Optical sensor to offer non-invasive monitoring of intracranial pressure

Dr Justin Phillips has been awarded £46,000 through a Royal Academy of Engineering and Leverhulme Trust Senior Research Fellowship so he can develop the device.

The money will allow him to undertake research for a year from September, by paying for a lecturer to cover his teaching and admin work at City University London.

“This is an optical sensor so it will work on infrared light,” said Phillips, a senior lecturer in biomedical engineering at the School of Mathematics, Computer Science and Engineering.

“The skull is fairly transparent to infrared, so the light passes through the skin and the bone and penetrates the brain tissue. The arteries in the brain are pulsating just like the arteries everywhere else.

“The probe detects some reflected light, and the light is reflected from the brain tissue and it is modulated by the pulse, so as the arteries pull an entry in time with the heartbeat they absorb a differing amount of light and you can record a pulse signal.

“By analysing the shape of the pulse signal, we can work backwards and calculate the pressure surrounding the arteries, which is the pressure we are trying to measure.”

One problem to overcome in developing the device will be eliminating readings from blood vessels in the scalp, Phillips said.

Raised ICP is a life-threatening condition that can result in the compression of brain tissue and a reduction in the flow of oxygenated blood to the brain.

Standard methods of monitoring are invasive, involving drilling the skull and inserting a sensor in the brain.

Non-invasive methods such as examining the retina or eardrum do not offer continuous monitoring and are tricky to perform.

Phillips previously worked on developing invasive methods of monitoring cerebral oxygen saturation in head injury patients using fibre-optic sensors. He now works on non-invasive monitoring, so his research will combine his past with his present.

“In our centre we build our own sensors and instrumentation,” Phillips said. “We are really a sensors and instrumentation group, and it is also biomedical applications.

“The area that we work in at City in our group is non-invasive monitoring, which means making measurements without puncturing the skin or taking blood, or causing pain or risk to the patient.”

He expects the sensor will be self-adhesive and about 5cm long and 2cm wide. It will be placed on a patient’s forehead and connected to a display to provide a continuous reading of the ICP.

Although Phillips will be conducting the research himself, he will be collaborating with doctors at Barts Health, which includes St Bartholomew’s and the Royal London hospitals.

He expects to develop a prototype within the year covered by the award. He also plans to talk with potential manufacturing partners and to apply for a grant to cover the clinical trial stage.