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Near-Infrared Spectroscopy for the Detection of Vulnerable Coronary Artery Plaques

Jay D. Caplan, SB, MBA^_*,a,_*, Sergio Waxman, MD^,,c, Richard W. Nesto, MD^,,c and James E. Muller, MD^_*,b

^_* InfraReDx Inc., Burlington, Massachusetts
Department of Cardiovascular Medicine, Lahey Clinic, Burlington, Massachusetts
Tufts Medical School, Boston, Massachusetts
Harvard Medical School, Boston, Massachusetts

View larger version (25K): [in a new window]   Figure 1 Near-infrared spectra of various pure substances possibly related to plaque vulnerability.

View larger version (94K): [in a new window]   Figure 2 The 3.2-F near-infrared spectroscopy catheter, showing ports for delivery and collection of light. The ruler is marked in centimeters.

View larger version (21K): [in a new window]   Figure 3 Figures of the porcine xenograft model and spectral results, testing the ability of the near-infrared (NIR) system to detect signal despite blood and motion. The spectroscopy catheter was placed in the perfused human coronary artery attached to the surface of a beating porcine heart in an open-chest preparation. The system was able to detect signals through blood from a spectral target on a beating heart similar to those obtained directly from the target without intervening blood or motion.

View larger version (91K): [in a new window]   Figure 4 Figures of the phantom simulating the human coronary artery and thin-cap fibroatheroma targets. The near-infrared spectroscopy catheter was placed in the blood-filled lumen of the phantom and then rotated and pulled back in a test of detection of the spatially resolved targets. The bottom panel shows the results of the scan, with distance along the lumen on the x-axis and arc of rotation on the y-axis. As indicated by the yellow signal, the scan successfully detected all eight targets.

View larger version (44K): [in a new window]   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of spectral findings in the left anterior descending (LAD) coronary artery of a patient with stable angina pectoris (unpublished data, on file InfraReDx, Inc., Burlington, Massachusetts).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.