Microvascular flow imaging by ultrasound for the evaluation of perivenous inflammation in superficial vein thrombosis: a pilot study

Background Inflammation plays a key role in venous thromboembolic disorder, contributing to both thrombus formation, resolution and long-term venous complications. Conventional ultrasound, although its efficacy for detecting thrombosis, does not allow in vivo assessment of local inflammatory activity. Microvascular Flow Imaging (MVFI) is a novel ultrasound modality that enables high-resolution assessment of slow microvascular flow. Purpose This pilot study aimed to evaluate the ability of MVFI and MVFI-derived Vascularity Index (VI) to quantify perivenous microvascularization as a surrogate marker of inflammation in acute superficial vein thrombosis (SVT). Methods This prospective single-center pilot study included consecutive patients with ultrasound-confirmed acute SVT. MVFI was performed within five days of symptom onset using standardized MV-Flow mode settings of Samsung RS85. VI was defined as the percentage of pixels with detectable flow within a predefined region of interest (ROI). Clinical signs and inflammatory markers (C-reactive protein [CRP], white blood cell count) were recorded. A subset of 10 patients underwent follow-up ultrasound at one month to assess changes over time in VI and inflammatory markers. Correlations were assessed using Spearman’s rank test, and paired comparisons using the Wilcoxon signed-rank test. Results Twenty-five patients with acute SVT were included (median age 60 years [50–67]; 52% male). SVT occurred most commonly following catheter placement (64%), and in patients with cancer (32%). At baseline, median VI was 21.3% [12.6–30.5] and CRP 27.1 mg/L [12.7–83.3]. No correlation was observed between VI and CRP levels at baseline. At one month, in the subgroup of patients with follow-up imaging, VI significantly decreased from a median of 27.4% to 2.7% (p<0.001), in parallel with CRP reduction from a median of 39.7 mg/L to 5.2 mg/L (p=0.003). A significant correlation between follow-up VI and CRP levels was observed (Spearman Rho: 0.662; p=0.004). Conclusion MVFI enables non-invasive quantification of perithrombotic microvascularization in acute SVT. The significant reduction of VI during follow-up supports its role as a novel imaging biomarker of thrombus-related inflammation. Larger studies are warranted to confirm its clinical utility and to explore its applicability in deep vein thrombosis.BarplotFigure