Optical EngineeringRemote semiquantitative two-dimensional flow transport imaging using microendoscopic probes
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A flexible microscope is configured, evaluated, and employed in the noninvasive investigation of fluid transport in a tissuelike model or porous, fibrous matrix. A simple optical configuration that employs microendoscopic probes, an objective lens, and a commercial CCD for detection, produces resolution performance in the range of 25 to 40 line pairs/mm (lp/mm). Remote, time-sequenced imaging is shown to be possible using this moderate resolution flexible microscope. The microendoscopes employed are 1 to 3 m in length and range in outer diameter from 1.5 to 2.5 mm; some contain a working lumen for the introduction of a tool or a fluid at the site of investigation. Target lighting is accomplished by an integral fiber bundle built into the endoscope and supplied from an external xenon discharge lamp. This instrumentation is combined with specialized image processing for quantitative, time-sequenced imaging of marker dye transport on a tissuelike model substrate. Quantitative absorbance imaging is accomplished by calibrating response for marker dye standards on the test substrate and correlating camera pixel grayscale values to solute concentration. The quantitative mapping (concentration versus time and position) of fluid transport is used to evaluate convective versus diffusive flow.