Power generating and control apparatus for the treatment of tissue

• US 20120095461A1
• Filed: 04/11/2011
• Published: 04/19/2012
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Vessix Vascular, Inc. (Boston Scientific Corporation)
• Inventors: Herscher, Bret, Perry, Michael, Krawzsenek, David, LaBarge, Aaron, Espinosa, Joseluis
• Granted Patent: US 9,277,955 B2
• Time in Patent Office: Days
• US Class Current: 606/45
• CPC Class Codes: A61B 17/22012 in direct contact with, or very close to, the obstruction or concrement for removing obstructions in blood vessels by laser A61B18/245
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 18/245 for removing obstructions in blood vessels or calculi
• CPC Class Codes: A61B 2018/00214 Expandable means emitting energy, e.g. by elements carried thereon
• CPC Class Codes: A61B 2018/0022 Balloons
• CPC Class Codes: A61B 2018/00422 Angioplasty
• CPC Class Codes: A61B 2018/00434 Neural system
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00684 using lookup tables
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00898 Alarms or notifications created in response to an abnormal condition
• CPC Class Codes: A61B 2018/1861 with an instrument inserted into a body lumen or cavity, e.g. a catheter
• CPC Class Codes: A61N 7/022 intracavitary

Abstract

Apparatus, systems, and methods are provided for the generation and control of energy delivery in a dosage to elicit a therapeutic response in diseased tissue. A balloon catheter can have electrodes attached to a power generator and controller such that the balloon and electrodes contact tissue during energy treatment. Energy selectively may be applied to tissue based on measured impedance to achieve gentle heating. Calibration of the apparatus and identification of attached accessories by computing the circuit impedance prior to energy dosage facilitate regulation of power delivery about a set point. Energy delivery can be controlled to achieve substantially uniform bulk tissue temperature distribution. Energy delivery may beneficially affect nerve activity.

Claims

1. A power generating apparatus for treatment of tissue having a circuit comprising:

a direct digital synthesizer (DDS) operatively coupled to a power amplifier;

a power output set point controller providing a signal;

a peak effective power sensor receiving voltage and current feedback measured at a power delivery target to measure impedance at the power delivery target, the peak effective power sensor providing a signal based on the feedback; and

a PID controller, operatively coupled to receive the signals from the power output set point controller and the peak effective power sensor, and operatively coupled to direct a modulating voltage signal to the power amplifier such that output of power from the circuit is maintained within a range about a power output set point in response to the measured impedance at the power delivery target.

2. The power generating apparatus of claim 1 wherein a digital-to-analog converter is coupled between the DDS and power amplifier.

3. The power generating apparatus of claim 1 wherein energy output is RF energy.

4. The power generating apparatus of claim 1 wherein the power delivery target is comprised of tissue.

5. The power generating apparatus of claim 1 wherein the DDS, power output set point controller, and peak effective power sensor comprise a field programmable gate array.

6. The power generating apparatus of claim 1 wherein the power amplifier is comprised of a variable gain amplifier and a linear power amplifier operatively coupled in series.

7. The power generating apparatus of claim 6 wherein the power amplifier is comprised of a linear power amplifier whose maximum output voltage is controlled by the current flowing in the power amplifier.

8. The power generating apparatus of claim 7 wherein output voltage from the linear power amplifier to the power delivery target during use comprises RF output voltage having a maximum available output limit over a range of load impedances of about 50 Ohm to about 500 Ohms.

9. The power generating apparatus of claim 7 wherein the maximum output voltage from the linear power amplifier limits the power dissipation within the power amplifier.

10. The power generating apparatus of claim 7 wherein the linear power amplifier controls the maximum output voltage using switched mode technology.

11. The power generating apparatus of claim 6 wherein the controller comprises a PID controller, and wherein the modulating voltage signal from the PID controller is received by the variable gain amplifier.

12. The power generating apparatus of claim 1 wherein the peak effective power sensor comprises a DDS, a current circuit further comprising square root and inverse tangent gates in parallel, and a voltage circuit further comprising square root and inverse tangent gates in parallel.

13. The power generating apparatus of claim 12 wherein the DDS of the peak effective power sensor has a voltage output with a low-pass filter, and a current output with a low-pass filter.

14. The power generating apparatus of claim 12 wherein output of the inverse tangent gates for the current circuit and the voltage circuit are operatively coupled to pass through a cosine gate.

15. The power generating apparatus of claim 1 wherein the voltage and current feedback from the power delivery target to the peak effective power sensor each comprise in-phase and quadrature signal components.

16. The power generating apparatus of claim 1 wherein the signal from the peak effective power sensor represents the effective power output of the circuit at the power delivery target.

17. The power generating apparatus of claim 1 wherein the controller comprises a PID controller having proportional, integral, and derivative calculation module, the modules receiving the signals from the peak effective power sensor and power set point controller, such that a modulating voltage signal is produced to regulate the power output of the circuit within a range about the set point.

