Contributing Editor, MEMS Investor Journal
The American Cancer Society estimates that there will be more than 1.5 million new cancer cases diagnosed in 2010. A biopsy is a widely used method of identifying malignant tumors by studying surgically removed tissue under the microscope. It is a time-consuming and stressful process even if the tumor proves benign. In fact, a large percentage of biopsies come up negative.
To address this problem, Dresden based Fraunhofer Institute for Photonic Microsystems is now developing a MEMS device that allows in vivo diagnostic procedures using an endoscope. Expected to be available in the near future, it is a minimally invasive alternative to biopsies with the added advantage of providing diagnosis in real time.
According to Dr. Michael Scholles, business manager for sensor and actuator systems at the Institute, “This is the first time that microscopic image recorders can be placed on an endoscope, resulting in what we call an endomicroscope. The solution was found in MEMS based image sensors because they magnify even the smallest object fields including cells without the need for a large lens. While classic endoscopy uses CCD or CMOS image sensors for macroscopic imaging, the required optics for these devices are too large for our application.”
Concept of the entire endomicroscope. In light gray to the right are the carrier and the scanning mirror and in green the tilted mirror. The two lenses for focusing the laser beam are shown in dark grey. All other parts are passive mechanical structures to support the parts in their proper position.
The laser-based sensor system utilizes an 8mm microscope head mounted at the tip of the endoscope. It can optically resolve and magnify tissue cells 10 to 20 micrometers in size and provide a resolution of 10 micrometers. In describing the system, Dr. Scholles says “We base it on a micro scanning mirror designed and manufactured at our Institute. While it is a mature technology, what we have here is a new application for this device. Our challenge is integrating all the necessary components -- the MEMS scanning mirror and its driver, passive optics and glass optical fiber bundles -- in such a small head.”
Light from the laser located in the operating theater is transmitted via optical fiber to the microscanner mirror at the tip of the endomicroscope. The mirror deflects the beam to illuminate the suspect tissue, and the image is returned to the external sensor. A detector gives precise measurement of the scanner mirror position indicating which area of the tissue is illuminated at a specific point in time. By combining the position and image sensor signals, a two-dimensional image is constructed for diagnosis by the physician.
The Fraunhofer Institute for Photonic Microsystems continues work on assembly techniques that will enable fabricating the tips in larger volumes. Looking ahead, Dr. Scholles envisions applications both in medical and biological microscopy and in technical endoscopy such as examining cavities in buildings and the inside of turbines and engines.
Copyright 2010 MEMS Investor Journal
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