FIBER OPTIC RS-OCT PROBE Team Members: John Acevedo Kelly Thomas Chris Miller Advisors: Dr. Patil Dr. Mahadevan-Jansen

Problem Statement  Develop a handheld device that can optically detect cancer in a timely manner

Background  Raman Spectroscopy (RS)  Optical Coherence Tomography (OCT)  RS-OCT  Current probe

Background  Raman Spectroscopy (RS)  Optical Coherence Tomography (OCT)  RS-OCT  Current probe

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 Raman Shift (cm -1 ) = f ( ) – f ( ) 1 0

Background  Raman Spectroscopy  Optical Coherence Tomography  RS-OCT  Current probe

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

Background  Raman Spectroscopy  Optical Coherence Tomography  RS-OCT  Current probe

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

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

Background  Raman Spectroscopy  Optical Coherence Tomography  RS-OCT  Current probe

Current Probe

Sample Arm 5” 8” Current design  Component to be miniaturized  Fiber optic

Design  Design Criteria  Limitations  Specific Aims

Design  Design Criteria  Limitations  Specific Aims

Design Criteria  Decrease size of probe to < 1cm 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

Design  Design Criteria  Limitations  Specific Aims

Limitations  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  Filter out the elastic and inelastic scattering  Match spatial focus of RS and OCT

Design  Design Criteria  Limitations  Specific Aims

Specific Aims 1. Combine RS-OCT techniques into a fiber optic device to replace sample arm of current probe 2. Maximize Raman detection time efficiency 3. Integrate multi-mode and single-mode fibers into probe without compromising RS-OCT functionality

Sample Arm Specifications  Preliminary Design  Electrostatic OCT component  Fiber Optic Outer-Ring RS component  Procedure of probe

Sample Arm Specifications  Preliminary Design  Electrostatic OCT component  Fiber Optic Outer-Ring RS component  Procedure of probe

Preliminary design  Forward facing  Electrostatic scanning probe for OCT component  Located in the center  Fiber-optic outer ring for RS component

Sample Arm Specifications  Preliminary Design  Electrostatic OCT component  Fiber Optic Outer-Ring RS component  Procedure of probe

Specifications  50 µm diameter single mode fiber plus cladding illuminates and detects elastic scattering in the area of interest  Cladding 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 wires with a 270 µm  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  Real-time

Real time Electrodes Fiber – light source and detection Ring of fibers is the RS component

How it works  Electrostatic driven cantilever to create a compact, wide angle, rapid scanning forward viewing probe 1. Cantilever is neutral and is attracted to electrode 2. Cantilever touches electrode and acquires the same potential 3. Charge dissipates from cantilever and repels from electrode 4. Cantilever touches ground and becomes neutral again 5. Process restarts enacting a scanning motion

Sample Arm Specifications  Preliminary Design  Electrostatic OCT component  Fiber Optic Outer-Ring RS component  Procedure of probe

Specifications  Multi-mode fibers (200 µm)set in a ring around the OCT component detect the inelastic scattering in the area of interest  Fibers are angle polished to direct the light into the same area of interest as the OCT image  Four narrow band (785 nm) light sources dispersed evenly around OCT component  Approx. 10 secs Ring indicates OCT Light Source Detection fiber

Sample Arm Specifications  Preliminary Design  Electrostatic OCT component  Fiber Optic Outer-Ring RS component  Procedure of probe

Procedure 1. Turn on OCT component 2. Acquire tomographical map 3. Detect area of interest 4. Turn off OCT component 5. Turn on RS component 6. Acquire biochemical composition of area of interest 7. Turn off RS component

Future work  Improve current design  Build prototype  Test prototype  Evaluate effectiveness  Modify design if needed  Prepare poster presentation

Conclusion  Our novel approach to create a fiber-optic sample arm for an RS-OCT probe plans to be 2000% smaller and 300% more efficient than the current sample arm!

Recommendations  Further increase detection efficiency of Raman to make it real-time  Further decrease sample arm size for endoscopic use

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,

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