Abstract
BackgroundAcoustic cavitation plays an important role in the medical treatment using high-intensity focused ultrasound (HIFU), but unnecessarily strong cavitation also could deform the morphology and enlarge the size of lesions. It is known that the increase of ambient hydrostatic pressure (Pstat) can control the acoustic cavitation. But the question of how the decrease of Pstat and dissolved oxygen concentration (DOC) influence the strength of cavitation has not been thoroughly answered. In this study, we aimed to investigate the relationship among the Pstat, DOC and the strength of cavitation.MethodsEx vivo bovine liver tissues were immersed in degassed water with different DOC of 1.0 mg/L, 1.5 mg/L and 2.0 mg/L. Ultrasound (US) of 1 MHz and the spatial and temporal average intensity (Isata) of 6500 W/cm2 was used to expose two groups of in vitro bovine livers for 2 s; one group was under atmospheric pressure (Pstat = 1 bar) and the other was under sub-atmospheric pressure (Pstat = 0.1 bar). Acoustic cavitation was detected by a passive cavitation detector (PCD) during the exposure process. Echo signals at the focal zone of HIFU were monitored by B-mode ultrasound imaging before and after exposure. The difference between two pressure groups was tested using paired sample t-test. The difference among different DOC groups was evaluated by one-way analysis of variance (ANOVA).ResultsThe results demonstrated a significant difference of broadband acoustic emissions from the cavitation bubbles, echo signals on B-mode image, morphology of lesions under various conditions of ambient pressure and DOC. The lesion volume in tissue was increased with the increase of ambient pressure and DOC.ConclusionCavitation could be suppressed through sub-atmospheric pressure and low DOC level in liver tissue, which could provide a method of controlling cavitation in HIFU treatment to avoid unpredictable lesions.
Highlights
Acoustic cavitation plays an important role in the medical treatment using high-intensity focused ultrasound (HIFU), but unnecessarily strong cavitation could deform the morphology and enlarge the size of lesions
Cavitation signal Under the conditions of atmospheric pressure and sub-atmospheric pressure, the broadband emissions from ex vivo bovine liver exposed by HIFU in degassed water
The violent collapse of transient cavitation is the only source of broadband emissions [15], these results indicated that each dissolved oxygen concentration (DOC) level had transient cavitation behavior during HIFU exposure under atmospheric pressure, but under the condition of sub-atmospheric pressure, only 2.0 mg/L had transient cavitation behavior
Summary
Acoustic cavitation plays an important role in the medical treatment using high-intensity focused ultrasound (HIFU), but unnecessarily strong cavitation could deform the morphology and enlarge the size of lesions. During HIFU treatment, acoustic cavitation plays an important role through the collapse of oscillating microbubbles in tissues [9, 10]. Chapelon et al [19,20,21] observed irregular lesion outside the focal zone when uncontrolled cavitation occurred during HIFU treatment, which affected the therapeutic effects of targeted tissue. They strongly recommended that acoustic cavitation during the treatment should be avoided
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