18. The power generating apparatus of claim 1 wherein the power output set point is about 0.001 Watts to about 50 Watts.

19. The power generating apparatus of claim 1 wherein the power output modulates about the set point by a maximum of about ±

20%.

20. The power generating apparatus of claim 1 wherein the power output modulates about the set point by a maximum of about ±

10%.

21. The power generating apparatus of claim 1 wherein the power output modulates about the set point by a maximum of about ±

5%.

22. The power generating apparatus of claim 1 wherein the power output modulates about the set point by a maximum of about ±

2%.

34. The apparatus of claim 1 wherein system operating software limits power generation to occur when measured impedance at the power delivery target is between about 50 Ohms and about 500 Ohms.

35. The apparatus of claim 1 wherein measured impedance at the power delivery target is used to determine capacitance and resistance at the power delivery target.

23. A method of calibrating an apparatus for the treatment of a power delivery target, the method comprising:

measuring circuit impedance at a low first circuit load;

measuring circuit impedance at a high second circuit load;

measuring circuit impedance at a third circuit load, the third circuit load being between the first circuit load and the second circuit load; and

calculating system impedance of a circuit of the apparatus with vector network analysis using the measured impedances such that a measure of real-time changes in overall circuit load impedance during power generation represents changes in impedance at the power delivery target of the apparatus, where power output of the apparatus is regulated about a power output set point based on the real-time measured changes in impedance at the power delivery target.

24. The method of claim 23 further comprising the use of a bi-linear transform to calculate impedance for the purpose of calibration and compensation of power.

25. The method of claim 24 wherein the bi-linear transform employs constants derived from the measurement of one or more circuit loads.

26. The method of claim 23 wherein the measurement of one or more circuit loads is further used to compensate the power delivered to the power delivery target.

27. The method of claim 23 further comprising the step of identifying an accessory attached to the apparatus by repeating the steps of calibration to ascertain the type of attached accessory based on its impedance characteristics.

28. The method of claim 23 wherein the power delivery target is tissue.

29. The method of claim 27 wherein the accessory comprises a catheter.

30. The method of claim 29 wherein the catheter further comprises electrodes.

31. The method of claim 30 wherein the number of electrodes present is determined by multiplexed sensing of the number of electrode circuits within the catheter attached to the apparatus.

32. A power generating apparatus for treatment of tissue comprising:

a DDS operatively coupled to a RF power amplifier;

a RF power output set point controller providing a signal;

a peak effective RF power sensor receiving voltage and current feedback measured at a RF power delivery target to measure impedance at the RF power delivery target, the peak effective RF power sensor providing a signal based on the feedback; and

a controller, operatively coupled to receive the signals from the RF power output set point controller and the peak effective RF power sensor, and operatively coupled to direct a modulating voltage signal to the RF power amplifier such that the output of RF power from the circuit is maintained within a range about the RF power output set point in response to measured impedance at the RF power delivery target.

33. A power generating and control apparatus for eccentric remodeling treatment of tissue about a lumen, the apparatus comprising:

a DDS operatively coupled to a RF power amplifier;

a RF power output set point controller providing a signal;

a peak effective RF power sensor receiving voltage and current feedback at the tissue to measure impedance about the circumference of the lumen, the peak effective RF power sensor providing a signal based on the feedback; and

a controller, operatively coupled to receive the signals from the RF power output set point controller and the peak effective RF power sensor, and operatively coupled to direct a modulating voltage signal to the RF power amplifier such that the output of RF power from the circuit is maintained within a therapeutic tissue remodeling range about the RF power output set point in response to the measured tissue impedance about the circumference of the lumen.

36. A method for calculating peak effective power comprising the steps of:

calculating uncorrected power;

calculating a power correction factor; and

multiplying the uncorrected power and the power correction factor to obtain peak effective power.

37. The method of claim 36 wherein the step of calculating uncorrected power is further comprised of calculating current amplitude, calculating voltage amplitude, and multiplying the resultant amplitudes to obtain the uncorrected power.

38. The method of claim 36 wherein the step of calculating the power correction factor is further comprised of calculating the phase angle between in-phase and quadrature voltage signals, calculating the phase angle between in-phase and quadrature current signals, and taking the cosine of the difference between the voltage and current phase angles.

39. A method for calculating peak effective power comprising the steps of:

measuring instantaneous RF voltage;

measuring instantaneous RF current; and

multiplying the RF voltage by the RF current to obtain peak effective power.

40. The method of claim 39 further comprising the step of integrating the calculated peak effective power over a period of time to obtain an average RF power.

41. A method for the controlled delivery of energy as a dosage to obtain a substantially uniform temperature distribution in tissue comprising the steps of:

positioning a plurality of energy delivery surfaces proximate to the tissue;

applying an energy dosage to the tissue by powering a first portion of the plurality of energy delivery surfaces in a sequenced pattern; and

applying an energy dosage to the tissue by powering a second portion of the plurality of energy delivery surfaces in a sequenced pattern.

42. The method of claim 41 further comprising controlling sequential energy delivery and tissue temperature distribution by measuring tissue impedance and applying energy such that measured tissue impedance is about constant.

