Spectral Optical Coherence Tomography in Retinology
Jerzy Nawrocki, Janusz Michalewski, Zofia Michalewska and
Dominik Odrobina
History and Development of Spectral Optical Coherence Tomography. It is 16 years since David Huang and colleagus in the James Fujimoto laboratory at the Massachusetts Institute of Technology developed optical coherence tomography (OCT). Folowing the introduction of Zeiss Stratus Optical Coherence Tomography (thrid-generration OCT or OCT 3) by Carl Zeiss Meditec INC., it became a ' gold standard' for ocular examination of macular diseases...
Spontaneous closure of stage III and IV idiopathic full-thickness macular holes- a two- case report
Zofia Michalewska, Sławomir Cisiecki, Bartosz Sikorski,
Janusz Michalewski, Jakub J. Kałużny, Maciej Wojtkowski,
Jerzy Nawrocki
Graefs Arch Clin Exp Ophthalmol
Background To document and study the spontaneous closure of stage III and IV idiopathic full-thickness macular holes by using oth optical coherence tomography (Stratus OCT) and spectral optical coherence tomography (SOCT).
Methods A two-center, two-case, observational study of stage III and IV macular holes is presented. OCT and SOCT were performed.
Results Macular holes spontaneously resolved after 4 to 12 weeks of observation...
Morphologically functional correlations of macular pathology connected with membrane formation in spectral optical coherence tomography (SOCT)
Janusz Michalewski, Zofia Michalewska,Sławomir Cisiecki,
Jerzy Nawrocki
Graefs Arch Clin Exp Ophthalmol
Background Preretinal mambrane formation is a frequently diagnosed disease in ophtalmology.Its pathogenesis is unclear. Optical coherence tomography is an important diagnostic tool in patients with epiretinal membranes. In our study we use high-speed and high- resoluyion spectral OCT. Our goal was to present different forms of ERM and to analyze the influence of some morphological changes on visual acuity.
Methods We evaluated 44 cases oh preretinal fibrosis. Patients were divided into two groups depending on macula morphology. High-resolution and 3D Soct scans were acguired from all patients and analyzed. Maximum retinal thickness and retinal thickness in the fovea were measured.Type of ERM, presence of retinal cysts and photoreceptor defects were recorded. We analyzed he influence of those data on visual acuity...
Three-dimensional Retinal Imaging with High-Speed Ultrahigh-Resolution Optical Coherence Tomography
M.Wojtkowski, V.J.Srinivasan, J.Fujimoto T.H.Ko,
J.Schuman, A.Kowalczyk, J.S.Duker
Ophthalmology, 112, 1736-1746 (2005)
Purpose: To demonstrate high-speed, ultrahigh-resolution, 3-dimensional optical coherence tomography (3D OCT) and new protocols for retinal imaging.
Methods: Ultrahigh-resolution OCT using broadband light sources achieves axial image resolutions of ~2 µm compared with standard 10-µm-resolution OCT current commercial instruments. High-speed OCT using spectral/Fourier domain detection enables dramatic increases in imaging speeds. Three-dimensional OCT retinal imaging is performed in normal human subjects using high-speed ultrahigh-resolution OCT. Three-dimensional OCT data of the macula and optic disc are acquired using a dense raster scan pattern. New processing and display methods for generating virtual OCT fundus images; cross-sectional OCT images with arbitrary orientations; quantitative maps of retinal, nerve fiber layer, and other intraretinal layer thicknesses; and optic nerve head topographic parameters are demonstrated.
Results: Three-dimensional OCT imaging enables new imaging protocols that improve visualization and mapping of retinal microstructure. An OCT fundus image can be generated directly from the 3D OCT data, which enables precise and repeatable registration of cross-sectional OCT images and thickness maps with fundus features. Optical coherence tomography images with arbitrary orientations, such as circumpapillary scans, can be generated from 3D OCT data. Mapping of total retinal thickness and thicknesses of the nerve fiber layer, photoreceptor layer, and other intraretinal layers is demonstrated. Measurement of optic nerve head topography and disc parameters is also possible. Three-dimensional OCT enables measurements that are similar to those of standard instruments, including the StratusOCT, GDx, HRT, and RTA.
