KR20160128854A

KR20160128854A - Wide-field scanning OCT probe and OCT system for otoscope using radial 3D scanning

Info

Publication number: KR20160128854A
Application number: KR1020150060900A
Authority: KR
Inventors: 김필운; 박기범
Original assignee: 주식회사 오즈텍
Priority date: 2015-04-29
Filing date: 2015-04-29
Publication date: 2016-11-08

Abstract

Provided are a wide-field scanning OCT probe and an OCT system for an auriscope using radial three-dimensional scanning. According to an embodiment of the present invention, the wide-field scanning OCT probe includes: a first relay lens having a first focus length (f1), and converting light, coming in parallel with each other through different routes, into convergence light; a second relay lens having a second focus length (f2), and converting the light, diffusing after convergence, into parallel light by changing its route; and a focus lens having a third focus length (f3), and converting the parallel light into the convergence light. Therefore, the present invention is capable of improving the reliability of the quality of an OCT image.

Description

[Field of the Invention] The present invention relates to a wide-field scanning OCT probe and an OCT system using radial 3D scanning,

The present invention relates to a wide-field scanning optical coherence tomography (OCT) probe and a radial 3-D scanning OCT system. More particularly, the present invention relates to a wide field scanning method and a three-dimensional radial scanning The present invention relates to an OCT probe using a radial scanning method and an OCT system using the same.

In general, the process of hearing is transmitted through a complex anatomical structure. The middle ear consists of the eardrum, ossicles, and middle ear cavity. The main role of such middle ear is to convert the external acoustic signal collected from the auditory canal into a mechanical vibration signal. However, such a fine structure may cause structural damage due to bacterial infection when exposed to the external environment. Damage due to otitis media is a major cause of hearing loss and hearing loss is currently one of the three most common diseases (hearing loss, heart disease, and arthritis).

On the other hand, the eardrum is the first position to diagnose the presence of any ear-related diseases, and the human eardrum has a diameter of approximately 7-10 mm. Commonly accepted diagnostic methods, such as otoscopy and endoscopy, can only photograph the surface layer of the eardrum.

Recently, optical coherence tomography (OCT) has been actively performed in otorhinolaryngology as a diagnostic technique for identifying various diseases because it can be taken tomographically. This OCT is a non-invasive, high-resolution (1-15 μm) deep-resolution cross-sectional imaging technique derived from a near-infrared wavelength band light source with low coherent interference effects.

The main OCT imaging technique is the line scanning method, which is used in various fields. In the line scanning method, the correlation between the scanning angle and the physical distance between the sample and the scanning mirror is important. This is because the scanning range in the line scanning is limited to 2-3 mm as a result of the size of the ear specula tip and the size of the ear canal.

Due to limitations of these techniques, some difficulties in the diagnosis of the entire eardrum reduce the reliability of the diagnostic procedure. In addition, these methods require large amounts of 2D data, which slows down the system. When the system speed decreases, it is a difficult problem to obtain reliable 3D images due to motion artifacts associated with both the patient and operator's movements.

JP 2010-051390 A

According to an aspect of the present invention, there is provided a method of enhancing the quality of a 3D image using a wide-field scanning method, A scanning OCT probe and a radial 3-D scanning OCT system.

According to an aspect of the present invention, there is provided a wide-field scanning OCT probe for an optical tomography scanner. The wide-field scanning OCT probe includes a first relay lens having a first focal length f1 and converting light entering parallel in different paths into convergent light; A second relay lens having a second focal length f2 and converting the light to be diffused after convergence into a parallel light by changing the path; And a focal lens having a third focal length f3 and converting the parallel light into convergent light.

In one embodiment, the wide-field scanning OCT probe can perform a three-dimensional radial scan by B-scan while rotating at a predetermined angle by a two-axis galvano-scan mirror.

In one embodiment, the wide-field scanning OCT probe includes a collimator for converting light incident from the light source into parallel light; And a galvano scan mirror for changing the path of the parallel light.

In one embodiment, the focal lengths f1 to f3 may be set so that the horizontal resolution of the photographed image is 15 mu m or less.

In one embodiment, the ratio of the focal length f3 of the focal lens to the focal length f2 of the second relay lens may be 1 to 2.

In one embodiment, the horizontal scanning range of the radial scanning may be 7 to 10 mm.

In one embodiment, the wide-field scanning OCT probe includes a filter for filtering a portion of the light reflected from the sample; A magnifying lens for diffusing the filtered light; And a CCD camera for capturing an image of the sample by the diffused light.

