Date post: | 11-Jan-2016 |
Category: |
Documents |
Upload: | hilda-hunt |
View: | 212 times |
Download: | 0 times |
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
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
Raman SpectroscopyOptical Coherence Tomography
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
Raman SpectroscopyOptical Coherence Tomography
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
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 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
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 secsRing indicates OCTLight 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 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.
Questions?