The Power Setting of Focused Ultrasound for the Palliative Treatment of Advanced Pancreatic Cancer: A Study in an Ex Vivo Bovine Liver

Abstract

High-intensity focused ultrasound (HIFU) ablation has been widely used in advanced pancreatic cancer in recent years. In numerous studies, HIFU has been shown to be safe, effective, and practicable, but there are a few HIFU-related adverse effects. The patients’ discomfort during therapy increased proportionally with increasing delivered energy and pain levels seemed to be independent of the dose of anesthetic or sedation. If the power used in therapy is too high, the temperature of the target area will rise rapidly, and the boiling and cavitation make the shape of the necrosis area difficult to control. In recent years, moderate-intensity focused ultrasound (MIFU) has also been shown to heat the tumor locally for palliative treatment. Choosing the appropriate power and effectively controlling the tissue temperature until reaching the threshold for thermal necrosis are of great significance for ensuring the safety of palliative treatment. In this study, an infrared temperature measurement experimental system was set up to measure the temperature rise at different power in an ex vivo bovine liver. It was found that when the acoustic intensity of the focused ultrasound was lower than the cavitation threshold (within the range of the MIFU), the temperature of the tissue kept rising at a steady rate and could still reach the thermal damage threshold temperature within tens of seconds. The results showed that the temperature induced by the MIFU was almost entirely dependent on the thermal effect, and the temperature of the tissue at the end of sonication was linearly related to the power. Finally, this study considered the effect of blood perfusion on the temperature for the application of focused ultrasound in the palliative treatment of advanced pancreatic cancer with the goal of providing a reference for the application of focused ultrasound in the palliative treatment of advanced pancreatic cancer.

Numerical Study on the Application of Near-Infrared Temperature Distribution Measurement of HIFU

“…VHA occur at the thermocouple tissue interface, caused by the difference in the densities between the thermocouple and the surrounding tissue [21]. In 2008,Morris et al showed temperature measurements using metal wire thermocouples can have an error of up to 80% [22].…”

“…For instance, waiting times such as 0.5 s after the start of ultrasound or 200 milliseconds [23], 2 s [24], and 5 s [25] after ultrasound cessation have been reported. Another method is simulation, used to estimate the temperature increase caused by viscous heating and correct the temperature reading [22]. No matter which method is used, there are inconveniences, which also highlight the limitations of thermocouples.…”

Direct Numerical Simulation of Bubble Cluster Collapse: Shape Evolution and Energy Transfer Mechanisms

“…Researchers generally aim to prevent and mitigate the impact of cavitation effects during the design phase. On the other hand, the cavitation phenomenon plays a crucial role in ultrasound-based therapeutic diagnosis [4,5], which requires prior cavitation prediction. Thus, to both prevent and leverage the cavitation effect, estimating its intensity in the target flow field is vital.…”