Photo-Thermal Coherent Confocal Microscope This work is supported in part by the Center for...
1
Photo-Thermal Coherent Confocal Photo-Thermal Coherent Confocal Microscope Microscope This work is supported in part by the Center for Subsurface Sensing and Imaging Systems, under the Engineering Research Centers Program of the National Science Foundation (Award Number EEC-9986821). Enter text and box will expand Introduction Confocal microscopy has been shown to be useful in imaging skin slightly below the junction of the dermis and epidermis. However, the depth of imaging is a significant limitation. We present a novel concept designed both to improve the depth of penetration and to increase the information content of images obtained with a reflectance confocal microscope. Using an approach similar to opto-acoustics, we plan to explore the use of laser heating to generate tissue expansion, which will be measured by the microscope. The microscope will incorporate a pulsed heating laser along the same optical path as the imaging laser in order to generate localized heating. This will result in periodic thermal expansion and contraction at the focus. Optical quadrature detection is used to measure the phase of the scattered light, and Doppler techniques will be employed to quantify the thermal expansion. For the purposes of imaging, two lasers of different wavelengths will be needed to resolve phase ambiguities in the expansion measurement. The motion resulting from thermal expansion will provide additional discrimination against multiply scattered light. It will also provide a measurement of a mechanical parameter, the coefficient of thermal expansion, which may aid in the characterization of different types of tissue. Abstract Confocal Microscopy provides resolutions down to 1μm but has limited depth penetration due to multiple scattering. Beyond 100 μm depth, signal to clutter ratio becomes too small 1 . Optical coherence tomography (OCT) uses coherent detection and has deeper penetration than confocal microscopy, but the resolution is not suitable to view cellular structure 2 . The Photo-Thermal Microscope provides a method to provide deeper penetration while maintaining the spatial resolution of confocal microscopy in applications such as skin imaging. State of the Art Sean Sullivan and Charles DiMarzio Optical Science Laboratory, Northeastern University, Boston, MA [1] J. B. Pawley, ed., “Handbook of Biological Confocal Microscopy”, 3rd ed. (Plenum, New York, 1996). [2] A. F. Fercher, W. Drexler, C. K. Hitzenberger, and T. Lasser, “Optical coherence tomography-principles and applications”, Rep. Prog. Phys. 66 (2003) 239-303. [3] D. O. Hogenboom, and C. A. DiMarzio, “Quadrature Detection of a Doppler Signal”, Applied Optics, 37(13), page 2569, 1998. PI CONTACT INFORMATION Prof. Charles A. DiMarzio, Northeastern University Phone: 617-373-2034 [email protected] References Increase depth of penetration. Filter out the out of focus scattered light. Increase information content by quantifying the coefficient of thermal expansion. Goals Condenser Lens Objective Lens Point Source of Light Point Detector Aperture In-focus plane containing illuminated spot Out-of-focus Planes Preliminary Results 0.042 0.044 0.046 0.048 0.05 0.052 0.054 0.056 0.038 0.04 0.042 0.044 0.046 0.048 0.05 0.052 IC hannel(V ) Q C hannel(V ) P hase W rapping 2*PiW rap S am ple 1 S am ple 2 0 0.2 0.4 0.6 0.8 1 0.0445 0.045 0.0455 0.046 0.0465 0.047 0.0475 M agnitude vs Tim e w ith H eating P ulse forR eference Tim e (m S ec) M agnitude (V ) Magnitude H eating P ulse 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 0.51 0.52 0.53 0.54 0.55 0.56 0.57 0.58 Tim e (m S ec) Phase (Radians) P hase vs Tim e w ith H eating P ulse forR eference P hase Heating Pulse 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.037 0.038 0.039 0.04 0.041 0.042 0.043 Tim e (m S ec) V oltage (V ) C hannelV oltages vs Tim e w ith H eating P ulse forR eference H eating Pulse IC hannel Q C hannel The pulsed heating laser directed along the same path as the imaging laser creates thermal expansion at the focus (shown above). A computer simulation of this process is shown at the upper right, where a pulse excites an expansion to either side of the focus. Using signal processing and Doppler techniques 3 , static scatterers away from the focus are filtered from dynamic scatterrers at the focus. Concept of Photo-Thermal Microscope T e m p e r a t u r e ( m K ) Distance (µm) Heat Source (W/m) Time (µsec) Distance (µm) Temperature Change (mK) Time (µsec) T e m p e r a t u r e ( m K ) Divergence of Position (µm) Time (µsec) T e m p e r a t u r e ( m K ) Radial Distance (µm) Unidirectional Position Change (µm) Time (µsec) T e m p e r a t u r e ( m K ) Distance (µm) The above microscope layout incorporates both heating and imaging lasers. The two combined beams are focused onto the sample, shown in pink. The back-scattered light