Electronically scanned optical coherence tomography with frequency modulated signals

• US 8,526,004 B2
• Filed: 04/18/2008
• Issued: 09/03/2013
• Est. Priority Date: 07/16/2001
• Status: Active Grant

• Current Assignee: Boston Scientific Scimed, Inc. (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Scimed, Inc. (Boston Scientific Corporation)
• Inventors: Barbato, Louis J.
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): HANSEN, JONATHAN M
• Application Number:
  US12/105,910
• Publication Number:
  US 20090012404A1
• Time in Patent Office: 1,964 Days
• Field of Search: 356/479, 356/497, 356/484, 356/489
• US Class Current: 356/484
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/6852 Catheters
• CPC Class Codes: G01B 9/02002 using two or more frequencies
• CPC Class Codes: G01B 9/02028 Two or more reference or object arms in one interferometer
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence

Abstract

An improved Optical Coherence Domain Reflectometry (OCDR) system is provided. One embodiment of this OCDR system outputs a detector signal carrying image depth information on multiple modulation frequencies, where each modulation frequency corresponds to a different image depth. The image depth information from the detector signal may be resolved by tuning to the desired modulation frequency. Another system for imaging body tissue uses multiple frequency modulators such that the light beam does not travel from an optical fiber to free space.

Claims

1. A method of interfacing an optical system for imaging body tissue to an ultrasound console comprising:

providing a source beam;

splitting the source beam into a reference beam and a sample beam;

splitting the reference beam into a plurality of intermediate beams;

directing each intermediate beam to a different one of a plurality of light modulators, each light modulator modulating the intermediate beam directed to that light modulator at a different unique modulation frequency;

directing the sample beam at a sample;

combining the sample beam, after being directed to the sample, with the plurality of modulated intermediate beams to form a light beam;

converting the light beam into a detector signal using a light detector, wherein the light beam comprises the plurality of modulated intermediate beams modulated at a plurality of different modulation frequencies, each modulation frequency corresponding to a different image depth of body tissue;

generating a tuner output signal from the detector using a tuner that is tuned to each of a plurality of the different modulation frequencies one at a time;

converting the tuner output signal into a serial analog signal, wherein an amplitude of the serial analog signal provides image brightness information and a time position within the serial analog signal provides image depth information; and

outputting the serial analog signal to the ultrasound console.

2. The method of claim 1, wherein image brightness information in the serial analog signal is arranged in order of increasing image depth.

3. The method of claim 1, wherein the serial analog signal has approximately the same length as an echo signal that the ultrasound console is configured to process.

4. The method of claim 1, wherein the serial analog signal has a length of approximately 8 ps.

5. The method of claim 1, further comprising synchronizing the output of the serial analog signal with an encoder pulse from an ultrasound motor encoder.

6. The method of claim 1,

wherein converting the tuner output signal into a serial analog signal comprises converting the tuner output signal into a sequence of digital data using an analog-to-digital converter;

storing the sequence of digital data into a buffer; and

converting an output of the digital data from the buffer into the serial analog signal using a digital-to-analog converter.

7. The method of claim 1, wherein the generating step comprises generating the tuner output signal from the detector signal using the tuner that is sequentially tuned to each of a plurality of the different modulation frequencies in an order of the modulation frequencies corresponding to increasing image depth.

8. The method of claim 1, wherein the generating step comprises sweeping the tuner through the plurality of different modulation frequencies when an ultrasound motor encoder outputs an encoder pulse.

9. The method of claim 6, wherein data in the sequence of digital data is arranged in order of data corresponding to increasing image depth.

10. The method of claim 1, wherein the generating step further comprises:

mixing the detector signal with an output signal of an oscillator; and

varying the frequency of the oscillator output signal.

11. A method of interfacing an optical system for imaging body tissue to a digital input of an ultrasound console comprising:

providing a source beam;

splitting the source beam into a reference beam and a sample beam;

splitting the reference beam into a plurality of intermediate beams;

directing each intermediate beam to a different one of a plurality of modulators, each modulator modulating the respective intermediate beam at a different unique modulation frequency;

directing the sample beam at a sample;

combining the sample beam, after being directed to the sample, with the plurality of modulated intermediate beams to form a light beam;

converting the light beam into a detector signal using a light detector, wherein the light beam comprises the plurality of modulated intermediate beams modulated at a plurality of different modulation frequencies, each modulation frequency corresponding to a different image depth of body tissue;

converting the detector signal into a sequence of digital data using, in part, a tuner that is tuned to each of a plurality of the different modulation frequencies one at a time, wherein the sequence of digital data comprises data corresponding to different image depths; and

outputting the sequence of digital data to the digital input of the ultrasound console.

12. The method of claim 11, wherein data in the sequence of digital data is arranged in order of increasing image depth.

13. The method of claim 11, further comprising synchronizing the output of the sequence of digital data with an encoder pulse from an ultrasound motor encoder.

14. The method of claim 11, wherein the converting step comprises

generating a tuner output signal from the detector signal using the tuner that is tuned to each of the plurality of the different modulation frequencies one at a time;

converting the tuner output signal into the sequence of digital data using an analog-to-digital converter;

storing the sequence of digital data into a buffer; and

outputting the sequence of digital data from the buffer to the digital input of the ultrasound console.

15. The method of claim 14, wherein the generating step comprises generating a tuner output signal from the detector signal using a tuner that is sequentially tuned to each of a plurality of the different modulation frequencies in an order of the modulation frequencies corresponding to increasing image depth.

16. The method of claim 14, wherein the generating step comprises sweeping the tuner through the plurality of different modulation frequencies when an ultrasound motor encoder outputs an encoder pulse.

17. The method of claim 14, wherein the generating step further comprises:

mixing the detector signal with an output signal of an oscillator; and

varying the frequency of the oscillator output signal.