Development of a multi-channel time-domain fluorescence mammograph

摘要

We developed an eight-channel scanning time-domain fluorescence mammograph capable of imaging the distribution of a non-specific fluorescent contrast agent in the female breast, besides imaging intrinsic absorption and scattering properties of healthy breast tissue and tumors. The apparatus is based on the PTB multi-channel laser pulse mammograph, originally designed for measurements of absorption and scattering coefficients at four selected wavelengths (λ = 652 nm, 684 nm, 797nm, and 830 nm). It was upgraded for time-resolved detection of fluorescence, excited at 735 nm by a ps diode laser with 10 mW output power and detected at wavelengths λ ≥ 780 nm. Cooled PMTs with GaAs photocathodes are used to detect laser and fluorescence photons at five positions in transmission and three positions in reflection. Measurements are performed with the breast being slightly compressed between two parallel glass plates. The transmitting and receiving fiber bundles are scanned synchronously over the breast in steps of typically 2.5 mm. At each scan position, distributions of times of flight of laser photons are measured by time-correlated single photon counting at eight detector positions, followed by measurements of distributions of times of arrival of fluorescence photons. The performance of the fluorescence mammograph was investigated by using breast-like phantoms with a fluorescent inhomogeneity with dye enrichment varying between 2:1 and 10:1 over background values.