from the sample returns along the same path until it is separated from the incoming beam at the 50/50 beam splitter, and directed towards the I and Q detectors. Using optical quadrature detection, the phase information can be extracted by mixing the reference beam with the backscattered light. Using Doppler techniques, the thermal expansion at the sample can then be measured using the phase changes for the imaging wavelength. Photo-Thermal Coherent Confocal Microscope Layout Q Detector I Detector PBS QWP 45° Dichroic Heating Laser Laser Controlle r Laser Controlle r Imaging Laser M1 M2 M3 50/50 BS POL 45° Objective Lens Oscilloscope Pinhole A second imaging laser will be added in order to eliminate phase ambiguities. Scanning instrumentation will be added to produce three-dimensional images. OQM configuration will be added to eliminate the DC terms of the interference. Future Work Our laboratory collaborates with skin-cancer researchers at Memorial Sloan Kettering Cancer Center, and with a manufacturer of commercial confocal microscopes. Members of these groups meet formally twice a year, and informally several times. The present research has been presented at these meetings and, if it proves successful, portions of it will be selected for development and technology transfer. Technology Transfer Significance to CenSSIS V alidating TestB ED s R1 R2 Fundam ental Science R3 S 1 S 4 S 5 S 3 S 2 B io-M ed Enviro- C ivil V alidating TestB ED s V alidating TestB ED s V alidating TestB ED s V alidating TestB ED s V alidating TestB ED s V alidating TestB ED s V alidating TestB ED s R1 R1 R1 R2 R2 R2 Fundam ental Science Fundam ental Science Fundam ental Science Fundam ental Science Fundam ental Science Fundam ental Science R3 R3 R3 S 1 S 4 S 5 S 3 S 2 B io-M ed Enviro- C ivil S 1 S 1 S 1 S 4 S 4 S 4 S 5 S 5 S 5 S 3 S 3 S 3 S 2 S 2 S 2 B io-M ed Enviro- C ivil Photo- therm al Photo- therm al Photo- therm al C onfoca l C onfoca l C onfoca l O ptical Q uadrature O ptical Q uadrature O ptical Q uadrature Betterskin im ages Betterskin im ages
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Transcript of Photo-Thermal Coherent Confocal Microscope This work is supported in part by the Center for...
Photo-Thermal Coherent Confocal MicroscopePhoto-Thermal Coherent Confocal Microscope
This work is supported in part by the Center for Subsurface Sensing and Imaging Systems, under the Engineering Research Centers Program of the National Science Foundation (Award Number EEC-9986821).
Enter text and box will expand
IntroductionIntroduction
Confocal microscopy has been shown to be useful in imaging skin slightly below the junction of the dermis and epidermis. However, the depth of imaging is a significant limitation. We present a novel concept designed both to improve the depth of penetration and to increase the information content of images obtained with a reflectance confocal microscope. Using an approach similar to opto-acoustics, we plan to explore the use of laser heating to generate tissue expansion, which will be measured by the microscope. The microscope will incorporate a pulsed heating laser along the same optical path as the imaging laser in order to generate localized heating. This will result in periodic thermal expansion and contraction at the focus. Optical quadrature detection is used to measure the phase of the scattered light, and Doppler techniques will be employed to quantify the thermal expansion. For the purposes of imaging, two lasers of different wavelengths will be needed to resolve phase ambiguities in the expansion measurement. The motion resulting from thermal expansion will provide additional discrimination against multiply scattered light. It will also provide a measurement of a mechanical parameter, the coefficient of thermal expansion, which may aid in the characterization of different types of tissue.
AbstractAbstract
Confocal Microscopy provides resolutions down to 1μm but has limited depth penetration due to multiple scattering. Beyond 100 μm depth, signal to clutter ratio becomes too small1.
Optical coherence tomography (OCT) uses coherent detection and has deeper penetration than confocal microscopy, but the resolution is not suitable to view cellular structure2.
The Photo-Thermal Microscope provides a method to provide deeper penetration while maintaining the spatial resolution of confocal microscopy in applications such as skin imaging.
State of the ArtState of the Art
Sean Sullivan and Charles DiMarzioOptical Science Laboratory, Northeastern University, Boston, MA
[1] J. B. Pawley, ed., “Handbook of Biological Confocal Microscopy”, 3rd ed. (Plenum, New York, 1996).[2] A. F. Fercher, W. Drexler, C. K. Hitzenberger, and T. Lasser, “Optical coherence tomography-principles and applications”, Rep. Prog. Phys. 66 (2003) 239-303.[3] D. O. Hogenboom, and C. A. DiMarzio, “Quadrature Detection of a Doppler Signal”, Applied Optics, 37(13), page 2569, 1998.
