Adaptive focusing and nulling hyperthermia annular and monopole phased array applicators

• US 5,441,532 A
• Filed: 03/04/1992
• Issued: 08/15/1995
• Est. Priority Date: 06/26/1991
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Fenn, Alan J.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US07/846,808
• Time in Patent Office: 1,259 Days
• Field of Search: 607/100-102, 607/154, 607/156, 128/653.1
• US Class Current: 607/101
• CPC Class Codes: A61N 5/02 using microwaves
• CPC Class Codes: A61N 5/04 Radiators for near-field treatment

Abstract

An R.F. hyperthermia phased array applicator uses adaptive nulling and focusing with non-invasive electric field probes to control the electric field intensity at selected positions in and around a target body to provide improved heating of solid tumors during hyperthermia treatment. A gradient search or matrix inversion algorithm is used to control the amplitude and phase weighting for the phased array transmit elements of the hyperthermia applicator. A 915 MHz monopole phased array hyperthermia applicator for heating brain tumors has an enclosed vessel including a plurality of monopole transmit antenna elements disposed as a circular arc array on a ground plane which has an aperture for positioning the tumor in proximity to the monopole antenna elements. Adaptive focusing with non-invasive electric field probes is used to maximize the electric field at the tumor site. Parallel plate microwave waveguides are used to direct R.F. energy from the monopole phased array to the tumor site. A microwave transmit and receive module generates amplitude and phase controlled transmit signals for exciting the monopole antenna elements, and receives passive microwave signals from the monopole antenna elements for taking non-invasive radiomerry temperature measurements of the tumor site.

Claims

1. A hyperthermia applicator for inducing a temperature rise in a target within a body, comprising

a plurality of electric field radiators, each for transmitting electric field radiation, comprising a phased-array of monopole antenna elements;

an RF reflecting groundplane surface for mounting the monopole antenna elements, wherein the monopole antenna elements are substantially perpendicularly mounted on a side of the RF reflecting groundplane surface, wherein the body containing the target is adapted to be disposed on the same side of the groundplane surface as the monopole antenna elements;

a plurality of controllable transmit weighting networks, each such network coupled to a respective electric field radiator, each weighting network controlling the phase and amplitude of the electric field radiation transmitted by the respective electric field radiator in response to a respective feedback signal;

a source of electric field radiation coupled to each electric field radiator through a respective weighting network;

at least one electric field probe adapted to be disposed outside the body for detecting electric field radiation from the plurality of radiators; and

a controller coupled to the electric field probe for receiving the detected electric field radiation outside the body and generating the respective feedback signals, and for adjusting the feedback signals in response to the detected electric field radiation outside the body so that the electric field radiation is controlled at the target inside the body.

2. The apparatus of claim 1 wherein the groundplane surface comprises an aperture through which the body containing the target is adapted to be disposed to allow positioning the target on the same side of the groundplane surface as the monopole antenna elements.

3. The apparatus of claim 2 wherein the monopole antenna elements are arranged in a circular arc of substantially constant radius, the body containing the target is a cranium and the radius is substantially the distance from the monopole antenna elements to the center of the aperture.

4. The apparatus of claim 2 wherein the monopole antenna elements are arranged in a circular arc of substantially constant radius, the body containing the target is a cranium and the radius is substantially the distance from the monopole antenna elements to a target position within the aperture.

5. The apparatus of claim 1 further comprising an RF reflecting screen mounted perpendicular to the groundplane surface behind the monopole antenna elements to reflect RF energy from the monopole antenna elements toward the target.

6. The apparatus of claim 5 wherein the RF reflecting screen is positioned between 1/8 to 1/2 wavelength from the monopole antenna elements.

7. The apparatus of claim 6 wherein the RF reflecting screen is positioned about 1/4 wavelength from the monopole antenna elements.

8. The apparatus of claim 1 further comprising an enclosure surrounding the monopole antenna elements and providing a vessel for enclosing a bolus of fluid between the monopole antenna elements and the body.

9. The apparatus of claim 8 wherein the vessel comprises a bolus of deionized water.

10. The apparatus of claim 1 wherein the monopole antenna elements are arranged in a circular arc of substantially constant radius.

