Special Collection: Ultrafast Contrast Imaging
- Quantification of 3-D intravascular flow is valuable for studying arterial wall diseases but currently there is a lack of effective clinical tools for this purpose. Divergence-free interpolation (DFI) using radial basis function (RBF) is an emerging approach for full-field flow reconstruction using experimental sparse flow field samples. Previous DFI reconstructs full-field flow from scattered 3-D velocity input obtained using phase-contrast magnetic resonance imaging with low temporal resolution.
- Bubble-seeded histotripsy (BSH) is a newly developed ultrasound-based mechanical fractionation technique using locally injected phase change nanodroplets (PCNDs) as sensitizers. The PCNDs are a kind of microbubble precursor compressed into submicron-size in droplets form, which were designed for local administration and will expand into microbubbles under ultrasound exposure. Previously, we reported that a combination of PCNDs injection and pulsed high-intensity focused ultrasound (pHIFU) with an acoustic intensity as low as about 3 kW/cm2 at 1.1 MHz, which is similar to the acoustic intensity of currently available HIFU coagulation therapy, was enough to induce tissue fractionation after significant antitumor effects in an in vivo study.
- In this study, a technique for high-frame-rate ultrasound imaging velocimetry (UIV) is extended first to provide more robust quantitative flow velocity mapping using ensemble correlation of images without coherent compounding, and second to generate spatio-temporal wall shear stress (WSS) distribution. A simulation model, which couples the ultrasound simulator with analytical flow solution, was implemented to evaluate its accuracy. It is shown that the proposed approach can reduce errors in velocity estimation by up to 10-fold in comparison with the coherent correlation approach.
- There is increasing recognition of the influence of the flow field on the physiology of blood vessels and their development of pathology. Preliminary work is reported on a novel non-invasive technique, microbubble void imaging, which is based on ultrasound and controlled destruction of microbubble contrast agents, permitting flow visualisation and quantification of flow-induced mixing in large vessels. The generation of microbubble voids can be controlled both spatially and temporally using ultrasound parameters within the safety limits.
- Ultrasound imaging is the most widely used method for visualising and quantifying blood flow in medical practice, but existing techniques have various limitations in terms of imaging sensitivity, field of view, flow angle dependence, and imaging depth. In this study, we developed an ultrasound imaging velocimetry approach capable of visualising and quantifying dynamic flow, by combining high-frame-rate plane wave ultrasound imaging, microbubble contrast agents, pulse inversion contrast imaging and speckle image tracking algorithms.