Tomografi keselarasan optik: Perbedaan antara revisi
Konten dihapus Konten ditambahkan
JohnThorne (bicara | kontrib) Dibuat dengan menerjemahkan halaman "Optical coherence tomography" |
Fitur saranan suntingan: 3 pranala ditambahkan. Tag: VisualEditor Suntingan perangkat seluler Suntingan peramban seluler Tugas pengguna baru Disarankan: tambahkan pranala |
||
| (20 revisi perantara oleh 7 pengguna tidak ditampilkan) | |||
Baris 1:
{{Infobox interventions|Name=
|OPS301={{OPS301|3-300}} }} ''' Tergantung pada sifat dari sumber cahaya (
== Pendahuluan ==
[[Berkas:HautFingerspitzeOCT.gif|jmpl|218x218px|Optical coherence tomogram dari ujung jari.
Mulai dari cahaya putih interferometri untuk ''in vivo'' okular mata pengukuran pencitraan dari jaringan biologis, terutama dari [[mata manusia]], diselidiki oleh beberapa kelompok di seluruh dunia. Pertama dua dimensi ''di vivo'' penggambaran
OCT juga telah digunakan untuk berbagai
<!--
[[Medical ultrasonography]], [[magnetic resonance imaging]] (MRI), confocal microscopy, and OCT are differently suited to morphological tissue imaging: while the first two have whole body but low resolution imaging capability (typically a fraction of a millimeter), the third one can provide images with resolutions well below 1 micrometer (i.e. sub-cellular), between 0 and 100 micrometers in depth, and the fourth can probe as deep as 500 micrometers, but with a lower (i.e. architectural) resolution (around 10 micrometers in lateral and a few micrometers in depth in ophthalmology, for instance, and 20 micrometers in lateral in endoscopy).<ref>{{cite journal|doi=10.1038/86589|pmc=1950821|pmid=11283681|year=2001|last1=Drexler|first1=Wolfgang|last2=Morgner|first2=Uwe|last3=Ghanta|first3=Ravi K.|last4=Kärtner|first4=Franz X.|last5=Schuman|first5=Joel S.|last6=Fujimoto|first6=James G.|title=Ultrahigh-resolution ophthalmic optical coherence tomography|journal=Nature Medicine|volume=7|issue=4|pages=502–7}}</ref><ref>{{cite journal|doi=10.1016/j.ophtha.2003.12.002|pmid=15019397|title=Confocal microscopy: A report by the American Academy of Ophthalmology|first8=WS|last8=Van Meter|first7=IJ|last7=Udell|first6=WJ|last6=Reinhart|first5=DM|last5=Meisler|first4=EJ|last4=Cohen|first3=MW|last3=Belin|first2=DC|year=2004|last2=Musch|last1=Kaufman|first1=S|journal=Ophthalmology|volume=111|issue=2|pages=396–406}}</ref>
OCT is based on [[optical interferometry#Low-coherence interferometry|low-coherence interferometry]].<ref>{{cite journal|doi=10.1109/51.870229|title=Current technical development of magnetic resonance imaging|year=2000|last1=Riederer|first1=S.J.|journal=IEEE Engineering in Medicine and Biology Magazine|volume=19|pages=34–41|issue=5|pmid=11016028}}</ref><ref>{{cite book|author1=M. Born |author2=E. Wolf |title=Principles of Optics: Electromagnetic Theory of Propagation, Interference, and Diffraction of Light|publisher=Cambridge University Press|year=2000|url=https://books.google.com/books?id=oV80AAAAIAAJ&printsec=frontcover|isbn=0-521-78449-2}}</ref>{{Page needed |date=October 2016}}<ref name="Fercher">{{cite journal|doi=10.1364/OL.13.000186|pmid=19742022|title=Eye-length measurement by interferometry with partially coherent light|year=1988|last1=Fercher|first1=A. F.|last2=Mengedoht|first2=K.|last3=Werner|first3=W.|journal=Optics Letters|volume=13|issue=3|pages=186–8|bibcode= 1988OptL...13..186F }}</ref> In conventional interferometry with long [[coherence length]] (i.e., laser interferometry), interference of light occurs over a distance of meters. In OCT, this interference is shortened to a distance of micrometers, owing to the use of broad-bandwidth light sources (i.e., sources that emit light over a broad range of frequencies). Light with broad bandwidths can be generated by using superluminescent diodes or lasers with extremely short pulses ([[femtosecond laser]]s). White light is an example of a broadband source with lower power.
Light in an OCT system is broken into two arms—a sample arm (containing the item of interest) and a reference arm (usually a mirror). The combination of reflected light from the sample arm and reference light from the reference arm gives rise to an interference pattern, but only if light from both arms have traveled the "same" optical distance ("same" meaning a difference of less than a coherence length). By scanning the mirror in the reference arm, a reflectivity profile of the sample can be obtained (this is time domain OCT). Areas of the sample that reflect back a lot of light will create greater interference than areas that don't. Any light that is outside the short coherence length will not interfere.<ref>{{cite journal |title= Optical Coherence Tomography: An Emerging Technology for Biomedical Imaging and Optical Biopsy |year=2000|last1= Fujimoto |first1= JG| last2= Pitris |first2= C.| last3= Boppart |first3= SA| last4= Brezinski |first4= ME|journal= Neoplasia |volume=2|pages=9–25|pmc= 1531864 }}</ref>
This reflectivity profile, called an [[A-scan]], contains information about the spatial dimensions and location of structures within the item of interest. A cross-sectional tomograph ([[B-scan]]) may be achieved by laterally combining a series of these axial depth scans (A-scan). A face imaging at an acquired depth is possible depending on the imaging engine used.