According to another aspect of the present invention, an OCT system for a goniometer is provided. The scanning OCT system includes a wide-field scanning OCT probe as described above; Light source; An optical coupler for dividing the light generated from the light source; A reference unit that receives and phase-scans and reflects a part of the divided light; An optical tomography unit converting the first reflected light received from the reference unit and the second reflected light received from the wide-field scanning OCT probe into an electrical signal to generate an OCT image; And an image processor for generating a 3D image from the photographed 2D image.

In one embodiment, the image processing unit includes a center point detecting unit for detecting a center point for radial scanning; And a center point adjusting unit for adjusting a deviation of the center point.

In one embodiment, the image processing unit may further include a 3D image generating unit that generates a 3D image using the 2D image acquired by the radial scanning.

The OCT probe using wide-field scanning and three-dimensional radial scanning according to an embodiment of the present invention and the OCT system using the OCT probe using the wide-field scanning and the 3D radial scanning according to an embodiment of the present invention scan across the center of the sample to facilitate the entire 2D scan, The reliability of the OCT image quality can be improved, and it can be advantageous to manufacture any hand-held OCT probe.

In addition, the embodiment of the present invention can improve the horizontal scanning range and increase the scanning area size by using the relay lens and the focus lens.

In addition, embodiments of the present invention can reduce the number of scans required for reasonable image quality by radial scanning, improve the data acquisition rate, and improve the speed of 3D image creation, thereby having an advantage in 3D scanning.

1 is a schematic block diagram of an OCT system for a goggle according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a major part of a wide-field scanning OCT probe according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a 3D reconstruction image according to a three-dimensional radial scanning type and the number of samples (64, 128, 256) according to an embodiment of the present invention.
FIG. 4 is a graph showing the horizontal resolution of the OCT image with respect to the ratio of the focal length f2 of the second relay lens to the focal length f3 of the focal lens of FIG. 2, and (b) tip of the scanning angle according to the scanning angle.
(B) a 2D OCT image of a human eardrum in a human eardrum with a 7 mm scanning range using a wide-field scanning OCT probe, (c) a 2-mm scanning range using a conventional line scanning method, Adhesive otitis media and (d) chronic otitis media.
6 (a) is an image obtained by superimposing a CCD camera image of a human thigh in the body and a shape of a ray scanning on the upper part of the image, (b) a 3D image of the eardrum, and (c) .
Fig. 7 is a graphical representation of (a) a 2 mm scanning range and a conventional 3D system, (b) an image obtained using a 7 mm scanning range and a wide-field OCT probe, and (c) A 3D volume reconstruction image of the cross-sectional OCT image of the guinea pig ear.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

The present invention provides a wide-field scanning OCT probe for otitis media and eardrum imaging using a relay configuration.

In most OCT applications, image acquisition is performed on a stably positioned sample positioned, for example, on a bench-top cradle used in ophthalmology. Thus, 3D image acquisition can be performed using a raster scanning method. In this way, images are acquired using a hand-held probe. In addition, the main shot samples themselves (e. G., Middle ear and eardrum) can not maintain an unchanging physical state during image acquisition. Therefore, since the initial position of the 3D scanning data may not coincide due to the movement of the human body, acquisition of the middle-sized 3D image using raster scanning is not easy compared to the radial scanning method.

By radial scanning, the present invention can be fixed at a certain point while the exact center point of the radial scans is maintained during scanning. This center point can be considered as the reference center image.

On the other hand, if a change in this reference center image is detected, discrepancies between the exact center point and the scanned data due to motion artifacts can be easily identified.

Thus, the radial scanning method is more effective than the raster scanning method because the motion artifacts that affect the accuracy of the raster scanning method can not be identified due to the absence of the reference center image.

The present invention can minimize motion artifacts due to the use of such reference center images and thus obtain 3D images without motion artifacts.

These motion artifacts have been found in many in-vivo studies, especially when hand-held probes are used, significantly worsening the image quality. Thus, the present invention provides an efficient lens configuration that reduces this movement by using a radial scanning method instead of the line scanning method.

This approach is more efficient when radial scanning requires a lot of time-consuming 3D scanning because the path always traverses the center of the sample. In addition, the present invention can reduce the number of B-scan images by radial scanning, and thus reduce the number of scans required for volume acquisition.

Referring to FIG. 1, the OCT system 100 for a microscope according to an embodiment of the present invention includes:

A light source 110, an optical coupler 120, a reference unit 130, a wide-field scanning OCT probe 140, a photo-tomography unit 150, and an image processing unit 200.

