Abstract
Conventional histotripsy uses ultrasound pulses longer than three cycles wherein the bubble cloud formation relies on the pressure-release scattering of the positive shock fronts from sparsely distributed single cavitation bubbles, making the cavitation event unpredictable and sometimes chaotic. Recently, we have developed three new strategic histotripsy pulsing techniques to further increase the precision of cavitation cloud and lesion formation. (1) Microtripsy: When applying histotripsy pulses shorter than three cycles, the formation of a dense bubble cloud only depends on the applied peak negative pressure (P-) exceeding an intrinsic threshold of the medium. With a P- not significantly higher than this, very precise sub-vocal-volume lesions can be generated. (2) Dual-beam histotripsy: A sub-threshold high-frequency pulse (perhaps from an imaging transducer) is enabled by a sub-threshold low-frequency pump pulse to exceed the intrinsic threshold and produces very precise lesions. (3) Frequency compounding: a near monopolar pulse can be synthesized using a frequency-compounding transducer (an array transducer consisting of elements with various resonant frequencies). By adjusting time delays for individual frequency components and allowing their principal negative peaks to arrive at the focus concurrently, a near monopolar pulse with a dominant negative phase can be generated (no complicating high peak positive shock fronts).
Published Version
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