43. The method of claim 42 wherein tissue impedance is used to infer tissue temperature, said tissue temperature being empirically related to an energy dosage.

44. The method of claim 41 wherein sequential energy delivery and uniformity of tissue temperature distribution is based on an energy dosage determined through accumulated damage theory.

45. The method of claim 41 wherein the plurality of energy delivery surfaces are operatively coupled to a power generation and control apparatus further comprising a DDS operatively coupled to a power amplifier, a power output set point controller providing a signal, voltage and current feedback, measured at a power delivery target, used to measure impedance at the power delivery target, a peak effective power sensor receiving the voltage and current feedback, providing a signal based on the feedback, and a PID controller, operatively coupled to receive the signals from the power output set point controller and the peak effective power sensor, and operatively coupled to direct a modulating voltage signal to the power amplifier such that the output of power from the circuit is maintained within a range about the power output set point in response to measured impedance at the power delivery target.

47. The method of claim 45 further comprising characterizing the location of nerves by measuring the impedance of tissue proximate to the plurality of energy delivery surfaces and directing the application of energy to a selected portion of energy delivery surfaces based on proximity to the location of nerves.

48. The method of claim 45 wherein energy dosage to permanently disrupt conduction of nerve signals results from the denaturing of the conductive properties of nerve tissue.

49. The method of claim 45 wherein energy dosage to permanently disrupt conduction of nerve signals results from ablation of nerve tissue.

46. A method for the controlled delivery of eccentrically targeted energy to affect nerve activity comprising the steps of:

positioning a plurality of energy delivery surfaces proximate to targeted tissue region containing nerves therein; and

applying an energy dosage to the tissue sufficient to permanently disrupt the conduction of nerve signals in a targeted tissue region using a power generation and control apparatus having a DDS operatively coupled to a power amplifier, a power output set point controller providing a signal, voltage and current feedback, measured at a power delivery target, used to measure impedance at the power delivery target, a peak effective power sensor receiving the voltage and current feedback, providing a signal based on the feedback, and a PID controller, operatively coupled to receive the signals from the power output set point controller and the peak effective power sensor, and operatively coupled to direct a modulating voltage signal to the power amplifier such that the output of power from the circuit is maintained within a range about the power output set point in response to measured impedance at the power delivery target.

50. A power generating apparatus for treatment of a target tissue, the power generating apparatus comprising:

a frequency synthesizer generating a frequency signal;

a power amplifier operatively coupling the frequency synthesizer to a power output, the output coupleable to the target tissue;

a power sensor configured to receive voltage and current feedback from the target tissue and to output measured impedance at the target tissue; and

a controller coupling the power sensor to the power amplifier, the controller having an input for receiving a power set point and transmitting, in response to the power set point and the measured impedance at the target tissue, a modulating signal to the power amplifier such that power output from the power amplifier to the target tissue per the frequency signal is maintained within a range about the power set point.

51. The power generating apparatus of claim 50 wherein the frequency synthesizer comprises a digital frequency synthesizer, and wherein a digital-to-analog converter couples the frequency synthesizer to the power amplifier.

52. The power generating apparatus of claim 50 wherein energy output to the target comprises RF energy.

53. An RF system comprising the power generating apparatus of claim 50, and further comprising an elongate catheter having an elongate flexible catheter body with a distal end configured for advancing into a blood vessel and a proximal end, a connector coupled to the proximal end and configured to couple to the output so that, in use, the catheter couples the output to the target tissue adjacent the distal end, wherein the measured impedance of the target tissue is independent of an impedance of the power generating apparatus and the catheter body.

54. A calibration module for calibrating an RF system in preparation for treatment of a target tissue, the RF system comprising a power generating apparatus including an impedance measurement circuit, the module comprising:

a first input for receiving a first impedance from the impedance measurement circuit of the power generating apparatus, the first impedance corresponding to a low circuit load on the power generating apparatus prior to coupling of the power generating apparatus to the target tissue;

a second input for receiving a second impedance from the impedance measurement circuit of the power generating apparatus, the second impedance corresponding to a high circuit load on the power generating apparatus prior to coupling of the power generating apparatus to the target tissue;

a third input for receiving a third impedance from the impedance measurement circuit of the power generating apparatus, the third impedance corresponding to an intermediate circuit load on the power generating apparatus, between the high load and the low load, prior to coupling of the power generating apparatus to the target tissue; and

a processor configured to calculate system impedance using the measured impedances so as to facilitate, in response to a measure of real-time changes in overall circuit load impedance during power application to the target tissue, changes in impedance at the target tissue, the overall circuit load impedance comprising impedance of the power generating apparatus and the impedance at target tissue.

55. The system of claim 56, wherein the RF system further comprises a catheter for coupling the power generating apparatus to the target tissue, wherein the processor is further configured to calculate another system impedance of the power generating apparatus and the catheter after coupling of the catheter to the power generating apparatus and before coupling of the catheter to the target tissue.