CN110731755A

CN110731755A - Polarization leveling method of catheter polarization-sensitive optical coherence tomography system

Info

Publication number: CN110731755A
Application number: CN201910955480.XA
Authority: CN
Inventors: 陈韵岱; 田峰; 郑博; 陆维; 陶魁园; 袁德胜; 刘江涛
Original assignee: NANJING WOFUMAN MEDICAL TECHNOLOGY Co Ltd
Current assignee: NANJING WOFUMAN MEDICAL TECHNOLOGY Co Ltd
Priority date: 2019-12-03
Filing date: 2019-12-03
Publication date: 2020-01-31

Abstract

A polarization leveling method for catheter polarization-sensitive optical coherence tomography system is characterized in that firstly, the polarization state of the light incident to a fiber coupler (12) from a reference arm is adjusted to be equal to the components of P light and S light by adjusting a second polarization controller (9), and the powers of two input ends of a balanced detector (17) and a second balanced detector (18) are adjusted to be equal, secondly, the polarization states of the P light and the S light incident to a sample from a sample arm are separated in time domain, and the intensities of the P light and the S light are adjusted to be equal by a polarization controller (3) and a polarization-maintaining fiber (4).

Description

Polarization leveling method of catheter polarization-sensitive optical coherence tomography system

Technical Field

The invention relates to the field of catheter imaging covering cardiovascular and cerebrovascular systems and the like by catheter Optical Coherence Tomography (OCT), in particular to a Polarization-sensitive OCT (Polarization-sensitive OCT) of catheters, namely, a method for adjusting birefringence information of a sample in a PS-OCT image, and specifically relates to a Polarization leveling method of a catheter Polarization-sensitive Optical Coherence Tomography system.

Background

The catheter OCT imaging technology is a blood vessel imaging method with the highest image resolution at present, particularly the catheter PS-OCT imaging technology, can solve the medical problem that the stability of atherosclerotic plaques is difficult to judge in vivo, in real time and rapidly, and can improve the prevention and treatment effect of atherosclerotic diseases. However, the existing OCT system has reached a level that may determine the property of the tissue plaque in terms of resolution, but is still insufficient in terms of tissue penetration ability, image sharpness, and accuracy of tissue plaque type determination, and using the PS-OCT technology, improving the performance of the related technology is a key direction for development of the OCT system, and is also a necessary way to solve the aforementioned key scientific problems.

In catheter OCT, catheter PS-OCT is an extension of catheter OCT technology, providing methods for quantitative measurement of tissue birefringence properties, where light birefringence changes the polarization state of light and can be correlated with proteins and biological macromolecules with directional structures such as collagen, actin, etc. catheter PS-OCT enhanced birefringence is closely related to the presence of large numbers of thick collagen fibers or intimal smooth muscle cells, so high resolution detection of catheter PS-OCT imaging can be applied to enhanced plaque stability measurements, furthermore catheter PS-OCT systems have the potential to evaluate plaque collagen and distinguish normal intima, fibrous plaque, lipid plaque, and calcification, for this reason catheter polarization sensitive optical coherence tomography systems and methods for plaque demodulation, where the light source employs a fast scanning light source, where polarization-preserving fibers are used to produce delays in orthogonal polarization states, polarization beam splitters for polarization collection, polarization diversity for simultaneous rendering of two orthogonal input polarization states in images, and polarization demodulation methods for polarization diversity, background signal cancellation, spectral transformation, spectral dispersion transformation, spectral transformation into binary polarization transformation, and final polarization tuning of polarization reference coordinates, where polarization tuning, etc. are key polarization tuning steps.

Disclosure of Invention

The invention aims to solve the problem that the existing OCT catheter optical coherence tomography system can only acquire blood vessel intensity information, and discloses polarization leveling methods of a catheter polarization-sensitive optical coherence tomography system.

The technical scheme of the invention is as follows:

A polarization leveling method for the polarization-sensitive optical coherence tomography system of catheter is characterized by that firstly, the polarization state of the light incident on the fiber coupler 12 from the reference arm is adjusted to be equal to the components of P light and S light by adjusting the second polarization controller 9, and the powers of the two input ends of the balanced detector 17 and the second balanced detector 18 are adjusted to be equal, secondly, the polarization state of the P light and the S light incident on the sample from the sample arm is separated in time domain, and the intensities of the P light and the S light are adjusted to be equal by the polarization controller 3 and the polarization-maintaining fiber 4.

The optical fiber coupler 12 is a 50:50 optical fiber coupler.

The lengths of the polarization maintaining optical fibers 4 are all 18.5 meters.

