Fiber Optic RS-OCT probe - PowerPoint PPT Presentation

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Fiber Optic RS-OCT probe

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Fiber Optic RS-OCT probe

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  1. Fiber Optic RS-OCT probe Advisors: Dr. Patil Dr. Mahadevan-Jansen John Acevedo Kelly Thomas Chris Miller

  2. Epithelial cancer types • Epithelium – cells that line hollow organs and make up the outer surface of the body (skin) • Basal Cell Carcinoma: • 1 million new cases are diagnosed each year in the U.S. • The basal cells line the deepest layer of the epidermis • Squamous Cell Carcinoma: • More than 700,000 new cases are diagnosed every year. • Chronic exposure to sunlight is the cause of most squamous cell carcinoma and basal cell carcinoma. • Optical imaging such as Optical Coherence Tomography (OCT) can noninvasively serve as a diagnostic and monitoring tool of epithelial cancers, and can evaluate therapeutic responses

  3. RS and OCT are complimentary Optical Coherence Tomography • Strengths • Micron-scale structural resolution • Real-time imaging speeds • Limitations • Insensitive to tissue biochemical composition Raman Spectroscopy • Strengths • Biochemical Specificity • Limitations • No spatial Information • Susceptible to sampling error

  4. Dr. Patil’s RS-OCT probe

  5. Procedure • Turn on OCT component • Acquire tomographical map • Detect area of interest • Turn off OCT component • Turn on RS component • Acquire biochemical composition of area of interest • Turn off RS component

  6. Reason for fiber optic RS-OCT probe • Improve detection and diagnosis of cancer • Hand held device will facilitate the use RS-OCT probe • A fiber optic probe will decrease the size of the current probe • Potential endoscopic use, non-invasive • Cost effective

  7. 8” 5” Problem Statement • Miniaturizing sample arm of current RS-OCT probe

  8. Design Criteria • Meet existing RS-OCT probe performance and functionality • Decrease size of probe to < 1 cm in diameter • Reach a scan rate of RS and OCT to 4 frames per second • Reach a scan range of at least 3 mm depth • OCT sensitivity of -95 dB • RS collection efficiency of 10 seconds • Spot size for OCT should be < 50 microns Determined by depth of focus

  9. RS and OCT existing designs Raman Spectroscopy • Current Probe Design • Direct light source surrounded by 7 detection fibers Optical Coherence Tomography • Current Probe Design • Forward facing • Bundle-based • MEMS mirror BP filter 785 nm Notch filters Spectrograph 7 300 mm fibers CCD Psample = 80 mW tacq < 5 sec

  10. Challenges • Quality compensation from combining RS and OCT • RS requires narrow band of light source and multi-mode fibers for optimum specificity • OCT requires broad band of light source and single-mode fibers for optimum specificity • Develop scanning technique for the OCT probe in such a small area • Spatial registration of RS and OCT data sets • Obtaining material for tests

  11. Current Design • Forward facing • Electrostatic scanning probe for OCT component • Located in the center • Fiber-optic array for RS component

  12. Electrostatic OCT component • 125 µm diameter single mode fiber illuminates and detects elastic scattering in the area of interest • Fiber placed in 250 µm diameter platinum alloy coil • Placed in the center of 400 µm diameter lumen of a triple lumen catheter • Two peripheral lumens contain 270 µm diameter wires • One serves as electrode and the other serves as ground leads • Driven by DC power supply, <5 µA, 1-3 kV • 1310 nm light source - broadband Munce, N.R. and Yang, V.X.D. et al. (2008).

  13. Electrostatic OCT component • Electrostatic driven cantilever to create a compact, wide angle, rapid scanning forward viewing probe • Cantilever is neutral and is attracted to electrode • Cantilever touches electrode and acquires the same potential • Charge dissipates through the polymer from the cantilever and repels from electrode • Cantilever touches ground and becomes neutral again • Process restarts enacting a scanning motion

  14. Fiber Optic Array RS Component • Multi-mode fibers (200 µm)set on either side of the OCT scanning fiber • One narrow band (785 nm) light sources on one side Light source Collection OCT Highest concentration of collection

  15. Future work • Build prototype • Test prototype • Evaluate effectiveness • Improve design by adding more collection fibers • Creating SolidWorks 3D design • Prepare poster presentation

  16. Current Progress • Voltage source and optical fibers have been obtained • Platinum coil or suitable replacement is needed • Find a suitable replacement for dissipative polymer if polymer cannot be obtained • Capacitor, resistor, inductor

  17. References • Patil, C.A. (2009). Development combined raman spectroscopy-optical coherence tomograpgy for the detection of skin cancer. Disertation submitted to faculty of Graduate school of Vanderbilt University. • Munce, N.R. and Yang, V.X.D. et al.(2008). Electrostatic forward-viewing scanning probe for doppler optical coherence tomography using a dissipative polymer catheter. Optical letters, 33, 7, 657-60.

  18. Questions?

  19. Specific Aims • Combine RS-OCT techniquesinto a fiber optic device to replace sample arm of current probe • Maximize Raman detection time efficiency • Integrate multi-mode and single-mode fibers into probe without compromising RS-OCT functionality

  20. Raman Spectroscopy • Inelastic scattering (Stokes and Anti-Stokes) • Occurs 1 in 10 million compared to elastic • Frequency of light scattered from a molecule dependent on structural characteristics of molecular bonds • Able to determine malignant from non-malignant tissue • Gives no spatial information • All sorts of epithelial diseases n0 n1 Raman Shift (cm-1) = f ( ) – f ( )

  21. Optical Coherence Tomography (OCT) • Sensitivity to microstructural features of disease • Measures tissue reflectivity as function of depth • Detects elastic scattering • Ability to image over transverse areas of tissue of greater than 5mm • Micron scale resolution (>25µm) • Real-time speed