Monitoring microvascular tortuosity and velocity distribution response of 4T1 tumor to the DOX-NDs treatment using super-resolution ultrasound imaging

Super-resolution ultrasound (SRUS) imaging has been gradually employed for the non-invasive evaluation of tumor intervention, while the comprehensive indicators such as vessel density (VD), tortuosity (VT) and velocity (VV) could easily conceal the local changes of the heterogeneous tumor microvasculature. Herein, our study attempts to construct the novel monitor manner for the local microvascular changes and verify its non-invasion quantitative evaluation of tumor response during intervention. Tumors were delineated into central and peripheral regions based on B-mode images. VD, regional mean VT, and VV indices were quantified for subsequent comparisons of tumor angiogenesis and vessel perfusion over time. SRUS images depicted a gradual reduction in tumor vascularity during treatment. Traditional quantitative data indicated solely a decline in central VD, with marginal VD and VT exhibiting negligible variations. Conversely, a distinct leftward shift in the VT distribution center was evident for peripheral vasculature. Moreover, the VV distribution illustrated a progressive rise in the count of rapidly flowing vessels in the periphery, implying a gradual shift of the tumor's blood supply center from the core to the outskirts. These findings offer a fresh perspective for utilizing SRUS imaging in evaluating intervention responses of highly heterogeneous tumors and guiding more precise therapeutic strategies.