Conclusion: Three-dimensional OCT imaging can be performed using high-speed ultrahigh-resolution OCT. Three-dimensional OCT provides comprehensive visualization and mapping of retinal microstructures. The high data acquisition speeds enable high-density data sets with large numbers of transverse positions on the retina, which reduces the possibility of missing focal pathologies. In addition to providing image information such as OCT cross-sectional images, OCT fundus images, and 3D rendering, quantitative measurement and mapping of intraretinal layer thickness and topographic features of the optic disc are possible. We hope that 3D OCT imaging may help to elucidate the structural changes associated with retinal disease as well as improve early diagnosis and monitoring of disease progression and response to treatment...
The applicability of standard resolution Spectral Optical Coherence Tomography for examination of the eye pathologies
A. Szkulmowska, I. Gorczyńska, T. Bajraszewski, A. Kowalczyk, J.Kałużny, M.Wojtkowski, J.Fujimoto
Proc. SPIE 5690, 85-90 (2005)
Since 1996 when the first publication on Spectral Optical Coherence Tomography (SOCT) appeared1 the method has also been quickly developed towards clinical applications. Technological advances such as development of fast CCD cameras as well as broadband light sources made possible high speed and 3-dimensional imaging as well as high resolution imaging. New methods enabling examination of thick structures were improved what resulted in full range imaging. Effective methods of data processing have been developed to compensate for dispersion and to improve the resolution.Despite of development of new imaging formats like 3D and OCT movies, the single section (B-scan) remains the most popular for medical diagnostic. In this case 100-fold increase of imaging speed is more then necessary to improve the patient comfort and to prevent from motion artefacts. In practice, ten fold increase of the imaging speed is sufficient to get rid of the artifacts. Therefore, it opens the possibility for significant increase of the density of lateral sampling (density of A-scans). This ultra-fast acquisition is achieved with linear, industrial cameras with A/D converters of no more then 12 bits. Comparing images obtained with 12- and 16-bits cameras we demonstrate that the most important factor that enhances the quality of the images is high density lateral scanning. Applying the standard resolution Spectral OCT device to clinical examinations we show that images of pathological retina are useful for diagnosis of the eye diseases...
Spectral Optical Coherence Tomography in ophthalmology
T. Bajraszewski, I. Gorczyńska, A. Szkulmowska, M. Szkulmowski,
P. Targowski, A. Kowalczyk
Proc. SPIE 5959 65-69 (2005)
An alternative method for time domain OCT is Spectral OCT where the optical delay line for depth scanning is eliminated what implies the possibility of very fast imaging with high sensitivity. Due to these two features, a considerable advancement in clinical studies is possible. High speed enables the collection of more information in shorter time. It improves the quality of images, because motion artifacts are easily avoided, as well as the sampling density in the image can be considerably increased. The latter improves signal to noise ratio and the resultant quality of cross-sectional images, which enables better visualization of intraretinal layers in case of retina studies. Moreover, high speed allows collection of enough data, in a reasonable time, to reconstruct the three-dimensional structure of an object. In addition, a real-time examination is possible, as well as the recording of tomographic movies to unravel morphological dynamics. The high sensitivity renders the light illuminating the eye less intense. The short exposure together with the high phase stability widens the range of measurable flows. Spectral OCT also offers direct access to spectral information, which facilitates post-processing manipulations such as spectral shaping10 and dispersion correction. Therefore, SOCT is the most appropriate technique for cross-sectional imaging of the cornea. SOCTbased instruments, in contrast to conventional OCT, are not commercially available, and only prototype instruments have so far been constructed.
The purpose of this study is to analyse the consequences of high speed imaging...
Standard Resolution Spectral domain Optical Coherence Tomography In Clinical Ophthalmic Imaging
A. Szkulmowska, M.Cyganek, P. Targowski, J. Kałuzny, A. Kowalczyk, M. Wojtkowski, J. Fujimoto
Proc. SPIE 5688, 69-76 (2005)
Spectral OCT is a mutation of traditional Time domain OCT. The main advantages of the SOCT are speed and sensitivity. Due to these two features the considerable advancement in clinical studies is possible. High speed enables collecting more information: it either allows to reconstruct three dimensional structure of an object or to increase sampling density in two dimensional cross-sectional imaging. The latter helps to improve signal to noise ratio and the resultant quality of cross-sectional images. In the case of retinal imaging this enables better visualization of intraretinal layers. High speed imaging also eliminates motion artifacts and the same helps to reconstruct true topography of the retina. It also enables reconstructing tomographic movies to unravel morphological dynamics. Finally it is feasible to examine the eye in real-time. Spectral OCT offers direct access to spectral information, which facilitates postprocessing manipulations such as spectral shaping and dispersion correction. Additionally, short exposure together with high phase stability widens the range of measurable flows. The purpose of this study is to demonstrate applicability of high speed SOCT method for imaging retinal pathologies in clinical conditions...
