16 - Optical Mammography

Abstract

This chapter provides an overview of optical mammography, a potentially powerful imaging modality for the human breast providing diagnostic information that is not available from other current imaging tools. Optical mammography plays an important clinical role as a stand-alone technique for breast cancer detection (especially in younger women) or for follow-up to treatment and can effectively complement other diagnostic imaging modalities such as X-ray mammography, ultrasound imaging, and magnetic resonance imaging. For breast optical tomography, the geometry of illumination and collection is more complex than for projection imaging, with a number of possible arrangements. For parallel-plate geometry, more illumination and collection points are used at the planes of illumination and collection, whereas for a circular geometry, arrays of illumination and collection optical fibers are arranged around the pendulous breast. The larger number of illumination and collection points yields data that is suitable for tomographic image reconstruction of the breast optical properties. Time-dependent methods, where the light source emission is not constant with time and the optical detection is time-resolved, afford the measurement of absorption and scattering features of breast tissue. Time-domain optical mammography is applied in several clinical trials according to the measurement scheme where the slightly compressed breast is raster-scanned in transmission geometry, and time-domain data are collected at every measurement position. Spectral information is obtained by injecting picosecond pulses at different wavelengths and collecting independently each of the transmitted pulses. The frequency-domain approach is based on modulating the intensity of the light source (at a frequency f that is typically in the order of 100 MHz) and performing phase-sensitive detection of the modulated optical signal.