The broad, long-term objective of the proposed research is to develop an imaging technology that provides both morphological and blood flow information for the diagnosis and management of diabetic retinopathy. This application proposes to demonstrate an advanced swept source optical coherence tomography (SS-OCT) system in the 1060nm spectral region. Although current high- resolution OCT centered at 820nm for ophthalmic applications provides a clear image of intraretinal layer, its penetration depth is insufficient for imaging the choroidal microvasculature. However, the choroid plays an important role in many ocular diseases, including diabetic retinopathy. Imaging and quantifying choroidal blood flow with functional OCT would provide valuable information in both diagnosing and managing these ocular diseases at earlier stages. It has been shown that center wavelength at 1060nm provides an optimal wavelength for imaging choroidal morphology and microvasculature due to deep penetration, low tissue dispersion, and 5 times higher exposure threshold level than that at 800nm, thus enabling higher sensitivity. The key technology to be addressed by this research effort is to develop a swept source based on ytterbium-doped fiber amplifier (YDFA) and the validation of this source in a SS-OCT system.
The specific aims of the phase I proposal are as follows: 1. Generate a 1060nm swept laser capable of a lasing range >70nm (18700GHz) with a 3dB range of >50nm (7.7 m depth resolution in tissue), a linewidth of <0.1nm, a peak power >10mW, and a sweep frequency of 250Hz. 2. Investigate limitations of the swept laser for wide sweep range, high power, and high speed operation at KHz rates. 3. Construct a SS-OCT system, and measure A-scan performance at 250Hz acquisition rate. The performance goals are to achieve a resolution ~8?m, a range >3mm, and a sensitivity of >120dB. 4. Identify tasks for Phase ll to increase both the bandwidth and sweep frequency of the light source. ? ?