Coherent noise-free ophthalmic imaging by spectral optical coherence tomography
A. Szkulmowska, M. Wojtkowski, I. Gorczynska, T. Bajraszewski,
M. Szkulmowski, P. Targowski, A. Kowalczyk, J.J. Kalużny
J. Phys. D: Appl.Phys 38, 2606-2611 (2005)
Optical coherence tomography (OCT) is an optical modality, which allows to determine the internal structure of weakly absorbing and scattering objects. The technique relies on an examination of a beam of low coherent light reflected back at the internal interfaces of the layered structure of an object. In order to determine the locations of these interfaces along the path of penetrating beam OCT uses interferometry. The light backreflected within the object is combined with the light reflected from a reference mirror and then is analysed by a detection system. Consecutive measurements with the beam in adjacent transversal positions provide the cross-section of the structure. Because this technique is non-contact, non-invasive and safe for the eyes (as long as exposure is limited to a certain level), the most advanced medical applications of OCT are in ophthalmology for diagnosing and staging of ocular diseases...
Ophthalmic Imaging by Spectral Optical Coherence Tomography
M. Wojtkowski, T. Bajraszewski, I. Gorczyńska, P. Targowski,
A. Kowalczyk, W. Wasilewski, Cz. Radzewicz
Am. J. Ophthalmology 138, 412-419 (2004)
OPTICAL COHERENCE TOMOGRAPHY (OCT) IS A new, but well-established, technique that offers a unique possibility of determining and visualizing the structure of objects that only weakly absorb and scatter light. The technique relies on an examination of the light scattered or reflected back from the internal structures of the object. Therefore it is noncontact, noninvasive, and safe for the object examined, as long as the exposure is limited to a certain level. Its axial resolution can be as high as 0.75 µm. It is natural that the most advanced medical applications of OCT are in ophthalmology, for the diagnosis, staging, and monitoring of ocular diseases. In conventional (that is, temporal) OCT, an optical delay line has to be mechanically scanned to record a single line (A-scan) in a tomographic image. The present state of this technique, including a critical comparison with other visualization techniques used in ophthalmology, such as ultrasonography, confocal microscopy, and scanning laser ophthalmoscopy, has been reviewed by Drexler at al...
In vivo human retinal imaging by Fourier domain optical coherence tomography
M. Wojtkowski, R. Leitgeb, A. Kowalczyk, T. Bajraszewski, A.F.Fercher
Journal of Biomedical Optics 7(3), 457-463 (2002)
Tomographic retinal imaging in vivo as well as the measurement of the thickness of retinal layers plays an important role in contemporary ophthalmic diagnosis. Instruments and techniques ike scanning laser ophthalmoscopy, ultrasonography, or partial coherence interferometry ~PCI! are successfully sed in ophthalmic clinics. Competitive optical coherence tomography ~OCT! joined the earlier-mentioned methods in the ast 12 years.4 The micron longitudinal resolution, high sensitivity, precision, and noncontact operations are responsible or the success of this technique in retinal imaging. Huang et al. reported the first tomogram of the human etina in vitro in 1991.5 The first OCT tomogram of the human optic disk in vivo was presented in 1993 by Fercher et al.6 The irst macular imaging in vivo done by Swanson et al.7 in 1993 and pathological retinal tomograms in vivo were performed hortly afterwards. Since then OCT has advanced as a powerful imaging modality for clinical applications demonstrating he detection and monitoring of macular diseases as well as early glaucoma diagnosis capabilities. The visualization f morphologic features of human retina structures ~macula, optic disk! as well as the precise quantification of the retinal erve fiber layer thickness are the most desirable parameters in ophthalmic early diagnosis... |