The light source 110 can generate light having a wide optical bandwidth and a short interference length, such as light having an interference length of about several micrometers. For example, the light source may have a characteristic that the central wavelength has a near-infrared wavelength band (800 nm to 1550 nm), a full width half maximum (FWHM) is 50 to 120 nm and a maximum output power is 5.3 mW , SLED (superluminescent diode).

The optical coupler 120 may receive the light generated from the light source 110 and then divide the received light and transmit the divided light to the reference unit 130 and the wide-field scanning OCT probe 140 through the optical fiber. In contrast, the optical coupler 120 receives the first reflected light from the reference unit 130 and the second reflected light from the wide-field scanning OCT probe 140, and transmits the received second reflected light to the optical tomography unit 150.

The reference unit 130 receives the divided light from the optical coupler 120 and performs phase scanning and reflection to transmit the first reflected light to the optical coupler 120. The reference unit 130 includes a collimator 132, And a reference mirror 136.

More specifically, the collimator 132 receives the light emitted from the optical coupler 120, converts the light into parallel light, and outputs the parallel light to the focus lens 134. The focal lens 134 can adjust the focal distance of the parallel light so that the parallel light converted through the collimator 132 converges on one focal point. The reference mirror 136 can change the optical path by receiving the light collected at one focal point through the focus lens 134 and then reflecting the first reflected light generated by the reflection to the focus lens 134 again.

The wide-field scanning OCT probe 140 irradiates the sample 300 with the light split and incident from the optical coupler 120, transfers the second reflected light from the sample 300 to the optical coupler 120, The user can take an image of the camera 300. This wide-field scanning OCT probe 140 is a handheld probe and includes a collimator 141, a galvanometer scan mirror 142, a filter mirror 143, a magnifying lens 144, a CCD camera 145, A relay lens 146, a second relay lens 147, a focus lens 148, and a diameter tip 149. [

More specifically, the collimator 141 receives the incident light divided by the optical coupler 120 and can convert the light into parallel light. The galvanometer scan mirror 142 receives the collimated light from the collimator 141 to change the optical path of the balanced light and then irradiates the light to the sample 300. The second reflected light reflected from the sample 300 is scanned The optical path of the second reflected light can be changed and transmitted to the optical coupler 120. [

The filter mirror 143 passes a part of the second reflected light reflected from the sample 300. The enlarged lens 144 enlarges a part of the passed light at a predetermined ratio, An image of the sample 300 can be taken.

1B, the first relay lens 146 has a first focal length f1 and converts the light that is incident on the galvanometer scan mirror 142 in parallel in different paths into convergent light can do. The second relay lens 147 has a second focal length f2 and can convert the light that has passed through the first relay lens 146 and diffused again after converging to the focus into a parallel light have. The focus lens 148 can convert the parallel light having the third focal length f3 and passed through the second relay lens 147 into the converged light.

At this time, the wide-field scanning OCT probe 140 can perform B-scan and three-dimensional radial scan while rotating at a certain angle by the two-axis galvanometer scan mirror 142.

Here, the focal length f1 of the first relay lens 146, the focal length f2 of the second relay lens 147, and the focal distance f3 of the focal lens 148 are the same as those of the wide-field scanning OCT probe 140 may be set to 15 mu m or less in horizontal resolution of the photographed image. The ratio of the focal length f3 of the focus lens 148 to the focal length f2 of the second relay lens 147 is preferably 1 to 2. In addition, the horizontal scanning range of the three-dimensional radial scanning by the wide-field scanning OCT probe 140 is preferably 7 to 10 mm.

The aperture stop 149 is formed with an aperture for irradiating the sample 300 with the light that has passed through the focus lens 148.

2, the light having passed through the galvanometer scan mirror 142 is directed to the focus lens 148 through the first relay lens 146 and the second relay lens 147. [ Here, the scanning angle between the end of the scanning range and the center point is represented by?.

The optical tomography unit 150 converts the first reflected light and the second reflected light incident from the optical coupler 120 into an electrical signal to generate an OCT image for the sample 300. The collimator 152 converts the first reflected light and the second reflected light, A diffraction grating 154, a focus lens 156, and a line scan camera 158.

More specifically, the collimator 152 receives the first reflected light and the second reflected light reflected from the reference unit 130 and the wide-field scanning OCT probe 140 through the optical coupler 120, Can be converted. The diffraction grating 154 can receive the converted balanced light through the collimator 152 and diffract it by wavelength. The focal lens 156 can adjust the focal length of the parallel light so that the parallel light diffracted through the diffraction grating 154 is collected in one focal point according to each wavelength band. The line scan camera 158 can scan an image of the sample 30 in a line state by collecting light in one focus according to each wavelength band through the focus lens 156 to generate an image of the sample 30, May be an oxide semiconductor (CMOS) line scanning camera.