The invention has the beneficial effects that:

the invention lays a foundation for the demodulation of catheter polarization-sensitive optical coherence tomography and can provide more characteristic information for cardiovascular and cerebrovascular diseases.

Drawings

FIG. 1 is a schematic diagram of the system structure of the present invention.

Fig. 2 is a flow chart of the reference arm offset leveling of the present invention.

Fig. 3 is a flow chart of sample arm leveling deflection according to the present invention.

Detailed Description

The invention is further illustrated in the following description with reference to the figures and examples.

As shown in fig. 1.

A catheter polarization-sensitive optical coherence tomography system as shown in FIG. 1, which includes a scanning light source 1, the emergent light of the scanning light source 1 enters from 1 port of 1:99 fiber coupler 2 and is distributed from 2 ports and 3 ports to sample arm and reference arm respectively in a ratio of 1: 99. the emergent light of 2 ports of 1:99 fiber coupler 2 enters into sample arm, the light beam entering into sample arm enters into polarization maintaining fiber 4 with length of 18.5 m after entering into three-ring controller 3, enters into 1 port of circulator 6, the light exits from 2 port of circulator 6, the emergent light enters into imaging catheter 11 through rotating mechanism 8, the light reflected by sample returns from imaging catheter 11 into circulator 6, and exits through 3 port of circulator 6. the emergent light of 3 port of 1:99 fiber coupler 2 enters into reference arm, the light entering into single-mode fiber 5 with length of 18.5 m, the emergent light enters into 1 port of circulator 7, enters into 2 port of light delay line, enters into reference arm through 2 port of circulator 7, the reflected light enters into single-mode fiber 5, the light enters into single-mode fiber 5 with length of 18.5 m, the emergent light enters into 1 port of ring splitter 1 port of 18, the polarization splitter 18, the polarization detector 17, the reflected light enters into polarization splitter 16, the polarization controlling fiber splitter 16, the polarization detector 17, the reflected light enters into polarization splitter 16, the polarization splitter, the polarization detector 17, the polarization splitter 16, the polarization detector 17, the polarization splitter 16, the polarization splitter, the polarization detector 17, the polarization detector 16, the polarization detector, the polarization beam splitter 16, the polarization beam splitter, the polarization detector 16.

The light source adopts a fast scanning light source, the polarization-maintaining optical fiber is adopted in the system to generate the delay of the orthogonal polarization state, the polarization diversity acquisition is carried out through the polarization beam splitter, the length of the polarization-maintaining optical fiber depends on the birefringence of the polarization-maintaining optical fiber to generate the phase delay equal to half of the imaging depth of the common OCT, the method ensures that the system can simultaneously present the polarization diversity imaging of the orthogonal two input polarization states in images, and the possibility is provided for subsequently eliminating the system birefringence change introduced by catheter rotation.

The analytical method matched with the method shown in the figure 1 comprises series steps of polarization leveling, background signal elimination, spectrum shaping, two-state dispersion elimination, interpolation Fourier transform, reference plane selection, polarization calculation, polar coordinate conversion to Cartesian coordinate and the like, and finally realizes vascular birefringence imaging, wherein the polarization leveling method comprises polarization leveling of a reference arm and a sample arm, firstly, the polarization state of light incident to a fiber coupler 12 of the reference arm is adjusted to be equal to the components of P light and S light by adjusting a second polarization controller 9, the power of two input ends of the light incident to a th balanced detector 17 and a second balanced detector 18 is adjusted to be equal, the adjusting process is shown in figure 2, secondly, the polarization state of the P light and the S light incident to the sample of the sample arm is separated in a time domain, the intensity of the P light and the S light is adjusted to be equal by a polarization controller 3 and a polarization-maintaining fiber 4, the adjusting process is shown in figure 3, and the two steps are sequential in time and cannot be adjusted back and forth.

The parts not involved in the present invention are the same as or can be implemented using the prior art.

Claims

The polarization leveling method of the catheter polarization-sensitive optical coherence tomography system is characterized in that firstly, the polarization state of light incident to a fiber coupler (12) from a reference arm is adjusted to be equal to the components of P light and S light by adjusting a second polarization controller (9), the powers of two input ends incident to a th balanced detector (17) and a second balanced detector (18) are adjusted to be equal, secondly, the polarization states of the P light and the S light incident to a sample from a sample arm are separated in a time domain, and the intensities of the P light and the S light are adjusted to be equal through a th polarization controller (3) and a polarization-maintaining fiber (4).
2. The method of claim 1, wherein the fiber coupler (12) is a 50:50 fiber coupler.
3. A method according to claim 1, characterized in that the length of the polarization maintaining fiber (4) is 18.5 meters.