== Penjelasan bagi orang awam ==
[[Berkas:OCT_OD_Retinal_Thickness_Map.jpg|jmpl|Peta ketebalan retina dari OCT retina ketebalan peta, mata kanan]]-->
[[Berkas:Retina-OCT800.png|jmpl|OCT scan retina di 800nm dengan resolusi aksial dari 3µm.]]
<!--
Optical Coherence Tomography, or ‘OCT’, is a technique for obtaining sub-surface images of translucent or opaque materials at a resolution equivalent to a low-power microscope. It is effectively ‘optical ultrasound’, imaging reflections from within tissue to provide cross-sectional images.<ref name="Michelessi">{{cite journal |author= Michelessi M, Lucenteforte E, Oddone F, Brazzelli M, Parravano M, Franchi S, Ng SM, Virgili G |title= Optic nerve head and fibre layer imaging for diagnosing glaucoma |journal=Cochrane Database Syst Rev |volume= |issue=11 |pages= CD008803 |date=2015 |pmid= 26618332 |doi= 10.1002/14651858.CD008803.pub2}}</ref>
OCT has attracted interest among the medical community because it provides tissue morphology imagery at much higher resolution (better than 10 µm) than other imaging modalities such as MRI or ultrasound.
-->
Kelebihan utama OCT adalah:
* Gambar di bawah permukaan hidup-hidup dengan resolusi mendekati mikroskopik
* Pencitraan segera dan langsung dari morfologi jaringan
* Tanpa penyiapan sampel atau subyek
* Tanpa radiasi yang menyebabkan ionisasi
<!--
OCT delivers high resolution because it is based on light, rather than sound or radio frequency. An optical beam is directed at the tissue, and a small portion of this light that reflects from sub-surface features is collected. Note that most light is not reflected but, rather, scatters off at large angles. In conventional imaging, this diffusely scattered light contributes background that obscures an image. However, in OCT, a technique called interferometry is used to record the optical path length of received photons allowing rejection of most photons that scatter multiple times before detection. Thus OCT can build up clear 3D images of thick samples by rejecting background signal while collecting light directly reflected from surfaces of interest.
Within the range of noninvasive three-dimensional imaging techniques that have been introduced to the medical research community, OCT as an echo technique is similar to [[ultrasound imaging]]. Other medical imaging techniques such as computerized axial tomography, magnetic resonance imaging, or positron emission tomography do not use the echo-location principle.<ref>{{cite web |url=https://www.mastereyeassociates.com/optical-coherence-tomography-scan |title=Optical Coherence Tomography provides better resolution than an MRI and Helps Diagnose Retina & Corneal Disease and Glaucoma, Part II |last=Unknown |first=Unknown |publisher=mastereyeassociates |date=June 13, 2017 |website=mastereyeassociates.com |access-date=June 13, 2017}} </ref>
The technique is limited to imaging 1 to 2 mm below the surface in biological tissue, because at greater depths the proportion of light that escapes without scattering is too small to be detected. No special preparation of a biological specimen is required, and images can be obtained ‘non-contact’ or through a transparent window or membrane. It is also important to note that the laser output from the instruments is low – eye-safe near-infra-red light is used – and no damage to the sample is therefore likely.
==Theory==
The principle of OCT is white light or low coherence interferometry. The optical setup typically consists of an interferometer (Fig. 1, typically [[Michelson interferometer|Michelson]] type) with a low coherence, broad bandwidth light source. Light is split into and recombined from reference and sample arm, respectively.
-->
{|
[[Berkas:OCT B-Scan Setup.GIF|jmpl|375px|Fig. 2 Typical optical setup of single point OCT. Scanning the light beam on the sample enables non-invasive cross-sectional imaging up to 3 mm in depth with micrometer resolution.]]
|
[[Berkas:Full-field OCT setup.png|jmpl|375px|Fig. 1 Full-field OCT optical setup. Components include: super-luminescent diode (SLD), convex lens (L1), 50/50 beamsplitter (BS), camera objective (CO), CMOS-DSP camera (CAM), reference (REF), and sample (SMP). The camera functions as a two-dimensional detector array, and with the OCT technique facilitating scanning in depth, a non-invasive three dimensional imaging device is achieved.]]
