By David Tse Mentor: Andreas H. Hielscher, Ph.D Columbia University Biomedical Engineering Department 500 West 120th Street ET351 Mudd Bldg., MC8904 New York, NY 10027

Near Diffuse Optical Tomography is an emerging imaging system that non-invasively analyzes the way light propagates with 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]

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 absorption and scattering properties involved. Created by: David Tse

 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

 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.

 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.

 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

 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.

1. Put intralipid (1%) in cylinder 2. Determine optimal gain settings and save it on LabView 3. Acquire 1000 frames of intralipid 1 for reference 4. Put India ink tube near source 5 5. Put India ink tube near source 7 6. Put India ink tube near source 1

Credits: Hyun Keol Kim, Molly Flexman S1 S5 S7 Observed Data: Expected Data:

1. Put intralipid (1%) in cylinder to the rim of the cylinder 2. Determine optimal gain settings and save it on LabView 3. 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.

 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.

 Professor Andreas H. Hielscher  Molly Flexman  Thomas Poschinger  Biomedical Engineering Department of Columbia University  Harlem Children Society  Dr. Sat Bhattacharya

 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 , aphs/CPS-%20Monographs/CPS-%20(General%20Monographs- aphs/CPS-%20Monographs/CPS-%20(General%20Monographs- 3.%20I)/INTRALIPID.html%20I)/INTRALIPID.html

Thank You!

 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.