Feature Of The Week 3/6/11: Researchers at Peking University and Shanghai Jiao Tong University Investigate System Tradeoffs for SD-OCT
Feature Of The Week 3/6/11: Although several reviews and reports have described the resolution, probing depth, and signal-to-noise ratio (SNR) of the SD-OCT system, the design and realization of such a system, including the CCD choice, grating parameters and focusing lens for spectrometric detection, is largely dependent on the working experience of the investigator. To the best of our knowledge, there are no reports which discuss how the configuration of the spectrometer hardware may affect the performance of the OCT system. Recent reports showed that while optimizing the image acquisition speed of optical frequency domain imaging (OFDI), a reduced dynamic detector range was able to maintain the same SNR and sensitivity. In this work we have evaluated the parameters for the spectrometer setup of an SD-OCT system. Hardware choices such as the pixel number and digitization of the CCD were compared, with the analysis of the period of the grating and the numerical aperture of the focusing lens. The spectral resolution decides the penetration depth of the SD-OCT, and the spectral range determines the axial resolution. With partial spectral detection, a compromise between axial resolution, side lobes, and penetration depth can be optimized. The simulations were confirmed experimentally, on static reflections as well as human retinal imaging using an OCT system with 2048 pixels and 12-bit digitization. The data shows that for retinal imaging in vivo, an 8-bit dynamic range can maintain the SNR level for capturing meaningful structural details in an SD-OCT image. Similar results has been reported in OFDI, however, the application of a smaller dynamic range in SD-OCT imaging has not been reported elsewhere. Further, with the application of 1024-pixels for a spectral resolution of 0.07 nm, the optical penetration depth is ~2 mm, which is physically limited by the scattering of the retinal tissue. Because less pixels with reduced dynamic range implies faster data transfer in a finite bandwidth, the proposed methods can be applied in fast SD-OCT imaging. In situations where the detector pixel number is set, partial spectral detection can be employed to increase the maximum probing depth at the cost of a slight drop in axial resolution, as the illumination spectrum generally has a smooth slope. Moreover, as the simulation can provide an environment to virtually construct and optimize a SD-OCT system based on your own application, this work should also be of highly interest to the SD-OCT system instrumentation.
For more details see recent Article. Courtesy Peng Xi.