Near-infrared Diffuse Optical Tomography studies on small animals

1. Near-infrared Diffuse Optical Tomography studies on small animals By David Tse Mentor: Andreas H. Hielscher, Ph.D Columbia University Biomedical Engineering Department 500 West 120th StreetET351 Mudd Bldg., MC8904New York, NY 10027

2. Background • 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]

3. 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 absorption and scattering properties involved. Created by: David Tse

4. 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

5. Goals • Big picture: Create a reliable Diffuse Optical Tomography (DOT) system to image finger arthritis and kidney tumors in mice. • Small Picture: • Test the system quality when imaging a strong absorbing substance. • Determine the effect of temperature on 1% intralipid.

6. 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.

7. 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

8. 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.

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

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

11. Methodology 2 • Put intralipid (1%) in cylinder to the rim of the cylinder • Determine optimal gain settings and save it on LabView • Heat flask with intralipid 1 in a microwave to bring the temperature up to 37 C. A thermometer is used to verify. • Acquire 400 frames of intralipid 1 (13 C) • Acquire 400 frames of intralipid 1 (37 C) • Repeat step 3 -5 three times.

12. Results cont’d

13. Results cont’d

14. 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.

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

16. 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 http://neuroimage.usc.edu/images/mouse1_small.jpg http://www.rxmed.com/b.main/b2.pharmaceutical/b2.1.monographs/CPS-%20Monographs/CPS-%20(General%20Monographs- %20I)/INTRALIPID.html

17. Thank You!

18. 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.