Ultrasound microvessel imaging: a step toward clinical integration in image‑guided radiotherapy

Ultrafast ultrasound imaging, enabled by plane-wave acquisition, achieves frame rates over 10,000 frames per second, which is more than 100 times faster than conventional clinical ultrasound. This high temporal resolution allows for visualization of microvascular flow, opening new opportunities in tumor localization and treatment response monitoring for radiotherapy. In this study, we evaluated the feasibility of ultrafast ultrasound microvessel imaging using a controlled phantom model. A vessel-mimicking tube was submerged in a water tank, and intermittent water flow with air gaps was introduced to simulate sparse flow dynamics. Data were acquired using a Verasonics Ultrafast Ultrasound system with a P4-2v phased array probe at a frame rate of ~800Hz. Beamformed IQ data were processed with rigid motion correction to reduce tank-induced disturbances, followed by singular value decomposition (SVD) filtering to isolate flow signals from noise and background motion. The resulting images demonstrated significantly enhanced visibility of air bubble motion and sparse flow features, confirming the ability of this method to detect low-amplitude flow. Local adaptive thresholding and Gaussian filtering further improved image quality. These findings validate the use of ultrafast ultrasound with SVD filtering and motion correction as a microvascular imaging technique. Future work will focus on translating this technique to in vivo imaging and integrating it into the radiation therapy workflow to further improve image-guided adaptive radiotherapy. A clinical study is planned to evaluate its potential for real-time tumor visualization and monitoring treatment response during radiotherapy.