Common-path Fourier-domain optical coherence tomography with a fiber optic probe integrated into a surgical needle

Abstract

Abstract-We have demonstrated in vivo three-dimensional imaging and estimated localized and quantitative hemoglobin oxygen saturation (SO 2 ) of blood vessel by using a simple, easy to operate common-path Fourier-domain optical coherence tomography (OCT) system. The common-path OCT system can be easily integrated with various surgical tools and we demonstrated its usefulness by imaging outer and inner intraocular tissues such as cornea and neurosensory retinal layers as well as detecting SO 2 level from a chicken embryo. The system uses 800nm near infrared broadband light sources and has axial resolution as low as 3μm in air. Self-adaptive scanning mechanism with real-time surface recognition and feedback control was also applied to the probe where the scanning probe tracks the sample surface variance and effective imaging depth was largely extended to the probe's free-moving range. I. INTRODUCTIONOptical coherence tomography (OCT) is one optical tomography modalit in which ballistic photons are detected rather than projecting the noncoherent photons having diffuse reflection or transmittance for achieving three dimensional images. OCT has unprecedented resolution compared to other imaging modalities such as ultrasound, X-ray computed tomography (CT), and Magnetic Resonance Imaging (MRI), because the axial (or longitudinal) resolution of OCT is determined by the coherence length of the source used which is inversely proportional to the source bandwidth [1].Unlike the conventional OCT systems that use Michelson Interferometers, this work is based on common-path Fourier-domain OCT (CP-FDOCT) which we believe is the one of the simplest, most versatile three dimensional imaging technique available and allows attachment of different kinds of probes [2]. This is possible since the scanning probe provides the reference and also serves as the transceiver. This configuration allows one to use arbitrary length of probe arm and also allows different probe attachments. Moreover, it doesn't have the problem of polarization and dispersion mismatch [3]. It is known that Fourier-domain (FD) systems are simpler, faster and better than that of time-domain (TD) systems since there is no need for mechanically A-scan. CP-FDOCT can be especially useful for ophthalmic applications [4], since the fiber optic probe can easily be integrated or attached to surgical tools and directly inserted into or placed in close proximity to the ocular tissues for image acquisition and surgical navigation for in-situ or in-vivo operation. Furthermore, the level of the hemoglobin (Hb) oxygen saturation (SO 2 ) can be easily obtained by measuring Hb and HbO 2 induced attenuation. Specifically, the SO 2 level was estimated from their spectral absorption characteristics by analyzing signal spectra [5]. Using this method, other groups have measured the SO 2 of human blood sample ex vivo [6] and in retina in vivo [7] in real time. Current OCT systems generally suffer from very limited imaging depth range of only 1~3mm, which restricts its clinical applicati...

Catheters for optical coherence tomography

“…A probe compatible with CP-OCT has been coupled with surgical tools to investigate intra-ocular and intravitreous locations of human being and rat as well. This surgical probe also has been used in a 0.8-μm common-path Fourier-domain OCT [109][110][111][112]. The fiber bundle probe has also been demonstrated with FD-OCT to eliminate the scanning at the distal end to image the tissue during microsurgery [113,114].…”

Optical Imaging Modalities for Biomedical Applications

“…Kang et al investigated a common-path interferometer based FD-OCT [134], [136] and used this for retinal imaging applications. Other common-path interferometer based approaches for time-domain OCT, using a free space interferometer, have also been demonstrated with limited success [141], [142]. Fiber optic-based technologies have been used for both frequency-domain and time-domain common-path OCT systems [132], [133], [135]- [139], [141].…”

“…Kang et al [134] recently demonstrated the efficacy of fiber optic common-path OCT with a comparative assessment of existing endoscopic technologies. The Fourier domain common path optical coherence tomography has thus shown promising potential for intraocular surgical applications relevant to retinal surgery as the model application [134], [142], [143].…”

High resolution hemoglobin oxygen saturation level imaging using Morlet wavelet transformed spectroscopic Optical Coherence Tomography

“…The interferometer and spectrometer design in our FD CP OCT system are described in Ref [9], shown in Fig 1.The reference surface is at the distal end of probe arm and the interference signal of reference and sample light is detected by a spectrometer. To achieve a broad bandwidth source output, multiple SLEDs were combined to serve as broadband source, which centers at 800nm.…”