Studies of the cavitational effects of clinical ultrasound by sonoluminescence: 1. Correlation of sonoluminescence with the standing wave pattern in an acoustic field produced by a therapeutic unit

Abstract

A Therasonic 1030 (Electro-Medical Supplies) therapeutic ultrasound generator operating at 1 Mkiz continuous wave was used to insonate aerated water at two temperatures, 22 "C and 37 "C. Using various acoustically reflecting materials, sound fields were set up with different standing wave components. Measurements of the acoustic pressure variations on the axis of the sound fields were made using a needle hydrophone and the results were compared with photographs of the spatial distributions of the image intensified sonoluminescent light output. The near field region was used, thereby simulating the clinical situation.Sustained sonoluminescence was observed for nominal intensities of 3 W cm-*, and acoustic reflections of greater than 40%. Under these conditions, if sonoluminescence did not appear spontaneously it could always be induced by rotating the transducer. Whenever bands of maximum light output formed they correlated closely with the pressure antinodes in the standing wave pattern. Very little light was produced by travelling wave fields.

Geometric Optimization of Sonoreactors for the Enhancement of Sonochemical Activity

“…Even though there was no direct evidence for the claim that the traveling wave field is dominant in the dispersed bright zone, the fact that the observation of stripes represents the formation of standing wave field can firmly support the claim. 33,39 Considering the distribution and brightness of the SCL as well as the relative intensity for 36 kHz, it seems that the highest liquid height was the best choice for sonochemical activity among all applied liquid heights in this study. As the liquid height increased, the total SCL intensity is increased as shown in Table 2 and the sonochemical activity (the cavitation yield) also increased.…”

“…33,34 As the liquid height is increased, larger and more stable standing wave field is formed and the antinodes and nodes are clearly visible.…”

Prediction of far-field acoustic emissions from cavitation clouds during shock wave lithotripsy for development of a clinical device

“…This third paper extends those methods to multiple bubbles because, in most practical cases, the erosive effect and the far-field emission will depend on the response of a cloud that can not only generate a summation of single-bubble effects, but can also generate important effects through the interactions between bubbles (such as cooperative bubble effects in the generation of erosion) [22][23][24]. The degree of influence of a bubble on its neighbours is dependent on their separation distance, size, composition clustering, the incident pressure field and the location and composition of any boundaries present (such as a kidney stone might represent) [25][26][27][28][29][30][31][32][33]. Recently, Lauer et al [34] simulated the collapse of two-dimensional arrays of cavities by a planar shock wave using the so-called 'conservative interface interaction' method where the fluid-fluid interface was tracked using a level-set approach to study the collapse mechanisms of arrays of cavities and the effects of separation distance.…”

Cavitation and non-cavitation regime for large-scale ultrasonic standing wave particle separation systems – In situ gentle cavitation threshold determination and free radical related oxidation

“…When they are large enough to be affected by the acoustic radiation force they will gather in the standing wave pressure anti-nodes. [37] As their size grows towards the size that would resonate at the applied frequency, their amplitude of oscillation increases until they fragment into many small bubbles in the transient cavitation event, creating radicals. Alternatively, for stable cavitation the radicals are generated during many stable resonating cycles without the fragmentation process.…”