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Damber Thapa, Benquan Wang, Yiming Lu, Taeyoon Son, Xincheng Yao; Sensitivity enhancement of intrinsic optical signal recording through split-spectrum-optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):451.
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© ARVO (1962-2015); The Authors (2016-present)
Intrinsic optical signal (IOS) imaging that measures transient light changes correlated with retinal physiological activation promises to be a new methodology for high resolution mapping of retinal neural dysfunctions. However, its practical applications for noninvasive examination of retinal function have been hindered by low signal-to-noise ratio (SNR) and small magnitude of IOSs. Split-spectrum amplitude-decorrelation has been demonstrated to improve image quality of optical coherence tomography (OCT) angiography.The purpose of this study is to test if the split-spectrum strategy can be used to enhance the sensitivity of IOS recording.
Freshly enucleated leopard frog (Rana Pipiens) eyes were used in this study. A spectral domain OCT (SD-OCT) that uses a broadband superluminescent diode (D-840-HP-I, Superlum, Ireland) with a center wavelength of 845.8 nm, full width at half maximum (FWHM, Δλ) of 100 nm, was constructed for functional OCT imaging of retinal IOSs. The full spectrum of SD-OCT was divided into three overlapping spectral bands: first band includes data in the wavelength range 780-850 nm, second band in the wavelength range 815-885 nm and third band in the wavelength range 850-920 nm. The splitted bands were zero padded to match the length of the full spectrum. Three IOS images were calculated separately from individual spectral band OCT first, and were merged into a single frame using a maximum projection method.
IOSs were calculated at the photoreceptor layer of the SD-OCT images. The proposed method considerably increased the IOS detection compared to the full spectrum method. The active pixel number (pixels that produce IOS) increased by at least two-fold and they were significantly greater (p>0.01) than those of the full spectrum. The peak amplitude amplified by at least twice using split-spectrum method compared to the full spectrum.
The experimental results show that IOS sensitivity can be improved by amalgamating IOSs from split-spectrum OCTs. The split-spectrum technique reduces the correlation between the spectral bands; therefore, the IOSs which are lost in one spectral band can be acquired from other spectral bands. The proposed method resolves some of the challenges encountered by IOS imaging to increase signal amplitude and SNR, which is essential for practical applications of functional IOS imaging.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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