WO2013081902A1 - Système et procédé d'amélioration de la qualité d'image en imagerie oct in vivo - Google Patents

Système et procédé d'amélioration de la qualité d'image en imagerie oct in vivo Download PDF

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Publication number
WO2013081902A1
WO2013081902A1 PCT/US2012/065991 US2012065991W WO2013081902A1 WO 2013081902 A1 WO2013081902 A1 WO 2013081902A1 US 2012065991 W US2012065991 W US 2012065991W WO 2013081902 A1 WO2013081902 A1 WO 2013081902A1
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WIPO (PCT)
Prior art keywords
optical
length
light source
scan
optical pathway
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Application number
PCT/US2012/065991
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English (en)
Inventor
Jianhua Wang
Michael Renxun WANG
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University Of Miami
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Publication of WO2013081902A1 publication Critical patent/WO2013081902A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
    • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
    • A61B3/102—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for optical coherence tomography [OCT]

Definitions

  • the present invention relates to a method and system for increasing scan depth of in vivo and in vitro optical coherence tomography imaging.
  • Optical coherence tomography is a non-contact and non-invasive imaging method that has been widely used for in vivo imaging in the field of ophthalmology.
  • Two broad categories of OCT techniques are time-domain OCT and spectral domain OCT.
  • Time-domain OCT requires the axial translation of the reference arm to obtain a reflectivity profile of the sample, with each pixel of image depth requiring movement of a reference arm of the OCT system.
  • Spectral domain OCT SD-OCT
  • SD-OCT allows the reference arm to remain in a single position, with the scan depth being calculated not by the distance of the reference arm, but by performing a Fourier-transform on the acquired data. The use of SD-OCT
  • the SD-OCT is based on a spectrometer containing a camera that collects the spectrum of light reflected from the eye and is much more sensitive than traditional time-domain OCT.
  • SD-OCT has been used to image the anterior and posterior segments of the eye, including the tear film, cornea, crystalline lens, vitreous humour and membrane, and retina.
  • the fast scanning speed enables a rapid scan of the eye in real time for structure and function, such as blood flow.
  • Recently, the use of OCT has been demonstrated in imaging molecules in active and passive ways with or without the aid of scattering media in diagnosis and monitoring disease progress in humans and animals.
  • Molecular imaging using OCT is showing promise in the diagnosis of ocular cancers.
  • SS-OCT swept-source OCT
  • SS-OCT uses a light source with changing wavelengths and a synchronized photodetector to perform spectral signal acquisition instead of a spectrometer used in SD-OCT.
  • the imaging functionality of SS-OCT is similar to SD-OCT.
  • Both SS-OCT and SD-OCT techniques offer a sensitivity advantage over the TD-OCT technique, thus producing clearer images with less noise.
  • the present invention advantageously provides a method and system for increasing the scan depth in in vivo and in vitro SD-OCT and SS-OCT imaging.
  • the method and system may address the limitation of decreased image quality with increased scan depth without the incorporation of an additional spectrometer, photodetector, light source, and optical scanning hardware on the sample arm.
  • the advantage is achieved by mimicking the functionality of a second reference arm, by altering the reference arm length (or optical distance). This may be achieved either by including two or more reference mirrors to a single reference arm to increase optical distance or by using a means for adjusting the optical distance of a reference arm having a single mirror. Therefore, the system and method may be used in any SD- OCT and/or SS-OCT system without necessitating the addition of costly dual-OCT systems.
  • FIG. 1A and IB show methods for increasing the optical coherence tomography (OCT) scan depth in accordance with the principles of the invention
  • FIG. 2A shows a schematic representation of an SD-OCT system having the functionality of two reference arms through the use of two reference mirrors;
  • FIG. 2B shows a schematic representation of an SS-OCT system having the functionality of two reference arms through the use of two reference mirrors;
  • FIG. 3 shows a schematic representation of an OCT system having the functionality of two reference arms through the use of fast mirror repositioning
  • FIG. 4 shows a schematic representation of an OCT system having the functionality of two reference arms through the use of fiber length stretching
  • FIG. 5 shows a schematic representation of an OCT system having the functionality of two reference arms through the use of optical fiber delay line
  • FIG. 6 shows the image enhancement that is possible when doubling OCT scan depth using the system and methods described herein.
  • the functionality of a dual-OCT system may be achieved without the need for an additional light source, photodetector, and spectrometer.
  • This functionality may be achieved by increasing the reference arm length, including through the use of multiple reference mirrors, fast mirror repositioning, fiber length stretching, and optical fiber delay line. The method used may depend on the desired speed, stability, and ease of use.
  • the term “arm” of the OCT system refers to, in general, an optical path along which light from a light source travels.
