In vivo microendoscopy for imaging deep regions of the brain

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The ability to image individual cells deep within the mammalian brain will open new research opportunities in both basic and clinical science. Current brain imaging techniques do not provide high-resolution images of the tissues. For example, brain scanning techniques such as magnetic resonance imaging (MRI) only achieve a resolution of a few millimeters. Within such an area there may be several thousand cells, each performing a unique task. Although modern light microscopes can achieve the resolution needed to see individual cells they can only visualize objects placed immediately in front of the microscope lens. Recall how frustrating it was in biology class to find the cells on the microscope slide! To create a method capable of imaging deep within the brain, that can also observe what single cells are doing, will require a new optical device. The internet boom has not only brought an enormous wealth of information to our fingertips but has driven the telecommunications industry to achieve significant developments in the area of micro-optics. Gradient refractive index (GRIN) lenses, in which light is guided as a consequence of the internal variations in optical medium, are now produced cheaply and with sub-millimeter dimensions. Currently the smallest GRIN lenses have the diameter of a human hair, around100 microns. Unlike traditional lenses, GRIN lenses are not ground to shape but generated by doping glass that can then be extruded to the desired diameter. A little like the method used to introduce the letters to seaside rock. Due to their tiny dimensions, GRIN lenses can be used to produce miniature endoscopes. GRIN lens based endoscopes will, like a traditional endoscope be able to achieve access to remote parts of the body, however , a GRIN lens endoscope will be minimally invasive as a consequence of being so small. Thus by combining key characteristics of these devices it will be possible to image individual cells within previously inaccessible parts of the brain.