A dual-band trans-rectal optical tomography system is constructed based on an endo-rectal near-infrared/ultrasound
applicator that has been developed previously in our laboratory. The endo-rectal NIR/US applicator consists of a
commercial bi-plane ultrasound and a NIR probe attached to the sagittal ultrasound transducer. The NIR probe consists
of 7 illumination & 7 detection channels that are distributed in parallel to and aside the sagittal TRUS transducer. The
emissions from a 780nm and an 830nm light sources are combined and delivered sequentially to the 7 NIR source
channels of the endo-rectal NIR/US probe. The 7 NIR detection channels are coupled to a spectrometer for separation of
the signals at two wavelengths illuminated from single source channel. The dual-band signals from all source channels
are acquired sequentially by a CCD camera synchronized with the source switching. The acquisition of dual-band trans-rectal
optical tomography data is accompanied by position-correlated concurrent trans-rectal ultrasound imaging. The
reconstruction of a target at dual-wavelength illumination is guided by a priori spatial information provided by the
sagittal trans-rectal ultrasound. Liquid phantoms with different hemoglobin concentration and oxygen saturation are used
to test the feasibility of dual-band trans-rectal optical tomography.
Near-infrared optical tomography is an interesting technique of imaging with high blood-based contrast. Unfortunately non-invasive NIR tomographic imaging has been restricted to specific organs like breast that can be transilluminated externally. In this paper, we demonstrate that near-infrared (NIR) optical tomography can be employed at the endoscope-scale, and implemented at a rapid sampling speed that allows translation to in vivo use. A spread-spectral-encoding technique based on a broadband light source is combined with light delivery by linear-to-circular fiber bundle, to provide endoscopic probing of multiple source/detector fibers for tomographic imaging as well as parallel sampling of all source-detector pairs for rapid data acquisition. Endoscopic NIR tomography is demonstrated by use of a 12mm diameter probe housing 8 sources and 8 detectors at 8 Hz frame rate. Transrectal NIR optical tomography by use of tissue specimen is also presented. This novel approach provides the key feasibility studies to allow this blood-based contrast imaging technology to be tried in cancer detection of internal organs via endoscopic interrogation.
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