Optical coherence tomography imaging for cancer diagnosis and therapy guidance

Optical Coherence Tomography (OCT) is an emerging optical technology that has shown great promise for early cancer detection. Using backreflected light to visualize tissue microstructure, OCT can provide information on nuclear size and shape, nuclear-to-cytoplasmic ratio, and the organization and structure of glands. It can also provide functional information, like blood flow, tissue birefringence, etc. These capabilities could potentially be employed in three ways: as a primary diagnostic test to replace biopsy, as a screening tool to direct biopsy, and as a diagnostic tool to guide therapy and monitor therapy response. In this paper we present an application of OCT for pancreatic cancer diagnosis and therapy guidance.

Spectral-domain low coherence interferometry/optical coherence tomography system for fine needle breast biopsy guidance

A novel technology and instrumentation for fine needle aspiration (FNA) breast biopsy guidance is presented. This technology is based on spectral-domain low coherence interferometry (SD-LCI). The method, apparatus, and preliminary in vitro/in vivo results proving the viability of the method and apparatus are presented in detail. An advanced tissue classification algorithm, preliminarily tested on breast tissue specimens and a mouse model of breast cancer is presented as well. Over 80% sensitivity and specificity in differentiating all tissue types and 93% accuracy in differentiating fatty tissue from fibrous or tumor tissue was obtained with this technology and apparatus. These results suggest that SD-LCI could help for more precise needle placement during the FNA biopsy and therefore could substantially reduce the number of the nondiagnostic aspirates and improve the sensitivity and specificity of the FNA procedures.

Spectral domain optical coherence tomography for quantitative evaluation of drusen and associated structural changes in non-neovascular age-related macular degeneration

Background/aims:

To demonstrate how spectral domain optical coherence tomography (SDOCT) can better evaluate drusen and associated anatomical changes in eyes with non-neovascular age-related macular degeneration (AMD) compared with time domain optical coherence tomography (TDOCT).

Methods:

Images were obtained from three eyes of three patients with AMD using an experimental SDOCT system. Both a titanium–sapphire (Ti:sapphire) laser and a superluminescent diode (SLD) were used as a broadband light source to achieve cross-sectional images of the retina. A qualitative and quantitative analysis was performed for structural changes associated with non-neovascular AMD. An automated algorithm was developed to analyse drusen area and volume from SDOCT images. TDOCT was performed using the fast macular scan (StratusOCT, Carl Zeiss Meditec, Dublin, California).

Results:

SDOCT images can demonstrate structural changes associated with non-neovascular AMD. A new SDOCT algorithm can determine drusen area, drusen volume and proportion of drusen.

Conclusions:

With new algorithms to determine drusen area and volume and its unprecedented simultaneous ultra-high speed ultra-high resolution imaging, SDOCT can improve the evaluation of structural abnormalities in non-neovascular AMD.

Large depth-high resolution full 3D imaging of the anterior segments of the eye using high speed optical frequency domain imaging

Three dimensional rapid large depth range imaging of the anterior segments of the human eye by an optical frequency domain imaging system is presented. The tunable source spans from 1217 to 1356 nm with an average output power of 60 mW providing a measured axial resolution of 10 mum in air based on the coherence envelope. The effective depth range is 4 mm, defined as the distance over which the sensitivity drops by 6 dB, achieved by frequency shifting the optical signal using acousto-optic modulators. The measured maximum sensitivity is 109 dB at a sample arm power of 14.7mW and A-lines rate of 43,900 per second. Images consisting of 512 depth profiles are acquired at an acquisition rate of 85 frames per second. We demonstrate an optical frequency domain imaging system capable of mapping in vivo the entire area of the human anterior segment (13.4 x 12 x 4.2 mm) in 1.4 seconds.

High-speed imaging of human retina in vivo with swept-source optical coherence tomography

We present the first demonstration of human retinal imaging in vivo using optical frequency domain imaging (OFDI) in the 800-nm range. With 460-muW incident power on the eye, the sensitivity is 91 dB at maximum and >85 dB over 2-mm depth range. The axial resolution is 13 mum in air. We acquired images of retina at 43,200 depth profiles per second and a continuous acquisition speed of 84 frames/s (512 A-lines per frame) could be maintained over more than 2 seconds.

Real-time measurement of the polarization transfer function

We present a simple method for measuring the Mueller matrix associated with a scattering medium. Without involving moving parts, four input states of polarization are generated sequentially, and for each of them all four Stokes vector parameters are simultaneously measured for the complete determination of the Mueller matrix. Two liquid-crystal variable retarders are used for controlling the input state of polarization, whereas the measurement of the state of polarization involves phase modulation with a single-pass photoelastic modulator, and Fourier analysis in two polarization channels. The setup is controlled by a computer, allowing for real-time measurement of the Mueller matrix. The method is tested on standard elements such as polarizers and quarter-wave plates, as well as on inhomogeneous particulate systems.