Nov 122011

About 3 -4% of the general population has or will develop a cerebral aneurysm, with most are without any symptoms. Aneurysm is an enlarged area of a blood vessel that usually develops at a branching point of artery and is caused by constant pressure from blood flow. It often grows gradually and becomes weaker as it stretches. Rupture of a cerebral aneurysm causes bleeding into the brain, often leading to a stroke. Endovascular embolization using micro-coils has emerged as a successful preventive treatment for aneurysms. The micro-coils are made from platinum wire (thickness 20–120 μm) wound at diameters of 200–500 μm for length up to 50 cm. Once the coil is inserted through the artery into the aneurysm, it forms a randomly tangled globe that promotes clotting of blood, thus preventing further inflow of blood and pressure rise. In about half of implanted patients,
the embolization process fails within 18 months, requiring frequent checks for the blood entry into the aneurysm using expensive, invasive, and potentially toxic methods, such as X-ray angiography and computer tomography. The group of Dr. Takahata at the University of British Columbia has reported a new method for monitoring blood entry into aneurysms, which is simple and inexpensive enough for frequent monitoring at home. In their method, the RF resonance of the micro-coils is used as a moisture sensor.  The RF resonant circuit is formed by self-inductance combined with parasitic capacitance, which is affected by tissue permittivity around the coil. At 100 MHz, for example, the dielectric constant of blood is 25 times higher than that of fibrous tissue. The RF coupling of the micro-coils would be done with an external antenna attached to the head of a patient. The present study was conducted using animal muscle tissues, with a clinical device
anticipated in 2-3 years.

  One Response to “Blood entry sensor for cerebral embolization using RF resonance of micro-coils”

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