Ultrasonic apparatus for thermotherapy with variable frequency for suppressing cavitation

• US 5,694,936 A
• Filed: 09/14/1995
• Issued: 12/09/1997
• Est. Priority Date: 09/17/1994
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Aida, Satoshi, Okamoto, Kazuya, Suzuki, Takuji, Fujimoto, Katsuhiko, Shibata, Mariko, Ishibashi, Yoshiharu, Saitoh, Shiroh
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): MANTIS MERCADER, ELENI M
• Application Number:
  US08/528,263
• Time in Patent Office: 817 Days
• Field of Search: 128/660.03, 601/2-4, 607/97
• US Class Current: 600/439
• CPC Class Codes: A61B 2017/00176 Two pulses, e.g. second pulse having an effect different from the first one
• CPC Class Codes: A61B 2017/22009 reduced or prevented
• CPC Class Codes: A61N 2007/0065 Concave transducers
• CPC Class Codes: A61N 2007/0073 using multiple frequencies
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00

Abstract

An ultrasonic diagnosis apparatus for raising tissue temperature for hypothermic treatments, including an ultrasonic source for generating an ultrasonic treatment wave and a driving means for driving the ultrasonic source such that a frequency of the ultrasonic treatment wave generated by the ultrasonic source changes with time. The frequency of the ultrasonic treatment wave is changed along the time axis. By this change in frequency, some bubbles formed by cavitation as a result of the ultrasonic treatment wave are divided, and some bubbles are collapsed and therefore eliminated. Side effect cavitation and spread of a thermal degeneration area is suppressed, and thermal degeneration can be accurately induced in a desired area, thereby realizing a reliable, safe ultrasonic thermotherapy. Since cavitation is positively suppressed, the total treatment period can be shortened because cavitation would otherwise interfere with and slow down the thermal degeneration process. Therefore, treatment throughput can be improved as compared with a case in which cavitation is left to naturally break and disappear.

Claims

1. An ultrasonic treatment apparatus for raising tissue temperature for thermotherapy treatments, comprising:

an ultrasonic source for generating an ultrasonic treatment wave; and

driving means for driving said ultrasonic source such that a frequency of the ultrasonic treatment wave generated by said ultrasonic source changes along a time axis such that cavitation is suppressed.

2. An apparatus according to claim 1, wherein said driving means includes driving signal generating means for generating a driving signal to said ultrasonic source and means for controlling said driving signal generating means.

3. An apparatus according to claim 1, wherein said driving means modulates an amplitude of a driving signal in accordance with the frequency of the ultrasonic treatment wave such that an output level of the ultrasonic treatment wave generated by said ultrasonic source is kept at a substantially constant level.

4. An apparatus according to claim 1, wherein the frequency of the ultrasonic treatment wave changes from a low frequency to a high frequency.

5. An apparatus according to claim 1, wherein the frequency of the ultrasonic treatment wave repeatedly changes at a period within a range of 500 μ

s to 50 ms.

6. An apparatus according to claim 1, wherein said driving means drives said ultrasonic source such that a first interval in which the frequency of the ultrasonic treatment wave is fixed to a specific frequency and a second interval in which the frequency of the ultrasonic treatment wave changes along the time axis;

and

said driving means alternates between said first and second interval.

7. An apparatus according to claim 6, wherein the specific frequency is set to a resonance frequency of at least one ultrasonic element of said ultrasonic source.

8. An apparatus according to claim 6, wherein the frequency of the ultrasonic treatment wave repeatedly changes at a period within a range of 500 μ

s to 50 ms in the second interval.

9. An apparatus according to claim 6, wherein the second interval is set not more than three times the first interval.

10. An apparatus according to claim 6, wherein the second interval is set not less than three times the first interval and not more than 10 times the first interval, and the frequency of the ultrasonic treatment wave repeatedly changes at a period within a range of 500 μ

s to 50 ms in the second interval.

11. An apparatus according to claim 1, wherein the frequency of the ultrasonic treatment wave changes within a range of at least 20% the resonance frequency unique to said ultrasonic source.

12. An apparatus according to claim 1, further comprising:

means for scanning a slice of a target object with an ultrasonic beam to repeatedly generate ultrasonic images on the basis of resultant reception signals;

difference means for obtaining a difference between two ultrasonic frame images generated at different times; and

means for counting, on the basis of a difference result from said difference means, timings at which the frequency of the ultrasonic treatment wave is changed.

13. The apparatus according to claim 1, wherein said driving means changes said frequency to break at least part of bubbles which appear with generation of said ultrasonic treatment wave.

14. The apparatus according to claim 1, further comprising an imaging probe for transmitting an ultrasonic wave for imaging, and for receiving an echo from a subject.

15. An ultrasonic treatment apparatus comprising:

an ultrasonic source for generating an ultrasonic treatment wave; and

driving means for driving said ultrasonic source such that a phase of the ultrasonic treatment wave generated by said ultrasonic source is modulated.

16. An apparatus according to claim 15, wherein the phase of the ultrasonic treatment wave is intermittently inverted.

17. An apparatus according to claim 15, further comprising:

means for scanning a slice of a target object with an ultrasonic beam to repeatedly generate ultrasonic images on the basis of resultant reception signals;

difference means for obtaining a difference between two ultrasonic frame images generated at different times; and

means for counting, on the basis of a difference result from said difference means, timings at which the phase of the ultrasonic treatment wave is modulated.

18. An ultrasonic treatment apparatus comprising:

a first ultrasonic source for generating an ultrasonic treatment wave;

a second ultrasonic source for generating an ultrasonic cavitation destruction wave having a frequency higher than that of the ultrasonic treatment wave; and

driving means for driving said first and second ultrasonic sources.

19. An apparatus according to claim 18, wherein said first and second ultrasonic sources are formed in a spherical pattern as a whole, said second ultrasonic source is located near the center, and said first ultrasonic source is located around said second ultrasonic source.

20. An apparatus according to claim 18, wherein the ultrasonic treatment wave is generated by a first piezoelectric layer, and the ultrasonic cavitation destruction wave is generated by simultaneously driving said first piezoelectric layer and a second piezoelectric layer stacked on said first piezoelectric layer.

21. An apparatus according to claim 18, wherein said driving means alternatively drives said first and second ultrasonic generators.

22. An apparatus according to claim 18, wherein said driving means simultaneously drives said first and second ultrasonic sources.