Acoustic radiation force induced accumulation and dynamics of microbubbles on compliant surfaces.

Ultrasound stimulated microbubbles have been shown to be capable of breaking up blood clots through micro-scale interactions occurring near the clot surface. However, only a small fraction of bubbles circulating in the bloodstream will be in close proximity to such boundaries, where they must be to elicit therapeutic effects. Here, the accumulation and subsequent behavior of microbubbles displaced from an overlying flow channel to a boundary under radiation forces were examined.

The microscale evolution of the erosion front of blood clots exposed to ultrasound stimulated microbubbles.

Serial two-photon microscopy of blood clots with fluorescently tagged fibrin networks was conducted during microbubble-mediated sonothrombolysis to examine the microscale evolution of the resulting erosion front. The development of a complex zonal erosion pattern was observed, comprised of a cell depleted layer of fibrin network overlying intact clot which then underwent progressive recession. The fibrin zone architecture was dependent on exposure conditions with 0.

The Effect of Short Duration Ultrasound Pulses on the Interaction Between Individual Microbubbles and Fibrin Clots.

In previous work, we examined microscale interactions between microbubbles and fibrin clots under exposure to 1 ms ultrasound pulses. This provided direct evidence that microbubbles were capable of deforming clot boundaries and penetrating into clots, while also affecting fluid uptake and inducing fibrin network damage. Here, we investigate the effect of short duration (15 μs) pulses on microscale bubble-clot interactions as function of bubble diameter (3-9 μm) and pressure.

In situ conversion of porphyrin microbubbles to nanoparticles for multimodality imaging.

Converting nanoparticles or monomeric compounds into larger supramolecular structures by endogenous or external stimuli is increasingly popular because these materials are useful for imaging and treating diseases. However, conversion of microstructures to nanostructures is less common. Here, we show the conversion of microbubbles to nanoparticles using low-frequency ultrasound.

The influence of compliant boundary proximity on the fundamental and subharmonic emissions from individual microbubbles.

The proximity of a solid-liquid boundary has been theoretically predicted to affect nonlinear microbubble emissions, but to date there has been no experimental validation of this effect. In this study, individual microbubbles (n = 15) were insonicated at f = 11 MHz as a function of offset distance from a compliant (agarose) planar boundary by employing an optical trapping apparatus. It was found that fundamental scattering increases while subharmonic scattering decreases as the microbubble approaches the boundary.

Interactions between individual ultrasound-stimulated microbubbles and fibrin clots.

The use of ultrasound-stimulated microbubbles (USMBs) to promote thrombolysis is well established, but there remains considerable uncertainty about the mechanisms of this process. Here we examine the microscale interactions between individual USMBs and fibrin clots as a function of bubble size, exposure conditions and clot type. Microbubbles (n = 185) were placed adjacent to clot boundaries ("coarse" or "fine") using optical tweezers and exposed to 1-MHz ultrasound as a function of pressure (0.

Scaling of the viscoelastic shell properties of phospholipid encapsulated microbubbles with ultrasound frequency.

Phospholipid encapsulated microbubbles are widely employed as clinical diagnostic ultrasound contrast agents in the 1-5 MHz range, and are increasingly employed at higher ultrasound transmit frequencies. The stiffness and viscosity of the encapsulating "shells" have been shown to play a central role in determining both the linear and nonlinear response of microbubbles to ultrasound. At lower frequencies, recent studies have suggested that shell properties can be frequency dependent.

The effect of boundary proximity on the response of individual ultrasound contrast agent microbubbles.

The effect of boundary proximity on ultrasound contrast agent microbubble emissions can play an important role in the context of both targeted microbubble imaging and contrast imaging of microvascular perfusion. In this study, individual microbubbles (n = 104) were insonicated as a function of distance from either a polystyrene membrane (Opticell(TM)) or a compliant agarose boundary up to offset distances of 1000 µm by use of an optical trapping setup. An 'acoustic spectroscopy' approach was employed, which entailed transmitting a sequence of tone bursts with centre frequencies ranging from 4 to 13.

Methylene blue microbubbles as a model dual-modality contrast agent for ultrasound and activatable photoacoustic imaging.

Ultrasound and photoacoustic imaging are highly complementary modalities since both use ultrasonic detection for operation. Increasingly, photoacoustic and ultrasound have been integrated in terms of hardware instrumentation. To generate a broadly accessible dual-modality contrast agent, we generated microbubbles (a standard ultrasound contrast agent) in a solution of methylene blue (a standard photoacoustic dye).

Real-time guidance of thermal and ultrashort pulsed laser ablation in hard tissue using inline coherent imaging.

Background And Objective: During tissue ablation, laser light can be delivered with high precision in the transverse dimensions but final incision depth can be difficult to control. We monitor incision depth as it progresses, providing feedback to ensure that material removal occurs within a localized target volume, reducing the possibility of undesirable damage to tissues below the incision.

Materials And Methods: Ex vivo cortical and cancellous bone was ablated using pulsed lasers with center wavelengths of 1,064 and 1,070 nm, while being imaged in real-time using inline coherent imaging (ICI) at rates of up to 300 kHz and axial resolution of ∼6 µm.

In situ 24 kHz coherent imaging of morphology change in laser percussion drilling.

We observe sample morphology changes in real time (24 kHz) during and between percussion drilling pulses by integrating a low-coherence microscope into a laser micromachining platform. Nonuniform cut speed and sidewall evolution in stainless steel are observed to strongly depend on assist gas. Interpulse morphology relaxation such as hole refill is directly imaged, showing dramatic differences in the material removal process dependent on pulse duration/peak power (micros/0.