Histotripsy excitation sequences optimized for bubble cloud formation using shock scattering
Methods and devices for producing cavitation in tissue are provided. In one embodiment, a shock scattering method of Histotripsy therapy comprises delivering an initiation pressure waveform from an ultrasound therapy transducer into tissue, the initiation pressure waveform being configured to produce at least one bubble in the tissue, delivering a scattering pressure waveform from the ultrasound therapy transducer into the at least one bubble within a life-cycle of the at least one bubble, and producing cavitation nuclei near the at least one bubble with the scattering pressure waveform. The scattering pressure waveform can be delivered during the life-cycle of the at least one bubble. In some embodiments, the scattering pressure waveform is delivered within 5 μs to 1 s of the initiation pressure waveform. Systems for performing shock scattering Histotripsy therapy are also discussed.
1. A method of treating tissue with ultrasound energy, comprising the steps of:
delivering a first pulse of a Histotripsy excitation sequence from an ultrasound therapy transducer, the first pulse comprising an initiation pressure waveform configured to produce at least one bubble in the tissue;
delivering a second pulse of the Histotripsy excitation sequence from the ultrasound therapy transducer, the second pulse comprising a scattering pressure waveform configured to interact with the at least one bubble within a life-cycle of the at least one bubble; and
producing cavitation nuclei near the at least one bubble with the scattering pressure waveform.
2. The method of claim 1 , wherein the scattering pressure waveform is delivered within 5 μs to 200 μs of the initiation pressure waveform.
3. The method of claim 1 , further comprising repeating the delivering the initiation pressure waveform and delivering the scattering pressure waveform steps until treatment of the tissue is completed.
4. The method of claim 1 , wherein a peak-to-peak pressure of the scattering pressure waveform is sufficient in amplitude create additional cavitation nuclei in the focal region.
5. The method of claim 1 , further comprising, after delivering the scattering pressure waveform, delivering a second scattering pressure waveform towards the at least one bubble and the cavitation nuclei.
6. The method of claim 5 , wherein the second scattering pressure waveform is delivered within 5 μs to 1 s of the scattering pressure waveform.
7. The method of claim 5 , further comprising delivering additional scattering pressure waveforms without delivering additional initiation pressure waveforms until the at least one bubble and/or the cavitation nuclei no longer remain in the tissue.
8. The method of claim 7 , wherein the additional scattering pressure waveforms are delivered every 5 μs to 1 s.
9. The method of claim 1 , wherein the Histotripsy excitation sequence comprising the initiation pressure waveform and the scattering pressure waveform has a sequence pulse repetition frequency ranging from 1-5000 Hz.
10. The method of claim 1 , wherein the scattering pressure waveform delivers less energy to intervening tissue than the initiation pressure waveform.
11. The method of claim 1 , wherein the initiation pressure waveform and the scattering pressure waveform have similar pressure amplitudes.
12. The method of claim 1 , wherein a pressure amplitude of the scattering pressure waveform is less than a pressure amplitude of the initiation pressure waveform.
13. The method of claim 1 , wherein a pressure amplitude of the scattering pressure waveform is more than a pressure amplitude of the initiation pressure waveform.
14. A method of treating tissue with ultrasound energy, comprising the steps of:
transmitting a first pulse of a Histotripsy excitation sequence from an ultrasound therapy transducer, the first pulse comprising an initiation pressure waveform configured to produce at least one bubble in the tissue;
during a life-cycle of the at least one bubble, transmitting a second pulse of the Histotripsy excitation sequence from the ultrasound therapy transducer, the second pulse comprising a scattering pressure waveform configured to interact with the at least one bubble, the scattering pressure waveform configured to become a shocked focal pressure waveform in the tissue having a shocked positive pressure half cycle and a shocked negative pressure half cycle, the shocked positive pressure half cycle being configured to impinge on the at least one bubble and to scatter, invert, and constructively interfere with the shocked negative pressure half cycle to form a negative pressure half cycle waveform; and
producing cavitation nuclei near the at least one bubble with a shock scattering mechanism between the positive pressure half cycle waveform and the at least one bubble.
15. A method of delivering ultrasound energy to tissue, comprising the steps of:
delivering a first pulse of a Histotripsy excitation sequence from an ultrasound therapy transducer, the first pulse comprising an initiation pulse configured to provide at least 5 MPa of peak negative pressure to produce at least one bubble in the tissue;
delivering a second pulse of the Histotripsy excitation sequence from the ultrasound therapy transducer, the second pulse comprising a first scattering pulse configured to interact with the at least one bubble within 5 μs to 200 μs of the initiation pulse; and
producing a cavitation cloud of nuclei near the at least one bubble with a shock scattering mechanism between the first scattering pulse and the at least one bubble.
16. An ultrasound therapy system, comprising:
an ultrasound therapy transducer; and
an ultrasound therapy generator coupled to the ultrasound therapy transducer, the ultrasound therapy generator configured to drive the ultrasound therapy transducer to deliver a first pulse of a Histotripsy excitation sequence comprising an initiation pressure waveform into tissue to produce at least one bubble in tissue, the ultrasound therapy generator being further configured to drive the ultrasound therapy transducer to deliver a second pulse of the Histotripsy excitation sequence comprising a first scattering pressure waveform within 5 μs to 200 μs of the initiation pressure waveform into the at least one bubble to produce cavitation nuclei near the at least one bubble.
17. The system of claim 16 , wherein a peak to peak pressure of the first scattering pulse is sufficient in pressure amplitude to produce cavitation nuclei near the at least one bubble.
18. The system of claim 16 , wherein the ultrasound therapy generator is further configured to drive the ultrasound therapy transducer to deliver at least one additional scattering pulse after the first scattering pressure waveform to produce cavitation nuclei near the at least one bubble.
19. The system of claim 16 , wherein the ultrasound therapy generator further comprises:
a controller configured to generate complex waveforms to initiate the initiation and scattering pressure waveforms;
a high voltage power supply coupled to the controller;
an amplifier configured to receive and amplify the complex waveforms from the controller and high voltage power supply; and
a matching network configured to match an impedance of the ultrasound therapy transducer to the amplifier.