Video-rate near infrared tomography for imaging thick tissue with dynamically varying absorption properties

摘要

A near-infrared (NIR) tomography system has been built to allow for imaging thick tissue at high frame rate. This tomography system uses a spectrally encoded source arrangement consisting of eight fibers coupled from temperature controlled single mode laser diode sources with about 1 nm spacing in their lasing wavelengths, having an overall spectrum confined to within 10 nm in the NIR region. Eight fiber-coupled, high-resolution, CCD based spectrometers were used to detect the intensities and decode their source origin locations. All detection CCDs were frame-synchronized using a computer controlled external TTL trigger circuit in order to preserve the temporal kinetics of the detected signals. A set of static heterogeneous phantom imaging was performed on a 64 mm thick resin phantom to verify the linearity and accuracy of the system and algorithm. Furthermore, to test the performance of this system at high frame rate, a dynamically varying absorption contrast study was realized by letting India ink diffuse into the phantom inclusion while continuously imaging it at 20 frames per second. The algorithm and the results from these phantom studies are presented. The 20 frames/second exposure rate and ability to image tissue beyond 60 mm thick makes this system perfect for potential clinical imaging of pulsatile hemodynamics in breast tumors.