|}
{|
[[Berkas:Fd-oct.PNG|jmpl|375px|Fig. 4 Spectral discrimination by fourier-domain OCT. Components include: low coherence source (LCS), beamsplitter (BS), reference mirror (REF), sample (SMP), diffraction grating (DG) and full-field detector (CAM) acting as a spectrometer, and digital signal processing (DSP)]]
|
[[Berkas:Ss-oct.PNG|jmpl|375px|Fig. 3 Spectral discrimination by swept-source OCT. Components include: swept source or tunable laser (SS), beamsplitter (BS), reference mirror (REF), sample (SMP), photodetector (PD), and digital signal processing (DSP)]]
|}
=== Time domain ===
''Time domain OCT'' berprinsip bahwa ''pathlength'' dari ''reference arm'' divariasi menurut waktu (cermin referensi ditranslasikan secara longitudinal). Suatu sifat low coherence interferometry adalah bahwa interferensi, yaitu seri fringe gelap dan terang, hanya dapat dicapai ketika perbedaan jalur terjadi di sepanjang koherensi sumber cahaya. [[Interferensi]] ini disebut ''auto correlation'' dalam suatu ''symmetric interferometer'' (kedua lengan mempunyai refleksivitas yang sama), atau ''cross-correlation'' pada kasus umum. Envelope modulasi ini berubah ketika pathlength difference divariasi, di mana puncak envelope selaras dengan pathlength matching.
Interferensi dua berkas cahaya yang koheren secara parsial dapat diekspresikan dengan persamaan intensitas sumber cahaya, <math>I_S</math>, sebagai
:<math> I = k_1 I_S + k_2 I_S + 2 \sqrt { \left ( k_1 I_S \right ) \cdot \left ( k_2 I_S \right )} \cdot Re \left [\gamma \left ( \tau \right ) \right] \qquad (1) </math>
di mana <math>k_1 + k_2 < 1</math> adalah rasio pembelahan sinar interferometer, dan <math> \gamma ( \tau ) </math> disebut ''complex degree of coherence'', yaitu interference envelope dan carrier yang tergantung pada ''reference arm scan'' atau time delay <math> \tau </math>, dan yang pemulihannya diamati oleh OCT.<!-- Due to the coherence gating effect of OCT the complex degree of coherence is represented as a Gaussian function expressed as<ref name="Fercher"/>
:<math> \gamma \left ( \tau \right ) = \exp \left [- \left ( \frac{\pi\Delta\nu\tau}{2 \sqrt{\ln 2} } \right )^2 \right] \cdot \exp \left ( -j2\pi\nu_0\tau \right ) \qquad \quad (2) </math>
where <math> \Delta\nu </math> represents the spectral width of the source in the optical frequency domain, and <math> \nu_0 </math> is the centre optical frequency of the source. In equation (2), the Gaussian envelope is amplitude modulated by an optical carrier. The peak of this envelope represents the location of the microstructure of the sample under test, with an amplitude dependent on the reflectivity of the surface. The optical carrier is due to the [[Doppler effect]] resulting from scanning one arm of the interferometer, and the frequency of this modulation is controlled by the speed of scanning. Therefore, translating one arm of the interferometer has two functions; depth scanning and a Doppler-shifted optical carrier are accomplished by pathlength variation. In OCT, the Doppler-shifted optical carrier has a frequency expressed as
:<math> f_{Dopp} = \frac { 2 \cdot \nu_0 \cdot v_s } { c } \qquad \qquad \qquad \qquad \qquad \qquad \qquad \quad (3) </math>
where <math> \nu_0 </math> is the central optical frequency of the source, <math> v_s </math> is the scanning velocity of the pathlength variation, and <math> c </math> is the speed of light.
[[File:Principle-TD-FD OCT.svg|thumb|450px|interference signals in TD vs. FD-OCT]]
The axial and lateral resolutions of OCT are decoupled from one another; the former being an equivalent to the coherence length of the light source and the latter being a function of the optics. The axial resolution of OCT is defined as
:{|
|-
|<math> \, {l_c} </math>
|<math>=\frac {2 \ln 2} {\pi} \cdot \frac {\lambda_0^2} {\Delta\lambda}</math>
|-
|
|<math>\approx 0.44 \cdot \frac {\lambda_0^2} {\Delta\lambda} \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad (4) </math>
|}
where <math> \lambda_0 </math> and <math> \Delta\lambda</math> are respectively the central wavelength and the spectral width of the light source -->.<ref name="hasilan otomatis1">{{cite book| title= Anterior & Posterior Segment OCT: Current Technology & Future Applications, 1st edition |year=2014|last1=Garg|first1=A. }}</ref>
<!--
===Frequency domain===
In frequency domain OCT (FD-OCT) the broadband interference is acquired with spectrally separated detectors (either by encoding the optical frequency in time with a spectrally scanning source or with a dispersive detector, like a grating and a linear detector array). Due to the [[Fourier analysis|Fourier]] relation ([[Wiener-Khintchine theorem]] between the auto correlation and the spectral power density) the depth scan can be immediately calculated by a Fourier-transform from the acquired spectra, without movement of the reference arm.<ref>{{cite journal|doi=10.1109/2944.796348|title=Optical coherence tomography (OCT): a review|year=1999|last1=Schmitt|first1=J.M.|journal=IEEE Journal of Selected Topics in Quantum Electronics|volume=5|pages=1205–1215|issue=4}}</ref><ref name="Fercher2">{{cite journal|doi=10.1016/0030-4018(95)00119-S|title=Measurement of intraocular distances by backscattering spectral interferometry|year=1995|last1=Fercher|first1=A|last2=Hitzenberger|first2=C.K.|last3=Kamp|first3=G.|last4=El-Zaiat|first4=S.Y.|journal=Optics Communications|volume=117|pages=43–48|bibcode= 1995OptCo.117...43F }}</ref> This feature improves imaging speed dramatically, while the reduced losses during a single scan improve the signal to noise ratio proportional to the number of detection elements. The parallel detection at multiple wavelength ranges limits the scanning range, while the full spectral bandwidth sets the axial resolution.
