Contrast Enhancement by Edge Effect Corrections in Frequency-domain Optical Mammography

Abstract

The planar tandem scan of light source and optical detector in a transmission geometry produces 2-D projection images of the human breast. This approach to near-infrared optical mammography suffers from the strong influence of edge effects: breast thickness variability, lateral photon losses, and variability in the optical coupling with breast tissue. Taking advantage of the information content of frequency-domain data, we have developed an algorithm for the correction of edge effects which is based on data at a single wavelength. We compare the images yielded by this single-wavelength algorithm with those provided by the ratio of the ac amplitudes at two wavelengths. The edge correction is excellent in both cases. However, the tumor detectability in the optical mammogram of a human breast affected by cancer is significantly better in the single-wavelength edge corrected image. We attribute this result to the similar effect caused by the tumor on the ac signal at the two wavelengths employed in this study (685 and 825 nm).