11. The appratus of claim 10 wherein the radius is between 5 and 20 cm.

12. The apparatus of claim 11 wherein the radius is between 10 and 15 cm.

13. The apparatus of claim 13 wherein the monopole antenna elements resonate at between 800 and 1000 MHz.

14. The apparatus of claim 13 wherein the monopole antenna elements resonate at substantially 915 MHz.

15. A hyperthermia applicator for inducing a temperature rise in a target within a body, comprising

a plurality of electric field radiators, each for transmitting electric field radiation;

a plurality of controllable transmit weighting networks, each such network coupled to a respective electric field radiator, each weighting network controlling the phase and amplitude of the electric field radiation transmitted by the respective electric field radiator in response to a respective feedback signal;

a source of electric field radiation coupled to each electric field radiator through a respective weighting network;

a plurality of electric field probe elements adapted to be disposed noninvasively along the perimeter of the body between the electric field radiators and the target for detecting electric field radiation from the plurality of radiators; and

a controller coupled to the electric field probe elements for receiving the detected electric field radiation outside the body and generating the respective feedback signals, and for adjusting the feedback signals in response to the detected electric field radiation outside the body so that the electric field radiation is controlled at the target inside the body;

wherein the controller comprises means for adjusting the feedback signals to minimize the difference in the electric field detected by adjacent electric field probe elements and thereby provide uniform electric field radiation into the body.

16. The apparatus of claim 15, wherein the adjusting means performs a gradient search algorithm to adjust the feedback signals.

17. The apparatus of claim 15, wherein the adjusting means performs a matrix inversion algorithm to adjust the feedback signals.

18. A hyperthermia applicator for inducing a temperature rise in a target within a body, comprising

a plurality of electric field radiators, each for transmitting electric field radiation, comprising a phased array of antenna elements;

a plurality of controllable transmit weighting networks, each such network coupled to a respective electric field radiator, each weighting network controlling the phase and amplitude of the electric field radiation transmitted by the respective electric field radiator in response to a respective feedback signal;

a source of electric field radiation coupled to each electric field radiator through a respective weighting network;

a plurality of electric field probe elements adapted to be disposed non-invasively in an electric field probe array between elements of the phased array and the target for detecting electric field radiation from the plurality of electric field radiators; and

a controller coupled to the electric field probe elements for receiving the detected electric field radiation and generating the respective feedback signals, and for adjusting the feedback signals in response to the detected electric field radiation to provide a particular electric field pattern across the electric field probe array and thereby focus radiation into the target,

wherein the elements of the phased array are adapted to be disposed symmetrically with respect to a bisector line going from the target to the phased array which bisects the elements of the phased array into symmetric right and left halves, the electric field probe elements of the electric field probe array are adapted to be disposed symmetrically with respect to the bisector line which bisects the electric field probe array into symmetric right and left halves, and the controller adjusts the feedback signals to minimize the difference in the electric field detected by electric field probe elements in the left and right halves of the electric field probe array to balance the electric field pattern with respect to the bisector line, and to minimize the difference in the electric field detected by the electric field probe elements in a direction along the bisector line.

19. The apparatus of claim 18, wherein the controller performs a gradient search algorithm to adjust the feedback signals.

20. The apparatus of claim 18, wherein the controller performs a matrix inversion algorithm to adjust the feedback signals.

21. The apparatus of claim 18 wherein the antenna elements of the phased array are arranged in a circular arc of substantially constant radius.

22. The apparatus of claim 21 wherein the phased array comprises an array of monopole antenna elements resonating at between 800 and 1000 MHz, and the radius of the circular arc is between 5 and 20 cm.

23. A hyperthermia applicator for inducing a temperature rise in a target located within a living body, comprising

a phased array of monopole antenna elements,

a source of electric field radiation coupled to each monopole antenna element,

and

an RF reflecting groundplane surface for mounting the monopole antenna elements, the monopole antenna elements being perpendicularly mounted to one side of the RF reflecting groundplane surface, and

the groundplane surface having an aperture adapted to accommodate a portion of the body to allow positioning the target proximate to the monopole antenna elements.

