Focusing electromagnetic radiation within a turbid medium using ultrasonic modulation

• US 9,232,896 B2
• Filed: 09/20/2012
• Issued: 01/12/2016
• Est. Priority Date: 09/20/2012
• Status: Active Grant

• Current Assignee: Elwha LLC (Intellectual Ventures LLC)
• Original Assignee: Elwha LLC (Intellectual Ventures LLC)
• Inventors: Baym, Michael H., Hyde, Roderick A., Kare, Jordin T., Wood, Lowell L. Jr.
• Primary Examiner(s): Brutus, Joel F
• Application Number:
  US13/623,681
• Publication Number:
  US 20140081102A1
• Time in Patent Office: 1,209 Days
• Field of Search: 600/407
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0086 using infrared radiation
• CPC Class Codes: A61B 5/0097 by applying acoustic waves and detecting light, i.e. acoustooptic measurements
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: G02F 1/33 Acousto-optical deflection devices circuit or control arrangements therefor G02F1/113

Abstract

The present disclosure provides various systems and methods for focusing electromagnetic radiation (EMR) within a diffusion medium, such as a turbid medium. A diffusion medium is irradiated with EMR. The EMR may be modulated by an acoustical wave focused on a focus volume within the diffusion medium. The EMR may be modulated by a beat frequency or other function of multiple focused acoustical waves. The EMR may be modulated at a harmonic of a fundamental frequency of one or more acoustical waves. A filter may filter the emerging EMR to remove all but specifically modulated EMR scattered from the focus volume. The modulated EMR may be focused and/or used for various purposes, including imaging. In some embodiments, the modulated EMR may be reflected and/or amplified by a phase conjugating mirror. Furthermore, in some embodiments, acoustical phase conjugation may be used to focus an acoustical wave on a focus volume.

Claims

1. A method for focusing electromagnetic radiation using phase conjugation of harmonically modulated electromagnetic radiation, comprising:

vibrating a focus volume within a diffusion medium at an acoustical frequency, f_a, using a focused acoustical wave;

irradiating the diffusion medium with electromagnetic radiation at a radiation frequency, f_r;

receiving diffused electromagnetic radiation scattered from the diffusion medium, including harmonically modulated electromagnetic radiation from the focus volume at a modulated frequency, f_r shifted by a harmonic of the acoustical frequency, Nf_a, where N is an integer greater than 1;

filtering received diffused electromagnetic radiation to remove electromagnetic radiation at the radiation frequency, f_r, and at modulated frequencies shifted by the first harmonic of the acoustical frequency, 1f_a; and

transmitting phase conjugated electromagnetic radiation of filtered harmonically modulated electromagnetic radiation, such that the phase conjugated electromagnetic radiation substantially converges at the focus volume.

2. The method of claim 1, further comprising:

receiving diffused phase conjugated electromagnetic radiation scattered substantially from the focus volume;

determining absorption rates of the phase conjugated electromagnetic radiation in hemoglobin in the focus volume at a plurality of radiation frequencies; and

calculating a blood oxygenation within the focus volume using the determined absorption rates.

3. The method of claim 1, wherein the diffusion medium comprises a brain, and wherein the radiation frequency, f_r, is between 700 nanometers and 1500 nanometers, and further comprising:

receiving diffused phase conjugated electromagnetic radiation scattered substantially from the focus volume; and

measuring a level of neuronal activity in the brain using functional near-infrared (fNIR) imaging.

4. The method of claim 1, further comprising:

receiving diffused phase conjugated electromagnetic radiation scattered substantially from the focus volume; and

generating an image of the focus volume using the received diffused phase conjugated electromagnetic radiation from the focus volume.

5. The method of claim 1, further comprising:

receiving diffused phase conjugated electromagnetic radiation scattered substantially from the focus volume; and

determining a characteristic of a motion of a fluid within the focus volume using a Doppler measurement of the received phase conjugated electromagnetic radiation from the focus volume.

6. The method of claim 1, wherein the electromagnetic radiation has a frequency bandwidth less than the acoustical frequency, f_a.

7. The method of claim 1, wherein the harmonically modulated electromagnetic radiation is modulated at a second harmonic, such that the harmonically modulated electromagnetic radiation is at a modulated frequency f_r shifted by the second harmonic of the acoustical frequency, 2f_a.

