NEAR-INFRARED DIFFUSE OPTICAL TOMOGRAPHY
STUDIES ON SMALL ANIMALSBy David Tse
Mentor: Andreas H. Hielscher, Ph.DColumbia University
Biomedical Engineering Department
500 West 120th StreetET351 Mudd Bldg., MC8904New York, NY 10027
Background•Near Diffuse Optical Tomography is an emerging imaging system that non-invasively analyzes the way light propagateswith respect to the absorption and scattering properties of the medium it’s in.•This imaging modality (system) provides access to information about the physiological properties of tissue including: oxyhemoglobin, deoxyhemoglobin, and blood volume with time sensitive resolution.
Figure 1: This is a reconstruction of a mouse a tumor. Notice that the tumor is an absorber of light. [1]
Background cont’d• Access to this knowledge will enable early detection
of, but not limited to: breast cancer, rheumatoid arthritis, diabetes, strokes.
• Images are reconstructed using complex algorithms that model the way light moves through a medium.
Figure 2: Light propagates through a media in a non- linear pathway, often based on the absorptionand scattering properties involved.Created by: David Tse
Optical vs. other imaging modalities?
X-ray/ct Pros: Details physical images Cons: Radiation is ionizing and damages DNA
Ultrasound Pros: No harmful effects, inexpensive, quick and convenient Cons: Resolution is grainy, and can only detect boundaries
MRI Pros: High resolution images Cons: Expensive
Pet Pros: Studies metabolic functions Cons: Expensive, and radioactive material is harmful
Optical Tomography Pros: Provides physiological images of hemodynamics Cons: Resolution is poor
Goals
Big picture: Create a reliable Diffuse Optical Tomography (DOT) system to image finger arthritis and kidney tumors in mice.
Small Picture: 1. Test the system quality when imaging a strong
absorbing substance.2. Determine the effect of temperature on 1%
intralipid.
Hypothesis I believe that the detectors will locate the
absorbing substance, but with moderately low resolution.
Also, as temperature increases, I believe that there will be an increased signal because the medium will become more scattering.
Materials DOT instrument
32 Detectors 16 Sources Computer 2 rings to bring the fibers into contact with the cylinder
1% Intralipid (100 mL) A solution of essential fatty acids that provides
nourishment (intravenously) to patients. In this project, we used it as a scattering medium.
India ink An ink used as a strong absorber in this application
Materials cont’d Caliper
An instrument for making fine size measurements. Microwave Thermometer MatLab program
A software program for analyzing and processing data. LabView program
A software program for collecting and displaying data over time.
Methodology 11. Put intralipid (1%) in cylinder2. Determine optimal gain settings and save it on LabView3. Acquire 1000 frames of intralipid 1 for reference 4. Put India ink tube near source 55. Put India ink tube near source 76. Put India ink tube near source 1
Results
Credits: Hyun Keol Kim, Molly Flexman
S1
S5
S7
Observed Data:
Expected Data:
Methodology 21. Put intralipid (1%) in cylinder to the rim of the cylinder2. Determine optimal gain settings and save it on LabView3. Heat flask with intralipid 1 in a microwave to bring the
temperature up to 37 C. A thermometer is used to verify.4. Acquire 400 frames of intralipid 1 (13 C)5. Acquire 400 frames of intralipid 1 (37 C)6. Repeat step 3 -5 three times.
Results cont’d
Results cont’d
Conclusion We found that we can correctly locate the strong
absorber in the cylinder filled with 1% intralipid using reconstruction algorithms. We are now ready to test the system with other objects
such as: fingers and mice.
Temperature has an effect on the signal of the optical properties of the intralipid (as temperature increases, the signal seems to increase). • The effect of this is conclusion is to be careful of the
temperature of the intralipid in future experiments—temperature must remain constant.
Acknowledgments Professor Andreas H. Hielscher Molly Flexman Thomas Poschinger Biomedical Engineering Department of
Columbia University Harlem Children Society Dr. Sat Bhattacharya
References Websites:
J. Masciotti et al, “ Monitoring Tumor Growth and Treatment in Small Animals with Magnetic Resonance and Optical Tomographic Imaging,” Proc of SPIE Vol. 6081, 2006
A.H. Hielscher et al, “Near-Diffuse Optical Tomography,” Disease Markers 18, pp.313-337, 2002
1. http://neuroimage.usc.edu/images/mouse1_small.jpg2. http://www.rxmed.com/b.main/b2.pharmaceutical/b2.1.mon
ographs/CPS-%20Monographs/CPS-%20(General%20Monographs-
3. %20I)/INTRALIPID.html
Thank You!
Reconstruction Two theories of light transfer:
Diffusion: simpler to implement, like diffusion of a dye through water – acceptable for fairly homogeneous media
Radiative transport Much more complicated algorithm – important
for very inhomogeneous media Complexity arises from the fact that it is an ill-
posed problem.
