Method for tuning lithotripsy frequency to target size
Methods and systems for tuning lithotripsy frequency to target size are disclosed. In one embodiment, a lithotripsy system for comminuting a stone in a body includes: a burst wave lithotripsy (BWL) therapy transducer configured to transmit smooth ultrasound waves within a burst of ultrasound waves toward the stone; and a controller configured to determine operating frequency of the ultrasound waves of the therapy transducer. The operating frequency of the ultrasound waves is determined as: f = Const . c d where: d is a diameter of the stone, f is the frequency of the ultrasound waves, c is a wave speed in the stone, and Const. is a predetermined constant.
1. A lithotripsy system for comminuting a stone in a body, comprising:
a burst wave lithotripsy (BWL) therapy transducer configured to transmit smooth ultrasound waves within a burst of ultrasound waves toward the stone; and
a controller configured to determine an operating frequency of the ultrasound waves of the therapy transducer;
wherein the operating frequency of the ultrasound waves is determined as:
f
=
Const
.
c
d
where:
d is a diameter of the stone,
f is the frequency of the ultrasound waves,
c is a wave speed in the stone, and
Const. is a predetermined constant.
2. The lithotripsy system of claim 1 , wherein the wave speed c is a shear wave speed, and wherein Const. corresponds to ¾.
3. The lithotripsy system of claim 1 , wherein the operating frequency is a first operating frequency, wherein the first operating frequency operates to break the stone into fragments of a given size range, wherein the controller is configured to determine a second operating frequency such that the second operating frequency (f2) is determined as:
f
2
=
Const
.
c
d
2
where:
d 2 is a diameter of the fragments, and
f 2 is the frequency of the ultrasound waves.
4. The lithotripsy system of claim 3 , wherein the therapy transducer is a first therapy transducer capable of generating the first operating frequency, the system comprising a second therapy transducer capable of generating the second operating frequency.
5. The lithotripsy system of claim 3 , wherein the second operating frequency is determined based on a target size of the fragments as:
f
2
≥
Const
.
c
d
final
where:
d final is a final target diameter of the fragments.
6. The lithotripsy system of claim 1 , wherein the burst of ultrasound waves of the BWL therapy transducer comprises at least 5 cycles of the ultrasound waves.
7. The lithotripsy system of claim 1 , wherein the burst of ultrasound waves of the BWL therapy transducer comprises at least 8 cycles of the ultrasound waves.
8. The lithotripsy system of claim 1 , wherein the ultrasound waves of the BWL therapy transducer are transmitted as the bursts of ultrasound waves, wherein the bursts of ultrasound waves are repeated in a frequency of 10 Hz.
9. The lithotripsy system of claim 1 , wherein the waves of the BWL therapy transducer are transmitted as bursts of ultrasound waves, wherein the bursts are repeated in a frequency of 20 Hz.
10. The lithotripsy system of claim 1 , wherein the burst wave lithotripsy (BWL) therapy transducer generates an acoustic pressure p 0 in a focal plane and a principal stress T zz in the stone, and wherein a ratio of T zz /p 0 is higher than 2.
11. The lithotripsy system of claim 10 , wherein the burst wave lithotripsy (BWL) therapy transducer causes an acoustic pressure p 0 in a focal plane and a principal stress T zz in the stone, and wherein a ratio of T zz /p 0 is higher than 4.
12. The lithotripsy system of claim 1 , wherein the ultrasound waves are sinusoidal waves.
13. A method for comminuting a stone in a body using an ultrasound, comprising:
determining an operating frequency of smooth ultrasound waves of a burst wave lithotripsy (BWL) therapy transducer, wherein the therapy transducer is configured to transmit the ultrasound waves within bursts of ultrasound waves at the operating frequency toward the stone; wherein the operating frequency is determined as:
f
=
Const
.
c
d
where:
d is a diameter of the stone,
f is the frequency of the ultrasound waves,
c is a wave speed in the stone, and
Const. is a predetermined constant; and
transmitting the ultrasound waves at the operating frequency toward the stone.
14. The method of claim 13 , wherein the wave speed c is a shear wave speed, and wherein Const. corresponds to ¾.
15. The method of claim 13 , wherein the operating frequency is a first operating frequency, wherein the first operating frequency operates to break the stone into fragments of a given size range, wherein a second operating frequency (f2) is determined as:
f
2
=
Const
.
c
d
2
where:
d 2 is a diameter of the fragments, and
f 2 is the frequency of the ultrasound waves.
16. The method of claim 15 , wherein the therapy transducer is a first therapy transducer capable of generating the first operating frequency, the method comprising generating the second operating frequency by a second therapy transducer.
17. The method of claim 13 , wherein the operating frequency of the ultrasound waves (f final ) is determined based on a target size of stone fragments as:
f
final
≥
Const
.
c
d
final
where:
d final is a final target diameter of the fragments.
18. The method of claim 17 , wherein entire treatment is executed with the therapy transducer operating at the operating frequency of the ultrasound waves f final .
19. The method of claim 13 , wherein the therapy transducer generates an acoustic pressure p 0 in a focal plane and a principal stress T zz in the stone, and wherein a ratio of T zz /p 0 is higher than 2.
20. The method of claim 19 , wherein the therapy transducer generates an acoustic pressure p 0 in a focal plane and a principal stress T zz in the stone, and wherein a ratio of T zz /p 0 is higher than 4.
21. The method of claim 13 , wherein the ultrasound waves are sinusoidal waves.