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Intracranial pressure measurement without wires

07 November 2012

Researchers have developed intracranial pressure sensors that can be implanted beneath the skull for the long term, and read from outside the body via a wireless link.

View of the not yet completely enclosed intracranial pressure sensor (photo courtesy of Fraunhofer IBMT)
View of the not yet completely enclosed intracranial pressure sensor (photo courtesy of Fraunhofer IBMT)

To this day it remains a mystery why the cerebral pressure in certain people suddenly increases. The consequences, however, are better understood: blood circulation is disrupted and after a while parts of the brain may die, similar to the effects of a stroke.

People with a heightened susceptibility to a rise in intracranial pressure have to undergo an invasive procedure involving the insertion of a probe through the skull. A cable connects the implanted the device to an external measuring device. Since cerebral pressure fluctuates, many measurements have to be taken in order to reach a definitive diagnosis of this disease. Patients therefore have to stay in hospital, typically for several days, and sometimes even weeks.

For some time now, medical device engineers have been working on an intracranial pressure probe that operates without a cable and can be read from the outside via wireless. But, to date, there is no established product on the market for long-term implantation, because the sensor casing – produced primarily from biologically compatible synthetics – allows moisture to penetrate, which destroys the sensor in just a few days – or even hours.

Now, researchers at the Fraunhofer Institute for Biomedical Engineering IBMT in St Ingbert, Germany have developed a small sensor that remains waterproof. Instead of bio-compatible materials, the sensor is encased in high-grade metal. From the outside, the probe resembles a button cell battery, measuring about one centimetre thick and two centimetres wide and containing a silicon pressure sensing element, similar to those used in automotive applications.

Part of the casing is a pliable metal membrane that reacts to pressure changes, transferring this movement to the silicon element. The measurement is subsequently transmitted wirelessly to a measuring device outside the body without need for batteries, since it is activated by the reading device. A patient is thus able to wear the months, or even a number of years, without requiring additional surgery.

The system will be shown at the Medica trade fair, Düsseldorf, November 14 - 17, 2012, Hall 10, stand F05.

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