Speckle reduction in optical coherence tomography by path length encoded angular compounding

• US 20060227333A1
• Filed: 03/31/2004
• Published: 10/12/2006
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: The General Hospital Corporation (Mass General Brigham, Inc.)
• Original Assignee: The General Hospital Corporation (Mass General Brigham, Inc.)
• Inventors: Iftimia, Nicusor, Bouma, Brett Eugene, Tearney, Guillermo J.
• Granted Patent: US 7,567,349 B2
• Time in Patent Office: Days
• US Class Current: 356/512
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/6852 Catheters
• CPC Class Codes: G01B 9/02028 Two or more reference or object arms in one interferometer
• CPC Class Codes: G01B 9/02082 Caused by speckles
• CPC Class Codes: G01B 9/02087 Combining two or more images of the same region
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01J 9/0215 by shearing interferometric methods
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 27/48 Laser speckle optics

Abstract

Speckle, a factor reducing image quality in optical coherence tomography (“OCT”), can limit the ability to identify cellular structures that are important for the diagnosis of a variety of diseases. The present invention allows for an implementation of an angular compounding, angular compounding by path length encoding (“ACPE”) for reducing speckle in OCT images. By averaging images obtained at different incident angles, with each image encoded by path length, ACPE maintains high-speed image acquisition and implements minimal modifications to OCT probe optics. ACPE images obtained from tissue phantoms and human skin in vivo demonstrate a qualitative improvement over traditional OCT and an increased signal-to-noise ratio (“SNR”). Accordingly, apparatus probe catheter, and method are provided for irradiating a sample. In particular, an interferometer may forward forwarding an electromagnetic radiation. In addition, a sample arm may receive the electromagnetic radiation, and can include an arrangement which facilitates a production of at least two radiations from the electromagnetic radiation so as to irradiate the sample. Such arrangement can be configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations.

Claims

1. An apparatus for irradiating a sample, comprising:

a) an interferometer forwarding an electromagnetic radiation; and

b) a sample arm receiving the electromagnetic radiation, the sample arm including an arrangement which facilitates a production of at least two radiations from the electromagnetic radiation so as to irradiate the sample, the arrangement being configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations.

2. The apparatus according to claim 1, further comprising:

c) a reference arm providing a further electromagnetic radiation, wherein the interferometer receives the first, second and further radiations, and forms a resultant signal based on the first, second and further radiations; and

d) a processing arrangement generating a first image based on the first radiation and a second image based on the second radiation, wherein the first and second images are different from one another.

3. The apparatus of claim 2, wherein the processing arrangement generates a further image based on the first and second images.

4. The apparatus of claim 3, wherein the further image has a noise that is smaller than a noise of the first image and a noise of the second image.

5. The apparatus according to claim 4, wherein the further image has a signal to noise ratio that is improved according to the equation:

6. The apparatus according to claim 5, wherein m=2 and N=3 images associated with the at least two radiations are obtained.

7. The apparatus according claim 3, wherein the further image is generated based on a mathematical combination of the first and second images.

8. The apparatus according to claim 2, wherein the sample is irradiated by the first irradiation at a first angle, wherein the sample is irradiated by the second radiation at a second angle, the first and second angles different from one another.

9. The apparatus according to claim 8, wherein the first and second angle are different from one another based on the delay and at least one of a phase and a incident angle of each of the first and second radiations.

10. The apparatus according to claim 2, further comprising a detector which detects the first electromagnetic energy, and forwards the detected energy to the processing arrangement.

11. The apparatus according to claim 1, wherein the arrangement includes two sections, each being configured to delay a respective one of the first and second radiations, and wherein a delay of the first radiation is greater than a delay of the second radiation.

12. The apparatus according to claim 1, wherein the delay of a path of the first radiation compared to a path of the second radiation is at least 500 μ

m in air.

13. The apparatus according to claim 1, wherein the delay of a path of the first radiation compared to a path of the second radiation is at least 1 mm in air.

14. The apparatus according to claim 1, wherein the arrangement has a refractive index of at least 1.5.

15. The apparatus according to claim 1, wherein the arrangement has a refractive index of at least 3.0.

16. The apparatus according to claim 1, wherein the arrangement includes silicon.

17. The apparatus according to claim 1, wherein the arrangement includes an anti-reflective coating on at least one surface thereof.

18. The apparatus according to claim 1, wherein the arrangement comprises an anti-reflection-coated BK 7 glass.

19. The apparatus according to claim 16, wherein the glass has a thickness of from about 1.6 mm to about 7.7 mm.

20. The apparatus according to claim 16, wherein the glass has a refractive index of from about 1.51 to about 3.5.

21. A catheter comprising:

a) an interferometer forwarding an electromagnetic radiation; and

b) a sample arm receiving the electromagnetic radiation, the sample arm including an arrangement which facilitates a production of at least two radiations from the electromagnetic radiation so as to irradiate the sample, the arrangement being configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations.

22. A probe for optical coherence tomography imaging, comprising:

a. an interferometer forwarding an electromagnetic radiation; and

b. a sample arm receiving the electromagnetic radiation, the sample arm including an arrangement which facilitates a production of at least two radiations from the electromagnetic radiation so as to irradiate a sample, the arrangement being configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations.

23. A method for irradiating a sample, comprising the steps of:

a. providing an electromagnetic radiation from an interferometer; and

b. in a sample arm, facilitating production of at least two radiations from the electromagnetic radiation so as to irradiate the sample, a first radiation of the at least two radiations being delayed with respect to a second radiation of the at least two radiations.

24. An apparatus for imaging, comprising:

a. a sample arm receiving an electromagnetic radiation, the sample arm including an arrangement which facilitates a production of at least two radiations from the electromagnetic radiation so as to irradiate a sample, the arrangement being configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations;

b. a device receiving the first and second radiations from the sample arm and at least one third radiation from a reference arm, wherein the first and second radiations interfere with the third radiation;

c. at least one of spectral separating unit which separates spectrum of at least one of the first, second and third radiations into frequency components; and

d. at least one detection arrangement including a plurality of detectors, each detector capable of detecting at least a portion of at least one of the frequency components.

25. An apparatus comprising:

a. at least one first arrangement providing at least one first electro-magnetic radiation to a sample arm and at least one second electro-magnetic radiation to a non-reflective reference arm, wherein a frequency of radiation provided by the first arrangement varies over time, wherein the sample arm receives the first electromagnetic radiation, the sample arm including an arrangement which facilitates a production of at least two radiations from the electromagnetic radiation so as to irradiate a sample, the arrangement being configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations; and

b. at least one second arrangement detecting an interference between the first and second radiations generated at the sample arm and the second electro-magnetic radiations generated at the reference.

26. An apparatus comprising:

a. at least one first arrangement providing at least one first electro-magnetic radiation to a sample arm and at least one second electromagnetic radiation to a reference arm, wherein at least one of the first and second electromagnetic radiation has a spectrum which changes over time, the spectrum containing multiple frequencies at a particular time, wherein the sample arm receives the first electromagnetic radiation, the sample arm including an arrangement which facilitates a production of at least two radiations from the electromagnetic radiation so as to irradiate a sample, the arrangement being configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations; and

b. at least one second arrangement detecting an interference between the first and second radiations generated at the sample arm and the second electro-magnetic radiations generated at the reference.