Differences in tissue water state have been measured in normal and malignant breast tissues. Broadband
Diffuse Optical Spectroscopy (DOS) has been used to acquire 650-1000 nm absorption spectra of normal
and tumor breast tissues from 7 patients in vivo. The absolute values of spectral differences between
normalized tissue water spectra and pure water spectra were combined and divided by the number of points
in the sum to form the bound water index (BWI). In all subjects, the average BWIs of line scan points were
significantly lower in tumor tissues (1.62 ± 0.27 x10-3) than normal tissues (3.06 ±0.51 x10-3, Wilcoxon
Ranked Sum Test z= 0.003 and power=0.98). These results imply that the water in tumors behaves more
like free water than the water in normal tissue.