The image processing unit 200 may generate a 3D image from the 2D image photographed by the optical tomography unit 150 and may include a center point detection unit 210, a center point adjustment unit 220, and a 3D image generation unit 230 have.

The center point detection unit 210 may detect a center point for radial scans, as shown in FIG. For example, since the center point can be fixed at a specific position by scanning across the center of the sample, the center point detection section 210 can detect this point as a reference center image.

The center point adjustment unit 220 can adjust the deviation caused by the motion of the patient or the operator based on the detected center point. For example, the center point adjuster 220 may adjust the center point to remove artifacts that may occur if the wide-field scanning OCT probe 140 fails to perform a normal three-dimensional radial scan due to motion of the patient or operator .

The 3D image generating unit 230 may generate a 3D image based on the 2D image whose center point deviation is adjusted in the center point adjusting unit 220. [ At this time, since the artifact can be reduced by adjusting the deviation of the center point, the 3D image generating unit 230 can generate a 3D image using a smaller 2D image.

Hereinafter, the experiments performed by the inventor and the results thereof will be described in order to find an optimal design condition for generating a 3D image using the wide-field scanning OCT probe 140 and three-dimensional radial scanning.

First, the focal distance f1 of the first relay lens 146 and the focal distance f3 of the focal lens 148 are varied in order to confirm the optimal horizontal resolution and the scanning range. At this time, the focal length of each lens affects the horizontal resolution, the scanning angle, and the light size. Therefore, in order to simplify the simulation, instead of using the focal length f2 of the second relay lens 147 and the focal length f3 of the focus lens 148 separately, the focus of the second relay lens 147 The ratio of the focal length f3 of the focus lens 148 to the distance f2 is applied.

4A shows the focal length f2 of the second relay lens 147 with respect to the focal length f1 of the first relay lens 146 of 10,20,30,40 mm. represents the horizontal resolution value with respect to the ratio of (f3). Here, the horizontal resolution of the OCT system 100 for a goniophotoscope is such that the focal length f1 of the first relay lens 146 decreases and the focal length f2 of the second relay lens 147 decreases, When the ratio of the focal length f3 of the first lens group increases.

In this experiment, the focal length f1 of the first relay lens 146 was finally fixed to 20 mm because of the length limitation of the galvanometer scan mirror 142 and the first relay lens 146. [ The incident beam size of the collimator 141 is assumed to be 1.5 mm. Further, in order to miniaturize the wide-field scanning OCT probe 140 and obtain a 15 mu m horizontal resolution, the focal length f3 of the focus lens 148 with respect to the focal length f2 of the second relay lens 147 The ratio was set at 1.5.

Fig. 4B shows the maximum scanning range for the light-free propagation. Here, by numerical analysis, the optimum value of the focal length f3 of the focus lens 148 for achieving the scanning range of 10 mm was 30 mm. However, the focal length f3 of the focus lens 148 was set at 50 mm because of the limitation imposed by the isometric length and the diameter of the diameter tip 149. Thus, the maximum scanning range and angle expanded to 7 mm and 4 ° respectively.

By considering the above-mentioned simulation results as well as the wide-field scanning OCT probe 140 design, the focal length f1 of the first relay lens 146 was set at 20 mm. The focal length f2 of the second relay lens 147 is set to 1.5 so that the ratio of the focal length f3 of the focal lens 148 to the focal length f2 of the second relay lens 147 is 1.5. And the focal length f3 of the focus lens 148 were set to 35 mm and 50 mm, respectively. The focal length f1 of the first relay lens 146 and the focal length f2 of the second relay lens 147 are set so that the focal length f1 of the first relay lens 146 and the focal length f2 of the second relay lens 147 f3 was used to calculate the focal length f3 of the focus lens 148 in consideration of the distance between the distal tip 149 and the eardrum from the OCT system 100 for gonioscopy.

5A is a 2 mm image obtained using a conventional line scanning method and a charge-coupled device (CCD) camera for a 2D eardrum in a human eardrum's internal body image, 7 mm wide-field image obtained using the scanning method. 5, the limit of the scanning length of 2 mm of the conventional eardrum was increased to 7 mm according to the present invention. Here, the image in the square box at the bottom of the image represents a ruler indicating the actual scanning range . In addition, geometric distortion artifacts that arise due to non-telecentric scanning of the sample have been corrected through indexing to flatten the curved portion of the distorted image. As can be seen in FIGS. 5A and 5B, it can be seen that the image area by scanning according to the present invention has been increased to obtain additional horizontal information about the middle ear of the human ear.

