Abstract
BackgroundThe global prevalence and incidence of renal calculi is reported to be increasing. Of the patients that undergo surgical intervention, nearly half experience symptomatic complications associated with stone fragments that are not passed and require follow-up surgical intervention. In a clinical simulation using a clinical prototype, ultrasonic propulsion was proven effective at repositioning kidney stones in pigs. The use of ultrasound to reposition smaller stones or stone fragments to a location that facilitates spontaneous clearance could therefore improve stone-free rates. The goal of this study was to determine an injury threshold under which stones could be safely repositioned.MethodsKidneys of 28 domestic swine were treated with exposures that ranged in duty cycle from 0%–100% and spatial peak pulse average intensities up to 30 kW/cm2 for a total duration of 10 min. The kidneys were processed for morphological analysis and evaluated for injury by experts blinded to the exposure conditions.ResultsAt a duty cycle of 3.3%, a spatial peak intensity threshold of 16,620 W/cm2 was needed before a statistically significant portion of the samples showed injury. This is nearly seven times the 2,400-W/cm2 maximum output of the clinical prototype used to move the stones effectively in pigs.ConclusionsThe data obtained from this study show that exposure of kidneys to ultrasonic propulsion for displacing renal calculi is well below the threshold for tissue injury.
Highlights
The global prevalence and incidence of renal calculi is reported to be increasing
The potential for tissue damage resulting from US has resulted in a need for safety guidelines to be established
Despite the decades of research on the bioeffects of US, safety guidelines for therapeutic US have yet to be established [3], and treatment levels that lie between traditional diagnostic and
Summary
The global prevalence and incidence of renal calculi is reported to be increasing. Of the patients that undergo surgical intervention, nearly half experience symptomatic complications associated with stone fragments that are not passed and require follow-up surgical intervention. The clinical uses of ultrasound (US) span both diagnostic and therapeutic applications. This broad range of applications is due to the variety of bioeffects that can be elicited in tissue with US. Guidance on the safety of diagnostic US was initiated in the 1970s, early discussions focused only on thermal bioeffects. It was not until the late 1980s that the safety of non-thermal mechanics was considered [1,2]. Despite the decades of research on the bioeffects of US, safety guidelines for therapeutic US have yet to be established [3], and treatment levels that lie between traditional diagnostic and
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