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

FIBER OPTIC RS-OCT PROBE

Team Members: John Acevedo Kelly Thomas Chris Miller

Advisors:Dr. PatilDr. 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-OCTCurrent 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 ( )

n1n0

Background

Raman SpectroscopyOptical Coherence Tomography

RS-OCTCurrent 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


RS-OCTCurrent 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


RS-OCTCurrent probe

Current Probe

RSOD1310 nm C

BD

BPF

AI/AODAQ

50/50

785 nmEC

LS

Spectrograph

CCD

Drive Waveform

FS

Sample

ProbeGC

Raman Subsystem

OCT Subsystem

RSOD1310 nm C

BD

BPF

AI/AODAQ

50/50

785 nmEC

LS

Spectrograph

CCD

Drive Waveform

FS

Sample

ProbeGC

Raman Subsystem

OCT Subsystem

Sample Arm

5”

8”

DC 1

DC 2

LP BP

RLD

G

OCT

Raman Excitation

Raman Scatter

F

RC OCT

DC 1

DC 2

LP BP

RLD

G

OCT

Raman Excitation

Raman Scatter

OCT

Raman Excitation

Raman Scatter

F

RC OCT

Current design Component to be miniaturized Fiber optic

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


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


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

Preliminary design

Forward facing Electrostatic scanning probe for OCT

component Located in the center

Fiber-optic outer ring for RS component

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 electrode2. Cantilever touches electrode and acquires the same

potential3. Charge dissipates from cantilever and repels from electrode4. Cantilever touches ground and becomes neutral again5. Process restarts enacting a scanning motion

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 secsRing indicates OCTLight Source

Detection fiber

Procedure

1. Turn on OCT component 2. Acquire tomographical map3. Detect area of interest4. Turn off OCT component5. Turn on RS component6. Acquire biochemical composition of

area of interest7. 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, 657-60.

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

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