Focusing electromagnetic radiation within a turbid medium using ultrasonic modulation

Patent metadata

Field	Value
Publication number	US-9232896-B2
Application number	US-201213623681-A
Country	US
Kind code	B2
Filing date	Sep 20, 2012
Priority date	Sep 20, 2012
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

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.

First claim

What is claimed is:

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

Assignees

• Elwha Llc

Inventors

• Baym Michael H
• Hyde Roderick A
• Kare Jordin T
• Wood Jr Lowell L

Classifications

• A61B5/14551

  for measuring blood gases · CPC title

• A61B5/0086

  using infrared radiation · CPC title

• A61B5/4064

  Evaluating the brain (for intracranial pressure A61B5/031; for cerebral blood gases A61B5/14553; using EEG A61B5/369) · CPC title

• A61B5/0097 Primary

  by applying acoustic waves and detecting light, i.e. acousto-optic measurements · CPC title

• G02F1/33 Primary

  Acousto-optical deflection devices {(circuit or control arrangements therefor G02F1/113)} · CPC title