Intraoperatively assessed optical properties of malignant and healthy breast tissue used to determine the optimum wavelength of contrast for optical mammography

We use spatially resolved diffuse remittance spectroscopy (DRS) for the measurement of absorption (µa) and reduced scattering (µ) coefficients of normal and malignant breast tissue in vivo during surgery. Prior to these measurements, the linearity of the measurement technique was evaluated on liquid optical phantoms. In addition, the reproducibility of in-vivo tissue measurements was determined on a healthy volunteer. We present results of the in-vivo measurement of optical properties in the wavelength range from 600 to 1100 nm performed during radical mastectomy. A total of 24 patients were included in the study. Both the absorption and reduced scattering properties show large variations. Significant differences in optical properties between normal (glandular plus lipid rich tissue) and tumor tissues are present in 74% of all patients. However, in some cases the tumor showed lower values than normal tissue, and in other cases this was the other way around. Thus, a general trend in optical properties is not observed. However, the average absorption contrast of all patients as a function of wavelength reveals an optimal contrast peak at 650 nm. We believe that this relates to a difference in vascular saturation between tumor and adjacent normal tissue.