnostic performance of ID for distinguishing bland from neoplastic PVT. In this retrospective single-center study, 104 patients with suspected PVT who underwent PCD-CT between 09/2022 and 08/2024 were included. Based on imaging, follow-up data, and multidisciplinary consensus, patients were classified into four groups: HCC with neoplastic PVT (n = 18), HCC with bland PVT (n = 29), bland PVT without malignancy (n = 31), and neoplastic PVT in non-HCC malignancies (n = 26). ID was measured in the late arterial phase (LAP) and portal venous phase (PVP) by two independent radiologists and compared with a CT feature-based score including vessel infiltration, thrombus extension, and arterial hyperenhancement. ID measurements demonstrated excellent inter- and intra-rater agreement (ICC ≥ 0.99). ID was significantly higher in neoplastic PVT in both phases. Diagnostic performance was high, with sensitivities and specificities of 100% and 95.9% in LAP and 93.1% and 100% in PVP (AUC 0.98 (95% CI: 0.95-1.00) and 0.97 (95% CI: 0.92-1.00)). The feature-based score showed lower accuracy. In non-HCC malignancies, ID achieved high diagnostic accuracy in PVP. ID derived from PCD-CT reliably differentiates neoplastic from bland PVT in HCC and outperforms conventional CT features. In non-HCC malignancies, ID is particularly accurate in the portal venous phase, supporting its broader clinical utility as an imaging biomarker in this contrast media phase. Question Can iodine density measured by photon-counting detector CT improve the differentiation between bland and neoplastic portal vein thrombosis? Findings Iodine density measurements obtained with photon-counting CT accurately differentiated neoplastic from bland portal vein thrombosis and outperformed established morphologic CT features. Clinical relevance Photon-counting CT-derived iodine density enables reliable, noninvasive identification of neoplastic portal vein thrombosis, thereby improving diagnostic confidence and treatment planning in patients with hepatocellular carcinoma and other malignancies.