Optical Coherence Tomography (OCT)

for noninvasive optical biopsy by structural and functional (blood flow) imaging at architectural level (2-20 μm resolution, 0.5-3 mm imaging depth)

Overview:

OCT can be envisioned as an optical analog of ultrasound except that it utilizes near infrared light rather than sound. As shown in the schematic (Fig.1), an OCT system includes a low coherence light source, an interferometer, a reference arm, an imaging probe delivering/collecting light to/from the sample (sample arm), and an optical detection system. Light source is a critical component in an OCT system, of which the spectrum bandwidth Δλ governs OCT axial resolution Δz (i.e. Δz = 2 ln 2λ²/πΔλ). Miniature flexible imaging probe is another critical component for enabling OCT imaging of internal organs.

Figure 1. Schematic of a fiber-optic OCT system. (Click to view detailed caption)

Our research focuses on development of:

  1. High-resolution imaging probes with aberration management, including side-viewing endoscope/catheter (see Fig.2) for intraluminal imaging, ultrathin (22-27 Gauge) imaging needle (see Fig.3) for interstitial imaging of solid organs, and forward-viewing scanning endoscope for 3D imaging of internal organs and guidance of biopsy;

Figure 2. Schematic and Photo of an OCT endoscope/catheter. (Click to view detailed caption)

Figure 3. Schematic and photo of an ultrathin OCT imaging needle (22-27 gauge). (Click to view detailed caption )

  1. Light sources such as broadband solid state lasers and high-speed swept fiber lasers (note: OCT A-scan rate equals to wavelength sweeping rate);

Figure 4. Spectrum of a home-built broadband solid-state laser and the corresponding OCT axial point-spread function. (Click to view detailed caption)

Figure 5. Spectrum of a home-built swept fiber laser and the corresponding OCT axial point-spread function. (Click to view detailed caption)

  1. Technologies to enable uniform data sampling in frequency domain as required for high-speed Fourier transform of the data in order to obtain accurate structural and blood flow images in real time (see Fig.6);

Figure 6. Illustration of uniform-K (spatial frequency domain) data sampling. (Click to view detailed caption)

  1. Methods for high-speed data acquisition, processing and storage to handle high-speed A-scan and data rate (400 MB/sec and above); and
  2. Imaging contrast agents, such as bio-functionalized gold nanoparticles appropriate for detection at different wavelengths to enhance the contrast and potentially molecular specificity of OCT imaging.

Figure 7. Representative OCT images. (Click to view detailed caption )

  1. Development of second generation ultrahigh resolution OCT endoscopy at a central wavelength of ~800 nm with chromatic aberration management in side-viewing endoscopes for 3D volumetric intraluminal imaging.

Figure 8. Ultrahigh resolution spectral domain OCT system with corresponding OCT axial point spread function.

Figure 9. Ultrahigh resolution diffractive catheter design and performance. (Click to view detailed caption )



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