Noninvasive volumetric imaging and morphometry of the rodent retina with high-speed, ultrahigh-resolution optical coherence tomography - PubMed (original) (raw)

Noninvasive volumetric imaging and morphometry of the rodent retina with high-speed, ultrahigh-resolution optical coherence tomography

Vivek J Srinivasan et al. Invest Ophthalmol Vis Sci. 2006 Dec.

Abstract

Purpose: To demonstrate high-speed, ultrahigh-resolution optical coherence tomography (OCT) for noninvasive, in vivo, three-dimensional imaging of the retina in rat and mouse models.

Methods: A high-speed, ultrahigh-resolution OCT system using spectral, or Fourier domain, detection has been developed for small animal retinal imaging. Imaging is performed with a contact lens and postobjective scanning. An axial image resolution of 2.8 mum is achieved with a spectrally broadband superluminescent diode light source with a bandwidth of approximately 150 nm at approximately 900-nm center wavelength. Imaging can be performed at 24,000 axial scans per second, which is approximately 100 times faster than previous ultrahigh-resolution OCT systems. High-definition and three-dimensional retinal imaging is performed in vivo in mouse and rat models.

Results: High-speed, ultrahigh-resolution OCT enabled high-definition, high transverse pixel density imaging of the murine retina and visualization of all major intraretinal layers. Raster scan protocols enabled three-dimensional volumetric imagingand comprehensive retinal segmentation algorithms allowed measurement of retinal layers. An OCT fundus image, akin to a fundus photograph was generated by axial summation of three-dimensional OCT data, thus enabling precise registration of OCT measurements to retinal fundus features.

Conclusions: High-speed, ultrahigh-resolution OCT enables imaging of retinal architectural morphology in small animal models. OCT fundus images allow precise registration of OCT images and repeated measurements with respect to retinal fundus features. Three-dimensional OCT imaging enables visualization and quantification of retinal structure, which promises to allow repeated, noninvasive measurements to track disease progression, thereby reducing the need for killing the animal for histology. This capability can accelerate basic research studies in rats and mice and their translation into clinical patient care.

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Figures

Figure 1

Figure 1

(A) Schematic of high-speed, ultrahigh-resolution OCT system for rat and mouse retinal imaging. Imaging is performed using contact lens and postobjective scanning. Spectral and Fourier domain detection are performed with a high-speed, high-resolution spectrometer. (B) Spectrum of the light source detected by the spectrometer, with and without numerical spectral shaping to smooth the spectrum. The compact, multiplexed superluminescent diode light source has BW = 145 nm at λc = 890 nm. (C) Axial PSF and without spectral shaping to reduce side lobes. The axial resolution is 2.8 _μ_m in tissue.

Figure 2

Figure 2

High-speed, ultrahigh-resolution OCT images from a normal C57BL6 mouse. (A) An OCT fundus image, created by axial summation of 3D-OCT data consisting of 256 images of 512 axial scans each, is shown. High-definition OCT images (B–D) with 2048 axial scans may be registered to the OCT fundus image. (E) Clear visualization of major intraretinal layers is enabled by OCT, as shown in the cropped, enlarged OCT image with ~600 axial scans.

Figure 3

Figure 3

High-speed, ultrahigh-resolution OCT images from a normal Long-Evans rat. (A) An OCT fundus image. High-definition images (B–D) with 2048 axial scans are registered to the fundus image. (E) Intraretinal layers are visualized in the cropped, enlarged OCT image with ~600 axial scans.

Figure 4

Figure 4

Using 3D-OCT data, visualization techniques such as volumetric rendering are possible. (A) A rendering of a normal Long-Evans rat retina. (B) It is possible to create virtual slices through 3D-OCT data and view images along arbitrary planes. Cut-away renderings can simultaneously show intraretinal structure and retinal topography (C).

Figure 5

Figure 5

Using 3D-OCT data, quantitative mapping of intraretinal layers is possible. (A) A fundus image of the Long-Evans rat retina. (B) Cross-sectional OCT images from the 3D-OCT data set are segmented to identify boundaries between retinal layers. Retinal (C) and NFL (D) thicknesses are shown in pseudocolor on the fundus image. The OCT fundus image (E) can be used for registration of baseline (blue) and repeated (red) measurements. This example shows repeated measurements performed 9 days apart. (F) Measurements of retinal thickness (using two different conventions), NFL, ONL, and photoreceptor OS thickness. Rows 1 to 2 and 4 to 5 (F) correspond to the white rectangular region (E), whereas row 3 (F) corresponds to the black rectangular region (E).

Figure 6

Figure 6

A comparison of cropped and enlarged OCT cross-sectional images (~600 axial scans) between normal, young-adult Sprague-Dawley (A) and Long-Evans (B) rats.

Figure 7

Figure 7

Comparisons between (A) representative histology and (B) OCT image in a young adult Long-Evans rat retina near the optic nerve head.

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