A parallel-detection frequency-domain near-infrared tomography system for hemoglobin imaging of the breast in vivo

A novel near-infrared frequency-domain system designed for tomographic brea st imaging is described. The setup utilizes five optical wavelengths, from 660 to 826 nm, and parallel detection with 16 photomultiplier tubes. Direct fiberoptic coupling with the tissue is achieved with a high precision posi tioning device using 16 motorized actuators (0.5 mum precision) arranged ra dially in a circular geometry. Images of breast tissue optical absorption a nd reduced scattering coefficients are obtained using a Newton-type reconst ruction algorithm to solve for the optimal fit between the measurement data and predicted data from a finite element solution to the frequency-domain diffusion equation. The design, calibration, and performance of the tomogra phic imaging system are detailed. Data acquisition from the system requires under 30 s for a single tomographic slice at one optical wavelength with a measurement repeatability for a single phantom on average of 0.5% in ac in tensity and 0.4 degrees in phase. Absorbing and scattering phantoms typical of in vivo breast optical properties were imaged over a range of object-to -background contrasts (50%-250%). The reconstructed absorption and scatteri ng images are accurate to within 20% of the expected value. (C) 2001 Americ an Institute of Physics.