<ref>{{cite journal|language=en|doi= 10.1364/BOE.8.003248 |title= Twenty-five years of optical coherence tomography: the paradigm shift in sensitivity and speed provided by Fourier domain OCT |year=2017|last1=de Boer|first1= Johannes F. |last2= Leitgeb |first2=R.|last3= Wojtkowski |first3=M.|journal= Biomed. Opt. Express |volume=8|issue = 7|pages=3248-3280}}</ref>
====Spatially encoded====
Spatially encoded frequency domain OCT (SEFD-OCT, spectral domain or Fourier domain OCT) extracts spectral information by distributing different optical frequencies onto a detector stripe (line-array CCD or CMOS) via a dispersive element (see Fig. 4). Thereby the information of the full depth scan can be acquired within a single exposure. However, the large signal to noise advantage of FD-OCT is reduced due to the lower dynamic range of stripe detectors with respect to single photosensitive diodes, resulting in an SNR ([[signal to noise ratio]]) advantage of ~10 [[decibel|dB]] at much higher speeds. This is not much of a problem when working at 1300 nm, however, since dynamic range is not a serious problem at this wavelength range.<ref name="hasilan otomatis1" />
The drawbacks of this technology are found in a strong fall-off of the SNR, which is proportional to the distance from the zero delay and a sinc-type reduction of the depth dependent sensitivity because of limited detection linewidth. (One pixel detects a quasi-rectangular portion of an optical frequency range instead of a single frequency, the Fourier-transform leads to the sinc(z) behavior). Additionally the dispersive elements in the spectroscopic detector usually do not distribute the light equally spaced in frequency on the detector, but mostly have an inverse dependence. Therefore, the signal has to be resampled before processing, which can not take care of the difference in local (pixelwise) bandwidth, which results in further reduction of the signal quality. However, the fall-off is not a serious problem with the development of new generation CCD or photodiode array with a larger number of pixels.
[[Optical heterodyne detection|Synthetic array heterodyne detection]] offers another approach to this problem without the need for high dispersion.
====Time encoded====
Time encoded frequency domain OCT (TEFD-OCT, or swept source OCT) tries to combine some of the advantages of standard TD and SEFD-OCT. Here the spectral components are not encoded by spatial separation, but they are encoded in time. The spectrum is either filtered or generated in single successive frequency steps and reconstructed before Fourier-transformation. By accommodation of a frequency scanning light source (i.e. frequency scanning laser) the optical setup (see Fig. 3) becomes simpler than SEFD, but the problem of scanning is essentially translated from the TD-OCT reference-arm into the TEFD-OCT light source.
Here the advantage lies in the proven high SNR detection technology, while swept laser sources achieve very small instantaneous bandwidths (=linewidth) at very high frequencies (20–200 kHz). Drawbacks are the nonlinearities in the wavelength (especially at high scanning frequencies), the broadening of the linewidth at high frequencies and a high sensitivity to movements of the scanning geometry or the sample (below the range of nanometers within successive frequency steps).
==Scanning schemes==
Focusing the light beam to a point on the surface of the sample under test, and recombining the reflected light with the reference will yield an interferogram with sample information corresponding to a single A-scan (Z axis only). Scanning of the sample can be accomplished by either scanning the light on the sample, or by moving the sample under test. A linear scan will yield a two-dimensional data set corresponding to a cross-sectional image (X-Z axes scan), whereas an area scan achieves a three-dimensional data set corresponding to a volumetric image (X-Y-Z axes scan), also called full-field OCT.