Figure 5c shows OCT and camera images of adhesive otitis media. Here, adhesive otitis media was obtained using a built-in probe CCD camera. Figure 5d, on the other hand, shows OCT and built-in probe CCD camera images of chronic otitis media. Here, each image was acquired in real time with a size of 1024 × 500 pixels.

Figure 6 shows an in-vivo image of chronic otitis media with perforations in the human eardrum. FIG. 6A is an image obtained by superimposing a shape of a radial scanning method on an image of an eardrum acquired by a probe CCD camera, FIG. 6B is a diagram illustrating a radial scanning method for a three-dimensional radial scanning image using a wide- And FIG. 6C is a 3D volume image of a transverse OCT image of the image of the eardrum of a person in the body.

6A and 6B, the green circle represents a form of a radial scanning method. Here, the green dotted arrows indicate the 0 °, 45 °, and 90 ° scan regions. At this time, the radial scanning is performed in the clockwise direction according to the displayed angle. Each radial scan procedure produces a cross-sectional image, and each scan is radially oriented with 0.72 degrees of separation. The positions used for Figs. 6A and 6B are represented by lines in each 2D image on the abnormal eardrum in Figs. 6C-6E.

Figure 7 illustrates a comparison of scanning ranges using a three-dimensional radial scanning method based on a wide-field scanning method for the same animal. The system of the present invention was verified by obtaining images of normal and diseased guinea pig models.

Figures 7a and 7b are 3D volume images of the entire eardrum of the guinea pig, which are rendered in two different ranges. 7A is a 3D image of a guinea pig eardrum acquired using an in-vivo line scanning method, and Fig. 7B is a 3D image of a guinea pig eardrum acquired using a radial scanning method.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100: OCT system for eye exam
110: Light source 120: Optocoupler
130: Reference part 132: Collimator
134: focus lens 136: reference mirror
140: Wide-Field Scanning OCT Probe
141: Collimator 142: Galvanometer scan mirror
143: filter mirror 144: magnifying lens
145: CCD camera 146: first relay lens
147: Second relay lens 148: Focus lens
149: dioptric tip 150:
152: collimator 154: diffraction grating
156: focus lens 158: line scan camera
200: image processing unit 210:
220: center point adjustment unit 230: 3D image generation unit
300: Sample

Claims

1. A three-dimensional OCT probe for a gonioscopy, comprising:
A first relay lens having a first focal length f1 and converting light incident in parallel on different paths into convergent light;
A second relay lens having a second focal length f2 and converting the light to be diffused after convergence into a parallel light by changing the path; And
And a focal lens having a third focal length (f3) and converting the parallel light into converging light.

The method according to claim 1,
A wide-field scanning OCT probe that performs three-dimensional radial scanning by B-scan while rotating at a certain angle by a two-axis galvano-scan mirror.

3. The method of claim 2,
A collimator for converting light incident from the light source into parallel light; And
Further comprising a galvano-scan mirror for changing the path of the parallel light.

3. The method of claim 2,
Wherein the focal lengths (f1 to f3) are set such that the horizontal resolution of the photographed image is 15 mu m or less.

5. The method of claim 4,
And a ratio of a focal length (f3) of the focal lens to a focal length (f2) of the second relay lens is 1 to 2. The wide-field scanning OCT probe according to claim 1,

3. The method of claim 2,
Wherein the horizontal scanning range of the radial scanning is 7 to 10 mm.

The method according to claim 1,
A filter for filtering a portion of the light reflected from the sample;
A magnifying lens for diffusing the filtered light; And
Further comprising a CCD camera for capturing an image of the sample by the diffused light.

A wide-field scanning OCT probe as claimed in any one of claims 1 to 7;
Light source;
An optical coupler for dividing the light generated from the light source;
A reference unit that receives and phase-scans and reflects a part of the divided light;
An optical tomography unit converting the first reflected light received from the reference unit and the second reflected light received from the wide-field scanning OCT probe into an electrical signal to generate an OCT image; And
And an image processor for generating a 3D image from the photographed 2D image.

9. The method of claim 8,
Wherein the image processing unit comprises:
A center point detecting unit for detecting a center point for the radial scans; And
And a center point adjusting unit for adjusting a deviation of the center point.

10. The method of claim 9,
Wherein the image processor further includes a 3D image generator for generating a 3D image using the 2D image acquired by the radial scan.