Remote-access slit-scanning confocal microscope for in vivo tumor diagnosis

Abstract

Microscopic fluorescence imaging of thick biological tissue has been successfully demonstrated with a fiber-based, slit-scanning, confocal microscope. The system developed under this research consists of an illumination arm, a fiber-optic imaging system, and a detection arm. The illumination arm is an anamorphic optical system that converts a circular, laser beam into a cylindrical beam forming a line image at the proximal face of the fiber-optic relay. This relay system is comprised of a fiber-optic imaging bundle, a miniature objective lens, and a miniature hydraulic positioning mechanism. It delivers illumination to a remote sample and simultaneously collects the fluorescence from the sample. The miniature objective lens and positioning mechanism were specially designed and fabricated for this system, allowing for high resolution imaging and optical sectioning in-vivo. The detection arm relays the fluorescence image at the proximal face of the fiber-optic relay with magnification onto a two-dimensional CCD. Characterization of the system has demonstrated a lateral resolution of three microns. The axial resolution when imaging a point object is 10 microns. When imaging a planar object, the axial resolution is 25 microns. Images are acquired at a rate of 2-4 frames per second and the imaging performance has been evaluated with different biological models including animal peritoneal tissue and human prostate tissue in-vitro. In-vivo images of human skin and rat peritoneum have also been acquired to demonstrate that patient motion does not adversely affect the performance of the system. These in-vitro and in vivo images demonstrate the capability of the system to resolve cell nuclear morphology, to visualize cell density and organization, and to image at selected depths below the tissue surface.