===Single point===
Systems based on single point, confocal, or flying-spot time domain OCT, must scan the sample in two lateral dimensions and reconstruct a three-dimensional image using depth information obtained by coherence-gating through an axially scanning reference arm (Fig. 2). Two-dimensional lateral scanning has been electromechanically implemented by moving the sample<ref name="Fercher2"/> using a translation stage, and using a novel micro-electro-mechanical system scanner.<ref>{{cite journal|doi=10.1016/j.sna.2004.06.021|title=Micromachined 2-D scanner for 3-D optical coherence tomography|year=2005|journal=Sensors and Actuators A: Physical|volume=117|pages=331–340|issue=2|last1=Yeow|first1=J.T.W.|last2=Yang|first2=V.X.D.|last3=Chahwan|first3=A.|last4=Gordon|first4=M.L.|last5=Qi|first5=B.|last6=Vitkin|first6=I.A.|last7=Wilson|first7=B.C.|last8=Goldenberg|first8=A.A.}}</ref>
===Parallel===
Parallel or full field OCT using a [[charge-coupled device]] (CCD) camera has been used in which the sample is full-field illuminated and en face imaged with the CCD, hence eliminating the electromechanical lateral scan. By stepping the reference mirror and recording successive ''en face'' images a three-dimensional representation can be reconstructed. Three-dimensional OCT using a CCD camera was demonstrated in a phase-stepped technique,<ref>{{cite journal|doi=10.1364/OE.11.000105|pmid=19461712|year=2003|last1=Dunsby|first1=C|last2=Gu|first2=Y|last3=French|first3=P|title=Single-shot phase-stepped wide-field coherencegated imaging|volume=11|issue=2|pages=105–15|journal=Optics Express|bibcode= 2003OExpr..11..105D }}</ref> using geometric phase shifting with a [[Linnik interferometer]],<ref>{{cite journal|doi=10.1016/S0143-8166(01)00146-4|title=Geometric phase-shifting for low-coherence interference microscopy|year=2002|last1=Roy|first1=M|last2=Svahn|first2=P|last3=Cherel|first3=L|last4=Sheppard|first4=CJR|journal=Optics and Lasers in Engineering|volume=37|pages=631–641|bibcode= 2002OptLE..37..631R|authorlink4= Colin_Sheppard|issue=6 }}</ref> utilising a pair of CCDs and heterodyne detection,<ref>{{cite journal|doi=10.1364/OL.28.000816|pmid=12779156|title=Full-field optical coherence tomography by two-dimensional heterodyne detection with a pair of CCD cameras|year=2003|last1=Akiba|first1=M.|last2=Chan|first2=K. P.|last3=Tanno|first3=N.|journal=Optics Letters|volume=28|issue=10|pages=816–8|bibcode= 2003OptL...28..816A }}</ref> and in a Linnik interferometer with an oscillating reference mirror and axial translation stage.<ref>{{cite journal|doi=10.1364/AO.41.000805|pmid=11993929|year=2002|last1=Dubois|first1=A|last2=Vabre|first2=L|last3=Boccara|first3=AC|last4=Beaurepaire|first4=E|title=High-resolution full-field optical coherence tomography with a Linnik microscope|volume=41|issue=4|pages=805–12|journal=Applied Optics|bibcode= 2002ApOpt..41..805D }}</ref> Central to the CCD approach is the necessity for either very fast CCDs or carrier generation separate to the stepping reference mirror to track the high frequency OCT carrier.
====Smart detector array====
A two-dimensional smart detector array, fabricated using a 2 µm [[CMOS|complementary metal-oxide-semiconductor]] (CMOS) process, was used to demonstrate full-field TD-OCT.<ref>{{cite journal|doi=10.1364/OL.26.000512|pmid=18040369|title=Optical coherence topography based on a two-dimensional smart detector array|year=2001|last1=Bourquin|first1=S.|last2=Seitz|first2=P.|last3=Salathé|first3=R. P.|journal=Optics Letters|volume=26|issue=8|pages=512–4|bibcode= 2001OptL...26..512B }}</ref> Featuring an uncomplicated optical setup (Fig. 3), each pixel of the 58x58 pixel smart detector array acted as an individual photodiode and included its own hardware demodulation circuitry.
==Selected applications==
Optical coherence tomography is an established medical imaging technique and is used across several medical specialties including ophthalmology and cardiology, and is widely used in basic science research applications.
=== Eyecare ===
OCT is heavily used by ophthalmologists and optometrists to obtain high-resolution images of the [[human eye|eye's]] anterior segment and [[retina]]. Owing to its cross-sectional capabilities, OCT provides a straightforward method of assessing axonal integrity in [[multiple sclerosis]]<ref>{{cite journal|last1=Dörr |first1=Jan |last2=Wernecke |first2=KD |last3=Bock |first3=M |last4=Gaede |first4=G |last5=Wuerfel |first5=JT |last6=Pfueller |first6=CF |last7=Bellmann-Strobl |first7=J |last8=Freing |first8=A |last9=Brandt |first9=AU |last10=Friedemann |first10=P |title=Association of retinal and macular damage with brain atrophy in multiple sclerosis.|journal=PLoS ONE |date=8 April 2011 |volume=6 |issue=4 |page=e18132 |doi=10.1371/journal.pone.0018132 |pmid=21494659 |url=http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0018132 |accessdate=21 November 2012 |bibcode=2011PLoSO...618132D |pmc=3072966 }} {{Open access}}</ref> and [[glaucoma]].<ref>{{cite journal|last1=Grewal|first1=DS|last2=Tanna|first2=AP|title=Diagnosis of glaucoma and detection of glaucoma progression using spectral domain optical coherence tomography.|journal=Current opinion in ophthalmology|date=March 2013|volume=24|issue=2|pages=150–61|doi=10.1097/ICU.0b013e32835d9e27|pmid=23328662}}</ref> OCT is also well suited to assess [[macular degeneration]],<ref>{{cite journal |last1=Keane |first1=PA |last2=Patel |first2=PJ |last3=Liakopoulos |first3=S |last4=Heussen |first4=FM |last5=Sadda |first5=SR |last6=Tufail |first6=A |title=Evaluation of age-related macular degeneration with optical coherence tomography |journal=Survey of Ophthalmology |date=September 2012 |volume=57 |issue=5 |pages=389–414 |pmid=22898648 |doi=10.1016/j.survophthal.2012.01.006}}</ref> and is considered the new standard for the assessment of [[macular edema|diabetic macular edema]].<ref name="Virgili">{{cite journal |last1=Virgili |first1=G |last2=Menchini |first2=F |last3=Casazza |first3=G |last4=Hogg |first4=R |last5=Das |first5=RR |last6=Wang |first6=X |last7=Michelessi |first7=M |title=Optical coherence tomography (OCT) for detection of macular oedema in patients with diabetic retinopathy |journal=Cochrane Database Syst Rev |volume= 1|page=CD008081 |date=7 January 2015 |pmid=25564068 |doi=10.1002/14651858.CD008081.pub3 |pmc=4438571}}</ref> More recently, ophthalmic OCT devices have been engineered to perform angiography, and have been used to assess retinal microvasculature pathology in diseases such as glaucoma and diabetic retinopathy.
