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Figure 5 Demonstration of spectral findings in the left anterior descending (LAD) coronary artery of a patient with stable angina pectoris (unpublished data, on file InfraReDx, Inc., Burlington, Massachusetts). A spectral scan of the LAD was performed during percutaneous coronary intervention. An analysis was performed of all spectra to determine the shapes (principal components) that contribute to the spectra obtained in each data point as the catheter scanned the artery. The top graph shows a shape of biologic interest that contributed to the individual spectra in varying degrees. The shape was not detected in a sample of blood only. The bottom graph shows the amount of that shape that was detected at each pixel as the catheter was pulled back (x-axis) and rotated (y-axis) within the coronary artery. The white areas indicate locations from which the shadow created by the guide wire was removed. Although interpretation of the spectral findings is not yet complete and a validated algorithm has not yet been applied to the data, the display shows the ability of the near-infrared (NIR) system to obtain relevant NIR signals from the coronary artery of a patient, despite the presence of cardiac motion and flowing blood. LV = loading vector; PCA = principal component analysis.