  • the “reference arm” is the optical path between the light source and one or more reflective elements (in the case of the reference arm, referred to as “reference mirrors”).
  • the “sample arm” is the optical path between the light source and tissue or other item to be visualized.
  • mirror refers to any reflective element capable of reflecting light.
  • optical distance refers to the product of the geometric length of the path light follows (for example, a light transmission pathway) and the index of refraction of the medium through which it propagates (such as an optical fiber or air).
  • the optical distance of the reference arm is the length of the path light from the light source travels to a reference mirror.
  • the optical distance of the reference arm may be altered using various methods (using the same medium), such as the use of more than one reference mirror, or a single mirror positionable using a translation stage, fiber stretching device, or fiber delay line.
  • A-scan (axial depth scan) refers to a reflectivity profile of tissue or other sample of interest, which contains information about the spatial dimensions and location of structures within the sample.
  • a "B-scan” may be generated from a series of A-scans by laterally combining the series of A-scans.
  • FIGS. 1A and IB flow charts of two embodiments of a method for increasing OCT scan depth are shown.
  • the general method involves lengthening the path of a reference arm light beam to generate different images.
  • the OCT system may be programmed to record data (scan the sample) at a predetermined scan depth that does not change during the procedure (Step 1).
  • the reference arm distance is increased using the means described herein.
  • the reference arm light may be directed from the light source along the reference arm having a zero delay line and to a first reference mirror having a first optical pathway length from the light source to accomplish a first series of A-scans or record a first series of images (Step 2).
  • images set by the Fourier transform computation include one image on top of the zero delay line and another below the zero delay line. One such image is used while the other is discarded.
  • the first series of retained A-scans may then be combined to generate a first B-scan image.
  • a beam-switching element such as a synchronized galvanometer, an optical chopper, a dial with a lens, an acousto-optic switch, an electro-optic switch, a magneto-optic switch, a thermo-optic switch, a MEMS (micro-electro-mechanical-system) based micro mirror switch, or a fast motorized translation stage
  • a beam-switching element such as a synchronized galvanometer, an optical chopper, a dial with a lens, an acousto-optic switch, an electro-optic switch, a magneto-optic switch, a thermo-optic switch, a MEMS (micro-electro-mechanical-system) based micro mirror switch, or a fast motorized translation stage
  • a beam-switching element such as a synchronized galvanometer, an optical chopper, a dial with a lens, an acousto-optic switch, an electro-optic switch, a magnet
  • the second optical pathway length is greater than the first optical pathway length, and may be chosen to correspond to a sample depth that is approximately double that of the first optical pathway length. However, the second optical pathway length may be chosen to correspond to a sample depth that is greater than but less than double that of the first optical pathway length.
  • the second series of A-scans may then be combined to generate a second B-scan image.
  • the images (either A-scans or B-scans) of Steps 2 and 3 may be combined to generate a composite image that has an effective scan depth that is approximately the sum of the depth of each image (for example, up to approximately twice the predetermined scan depth) (Step 4). Additionally, any number of reference mirrors may be used to increase the reference arm length and achieve the desired scan depth.
  • each reference mirror may be imaged from cornea to retina.
  • combined imaging depth using these four reference mirrors may be between approximately 30 mm and approximately 40 mm.
  • the more reference mirrors that are used to increase the reference arm length the deeper the scan depth that may be achieved.
  • the method of FIG. IB uses the same principal as that of FIG. 1 A. That is, the method of FIG. IB may achieve a greater scan depth without adjusting the predetermined or programmed scan depth of the OCT system (Step 1) by increasing the reference arm length.
  • first and second scans are accomplished not by redirecting the light from a first reference mirror to a second reference mirror, but by repositioning a single reference mirror from a first position to a second position (Step 3).
  • an element such as a motorized translation stage may be used to physically reposition the reference mirror from a first optical distance (optical path length) to a second optical distance to accomplish a second series of A- scan measurements.
  • the optical path length of the reference arm may be altered using a fiber stretching device (such as is shown in FIG. 4).
  • the light from the light source may be directed along a second optical path that includes a fiber delay line (such as is shown in FIG. 5).
  • a first scan depth image may be generated when the reference mirror is at a first optical distance (or reference arm distance)
  • a second scan depth image may be generated when the reference mirror is at a second optical distance (or reference arm distance).
  • the second optical distance is greater than the first optical distance.
  • the first and second series of A-scans may then be combined to generate a first and second B-scan image, respectively.
