Although conventional Doppler techniques have been widely applied to detect the flow velocity in large vessels, its sensitivity is insufficient to detect and quantify slow microvascular flow: the slow flow is difficult to be distinguished from the tissue motion that manifests similar dynamics. Ultrasensitive Doppler (USD) is capable of imaging the flow in small vessels, which set stages for quantifying tissue perfusion. We developed a 3-D USD method by combining ultrafast ultrasound and spatio-temporal clutter filtering. This method was validated in vitro and evaluated in vivo in women with palpable breast masses. The 3-D USD revealed increased flow in malignant lesions with respect to benign ones. Additionally, we characterized commercial USD implementations by Canon and Siemens Healthineers. In a blood-flow-mimicking phantom experiment, where 0.25–14.0 mm/s flows were generated through a syringe pump, the USD method showed excellent linear relation between imposed and measured flow although an offset of 1.25 mm/s was present over the full range. Recently, USD was evaluated to improve diagnosis in patients at the (neonatal) intensive care unit and in women with a palpable breast mass. The first study revealed that with USD slow flow in the cerebral cortex can be visualized as well as feeding arteries in the centre of the gyrus. With conventional Doppler, only the large feeding arteries in the base of the gyrus can be visualized. Initial measurements in breast reveal more flow close to malignant than near benign lesions.
Korte et al. (Wed,) studied this question.