8. The method of claim 1, wherein the harmonically modulated electromagnetic radiation is modulated at a third harmonic, such that the harmonically modulated electromagnetic radiation is at a modulated frequency f_r shifted by the third harmonic of the acoustical frequency, 3f_a.

9. The method of claim 1, wherein the harmonically modulated electromagnetic radiation includes electromagnetic radiation modulated at a plurality of harmonics, including electromagnetic radiation modulated at first, second, third, and fourth harmonics, such that the harmonically modulated electromagnetic radiation includes modulated frequencies f_r shifted by the first harmonic of the acoustical frequency 1f_a, f_r shifted by the second harmonic of the acoustical frequency 2f_a, f_r shifted by the third harmonic of the acoustical frequency 3f_a, and f_r shifted by the fourth harmonic of the acoustical frequency 4f_a.

10. The method of claim 9, further comprising:

receiving diffused phase conjugated electromagnetic radiation modulated at the plurality of harmonics scattered substantially from the focus volume; and

generating an image of the focus volume using the received diffused phase conjugated electromagnetic radiation from the focus volume.

11. The method of claim 1, wherein transmitting the phase conjugated electromagnetic radiation is performed in real-time using a phase conjugate mirror (PCM).

12. The method of claim 1, wherein transmitting the phase conjugated electromagnetic radiation is performed using degenerate four-wave mixing in a phase conjugate mirror (PCM).

13. The method of claim 1, wherein vibrating the focus volume comprises vibrating an elongated volume having a first end and a second end;

and

wherein the acoustical frequency of the elongated volume is configured to transition from a first acoustical frequency at the first end of the elongated volume to a second acoustical frequency at the second end of the elongated volume, such that the harmonically modulated electromagnetic radiation is shifted by a distinct acoustical frequency depending on from where along the elongated volume the electromagnetic radiation was scattered.

14. The method of claim 13, further comprising using acoustical diffraction of the focused acoustical wave in order to cause the acoustical frequency of the elongated volume to transition from a first acoustical frequency at the first end of the elongated volume to a second acoustical frequency at the second end of the elongated volume.

15. The method of claim 1, further comprising:

shifting the frequency of the phase conjugated electromagnetic radiation by Nf_a, such that the frequency of the phase conjugated electromagnetic radiation that substantially converges at the focus volume is the radiation frequency, f_r.

16. A system for focusing electromagnetic radiation using phase conjugation of harmonically modulated electromagnetic radiation, comprising:

a transducer configured to generate a focused acoustical wave to vibrate a focus volume within a diffusion medium at an acoustical frequency, f_a;

a light source configured to irradiate the diffusion medium with electromagnetic radiation at a radiation frequency, f_r;

a receiver configured to receive diffused electromagnetic radiation scattered from the focus volume, including harmonically modulated electromagnetic radiation from the focus volume at a modulated frequency, f_r shifted by Nf_a, where N is an integer greater than 1;

a filter configured to remove electromagnetic radiation at the radiation frequency, f_r, and at modulated frequencies shifted by the first harmonic of the acoustical frequency, 1f_a, from the received diffused electromagnetic radiation; and

a transmitter configured to transmit phase conjugated electromagnetic radiation of the filtered harmonically modulated electromagnetic radiation, such that the phase conjugated electromagnetic radiation substantially converges at the focus volume.

17. The system of claim 16, wherein the transmitter is configured to transmit phase conjugated electromagnetic radiation of the filtered harmonically modulated electromagnetic radiation, such that the phase conjugated electromagnetic radiation substantially converges at the focus volume to activate a drug within the focus volume.

18. The system of claim 16, wherein the transmitter comprises a phase conjugate mirror configured to use a pumping beam to create an energy build up in a non linear standing wave in order to amplify the phase conjugated electromagnetic radiation relative to the amplitude of the filtered harmonically modulated electromagnetic radiation.

19. The system of claim 16, wherein the radiation frequency, f_r, comprises an infrared frequency.

20. The system of claim 16, wherein the light source is configured to sweep the radiation frequency, f_r, between an initial frequency and a final frequency.

21. The system of claim 16, further comprising:

an ultrasonic receiver configured to receive diffused acoustical waves scattered from the focus volume within the diffusion medium; and

an acoustical transmitter configured to transmit phase conjugated acoustical waves of the received diffused acoustical waves, such that the phase conjugated acoustical waves substantially converge at the focus volume.

