Confocal device and application strategies for endoluminal optical coherence microscopy

摘要

While endoscopic optical coherence tomography has been established successfully in vivo, implementation of endoluminal optical coherence microscopy remains demanding, as a suitable confocal probe is lacking. A miniaturized confocal laser scanning microscope is presented, which fulfills the requirements for endoluminal optical coherence microscopy. First, imaging experience gained for optical coherence microscopy of animal gastrointestinal tissue samples is described. For this purpose, a laboratory scale optical coherence microscope with an image acquisition time of 1 min 30 s was employed. Cellular membranes can be identified throughout the gastrointestinal organs. Frequency domain image analysis can be used to distinguish columnar from squamous epithelium. Profilometric information on sample surfaces can be obtained directly as isophase lines. Second, the miniaturized confocal laser scanning microscope is characterized. Having an effective diameter of 25 mm, it houses a single-mode optical fiber, a scanning mirror and an objective lens. The micro-electro-mechanical mirror with a gimballed suspension allows two dimensional scanning without introducing an optical path difference. The sinusoidal movement of both axes has to be considered to approximate cartesian image coordinates. Field geometry is illustrated as a function of excitation amplitude and frequency. Acceptable image quality is achieved for a frame rate of 0.5 Hz. A strategy to position the focal plane axially within the sample volume is discussed.