The role of cavitation in vascular occlusion

Abstract

Ed Carstensen’s papers on the effects of ultrasound on plants were amongst the first that attracted me to study ultrasound bio-effects. It was little surprise to me that, when I first started looking at HIFU, his name was on many of the seminal papers in this area. And now, his papers on cavitation and vasculature inform our current research. Ed’s influence on bio-effects research stretches far beyond the borders of the USA Vascular occlusion has the potential to treat life-threatening conditions including twin-twin transfusion syndrome (occurring in fetuses that share a placenta). Sheep placental vessels have been used to develop HIFU treatment guidance, delivery (1.66MHz) and monitoring. Ultrasound imaging guidance/flow monitoring, with simultaneous acoustic cavitation detection in 82 targets in 14 pregnant sheep resulted in flow occlusion in 90%. Adverse events included skin erythema (18/82) and burns (10/82), but all resolved over 21 days. Analysis of acoustic cavitation required low pass (software) filtering and careful choice of broadband integration range (0.1 to 1.1 MHz). 9% of successful treatments displayed detectable broadband, 32% with half-harmonic and 1% with drive-voltage fluctuations. In conclusion, treatment is possible, side effects are manageable, and acoustic cavitation appears not to be essential for successful occlusion.