Ultrasound based method and apparatus for stone detection and to facilitate clearance thereof
Described herein are methods and apparatus for detecting stones by ultrasound, in which the ultrasound reflections from a stone are preferentially selected and accentuated relative to the ultrasound reflections from blood or tissue. Also described herein are methods and apparatus for applying pushing ultrasound to in vivo stones or other objects, to facilitate the removal of such in vivo objects.
1. A method for applying an in vivo force to a stone in a body, the method comprising applying pushing ultrasound prior to lithotripsy of said stone to non-invasively push said stone in vivo without fragmenting said stone, said pushing ultrasound inducing displacement of said stone, said pushing ultrasound applied while pushing said stone, and said pushing ultrasound having an I SPTA >3 W/cm 2 .
2. The method of claim 1 wherein said pushing ultrasound has I SPTA >4 W/cm 2 .
3. The method of claim 1 wherein said pushing ultrasound has a pressure amplitude in the range of about 5 MPa to about 30 MPa.
4. The method of claim 3 wherein said pushing ultrasound has a pressure amplitude in the range of about 10 MPa to about 20 MPa.
5. The method of claim 4 wherein said pushing ultrasound has a pressure amplitude in the range of about 13 MPa to about 18 MPa.
6. The method of claim 1 wherein said pushing ultrasound operates at a range of about 5-10 pulses per cycle.
7. The method of claim 6 wherein said pushing ultrasound pulses have a duration of about 100 μs or greater.
8. The method of claim 1 wherein a frequency of said pushing ultrasound is in the range of about 0.25-5 MHz.
9. The method of claim 8 wherein said frequency of said pushing ultrasound is in the range of about 1-4 MHz.
10. The method of claim 9 wherein said frequency of said pushing ultrasound is in the range of about 1-3 MHz.
11. The method of claim 1 wherein a duty cycle of pushing ultrasound pulses is greater than 1% over a period of about 1 s.
12. The method of claim 1 wherein a spatial peak pulse average intensity of said pushing ultrasound is greater than 190 W/cm 2 .
13. The method of claim 1 wherein the spatial peak time average intensity of said pushing ultrasound is greater than 720 mW/cm 2 .
14. The method of claim 1 wherein an intensity and duration of the pushing ultrasound does not cause thermal coagulation of tissue.
15. The method of claim 1 wherein said displacement is at a rate of about at least one centimeter per second.
16. The method of claim 1 wherein said force is applied to urge said stone toward an exit location.
17. The method of claim 16 wherein one or more stones are located in a kidney, and said exit location is an exit from the kidney.
18. The method of claim 1 comprising the further step of fragmenting the stone by lithotripsy after applying the pushing ultrasound.
19. The method of claim 1 comprising the further step of detecting said stone before an application of displacing ultrasound.
20. The method of claim 19 wherein said stone is detected through imaging.
21. The method of claim 20 wherein said imaging is accomplished by one or more of fluoroscopy, computer tomography, low-dose stone protocol computer tomography, B-mode ultrasound, Doppler ultrasound, and MRI.
22. The method of claim 21 wherein said imaging is accomplished with Doppler ultrasound.
23. The method of claim 22 wherein locating the stone comprises use of a twinkling artifact of Doppler ultrasound.
24. The method of claim 21 wherein said imaging is accomplished with B-mode ultrasound.
25. The method of claim 21 wherein the imaging comprises real-time imaging.
26. The method of claim 21 wherein said imaging is accomplished with Doppler ultrasound or B-mode wherein a frequency of said imaging ultrasound is in the range of about 1-5 MHz.
27. The method of claim 26 wherein said frequency of said imaging ultrasound is in the range of about 2-4 MHz.
28. The method of claim 27 wherein said frequency of said imaging ultrasound is in the range of about 2-3 MHz.
29. A system for applying an in vivo force to a stone in a body, the system comprising
a. a computer processing unit (CPU);
b. an ultrasound transducer;
c. a user interface
wherein each of said ultrasound transducer and user interface are operatively connected through said central processing unit, said ultrasound transducer being operable to apply pushing ultrasound waves having an I SPTA >3 W/cm 2 prior to lithotripsy of said stone to non-invasively displace said stone in vivo without fragmenting said stone, said pushing ultrasound applied while pushing said stone.
30. The system of claim 29 further comprising an imaging apparatus and a pushing ultrasound apparatus.
31. The system of claim 30 wherein said imaging apparatus is operable to use Doppler ultrasound or B-mode ultrasound.
32. The system of claim 31 wherein said imaging ultrasound is operable to produce a frequency in the range of about 1-5 MHz.
33. The system of claim 31 wherein said Doppler ultrasound is operable to produce a twinkling artifact which is used to facilitate locating said stone.
34. The system of claim 30 wherein said imaging apparatus and said pushing ultrasound apparatus are operable simultaneously to allow the use of real time imaging of one or more stones during application of force thereto.
35. The system of claim 30 wherein said pushing ultrasound apparatus comprises a handle, a transducer mounted on said handle, and an acoustic coupling operatively engaged with said transducer.
36. The system of claim 35 wherein said transducer has a fixed focal length.
37. The transducer of claim 35 wherein said transducer has a variable focal length.
38. The system of claim 29 wherein said transducer is operable to apply Doppler ultrasound to an anatomical region, such that said Doppler ultrasound detects a stone and laminar blood flow, and wherein said central processing unit is operable to optimize an image of said stone in twinkling format relative to said laminar blood flow, whereby said stone is more apparent on said image.
39. The system of claim 38 wherein said central processing unit is operable to suppress detection of said laminar blood flow.
40. The system of claim 39 wherein said system is operable to select a point on a displayed image to indicate an anatomical site at which to apply focused ultrasound waves to said stone thereby to cause displacement of said one or more stones.
41. The system of claim 40 wherein said system is operable to detect movement of said stone, and said system is operable to automatically refocus on a new location and transmit focused ultrasound to said new location.
42. The system of claim 38 wherein said central processing unit is operable to enhance said image of said stone in a display.
43. The system of claim 38 wherein said central processing unit is operable to display said stone in color on said image.
44. The system of claim 38 wherein said transducer is operable to apply B-mode ultrasound to confirm detection of said stone.
45. The system of claim 38 wherein said transducer is operable to apply B-mode ultrasound to the stone at a plurality of angles.