=== Cardiology ===
In the setting of cardiology, OCT is used to image [[coronary arteries]] in order to visualize vessel wall lumen morphology and microstructure at a resolution 10 times higher than other existing modalities such as intravascular ultrasounds and x-ray angiography ([[Intracoronary Optical Coherence Tomography]]). For this type of application, approximately 1 mm in diameter fiber-optics catheters are used to access artery lumen through semi-invasive interventions, i.e. [[Percutaneous coronary intervention]]. The first demonstration of endoscopic OCT was reported in 1997, by researchers in James Fujimoto laboratory at Massachusetts Institute of Technology, including Prof. [[Guillermo James Tearney]] and Prof. [[Brett Bouma]].<ref>{{cite journal |last1=Tearney |first1=GJ |last2=Brezinski |first2=ME |last3=Bouma |first3=BE |last4=Boppart |first4=SA |last5=Pitris |first5=C |last6=Southern |first6=JF |last7=Fujimoto |first7=JG |date=27 June 1997 |title=In vivo endoscopic optical biopsy with optical coherence tomography |url=http://science.sciencemag.org/content/276/5321/2037.long |journal=Science |volume=276 |issue= 5321 |pages=2037–2039 |pmid=9197265 |doi=10.1126/science.276.5321.2037}}</ref> The first TD-OCT imaging catheter and system was commercialized by [[LightLab Imaging, Inc.]], a company based in Massachusetts in 2006. The first FD-OCT imaging study was reported by the laboratory of Prof. Guillermo James Tearney and Prof. Brett Bouma based at [[Massachusetts General Hospital]] in 2008.<ref>{{cite journal |last1=Tearney |first1=GJ |last2=Waxman |first2=S |last3=Shishkov |first3=M |last4=Vakoc |first4=BJ |last5=Suter |first5=MJ |last6=Freilich |first6=MI |last7=Desjardins |first7=AE |last8=Oh |first8=WY |last9=Bartlett |first9=LA |last10=Rosenberg |first10=M |last11=Bouma |first11=BE |date=November 2008 |title=Three-Dimensional Coronary Artery Microscopy by Intracoronary Optical Frequency Domain Imaging |doi=10.1016/j.jcmg.2008.06.007 |journal={{abbr|JACC|Journal of the American College of Cardiology}} Cardiovascular Imaging |volume=1 |issue=6 |pages=752–761 |url=http://www.sciencedirect.com/science/article/pii/S1936878X08003616 |pmid=19356512 |pmc=2852244 }}</ref> Intravascular FD-OCT was first introduced in the market in 2009 by LightLab Imaging, Inc.<ref>{{cite web |url=http://www.prnewswire.com/news-releases/lightlab-imaging-returns-to-europcr-2010-with-strong-and-growing-worldwide-acceptance-of-c7-xr-oct-imaging-system-94607959.html |title=LightLab launches FD-OCT in Europe |access-date=9 September 2016}}</ref> and [[Terumo]] Corporation launched a second solution for coronary artery imaging in 2012. The higher imaging speed of FD-OCT enabled the widespread adoption of this imaging technology for coronary artery imaging. It is estimated that >100,000 FD-OCT coronary imaging cases are performed yearly, and that the market is increasing by approximately 20% every year.<ref>{{cite web |url=http://www.bioopticsworld.com/articles/print/volume-9/issue-6/optical-coherence-tomography-beyond-better-clinical-care-oct-s-economic-impact.html |title=Optical Coherence Tomography: Beyond better clinical care: OCT's economic impact |last=Swanson |first=Eric |date=13 June 2016 |website=BioOptics World |access-date=9 September 2016}}</ref>
=== Oncology ===
Endoscopic OCT has been applied to the detection and diagnosis of [[cancer]] and [[precancerous lesions]], such as [[Barrett's esophagus]] and esophageal [[dysplasia]].<ref>{{cite web |url=http://www.bioopticsworld.com/articles/print/volume-6/issue-3/features/optical-coherence-tomography-gastroenterology--advanced-oct--nex.html |title=Next-gen OCT for the esophagus |date=1 May 2013 |website=BioOptics World |access-date=9 September 2016}}</ref>
=== Research applications ===
