A small volume of an erythrocyte suspension was subjected to the action of a manipulated gas bubble set into stable oscillation at 20 kilohertz. Release of hemoglobin occurred when the oscillation amplitude exceeded a critical threshold. Hydrodynamic stresses resulting from acoustically induced small-scale eddying motion near the bubble may be the mechanism of hemolysis.

Mohs micrographic surgery is safe, with a very low rate of adverse events, an exceedingly low rate of serious adverse events, and an undetectable mortality rate. Common complications include infections, followed by impaired wound healing and bleeding. Bleeding and wound-healing issues are often associated with preexisting anticoagulation therapy, which is nonetheless managed safely during MMS. We are not certain whether the small effects seen with the use of sterile gloves and antiseptics and antibiotics are clinically significant and whether wide-scale practice changes would be cost-effective given the small risk reductions.

By controlled irradiation of erythrocyte suspensions at 20 kHz it is demonstrated that shear associated with acoustic microstreaming can be an important mechanism for biological effects of sound. Two effective sources of acoustic microstreaming are stable oscillating gas bubbles and transversely oscillating wires. The threshold displacement amplitude for achieving critical shear can be reduced by increasing the solvent viscosity and reducing the radius of the source of acoustic streaming. The threshold stress was found to decrease by 55% or more when the sample was heated to 45°C or higher for 10 min. This suggests that synergism exists between mechanical and thermal mechanisms for sonic effects. Mass transfer associated with small-scale acoustic streaming controls the rate of cell disruption.

No abstract

A theory is developed for acoustic radiation pressure exerted by a plane wave on a perfect absorber, using Euler's momentum theorem. For the case of an open vessel, the radiation pressure P equals the mean energy density E even when nonlinearities of the medium and distortion of wave form are taken into account. For a closed vessel P equals [1 + 12(B/A)]E. The term B/A describes the non-linearity in the pressure-density relation for the medium and equals γ−1 for the case of an ideal gas under adiabatic conditions.

No abstract

Quantitative ultrasound (QUS) parameters are temperature dependent. We examined the effect of temperature on QUS using Lunar Achilles+ and Hologic Sahara units. In vivo studies were performed in a cadaveric foot and in 5 volunteers. QUS scans were performed in the cadaveric foot, using both machines, at temperatures ranging from 15 to 40 degrees C. To assess the effect of change in water bath temperature in the Achilles+, independently of foot temperature, 5 volunteers were studied at water temperatures ranging from 10 to 42 degrees C. In the cadaveric foot there were strong negative correlations between temperature and speed of sound (SOS) but a moderately positive correlation between temperature and broadband ultrasound attenuation (BUA). Stiffness and the Quantitative Ultrasound Index (QUI) in the cadaveric foot showed strong negative correlations with temperature, reflecting their high dependence on SOS. In the 5 volunteers, in whom foot temperature was assumed to be constant, there was a small change in Stiffness in the Achilles+, with variation in water temperature. In conclusion, while there are opposite effects of temperature on SOS and BUA in vivo, there is still a significant effect of temperature variation on Stiffness and the QUI. This may have clinical significance in particular subjects. The precision of QUS may be affected by temperature variation of the environment or of the patient's limb. Instruments utilizing a water bath may be able partly to compensate for changes in environmental temperature, but standardization of water bath temperature is crucial to maximize precision.

The effects of continuous wave ultrasound at a frequency of 1 MHz in the intensity range of 0-1.4 W/cm2 on an oxidized cholesterol bilayer lipid membrane (BLM) were observed. Ultrasound at 1.5 W/cm2 broke the membrane; in the range from 0.5 to 1.4 W/cm2, it accelerated the draining of the bulk lipid solution from the annulus to the Teflon support. At all intensities it has no effect on the conductance, the capacitance, or the dependence of each on the voltage applied across the membrane. Electrical parameters were measured in the presence of aqueous solutions of NaCl, KCl, and distilled water. The motivation and results of this project are explained in relation to an overall objective of determining the specific effects of ultrasound on biological membranes.