This study aimed to noninvasively measure tissue perfusion in humans in response to nitric oxide inhibition and inhalation using hyperspectral imaging. The study involved 9 healthy nonsmoking subjects who were given an NO inhibitor while hyperspectral images were collected, followed by inhalation of NO gas. The imaging system allowed for spectroscopic determination of hemoglobin oxygen saturation levels. Results showed changes in hemoglobin levels and tissue perfusion in response to NO inhibition and inhalation. Noninvasive hyperspectral imaging provides a method to assess spatial and temporal changes in perfusion that could help evaluate vascular diseases and treatments.

1. Noninvasive Determination of Spatially Resolved and Time-Resolved Tissue Perfusion in Humans During Nitric Oxide Inhibition and Inhalation by Use of a Visible-Reflectance Hyperspectral Imaging Technique Karel J. Zuzak ,at all ( Circulation. 2001;104:2905-2910.)

2. Nitric Oxide (NO) Endothelium-derived relaxing factor (EDRF)

3. NADPH O 2 + Production of NO

4. Effector mechanisms of NO Ca 2+ NO-dependent Vasodilators -Acetylcholine -Bradykinin Blood Flow Shearing Forces R Endothelial Cell Smooth Muscle Cell NOS GC cGMP Lumen Ca 2+ K +

5. Cardiovascular disease Diabetes mellitus Type I,II Cardiovascular disease Endothelial dysfunction

10. Methods Noninvasively Real time in vivo

11. Spectroscopic Determination of Percentage of HbO2 541 576 555

12. Imaging system. Liquid crystal tunable filter (LCTF) Charge-coupled device detector (CCD) Analog-to-digital converter (ADC)

13. Instrumentation A quartz tungsten halogen light source (Oriel Instruments) A mirror ,Liquid crystal tunable filter(LCTF) (Cambridge Research and Instrumentation) Lens (Nikon) CCD detector (Roper Scientific) GX1P computer (Dell)

14. Spectroscopic Determination of Percentage of HbO 2 Reference spectra of a 100% HbO 2 and deoxy-Hb Standard methods using blood collected from a healthy, nonsmoking 7 mL of hemolysates was mixed with 30 mg of sodium dithionite The HbO 2 spectrum displays distinct peaks at 541 and 576 nm Deoxy-Hb displays a single peak at 555 nm

15. Study Population 9 nonsmoking healthy (5 men and 4 women) Average age of 32±4 years Clinical history, physical examination ECG, and routine laboratory analyses No evidence of cardiovascular disease

16. Protocol refrained drinking alcohol and beverages containing caffeine for ≥12 hours

17. Protocol 1. breathed room air Tem~22°C 5% dextrose in water (D5W) 1 mL/min NG-monomethyl-L-arginine (L-NMMA) 4 to 8 mol/min 20 min 2. NO 80 ppm blood flow was measured by venous occlusion plethysmography(Hokanson) NOS inhibitor during which time hyperspectral images were collected

18. Statistical Analysis Differences between population means were compared by a 2-tailed

19. Results

22. Results

23. Results

24. Discussion Noninvasive techniques for providing rapid, repetitive assessment of tissue perfusion could be of considerable utility in the management of a variety of vascular diseases. In addition to assessing and quantifying the concentration of a specific chemical species, such as HbO 2 and deoxy-Hb,

25. Discussion hyperspectral imaging provides representations of the spatial distribution of a molecular species at a given time or over time. Accordingly, acquisition of a time-resolved profile representing the spatial dynamics of physiologically important molecules indicative of tissue perfusion could prove useful in assessing the efficacy of a given therapeutic intervention on vascular disease.

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