  • the images (either A-scans or B-scans) of Steps 2 and 4 may be combined to generate a composite image that has an effective scan depth that is up to approximately twice the predetermined scan depth (Step 5).
  • FIGS. 2A and 2B schematic representations of an SD-OCT system 10 and SS-OCT system 10, respectively, having two reference mirrors 12, 14 is shown.
  • the system 10 of FIG. 2A may include optical fiber 15, a light source 16 (for example, a laser or a low-coherence superluminescent diode (SLD)), a beam splitter 18 (for example, a 50:50 fiber coupler), a reference arm 20, and a sample arm 22.
  • the sample to be scanned may be an eye, as shown in FIGS. 2A and 2B.
  • the OCT system 10 may further include an optical isolator 24, one or more polarization controllers 26, diffraction grating 28, one or more lenses 30, a line scan camera 32 (for example, a having a charge coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS), or InGaAs camera), a digital/analog converter 33, a digital signal processing unit 34 (for example, being located within or integrated with a computer 36), and a video camera 37.
  • the diffraction grating 28, line scan camera 32, and one or more lenses 30 may together make up a spectrometer 38 in the SD-OCT system 10.
  • the system 10 may also include a power source, one or more user input devices, one or more video cameras, one or more monitors, cables, and one or more control units (not shown).
  • the SS- OCT system 10 of FIG. 2B may include the same components as the SD-OCT system 10 of FIG. 2A, except that a photodetector 39 instead of a spectrometer 38 may be in communication with the signal processing unit 34 and/or computer 36.
  • the reference arm 20 includes two reference mirrors 12, 14, although any number of reference arm mirrors may be used (as described in FIG. 1A).
  • the reference arm 20 may also include one or more lenses 30, one or more filters 40 (such as a neutral density filter), a dispersion compensator 42, a switching mirror 44, and a synchronized galvanometer driver 46.
  • beam-switching elements other than a galvanometer driver 46 and switching mirror 44 may be used, such as an optical chopper, a dial with a lens, an acousto-optic switch, an electro-optic switch, a magneto-optic switch, a thermo-optic switch, a MEMS (micro-electro-mechanical-system) based micro mirror switch, or a fast motorized translation stage.
  • the sample arm 22 may include one or more lenses 30 and an X-Y scanner 48.
  • the reference mirrors 12, 14 may allow the system 10 to have the functionality of two reference arms. Unlike a dual-OCT configuration, which requires complex reference arm modulation and computation recovery of the OCT image, the present system may avoid the use of, for example, two light sources and two spectrometers. Likewise, scan depth may be increased without the need for phase unwrapping of the normally discarded image. As described in FIG. 1A, a beam-switching element may be used to selectively direct the reference arm 20 light along the optical reference arm to a first reference mirror 12 having a first optical pathway length to a second reference mirror 14 having a second optical pathway length to accomplish two series of scans.
  • the OCT system 10 includes only one reference mirror 50.
  • Light travels from a light source 16 (not shown in FIG. 3) along the reference arm optical pathway 20 (such as through an optical fiber 15) and then through a lens 30, creating a collimated beam of light 52.
  • the collimated beam of light 52 then travels to the reference mirror 50.
  • the reference mirror 50 may be physically repositioned, such as by a translation stage 54. Repositioning the reference mirror 50 will adjust the optical path length (optical distance) of the reference arm, without changing the medium through which the light travels, thereby adding the functionality of a dual-OCT system.
  • the scan depth may be doubled using the method as described in FIG. IB above.
  • Fiber length stretching may be used to adjust the optical path length (optical distance) of the reference arm.
  • an optical fiber 15 may be wound one or more times around a fiber stretching device 58, such as a piezoelectric modulator, which may expand and contract, thereby stretching the optical fiber 15. This stretching may induce a temporal delay on the light within, thereby affecting the optical distance.
  • An increased scan depth may be achieved using the method as described in FIG. IB above.
  • optical fiber delay may include one or more beam switching elements 60 (such as a MEMS (micro-electro-mechanical-system) based micro mirror switch) to adjust the optical distance by redirecting light from the light source along a second optical path (fiber delay line).
  • beam switching elements may be used to redirect light along either a straight (shorter) optical path 62 or a longer optical path 64, such as a path that includes one or more loops 66 of optical fiber 15 to extend the length of the optical path 64.
  • each scan 68A, 68B may be performed with a depth of 7.3 mm.
  • the first scan 68A may be obtained using a first optical path length (for example, using a first reference mirror or a reference mirror in a first position).
  • the second scan 68B may be obtained using a second optical path length (for example, using a second reference mirror, a reference mirror in a second position, or an optical path length altered using any of the means described herein).
  • the scan depth is effectively doubled to give a composite image 70 of 14.6 mm, provided that the length of the optical path to each of the two reference mirrors 12, 14 is such that the two depth pictures can be combined to form such a larger depth OCT image.