Researchers have used OCT to produce detailed images of mice brains, through a "window" made of zirconia that has been modified to be transparent and implanted in the skull.<ref name=Nanomedicine201308>{{cite journal |last1=Damestani |first1=Yasaman |last2=Reynolds |first2=Carissa L. |last3=Szu |first3=Jenny |last4=Hsu |first4=Mike S. |last5=Kodera |first5=Yasuhiro |last6=Binder |first6=Devin K. |last7=Park |first7=B. Hyle |last8=Garay |first8=Javier E. |last9=Rao |first9=Masaru P. |last10=Aguilar |first10=Guillermo |year=2013 |title=Transparent nanocrystalline yttria-stabilized-zirconia calvarium prosthesis |journal=Nanomedicine |volume=9 |issue=8 |pages=1135–8 |publisher=Elsevier |doi=10.1016/j.nano.2013.08.002 |pmid=23969102 |url=http://www.nanomedjournal.com/article/S1549-9634(13)00361-4/abstract |accessdate=September 11, 2013 |lay-summary=http://www.latimes.com/science/sciencenow/la-sci-sn-window-brain-20130903,0,6788242.story <!-- |lay-title=A window to the brain? It's here, says UC Riverside team |lay-last=Mohan |lay-first=Geoffrey --> <!--|lay-date=September 4, 2013 |lay-source=Los Angeles Times }}</ref> Optical coherence tomography is also applicable and increasingly used in [[industrial engineering|industrial applications]], such as [[nondestructive testing]] (NDT), material thickness measurements,<ref>{{cite patent |country=US |number=7116429 B1 |status=patent |title=Determining thickness of slabs of materials |gdate=2006-10-03 |fdate=2003-01-18 |pridate=2003-01-18 |invent1=Walecki, Wojciech J. |invent2=Van, Phuc |assign1=Walecki, Wojciech J. |assign2=Van, Phuc }}.</ref> and in particular thin silicon wafers<ref>{{cite journal |first1=Wojtek J. |last1=Walecki |first2=Fanny |last2=Szondy |title=Integrated quantum efficiency, reflectance, topography and stress metrology for solar cell manufacturing |journal=Proc. SPIE |volume=7064 |page=70640A |date=2008 |doi=10.1117/12.797541 }}</ref><ref>{{cite journal |first1=Wojciech J. |last1=Walecki |first2=Kevin |last2=Lai |first3=Alexander |last3=Pravdivtsev |first4=Vitali |last4=Souchkov |first5=Phuc |last5=Van |first6=Talal |last6=Azfar |first7=Tim |last7=Wong |first8=S.H. |last8=Lau |first9=Ann |last9=Koo |title=Low-coherence interferometric absolute distance gauge for study of MEMS structures |journal=Proc. SPIE |volume=5716 |page=182 |date=2005 |doi=10.1117/12.590013 }}</ref> and compound semiconductor wafers thickness measurements<ref>{{cite journal |last1=Walecki |first1=W.J. |last2=Lai |first2=K. |last3=Souchkov |first3=V. |last4=Van |first4=P. |last5=Lau |first5=S. |last6=Koo |first6=A. |date=2005 |url=http://onlinelibrary.wiley.com/doi/10.1002/pssc.200460606/abstract |title=Novel noncontact thickness metrology for backend manufacturing of wide bandgap light emitting devices |journal=Physica status solidi (c) |volume=2 |pages=984–989 |doi=10.1002/pssc.200460606 }}</ref><ref>{{cite journal |first1=Wojciech |last1=Walecki |first2=Frank |last2=Wei |first3=Phuc |last3=Van |first4=Kevin |last4=Lai |first5=Tim |last5=Lee |first6=S.H. |last6=Lau |first7=Ann |last7=Koo |title=Novel low coherence metrology for nondestructive characterization of high-aspect-ratio microfabricated and micromachined structures |journal=Proc. SPIE |volume=5343 |page=55 |date=2004 |doi=10.1117/12.530749}}</ref> surface roughness characterization, surface and cross-section imaging<ref>
{{Cite report |last1= Guss |first1= G. |last2= Bass |first2= I. |last3= Hackel |first3= R. |last4= Demos |first4= S.G. |title=High-resolution 3-D imaging of surface damage sites in fused silica with Optical Coherence Tomography |publisher=[[Lawrence Livermore National Laboratory]] |id=UCRL-PROC-236270 |date=November 6, 2007 |url=https://e-reports-ext.llnl.gov/pdf/354371.pdf |format=PDF |accessdate=December 14, 2010}}</ref><ref>{{cite conference |first1=W |last1=Walecki |first2=F |last2=Wei |first3=P |last3=Van |first4=K |last4=Lai |first5=T |last5=Lee |url=http://www.gaas.org/Digests/2004/2004Papers/8.2.pdf |format=PDF |title=Interferometric Metrology for Thin and Ultra-Thin Compound Semiconductor Structures Mounted on Insulating Carriers |conference=CS Mantech Conference |date=2004 }}</ref> and volume loss measurements. OCT systems with feedback can be used to control manufacturing processes.
