(Color online) Thrombus on a silk thread.
(Color online) Experimental setup: (1) Needle hydrophone for passive cavitation detection system, (2) flow inlet, (3) data analysis, (4) microbubble infusion, (5) unidirectional flow pump, (6) hemispherical helmet transducer filled with deionized, degassed water, (7) human calvaria mounted on an acrylic fixture, and (8) human blood clot.
Scanning electron micrograph of a human citrate blood clot before HIFU treatment (left column) and after HIFU treatment (right column). The images on the left show a dense fibrin fiber network with numerous cells incorporated into the matrix prior to HIFU exposure.
Dynamics of a single bubble wholly embedded in a blood clot, for various acoustic input amplitudes, , , and MPa for a bubble with initial radius R 0 = 1 μm.
Sketch of the deformation. The bubble expands from in the reference configuration, to R(t) in the deformed configuration. Accompanying this is a deformation of the surrounding clot matrix. In particular, an individual fibrin fiber aligned closely with in the reference configuration is deformed to lie more closely to and stretched when .
The number and fraction of broken fibers for the bubble dynamics shown in Fig. 4 . (a) Estimates of the number of broken fibers in a shell of thickness , plotted as a function of the distance from the bubble center in the reference configuration. (b) The fraction of broken fibers is also shown as a function of distance from bubble center. As expected, the highest fraction of fibers broken are close to the initial bubble surface.
The work done on the liquid outside the bubble by the acoustic wave as the bubble radius changes from R 0 to as a function of viscosity. Various acoustic input amplitudes, , 1.0, and 1.5 MPa for a bubble with initial radius R 0 = 1 μm are shown. The location of the maximum of each curve serves to define .
(Color online) The array transducer in position above the calvaria.
(Color online) Instantaneous pressure distribution in a two-dimensional slice of the three-dimensional computational domain. Contours vary from −0.51 to 0.51 MPa. Geometrical focus is at the bottom tip of the line running along the central ordinate of the plot.
Temporal variation of the pressure at the focus for a median density skull.
Radial dynamics of a bubble in water with initial radius of 0.27 μm in the left column and 8.0 μm in the right column located at the focus for lower, median, and higher density skulls.
Acoustic power spectrum of a bubble in water with an initial radius of 0.27 μm in the left column and 8.0 μm in the right column located at the focus for lower, median, and higher density skulls.
The maximum radii in μm (left) and amount of energy available to break fibers and red blood cells in nJ (right) along the x and y axes as the initial bubble radius is varied for a calvaria of median density. The z plots (not shown) are similar to x plots. The focus is located at 0 mm on each axis.
The total number of fibers broken and the energy used breaking them for various applied acoustic magnitudes.
The work done by the acoustic wave, the work done by the gas pressure, the work done by surface tension, the stored energy in the fluid and the viscous loss in the fluid for a bubble embedded in a clot with no damage and a bubble embedded in a broken clot with viscosity for a R 0 = 1 μm bubble for various applied acoustic pressure magnitudes. The maximum number of broken fibers is computed using the upper bound from Eq. (23) divided by the energy to break a single fibrin fiber.
The amount of work done by the acoustic wave on the bubble until collapse, , is transferred to the kinetic energy of the jet. This provides an upper bound for the number of fibers broken.
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