Figure 1. Instrument and probe placement.

(a) Diagram of diffuse correlation spectroscopy and probe placement on a breast in sagittal view. Near-infrared light from a 786 nm long coherence laser is delivered to the breast surface via a multi-mode optical fiber (source fiber) attached to a hand-held probe. A single-mode optical fiber (detector fiber) attached to the hand-held probe collects and relays the light signal to a photon-counting avalanche photodiode (APD). An autocorrelator board calculates normalized temporal intensity autocorrelation functions of the detected light and passes the functions onto the computer for further postprocessing. (b) Schematic of probe configuration and its placement on a breast in coronal view. A source-detector separation of 2.5 cm was used in this study.