Rapid NIR optical tomography at 35 frames per second by spectrally-encoded parallel light delivery

NIR tomography has advanced considerably over the past decade. The historical developments which have led to creation of NIR tomography have largely resulted in systems which were optimized for signal accuracy and high numbers of point measurements, rather than speed of acquisition. One of the key technological designs limiting the acquisition speed is the requirement that the source light be delivered sequentially or through frequency encoding of the time signal. The approach presented here provides a method to introduce all sources and all detectors simultaneously with no moving parts and retaining the dynamic range of the detector, by separating the signals spatially prior to detection. This is achieved by spectral wavelength encoding of the sources, which allows many sources to be input into the tissue at the same time, followed by spectral-decoding of all detection channels in parallel using a spectrometer and CCD detector. A data acquisition speed of 35Hz frame rate has been achieved with this configuration. The described system features 8 sources at an overall 785nm center band and 8 detectors evenly deployed in a 27mm array designed for imaging with small animal tissues. This paper discusses the design, instrumentation of the system, and the imaging characteristics.