Large Volume Coagulation Utilizing Multiple Cavitation Clouds Generated by Array Transducer Driven by 32 Channel Drive Circuits

Abstract

The results of nanoindentation testing strongly rely on load-displacement curves, but an abnormal load-displacement curve with obvious inflection in the unloading portion was commonly observed in previously published papers and the reason is not clear. In this paper, possible reasons involved in a custom-made indentation instrument, such as sensors, control and assembly issues, are analyzed and discussed step by step. Experimental results indicate that non-ideal assembly of the precision driving unit strongly affects the shape of the load-displacement curve and its affecting mechanism is studied by theoretical analysis and finite element simulations. This paper reveals the reason leading to the abnormal load-displacement curve, which is helpful for debugging of indentation instruments and can enhance comparability of indentation results.

Enhancement of High-Intensity Focused Ultrasound Heating by Short-Pulse Generated Cavitation

“…The larger coagulation region contributed to the efficient use of the ultrasonically generated heat through minimizing the surface-area-to-volume ratio. Similarly, as mentioned in the previous section, multi-trigger HIFU sequences for the lateral enlargement of the treated region have been investigated to effectively coagulate a target tissue [29,[32][33][34][35]. Figure 7 shows the high-speed images of bubble clouds generated by trigger pulses in six focal positions [34].…”

“…The effect of bubble-enhanced ultrasonic heating has been quantitatively assessed by measuring temperature increase with a thermocouple or magnetic resonance (MR) thermometry in many studies [11,13,[15][16][17][18][19][20][21][22][23][30][31][32][33]35]. Figure 8 shows the temperature increases with and without the exposure of trigger pulses in a PAA gel including 15% BSA placed in a water tank [31].…”

“…Multi-trigger HIFU sequences using spot scanning trigger pulses can generate a large coagulation volume of a nearly cylindrical shape [32][33][34][35]. Figure 10 shows coagulation volumes and their standard deviations of chicken breast tissues by various HIFU sequences [33].…”

“…Although increased heat depositions were obtained using microbubbles in the previous research, distorted coagulation regions or temperature distribution were observed, such as tad-pole shaped [12,22,24] or pre-focal [13,19,[24][25][26] heating regions. A "trigger 2 of 20 HIFU" sequence that consists of high-intensity short pulses and following moderate-intensity long bursts has been investigated to avoid such distorted coagulation regions while enhancing the ultrasonic heating [27][28][29][30][31][32][33][34][35][36].…”

Estimation of sonodynamic treatment region with sonochemiluminescence in gel phantom

“…[11][12][13][14][15] The trigger pulse creates a cavitation cloud [16][17][18] upstream of the HIFU focus typically through a shock scattering mechanism. A microbubble, generated by the negative pressure of the preceding HIFU wave, reflects the succeeding HIFU wave, converting its highly positive pressure to negative pressure, which further generates cavitation microbubbles upstream.…”