22. The system of claim 16, further comprising:

a second transducer configured to generate a second acoustical wave within the diffusion medium, such that the acoustical frequency, f_a, is a function of the frequency of the focused acoustical wave and the frequency of the second acoustical wave.

23. The system of claim 22, wherein the acoustical frequency, f_a, is an absolute value of a difference between the frequency of the focused acoustical wave and the frequency of the second acoustical wave, such that the acoustical frequency, f_a, is a beat frequency of the focused acoustical wave and the second acoustical wave.

24. The system of claim 16, wherein the transducer is configured to sequentially vibrate each of a plurality of focus volumes within the diffusion medium,

wherein the light source is configured to irradiate the sequentially vibrated plurality of focus volumes within the diffusion medium,

wherein the receiver is configured to sequentially receive diffused electromagnetic radiation scattered from the diffusion medium, including harmonically modulated electromagnetic radiation from each of the sequentially vibrated focus volumes at the modulated frequency, f_r shifted by Nf_a,

wherein the filter is configured to sequentially remove electromagnetic radiation at the radiation frequency, f_r, and at modulated frequencies shifted by the first harmonic of the acoustical frequency, 1f_a, from the received diffused electromagnetic radiation,

wherein the transmitter is configured to sequentially transmit phase conjugated electromagnetic radiation of the sequentially filtered harmonically modulated electromagnetic radiation, such that the phase conjugated electromagnetic radiation substantially converges at each of the plurality of focus volumes, sequentially,

wherein the receiver is further configured to sequentially receive diffused phase conjugated electromagnetic radiation scattered substantially from each of the plurality of focus volumes, including harmonically modulated electromagnetic radiation from each of the sequentially vibrated focus volumes at the modulated frequency, f_r shifted by Nf_a,

wherein the system further comprises an imaging device configured to sequentially generate an image of each of the focus volumes using the received diffused phase conjugated electromagnetic radiation from each of the focus volumes, and

wherein the system further comprises an image merger module configured to merge the images of each of the plurality of focus volumes to form an image of the diffusion medium.

25. A method for focusing an ultrasonic wave in an acousto-optical radiation system using acoustical phase conjugation, comprising:

vibrating a focus volume within a diffusion medium at an acoustical frequency, f_a, using an acoustical wave;

receiving diffused acoustical waves scattered from the focus volume within the diffusion medium;

transmitting phase conjugated acoustical waves of the received diffused acoustical waves, such that the phase conjugated acoustical waves substantially converge at the focus volume;

irradiating the diffusion medium with electromagnetic radiation at a radiation frequency, f_r; and

receiving diffused electromagnetic radiation from the diffusion medium, including modulated electromagnetic radiation from the focus volume at a modulated frequency f_r shifted by f_a;

wherein the modulated electromagnetic radiation comprises harmonically modulated electromagnetic radiation modulated at a harmonic of a fundamental frequency of the electromagnetic radiation, such that the harmonically modulated electromagnetic radiation is at a modulated frequency f_r shifted by a harmonic of the acoustical frequency, Nf_a, where N is an integer.

26. The method of claim 25, further comprising:

determining absorption rates of the modulated electromagnetic radiation in hemoglobin in the focus volume at a plurality of radiation frequencies; and

calculating a blood oxygenation within the focus volume using the determined absorption rates.

27. The method of claim 25, further comprising:

transmitting phase conjugated electromagnetic radiation of the filtered modulated electromagnetic radiation, such that the phase conjugated electromagnetic radiation substantially converges at the focus volume.

28. The method of claim 27, further comprising:

receiving diffused phase conjugated electromagnetic radiation scattered substantially from the focus volume;

determining absorption rates of the phase conjugated electromagnetic radiation in hemoglobin in the focus volume at a plurality of radiation frequencies; and

calculating a blood oxygenation of within the focus volume using the determined absorption rates.

29. The method of claim 27, wherein transmitting the phase conjugated electromagnetic radiation is performed using degenerate four-wave mixing in a phase conjugate mirror (PCM).

30. The method of claim 27, further comprising:

shifting the frequency of the phase conjugated electromagnetic radiation by f_a, such that the frequency of the phase conjugated electromagnetic radiation that substantially converges at the focus volume is the radiation frequency, f_r.

