Optical coherence tomography for experimental neuroendoscopy

Optical coherence tomography (OCT) is a non-invasive and non-contact imaging technology that has been applied to several biomedical applications. We have recently demonstrated that OCT allows discrimination of tumor adjacent brain, diffuse and solid tumor tissue and that this technology may be used to detect residual tumor within the resection cavity during resection of intrinsic brain tumors. Here we show that an OCT integrated endoscope can image the endoventricular anatomy and other endoscopically accessible structures in a human brain specimen. A Sirius 713 optical coherence tomography device was mounted to a modified rigid endoscope. A formalin-fixed human brain specimen was used to simulate endoscopic visualization of brain anatomy and two specimens of fixed malignant tumors with endoventricular growth patterns. Simultaneous OCT imaging and endoscopic video imaging of the visible spectrum was possible using a graded index rod endoscope. OCT imaging of a human brain specimen in water allowed an in-depth view into structures like the walls of the ventricular system, the choroid plexus or the thalamostriatal vein. OCT further allowed imaging of structures beyond tissue barriers or opaque media. In this fixed specimen OCT allowed discrimination of vascular structures down to a diameter of 50 μm. In vessels larger that 100 μm the lumen could be discriminated and within larger blood vessels a layered structure of the vascular wall as well as endovascular plaques could be visualized. This in vitro pilot study has demonstrated that OCT integrated into neuroendoscopes may add information that cannot be obtained by the video imaging alone. This technology may provide an extra margin of safety by providing cross-sectional images of tissue barriers within optically opaque conditions.