24. The applicator of claim 23 wherein the target is located within the cranium of the living body and the applicator further comprises an RF reflecting screen mounted perpendicular to the groundplane surface behind the monopole antenna elements to reflect RF energy from the monopole antenna elements toward the target.

25. The applicator of claim 24 wherein the RF reflecting screen is positioned between 1/8 to 1/2 wavelength from the monopole antenna elements.

26. The applicator of claim 25 wherein the RF reflecting screen is positioned about 1/4 wavelength from the monopole antenna elements.

27. The applicator of claim 23 wherein the target is located within the cranium of the living body and further comprising an enclosure surrounding the monopole antenna elements and providing a vessel for enclosing a bolus of fluid between the monopole antenna elements and the cranium.

28. The applicator of claim 27 wherein the vessel comprises a bolus of deionized water.

29. The applicator of claim 23 wherein the monopole antenna elements are arranged in a circular arc of substantially constant radius.

30. The applicator of claim 29 wherein the radius is between 5 and 20 cm.

31. The applicator of claim 30 wherein the radius is between 10 and 15 cm.

32. The applicator of claim 29 wherein the monopole antenna elements resonate at between 800 and 1000 MHz.

33. The applicator of claim 32 wherein the monopole antenna elements resonate at substantially 915 MHz.

34. The applicator of claim 23 wherein the monopole antenna elements are arranged in a circular arc of substantially constant radius and the radius is substantially the distance from the monopole antenna array to the center of the aperture.

35. The applicator of claim 23 wherein the monopole antenna elements are arranged in a circular arc of substantially constant radius and the radius is substantially the distance from the monopole antenna array to a target position within the aperture.

36. The applicator of claim 33 wherein the monopole antenna elements are 1/4 wavelength vertical antennas.

37. The applicator of claim 33 wherein the monopole antenna elements are helical antennas.

38. A method for inducing a temperature rise in a target within a body, comprising the steps of:

providing a plurality of monopole phased array electric field radiators mounted on a side of an RF reflecting groundplane surface;

positioning the body containing the target through an aperture in the ground plane surface so that the target is on the same side of the groundplane surface as the electric field radiators;

coupling a source of electric field radiation to each electric field radiator through a controllable transmit weighting network coupled to a respective electric field radiator;

controlling the phase and amplitude of the electric field radiation transmitted by the respective electric field radiator with each weighting network in response to a respective feedback signal;

detecting electric field radiation from the phased array of radiators with a plurality of electric field probe elements disposed noninvasively between the phased array of radiators and the target; and

receiving the detected electric field radiation and generating the respective feedback signals for adjusting the controllable transmit weighting network in response to the detected electric field radiation so that the electric field radiation is controlled at the target inside the body.

39. The method of claim 38 further comprising the step of positioning an RF reflecting screen behind the electric field radiators to direct RF energy from the electric field radiators toward the target.

40. The method of claim 38 further comprising the step of surrounding the electric field radiators with an enclosed vessel for containing a bolus of fluid between the electric field radiators and the body.

41. The method of claim 38 further comprising the step of arranging the electric field radiators in a circular arc of substantially constant radius.

42. A method for inducing a temperature rise in a target within a body, comprising the steps of:

positioning a phased array of electric field radiators nearby a target;

coupling a source of electric field radiation to each electric field radiator through a controllable transmit weighting network coupled to a respective electric field radiator;

controlling the phase and amplitude of the electric field radiation transmitted by the respective electric field radiator with each weighting network in response to a respective feedback signal;

detecting electric field radiation from the phased array of radiators with a plurality of electric field probe elements disposed non-invasively between the phased array of radiators and the target; and

receiving the detected electric field radiation and generating the respective feedback signals for adjusting the controllable transmit weighting network in response to the detected electric field radiation to minimize the difference in the electric field detected by adjacent electric field probe elements and thereby provide uniform electric field radiation into the body.

43. The method of claim 42, further comprising the step of positioning the electric field probe elements non-invasively along the perimeter of the body between the electric field radiators and the target.

