Raman spectroscopy has the potential to provide real-time, in situ diagnosis of breast cancer during needle biopsy or surgery via an optical fiber probe. Understanding the chemical/morphological basis of the Raman spectrum of breast tissue is a necessary step in developing Raman spectroscopy as a tool for in situ breast cancer diagnosis. To understand the relationship between the Raman spectrum of a sample of breast tissue and its disease state, near-infrared Raman spectroscopic images of human breast tissue were acquired using a confocal microscope. These images were then compared with phase contrast and hematoxylinand eosin-stained images to develop a chemical/morphological model of breast tissue Raman spectra. This model fits macroscopic tissue spectra with a linear combination of basis spectra derived from spectra of the cell cytoplasm, cell nucleus, fat, b-carotene, collagen, calcium hydroxyapatite, calcium oxalate dihydrate, cholesterol-like lipid deposits and water. Each basis spectrum represents data acquired from multiple patients and, when appropriate, from a variety of normal and diseased states. The model explains the spectral features of a range of normal and diseased breast tissue samples, including breast cancer. It can be used to relate the Raman spectrum of a breast tissue sample to diagnostic parameters used by pathologists.

Background-Lesion composition, rather than size or volume, determines whether an atherosclerotic plaque will progress, regress, or rupture, but current techniques cannot provide precise quantitative information about lesion composition. We have developed a technique to assess the pathological state of human coronary artery samples by quantifying their chemical composition with near-infrared Raman spectroscopy. Methods and Results-Coronary artery samples (nϭ165) obtained from explanted recipient hearts were illuminated with 830-nm infrared light. Raman spectra were collected from the tissue and processed to quantify the relative weights of cholesterol, cholesterol esters, triglycerides and phospholipids, and calcium salts in the examined artery location. The artery locations were then classified by a pathologist and grouped as either nonatherosclerotic tissue, noncalcified plaque, or calcified plaque. Nonatherosclerotic tissue, which included normal artery and intimal fibroplasia, contained an average of Ϸ4Ϯ3% cholesterol, whereas noncalcified plaques had Ϸ26Ϯ10% and calcified plaques Ϸ19Ϯ10% cholesterol in the noncalcified regions. The average relative weight of calcium salts was 1Ϯ2% in noncalcified plaques and 41Ϯ21% in calcified plaques. To make this quantitative chemical information clinically useful, we developed a diagnostic algorithm, based on a first set of 97 samples, that demonstrated a strong correlation of the relative weights of cholesterol and calcium salts with histological diagnoses of the same locations. This algorithm was then prospectively tested on a second set of 68 samples. The algorithm correctly classified 64 of these new samples, thus demonstrating the accuracy and robustness of the method. Conclusions-The pathological state of a given human coronary artery may be assessed by quantifying its chemical composition, which can be done rapidly with Raman spectroscopic techniques. When Raman spectra are obtained clinically via optical fibers, Raman spectroscopy may be useful in monitoring the progression and regression of atherosclerosis, predicting plaque rupture, and selecting proper therapeutic intervention. (Circulation. 1998;97:878-885.)