Quantitative image markers of super-resolution ultrasound

Super-resolution ultrasound, with its ability to achieve sub-diffraction resolution and directly track microvascular flow velocity in vivo, offers a level of vascular information inaccessible previously. To fully realise its clinical value, quantitative vascular markers have been explored. In this review, we explore the quantitative super-resolution markers that have been reported, with a focus on occasions where markers have been applied in a clinical or pre-clinical setting, comparing healthy and diseased cases to test the validity and usefulness of these markers. We define all the used markers from structural markers such as vessel density to velocity metrics such as flow rate, we then provide a summary showing what has been attempted and what has been found successful. We hope that this review can act as a guide both as to the range of markers that currently exist as well as indications as to what markers show potential for each clinical application.