Two-dimensional phased arrays of sources and detectors for depth discrimination in diffuse optical imaging

We present a multisource, multidetector phased-array approach to diffuse optical imaging that is based on postprocessing continuous-wave data. We previously showed that this approach enhances the spatial resolution of diffuse optical imaging. We now demonstrate the depth discrimination capabilities of this approach and its potential to perform tomographic sectioning of turbid media. The depth discrimination results from the dependence of the sensitivity function on the depth coordinate z. To demonstrate the potential of this approach, we perform an experimental study of a turbid medium containing cylindrical inhomogeneities that are placed 2.0, 3.0, and 4.0 cm from a seven-element, 2-D source array. A single detector element is placed at a distance of 6.0 cm from the source array, and the measurement is repeated after switching the positions of the detector and the source array to simulate the case where both sources and detectors consist of a 2-D array of elements. We find that the proposed phased-array method is able to separate cylinders at different depths, thus showing cross-sectioning capabilities.