44. The method of claim 42, wherein the receiving step further comprises performing a gradient search algorithm to adjust the feedback signals.

45. The method of claim 42, wherein the receiving step further comprises performing a matrix inversion algorithm to adjust the feedback signals.

46. A method for inducing a temperature rise in a target within a body, comprising the steps of:

arranging a plurality of electric field radiators of a hyperthermia phased array symmetrically with respect to a bisector line going from the target to the phased array which bisects the radiators of the phased array into symmetric right and left halves;

coupling a source of electric field radiation to each electric field radiator through a controllable transmit weighting network coupled to a respective electric field radiator;

controlling the phase and amplitude of the electric field radiation transmitted by the respective electric field radiator with each weighting network in response to a respective feedback signal;

detecting electric field radiation from the phased array of electric field radiators with an electric field probe array comprising a plurality of electric field probe elements disposed noninvasively between the phased array of electric field radiators and the target;

arranging electric field probe elements of the electric field probe array symmetrically with respect to the bisector line which bisects the electric field probe array into symmetric right and left halves; and

receiving the detected electric field radiation and generating the respective feedback signals for adjusting the controllable transmit weighting network in response to the detected electric field radiation so that the electric field radiation is controlled at the target inside the body by adjusting the feedback signals to minimize the difference in the electric field detected by electric field probe elements in the left and right halves of the electric field probe array to balance the electric field pattern with respect to the bisector line, and to minimize the difference in the electric field detected by the electric field probe elements in a direction along the bisector line.

47. The method of claim 46, wherein adjusting the feedback signals comprises performing a gradient search algorithm.

48. The method of claim 46, wherein adjusting the feedback signals comprises performing a matrix inversion algorithm.

49. A hyperthermia applicator for inducing a temperature rise in a target within a body, comprising

a first plurality of electric field radiators, each for transmitting electric field radiation, comprising a phased-array of monopole antenna elements;

a first RF reflecting groundplane surface disposed adjacent and substantially perpendicular to the monopole antenna elements, the monopole antenna elements being disposed on a side of the RF reflecting groundplane surface;

a plurality of controllable transmit weighting networks, each such network coupled to a respective monopole antenna element, each weighting network controlling the phase and amplitude of the electric field radiation transmitted by the respective monopole antenna element in response to a respective feedback signal;

a source of electric field radiation coupled to each monopole antenna element through a respective weighting network;

at least one electric field probe for detecting electric field radiation from the plurality of monopole antenna elements; and

a controller coupled to the electric field probe for receiving the detected electric field radiation and generating the respective feedback signals, and for adjusting the feedback signals in response to the detected electric field radiation so that the electric field radiation is controlled at the target inside the body.

50. The hyperthermia applicator of claim 49, further comprising a second RF reflecting groundplane surface disposed opposite to the first RF reflecting groundplane surface such that the monopole antenna elements are disposed between the first and second RF reflecting groundplane surfaces.

51. The hyperthermia applicator of claim 50, further comprising

an RF reflecting screen mounted substantially perpendicular to the first and second groundplane surfaces behind the monopole antenna elements to form a waveguide for directing RF energy from the monopole antenna elements toward the target.

52. The hyperthermia applicator of claim 51, wherein the first and second groundplane surfaces are substantially parallel to each other.

53. The hyperthermia applicator of claim 51, wherein the first and second groundplane surfaces are disposed at an angle to one another forming a waveguide horn.

54. The hyperthermia applicator of claim 50, further comprising

a second plurality of electric field radiators comprising a second phased array of monopole antenna elements disposed adjacent and substantially perpendicular to the second RF reflecting groundplane surface on the side of the second RF reflecting groundplane surface opposite the first phased array of monopole antenna elements;

and

a third RF reflecting groundplane surface disposed opposite to the second RF reflecting groundplane surface such that the second phased array of monopole antenna elements are disposed between the second and third RF reflecting groundplane surfaces.

55. The hyperthermia applicator of claim 49, wherein the electric field probe comprises an invasive probe for placement inside the target within the body.

56. The hyperthermia applicator of claim 49, wherein the electric field probe comprises a non-invasive probe for placement outside the body.