With high speed data acquisition,<ref>{{cite journal |first1=Wojciech J. |last1=Walecki |first2=Alexander |last2=Pravdivtsev |first3=Manuel, II |last3=Santos |first4=Ann |last4=Koo, |title=High-speed high-accuracy fiber optic low-coherence interferometry for in situ grinding and etching process monitoring |journal=Proc. SPIE |volume=6293 |page=62930D |date=August 2006 |doi=10.1117/12.675592 }}</ref> and sub-micron resolution, OCT is adaptable to perform both inline and off-line.<ref>See, for example: {{cite web |url=http://www.zebraoptical.com/InterferometricProbe.html |title=ZebraOptical Optoprofiler: Interferometric Probe }}</ref> Due to the high volume of produced pills, an interesting field of application is in the pharmaceutical industry to control the coating of tablets.<ref>{{cite patent |country=EP |number=2799842 |status=application |title=A device and a method for monitoring a property of a coating of a solid dosage form during a coating process forming the coating of the solid dosage form |pubdate=2014-11-05 |gdate= |fdate=2014-04-29 |pridate=2013-04-30 |invent1=Markl, Daniel |invent2=Hannesschläger, Günther |invent3=Leitner, Michael |invent4=Sacher, Stephan |invent5=Koller, Daniel |invent6=Khinast, Johannes }}; {{cite patent |country=GB |number=2513581 |status=application }}; {{cite patent |country=US |number=20140322429 A1 |status=application |url=https://www.google.com/patents/US20140322429 }}.</ref> Fiber-based OCT systems are particularly adaptable to industrial environments.<ref>{{cite journal |first1=Wojtek J. |last1=Walecki |first2=Fanny |last2=Szondy |url=http://lib.semi.ac.cn:8080/tsh/dzzy/wsqk/SPIE/vol7322/73220K.pdf |title=Fiber optics low-coherence IR interferometry for defense sensors manufacturing |journal=Proc. SPIE |volume=7322 |page=73220K |date=30 April 2009 |doi=10.1117/12.818381 }}</ref> These can access and scan interiors of hard-to-reach spaces,<ref>{{Cite web |last1=Dufour |first1=Marc |last2=Lamouche |first2= Guy |last3=Gauthier |first3=Bruno |last4=Padioleau |first4=Christian |last5=Monchalin |first5=Jean-Pierre |title=Inspection of hard-to-reach industrial parts using small diameter probes |website=[[SPIE|SPIE - The International Society for Optical Engineering]] |date=13 December 2006 |url=http://spie.org/documents/newsroom/imported/467/2006100467.pdf |format=PDF |doi=10.1117/2.1200610.0467 |accessdate=December 15, 2010}}</ref> and are able to operate in hostile environments—whether radioactive, cryogenic, or very hot.<ref>{{Cite journal | last1 = Dufour | first1 = M. L. | last2 = Lamouche | first2 = G. | last3 = Detalle | first3 = V. | last4 = Gauthier | first4 = B. | last5 = Sammut | first5 = P. | title = Low-Coherence Interferometry, an Advanced Technique for Optical Metrology in Industry |url = http://www.ndt.net/abstract/wcndt2004/671.htm| doi = 10.1784/insi.47.4.216.63149 | journal = [[British Institute of Non-Destructive Testing|Insight - Non-Destructive Testing and Condition Monitoring]] | issn = 1354-2575| volume = 47 | issue = 4 | pages = 216–219 |date=April 2005 | pmid = | pmc = }}</ref> Novel optical biomedical diagnostic and imaging technologies are currently being developed to solve problems in biology and medicine.<ref>{{Cite web |doi=10.1117/2.3201406.03 |title=Developing new optical imaging techniques for clinical use |date=11 June 2014 |website=SPIE |first1=Stephen |last1=Boppart |url=http://www.spie.org/newsroom/boppart-video }}</ref>
As of 2014, attempts have been made to use optical coherence tomography to identify root canals in teeth, specifically canal in the maxillary molar, however, there's no difference with the current methods of dental operatory microscope.<ref>{{cite journal |last1=Iino |first1=Y |last2=Ebihara |first2=A |last3=Yoshioka |first3=T |last4=Kawamura |first4=J |last5=Watanabe |first5=S |last6=Hanada |first6=T |last7=Nakano |first7=K |last8=Sumi |first8=Y |last9=Suda |first9=H |title=Detection of a second mesiobuccal canal in maxillary molars by swept-source optical coherence tomography |journal=Journal of Endodontics |date=November 2014 |volume=40 |issue=11 |pages=1865–1868 |doi=10.1016/j.joen.2014.07.012 |pmid=25266471 }}</ref>{{primary source inline|reason=Investigational study in which the authors collected the imaging data. |date=October 2016}} Research conducted in 2015 was successful in utilizing a smartphone as an OCT platform, although much work remains to be done before such a platform would be commercially viable.<ref>{{cite web |first1=Hrebesh M. |last1=Subhash |first2=Josh N. |last2=Hogan |first3=Martin J. |last3=Leahy |date=May 2015 |title=Multiple-reference optical coherence tomography for smartphone applications |website=SPIE |url=http://spie.org/x113407.xml |doi=10.1117/2.1201503.005807 }}</ref>
== See also ==
* [[Angle-resolved low-coherence interferometry]]
* [[Ballistic photon]]
* [[Interferometry]]
* [[Leica Microsystems]]
* [[Novacam Technologies]]
* [[Optical heterodyne detection]]
* [[Optical projection tomography]]
* [[Terahertz tomography]]
* [[Tomography]]
* [[Confocal microscopy]]
* [[Medical imaging]]
-->
== Referensi ==
{{reflist}}
{{Authority control}}
[[Kategori:Peralatan medis]]
| |||