PI CONTACT INFORMATIONProf. Charles A. DiMarzio, Northeastern University
Phone: 617-373-2034 [email protected]
ReferencesReferences
Increase depth of penetration.
Filter out the out of focus scattered light.
Increase information content by quantifying the coefficient of thermal expansion.
GoalsGoals
Condenser Lens Objective Lens
Point Sourceof Light
Point Detector Aperture
In-focus plane containing illuminated spot
Out-of-focus Planes
Preliminary ResultsPreliminary Results
0.042 0.044 0.046 0.048 0.05 0.052 0.054 0.056
0.038
0.04
0.042
0.044
0.046
0.048
0.05
0.052
I Channel (V)
Q C
hann
el (
V)
Phase Wrapping
2*Pi Wrap
Sample 1
Sample 2
0 0.2 0.4 0.6 0.8 10.0445
0.045
0.0455
0.046
0.0465
0.047
0.0475
Magnitude vs Time with Heating Pulse for Reference
Time (mSec)
Mag
nitu
de (
V)
Magnitude
Heating Pulse
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.5
0.51
0.52
0.53
0.54
0.55
0.56
0.57
0.58
Time (mSec)
Pha
se (
Rad
ians
)
Phase vs Time with Heating Pulse for Reference
Phase
Heating Pulse
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.037
0.038
0.039
0.04
0.041
0.042
0.043
Time (mSec)
Vol
tage
(V
)
Channel Voltages vs Time with Heating Pulse for Reference
Heating Pulse
I Channel
Q Channel
The pulsed heating laser directed along the same path as the imaging laser creates thermal expansion at the focus (shown above).
A computer simulation of this process is shown at the upper right, where a pulse excites an expansion to either side of the focus.
Using signal processing and Doppler techniques3, static scatterers away from the focus are filtered from dynamic scatterrers at the focus.
Concept of Photo-Thermal MicroscopeConcept of Photo-Thermal Microscope
Tem
perature (mK
)
Distance (µm)
Heat Source (W/m)
Tim
e (µ
sec)
Distance (µm)
Temperature Change (mK)
Tim
e (µ
sec)
Tem
perature (mK
)
Divergence of Position (µm)
Tim
e (µ
sec)
Tem
perature (mK
)
Radial Distance (µm)
Unidirectional Position Change (µm)
Tim
e (µ
sec)
Tem
perature (mK
)
Distance (µm)
The above microscope layout incorporates both heating and imaging lasers. The two combined beams are focused onto the sample, shown in pink. The back-scattered light from the sample returns along the same path until it is separated from the incoming beam at the 50/50 beam splitter, and directed towards the I and Q detectors. Using optical quadrature detection, the phase information can be extracted by mixing the reference beam with the backscattered light. Using Doppler techniques, the thermal expansion at the sample can then be measured using the phase changes for the imaging wavelength.
Photo-Thermal Coherent Confocal Microscope LayoutPhoto-Thermal Coherent Confocal Microscope Layout
Q Detector
I Detector
PBS
QWP 45°
Dichroic
Heating LaserLaser
Controller
Laser Controller
Imaging Laser
M1M2
M3
50/50 BS
POL 45°
Objective Lens
Oscilloscope
Pinhole
A second imaging laser will be added in order to eliminate phase ambiguities.
Scanning instrumentation will be added to produce three-dimensional images.
OQM configuration will be added to eliminate the DC terms of the interference.
Future WorkFuture Work
Our laboratory collaborates with skin-cancer researchers at Memorial Sloan Kettering Cancer Center, and with a manufacturer of commercial confocal microscopes. Members of these groups meet formally twice a year, and informally several times. The present research has been presented at these meetings and, if it proves successful, portions of it will be selected for development and technology transfer.
Technology Transfer Technology Transfer
Significance to CenSSISSignificance to CenSSIS
ValidatingTestBEDs
R1
R2FundamentalScience
R3
S1
S4
S5
S3
S2
Bio-Med Enviro-Civil
ValidatingTestBEDsValidatingTestBEDsValidatingTestBEDsValidatingTestBEDsValidatingTestBEDsValidatingTestBEDsValidatingTestBEDs
R1R1R1
R2R2R2FundamentalScienceFundamentalScienceFundamentalScienceFundamentalScienceFundamentalScienceFundamentalScience
R3R3R3
S1
S4
S5
S3
S2
Bio-Med Enviro-Civil
S1S1S1
S4S4S4
S5S5S5
S3S3S3
S2S2S2
Bio-Med Enviro-Civil
Photo-thermalPhoto-
thermalPhoto-
thermal
ConfocalConfocalConfocal
Optical Quadrature
Optical Quadrature
Optical Quadrature
Better skin imagesBetter skin images
