FIBER OPTIC RS-OCT PROBE

John Acevedo Kelly Thomas Chris MillerAdvisors: Dr. PatilDr. Mahadevan-Jansen

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

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

Dr. Patil’s RS-OCT 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

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

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

Problem Statement

5”

8”

Miniaturizing sample arm of current RS-OCT probe

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

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

Spectrograph

CCD

785 nm

7300 mm

fibers

BPfilter

Notchfilters

Psample = 80 mWtacq < 5 sec

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

Current Design

Forward facing Electrostatic scanning probe for OCT

component Located in the center

Fiber-optic array for RS component

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).

Electrostatic OCT component Electrostatic driven cantilever to create a compact, wide

angle, rapid scanning forward viewing probe1. Cantilever is neutral and is attracted to electrode2. Cantilever touches electrode and acquires the same

potential3. Charge dissipates through the polymer from the cantilever

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

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

Highest concentration of collection

OCT

Future work

Build prototype Test prototype Evaluate effectiveness Improve design by adding more

collection fibers Creating SolidWorks 3D design Prepare poster presentation

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

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.

Questions?

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

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

diseasesRaman Shift (cm-1) = f ( ) – f ( )

n1n0

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