Abstract

An upgraded optical coherence tomography system with integrated retinal tracker (TOCT) was developed. The upgraded system uses improved components to extend the tracking bandwidth, fully integrates the tracking hardware into the optical head of the clinical OCT system, and operates from a single software platform. The system was able to achieve transverse scan registration with sub-pixel accuracy (∼10 μm). We demonstrate several advanced scan sequences with the TOCT, including composite scans averaged (co-added) from multiple B-scans taken consecutively and several hours apart, en face images collected by summing the A-scans of circular, line, and raster scans, and three-dimensional (3D) retinal maps of the fovea and optic disc. The new system achieves highly accurate OCT scan registration yielding composite images with significantly improved spatial resolution, increased signal-to-noise ratio, and reduced speckle while maintaining well-defined boundaries and sharp fine structure compared to single scans. Precise re-registration of multiple scans over separate imaging sessions demonstrates TOCT utility for longitudinal studies. En face images and 3D data cubes generated from these data reveal high fidelity image registration with tracking, despite scan durations of more than one minute.

© 2005 Optical Society of America

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References

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Appl. Opt. (1)

J. Biomedical Opt. (2)

M. Wojtkowski, R. Leitgeb, A. Kowalczyk, T. Bajraszewski, and A. F. Fercher, �??In vivo hurman retinal imaging by Fourier domain optical coherence tomography,�?? J. Biomedical Opt. 7, 457-463 (2002).
[CrossRef]

Daniel X. Hammer, R. Daniel Ferguson, John C. Magill, Lelia Adelina Paunescu, Siobahn Beaton, Hiroshi Ishikawa, Gadi Wollstein, and Joel S. Schuman, �??An Active Retinal Tracker for Clinical Optical Coherence Tomography Systems,�?? J. Biomedical Opt. 10, 024038 (2005).
[CrossRef]

Opt. Commun. (1)

A. F. Fercher, C. K. Hitzenberger, G. Kamp, and S. Y. El-Zaiat, �??Measurement of intraocular distances by backscattering spectral interferometry,�?? Opt. Commun. 117, 43-48 (1995).
[CrossRef]

Opt. Express (5)

R. D. Ferguson, D. X. Hammer, A. E. Elsner, R. H. Webb, S. A. Burns, and J. J. Weiter, "Wide-field retinal hemodynamic imaging with the tracking scanning laser ophthalmoscope," Opt. Express 12, 5198-5208 (2004), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-21-5198.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-21-5198.</a>
[CrossRef] [PubMed]

A. Podoleanu, J. A. Rogers, D. A. Jackson, and S. Dunne, �??Three dimensional OCT images from retina and skin,�?? Opt. Express 7, 292-298 (2000), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-7-9-292.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-7-9-292.</a>
[CrossRef] [PubMed]

D. X. Hammer, R. D. Ferguson, J. C. Magill, M. A. White, A. E. Elsner, and R. H. Webb, �??Image stabilization for scanning laser ophthalmoscopy,�?? Opt. Express 10, 1542-1549 (2002), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-10-26-1542.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-10-26-1542.</a>
[PubMed]

N. A. Nassif, B. Cense, B. H. Park, M. C. Pierce, S. H. Yun, B. E. Bouma, G. J. Tearney, T. C. Chen, and J. F. de Boer, �??In vivo high-resolution video-rate spectral-domain optical coherence tomography of the human retina and optic nerve,�?? Opt. Express 12, 367-376 (2004), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-3-367.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-3-367.</a>
[CrossRef] [PubMed]

B. Cense, N. A. Nassif, T. C. Chen, M. C. Pierce, S. Yun, B. H. Park, B. E. Bouma, G. J. Tearney, and J. F. de Boer, �??Ultrahigh-resolution high-speed retinal imaging using spectral-domain optical coherence tomography,�?? Opt. Express 12, 2435-2447 (2004), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-11-2435.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-11-2435.</a>
[CrossRef] [PubMed]

Opt. Lett. (1)

Other (1)

R. D. Ferguson, �??Servo Tracking System Utilizing phase-Sensitive Detection of Reflectance Variation,�?? U. S. Patent #5,767,941 and #5,943,115.

Supplementary Material (2)

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Figures (10)

Fig. 1.
Fig. 1.

Optical schematic of TOCT (flattened for clarity). SLD: superluminescent diode, LD: laser diode, W: wedge, D1-2: dichroic beamsplitters, L1-3: fiber collimating lenses, TG: tracking galvanometer-driven mirrors, IG: OCT imaging galvanometer-driven mirrors, RS: resonant scanners, S1: split aperture, SL: scan lens, OL: ophthalmoscopic lens. Retinal and pupil conjugates shown (rx and px).

Fig. 2.
Fig. 2.

Photograph of TOCT3 system (a). Photograph of optical head (viewed from the top) illustrating location of tracker optics (b).

Fig. 3.
Fig. 3.

Front panel of the TOCT3 acquisition software.

Fig. 4.
Fig. 4.

Peripapillary OCT scans comparing tracking (a,c,e) and non-tracking (b,d,f). 24 scans were collected sequentially. (a,b) Each horizontal line of the en-face profile was created by summing the A-scans in the frame. (c,d) Composite image created by aligning and co-adding all the frames. (e,f) Single frames used to create the composite images in c and d. Vertical lines show location of a blood vessel in single and composite images. Scale bar = 250 μm.

Fig. 5.
Fig. 5.

Averaged line profiles of the region of a blood vessel for each frame used to create the composite image in Fig. 4c and 4d for (a) tracking and (b) non-tracking. Each pixel is ∼21 μm.

Fig. 6.
Fig. 6.

Repeatibility of tracking. En-face (a,b) and composite (c,d) images created by co-adding 48 frames from two sets of scans taken 2 hours apart. Scale bar = 250 μm.

Fig. 7.
Fig. 7.

Line scan through disc and fovea: (a) single image, (b) composite image (24 co-added frames) with tracking, and (c) composite image without tracking. Scale bar = 250 μm.

Fig. 8.
Fig. 8.

Magnified TOCT composite (24 frame) image of fovea with labeled retinal layers. Small retinal vessels are also identified with circles. NFL: nerve fiber layers, GCL: ganglion cell layer, IPL: inner plexiform layer, INL: inner nuclear layer, OPL: outer plexiform layer, ONL: outer nuclear layer, ELM: external limiting membrane, PL: photoreceptor layer (interface between inner and outer segments delineated by bright reflection), RPE: retinal pigment epithelium, C: choriocapillaris and choroid.

Fig. 9.
Fig. 9.

(3.5 Mb) En face (left) and cross-sectional scans (right) through the macular region. Fovea is dark region in the center on the right and the region without overlying nerve fiber layer on the right.

Fig. 10.
Fig. 10.

(1.7 Mb) En face (left) and cross-sectional scans (right) through the optic nerve head.

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