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Abstract

La présente invention concerne un procédé et un système permettant d'accroitre la profondeur d'exploration en imagerie par tomographie à cohérence optique (OCT). Lesdits procédé et système permettent effectivement de doubler la profondeur d'exploration en OCT, comme avec des systèmes OCT à double balayage, mais le coût en moins. L'avantage est obtenu soit en intégrant au moins deux miroirs de référence au niveau d'un unique bras de référence afin d'augmenter la distance optique, soit en utilisant un moyen d'ajustement de la distance optique d'un bras de référence comportant un unique miroir (par exemple au moyen d'une plateforme de translation, d'un dispositif d'étirage de fibres ou d'une ligne à retard fibrée). Ces système et procédé peuvent être utilisés dans un quelconque système de SD-OCT ou de SS-OCT sans qu'il soit nécessaire d'y ajouter de systèmes coûteux d'OCT à double balayage.
PCT/US2012/065991 2011-11-30 2012-11-20 Système et procédé d'amélioration de la qualité d'image en imagerie oct in vivo WO2013081902A1 (fr)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103565405A (zh) * 2013-11-15 2014-02-12 浙江大学 基于分段光谱光程编码的谱域oct探测系统及方法
WO2016023502A1 (fr) * 2014-08-13 2016-02-18 The University Of Hong Kong Tomographie par coherence optique a suppression des lobes secondaires a inversion de phase
WO2017133083A1 (fr) * 2016-02-05 2017-08-10 浙江大学 Système et procédé d'angiographie basés sur la division d'espace plein du spectre de modulation et combinaison basée sur un angle
CN108095704A (zh) * 2018-02-13 2018-06-01 天津恒宇医疗科技有限公司 一种单光源双波段oct成像系统
US10743758B2 (en) 2015-03-25 2020-08-18 Amo Development, Llc Multiple depth optical coherence tomography system and method and laser eye surgery system incorporating the same
CN113520300A (zh) * 2020-04-22 2021-10-22 晋弘科技股份有限公司 扫描装置以及光学同调断层扫描系统

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US20090057543A1 (en) * 2007-09-04 2009-03-05 Fujifilm Corporation Optical scanning probe, optical scanning probe device and method for controlling the optical scanning probe
JP2010158265A (ja) * 2009-01-06 2010-07-22 Topcon Corp 光画像計測装置及びその制御方法
EP2377456A1 (fr) * 2008-12-18 2011-10-19 FUJIFILM Corporation Sonde optique et dispositif optique d'observation

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090057543A1 (en) * 2007-09-04 2009-03-05 Fujifilm Corporation Optical scanning probe, optical scanning probe device and method for controlling the optical scanning probe
EP2377456A1 (fr) * 2008-12-18 2011-10-19 FUJIFILM Corporation Sonde optique et dispositif optique d'observation
JP2010158265A (ja) * 2009-01-06 2010-07-22 Topcon Corp 光画像計測装置及びその制御方法
US20110267583A1 (en) * 2009-01-06 2011-11-03 Kabushiki Kaisha Topcon Optical image measuring device and control method thereof

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103565405A (zh) * 2013-11-15 2014-02-12 浙江大学 基于分段光谱光程编码的谱域oct探测系统及方法
WO2016023502A1 (fr) * 2014-08-13 2016-02-18 The University Of Hong Kong Tomographie par coherence optique a suppression des lobes secondaires a inversion de phase
US10743758B2 (en) 2015-03-25 2020-08-18 Amo Development, Llc Multiple depth optical coherence tomography system and method and laser eye surgery system incorporating the same
WO2017133083A1 (fr) * 2016-02-05 2017-08-10 浙江大学 Système et procédé d'angiographie basés sur la division d'espace plein du spectre de modulation et combinaison basée sur un angle
CN108095704A (zh) * 2018-02-13 2018-06-01 天津恒宇医疗科技有限公司 一种单光源双波段oct成像系统
CN108095704B (zh) * 2018-02-13 2024-04-23 天津恒宇医疗科技有限公司 一种单光源双波段oct成像系统
CN113520300A (zh) * 2020-04-22 2021-10-22 晋弘科技股份有限公司 扫描装置以及光学同调断层扫描系统

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