31. The method of claim 27, further comprising:

shifting the frequency of the phase conjugated electromagnetic radiation by a calibration frequency, f_c, such that the frequency of the phase conjugated electromagnetic radiation is useful for electromagnetic radiation therapy.

32. The method of claim 25, wherein the acoustical frequency, f_a, is generated using the acoustical wave and a second acoustical wave, such that the acoustical frequency, f_a, is a function of the frequency of the acoustical wave and the frequency of the second acoustical wave.

33. The method of claim 32, wherein the second acoustical wave is focused.

34. The method of claim 32, wherein the acoustical frequency, f_a, is an absolute value of a difference between the frequency of the acoustical wave and the frequency of the second acoustical wave, such that the acoustical frequency, f_a, is a beat frequency of the acoustical wave and the second acoustical wave.

35. A system for focusing an ultrasonic wave in an acousto-optical radiation system using acoustical phase conjugation, comprising:

a transducer configured to generate an acoustical wave to vibrate a focus volume within a diffusion medium at an acoustical frequency, f_a;

an ultrasonic receiver configured to receive diffused acoustical waves scattered from the focus volume within the diffusion medium;

an acoustical transmitter configured to transmit phase conjugated acoustical waves of received diffused acoustical waves, such that the phase conjugated acoustical waves substantially converge at the focus volume;

a light source configured to irradiate the diffusion medium with electromagnetic radiation at a radiation frequency, f_r; and

a receiver configured to receive diffused electromagnetic radiation scattered from the focus volume, including modulated electromagnetic radiation from the focus volume at a modulated frequency, f_r shifted by the acoustical frequency, f_a,

wherein the modulated electromagnetic radiation comprises harmonically modulated electromagnetic radiation modulated at a harmonic of a fundamental frequency of the electromagnetic radiation, such that the harmonically modulated electromagnetic radiation is at a modulated frequency f_r shifted by a harmonic of the acoustical frequency, Nf_a, where N is an integer.

36. The system of claim 35, further comprising a filter configured to remove electromagnetic radiation at the radiation frequency, f_r.

37. The system of claim 35, wherein the diffusion medium comprises a brain,

wherein the radiation frequency, f_r, is between 700 nanometers and 1500 nanometers, and

wherein the system further comprises a neuronal activity module configured to measure a level of neuronal activity in the brain using functional near-infrared (fNIR) imaging.

38. The system of claim 35, further comprising an imaging device configured to generate an image of the focus volume using the received diffused phase conjugated electromagnetic radiation from the focus volume.

39. The system of claim 35, wherein the modulated electromagnetic radiation is modulated at a second harmonic, such that the harmonically modulated electromagnetic radiation is at a modulated frequency f_r shifted by the second harmonic of the acoustical frequency, 2f_a.

40. The system of claim 35, wherein the modulated electromagnetic radiation includes electromagnetic radiation modulated at a plurality of harmonics, including electromagnetic radiation modulated at first, second, third, and fourth harmonics, such that the harmonically modulated electromagnetic radiation includes modulated frequencies f_r shifted by the first harmonic of the acoustical frequency 1f_a, f_r shifted by the second harmonic of the acoustical frequency 2f_a, f_r shifted by the third harmonic of the acoustical frequency 3f_a, and f_r shifted by the fourth harmonic of the acoustical frequency 4f_a.

41. The system of claim 40, further comprising an imaging device configured to generate an image of the focus volume using filtered harmonically modulated electromagnetic radiation from the focus volume.

42. The system of claim 35, wherein the focus volume comprises an elongated focus volume having a first end and a second end,

wherein the transducer is configured to vibrate the elongated volume, and

wherein the acoustical frequency of the elongated volume is configured to transition from a first acoustical frequency at the first end of the elongated volume to a second acoustical frequency at the second end of the elongated volume, such that the harmonically modulated electromagnetic radiation is configured to be shifted by a distinct acoustical frequency depending on from where along the elongated volume the electromagnetic radiation was scattered.

43. The system of claim 42, further comprising an acoustical diffraction system configured to diffract the acoustical wave such that the acoustical frequency of the elongated volume transitions from a first acoustical frequency at the first end of the elongated volume to a second acoustical frequency at the second end of the elongated volume.