Synthetic wavelength based phase unwrapping in spectral domain optical coherence tomography

Hendargo, Hansford C.; Zhao, Mingtao; Shepherd, Neal; Izatt, Joseph A.

doi:10.1364/oe.17.005039

Cited by 41 publications

(26 citation statements)

References 30 publications

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“…We propose a digital spectral shaping method that combines two existing methods to rectify this. The first method, referred to as the window method, passes the camera's response through a Gaussian window [42,43]. The second technique, referred to as the function method, reshapes the spectrum to a Gaussian, rather than just filtering it [44].…”

Section: Spectral Shapingmentioning

confidence: 99%

“…Digital shaping methods such as those using deconvolution [40,41] can optimize the coherence profile, but these involve complex algorithms that require a great deal of computing time. Simpler shaping methods are also available such as passing the detected spectrum through a window [42,43], which may only reduce sidelobes, rather than eliminating them, or using a function to modify its shape [44], which can be plagued by increased noise in the image. We present a combination of the windowing and function digital spectral shaping techniques that requires little computing time, reduces sidelobes and minimizes image degradation to noise and loss of resolution.…”

Section: Introductionmentioning

confidence: 99%

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A dual-modal retinal imaging system with adaptive optics

Meadway¹,

Girkin²,

Zhang³

2013

Opt. Express

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An adaptive optics scanning laser ophthalmoscope (AO-SLO) is adapted to provide optical coherence tomography (OCT) imaging. The AO-SLO function is unchanged. The system uses the same light source, scanning optics, and adaptive optics in both imaging modes. The result is a dual-modal system that can acquire retinal images in both en face and cross-section planes at the single cell level. A new spectral shaping method is developed to reduce the large sidelobes in the coherence profile of the OCT imaging when a non-ideal source is used with a minimal introduction of noise. The technique uses a combination of two existing digital techniques. The thickness and position of the traditionally named inner segment/outer segment junction are measured from individual photoreceptors. In-vivo images of healthy and diseased human retinas are demonstrated. 1178-1181(1991). 4. T. Wilson, Confocal Microscopy (Academic Press, 1990. 5. A. Roorda, "Applications of adaptive optics scanning laser ophthalmoscopy," Optom. Vis. Sci. 87(4), 260-268 (2010). 6. R. Yadav, K. S. Lee, J. P. Rolland, J. M. Zavislan, J. V. Aquavella, and G. Yoon, "Micrometer axial resolution OCT for corneal imaging," Biomed. Opt. Express 2(11), 3037-3046 (2011 27(1), 45-88 (2008). 62. B. Cense, N. Nassif, T. Chen, M. Pierce, S. H. Yun, B. Park, B. Bouma, G. Tearney, and J. de Boer, "Ultrahighresolution high-speed retinal imaging using spectral-domain optical coherence tomography," Opt. Express 12(11), 2435-2447 (2004).

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Section: Spectral Shapingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A dual-modal retinal imaging system with adaptive optics

Meadway¹,

Girkin²,

Zhang³

2013

Opt. Express

View full text Add to dashboard Cite

show abstract

“…A large bandwidth decreases the spectral fitting range and a small bandwidth leads not only to reduced resolution, but also lower SNR. 36 In our experiment, we empirically used ð0.04 × 10 5 Þ rad∕cm for phantom experiments and ð0.06 × 10 5 Þ rad∕cm for animal experiments. (Note that the subband width is twice the standard deviation of the Gaussian window used in STFT.)…”

Section: Discussionmentioning

confidence: 99%

“…(Note that the subband width is twice the standard deviation of the Gaussian window used in STFT.) We used a larger bandwidth in animal experiments to limit the phase noise, 36 since the SNR of in vivo data is naturally lower than that of the phantom data. A more thorough investigation will be necessary to provide comprehensive evaluation of the effects of subband selection for spectroscopic Doppler analysis.…”

Section: Discussionmentioning

confidence: 99%

Spectroscopic Doppler analysis for visible-light optical coherence tomography

2017

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Abstract. Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between −π and π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the need for phase unwrapping using spectroscopic Doppler analysis. We split the whole vis-OCT spectrum into a series of narrow subbands and reconstructed vis-OCT images to extract corresponding Doppler phase shifts in all the subbands. Then, we quantified flow velocity by analyzing subband-dependent phase shift using linear regression. In the phantom experiment, we showed that spectroscopic Doppler analysis extended the measurable absolute phase shift range without conducting phase unwrapping. We also tested this method to quantify retinal blood flow in rodents in vivo.

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“…However, phase wrapping can be avoided by decreasing the voltage on the coil, increasing the distance between the coil and the sample, or by employing phase-unwrapping algorithms. 21 This technique would substantially benefit from higher A-scan rates, which would allow the acquisition of large fields of view with both high spatial and temporal sampling along both the fast and slow axes, which may increase the sensitivity 13 and dynamic range of MM measurements.…”

Section: Discussionmentioning

confidence: 99%

Volumetric full-range magnetomotive optical coherence tomography

et al. 2014

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Abstract. Magnetomotive optical coherence tomography (MM-OCT) can be utilized to spatially localize the presence of magnetic particles within tissues or organs. These magnetic particle-containing regions are detected by using the capability of OCT to measure small-scale displacements induced by the activation of an external electromagnet coil typically driven by a harmonic excitation signal. The constraints imposed by the scanning schemes employed and tissue viscoelastic properties limit the speed at which conventional MM-OCT data can be acquired. Realizing that electromagnet coils can be designed to exert MM force on relatively large tissue volumes (comparable or larger than typical OCT imaging fields of view), we show that an order-of-magnitude improvement in three-dimensional (3-D) MM-OCT imaging speed can be achieved by rapid acquisition of a volumetric scan during the activation of the coil. Furthermore, we show volumetric (3-D) MM-OCT imaging over a large imaging depth range by combining this volumetric scan scheme with full-range OCT. Results with tissue equivalent phantoms and a biological tissue are shown to demonstrate this technique.

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Synthetic wavelength based phase unwrapping in spectral domain optical coherence tomography

Cited by 41 publications

References 30 publications

A dual-modal retinal imaging system with adaptive optics

A dual-modal retinal imaging system with adaptive optics

Spectroscopic Doppler analysis for visible-light optical coherence tomography

Volumetric full-range magnetomotive optical coherence tomography

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