Comparative study of optical sources in the near infrared for optical coherence tomography applications

Quantitative comparison of the OCT imaging depth at 1300 nm and 1600 nm

One of the present challenges in optical coherence tomography (OCT) is the visualization of deeper structural morphology in biological tissues. Owing to a reduced scattering, a larger imaging depth can be achieved by using longer wavelengths. In this work, we analyze the OCT imaging depth at wavelengths around 1300 nm and 1600 nm by comparing the scattering coefficient and OCT imaging depth for a range of Intralipid concentrations at constant water content. We observe an enhanced OCT imaging depth for 1600 nm compared to 1300 nm for Intralipid concentrations larger than 4 vol.%. For higher Intralipid concentrations, the imaging depth enhancement reaches 30%. The ratio of scattering coefficients at the two wavelengths is constant over a large range of scattering coefficients and corresponds to a scattering power of 2.8 ± 0.1. Based on our results we expect for biological tissues an increase of the OCT imaging depth at 1600 nm compared to 1300 nm for samples with high scattering power and low water content.

Performance of single-scattering model versus multiple-scattering model in the determination of optical properties of biological tissue with optical coherence tomography

Tissue optical properties can be determined with optical coherence tomography (OCT) by fitting a model to the OCT signal. Using calibrated samples in the fixed focus geometry, the validity of the single-scattering and multiple-scattering models for both highly scattering and weakly scattering media (scattering coefficients mu(s) ranging from 1.25 to 25.11mm(-1)) has been investigated. The results show that, with a proper correction for the confocal properties of the sample arm, both models are appropriate to extract the scattering coefficients of weakly scattering media. For highly scattering media, the multiple scattering should be taken into account, and the multiple-scattering model can provide higher accuracy. Finally, the scattering properties of in vitro rat liver and in vivo human skin are determined. The results are useful for quantitatively characterizing tissue scattering in biomedical research and clinical diagnosis.

Mapping of cerebro-vascular blood perfusion in mice with skin and skull intact by Optical Micro-AngioGraphy at 1.3 mum wavelength

Optical micro-angiography (OMAG) was developed to achieve volumetric imaging of the microstructures and dynamic cerebrovascular blood perfusion in mice with capillary level resolution and high signal-to-background ratio. In this paper, we present a high-speed and high-sensitivity OMAG imaging system by using an InGaAs line scan camera and broadband light source at 1.3 mum wavelength for enhanced imaging depth in tissue. We show that high quality imaging of cerebrovascular blood perfusion down to capillary level resolution with the intact skin and cranium are obtained in vivo with OMAG, without the interference from the blood perfusion in the overlaying skin. The results demonstrate the potential of 1.3 mum OMAG for high-speed and high-sensitivity imaging of blood perfusion in human and small animal studies.