In-repair sensor measures blood flow past brain aneurysm
- Autore:Ella Cai
- Rilasciare il:2018-08-07
US and Korean researches at have built a super-stretchy flow sensor into a brain aneurysm ‘diverter’ – a device much like the ‘stents’ used to repair heart blood vessels.
This kind of aneurysm is a balloon-like bulge on the side of the vessel and the diverter is a wire mesh tube which is expanded inside the blood vessel, making most of the blood flow along the vessel rather that swirling around in the bulge. The vessels are small, and diverters are at most 10mm long.
This, according to Georgia Tech, which is part of the consortium, allows local blood clots to grow within the sac of the aneurysm and fill it. “Repairing the damaged artery takes months or even years, during which the flow diverter must be monitored using MRI and angiogram technology,” said the university.
The team is trying to build a suitable sensor into a diverter, and along the way has created a new type of diverter – using a highly-porous thin film nitinol.
The sensor is a membrane hundred nanometers thick made of two metal layers surrounding a dielectric material and encapsulated in a soft elastomer, which wraps around the flow diverter. Transfer printing is among the fabrication techniques used.
“The membrane is deflected by the flow through the diverter, and depending on the strength of the flow, the velocity difference, the amount of deflection changes,” said GaTech researcher Woon-Hong Yeo. “We measure the amount of deflection based on the capacitance change, because the capacitance is inversely proportional to the distance between two metal layers.”
Application in the brain creates significant challenges.
“The sensor has to be compressed for placement, so it must be capable of stretching 300 or 400%,” said Yeo. “The sensor structure has to be able to endure that kind of handling while being conformable and bending to fit inside the blood vessel.”
As well as nitinol (a nickel-titanium alloy), gold and magnesium have been tried. “All can be safely used in the body, but magnesium offers the potential to be dissolved into the bloodstream after it is no longer needed,” said GaTech.
The proof-of-principle sensor was connected to a guide wire for in-vitro testing, and now the team is working on a wireless version that could be implanted in a living animal.
Alongside Georgia Tech, institutions involved included Virginia Commonwealth University, University of Pittsburgh, Korea Advanced Institute of Science and Technology, Chonnam National University and Washington State University.
The work is published as ‘Stretchable, implantable, nanostructured flow-diverter system for quantification of intra-aneurysmal hemodynamics‘ in ACS Nano.
This kind of aneurysm is a balloon-like bulge on the side of the vessel and the diverter is a wire mesh tube which is expanded inside the blood vessel, making most of the blood flow along the vessel rather that swirling around in the bulge. The vessels are small, and diverters are at most 10mm long.
This, according to Georgia Tech, which is part of the consortium, allows local blood clots to grow within the sac of the aneurysm and fill it. “Repairing the damaged artery takes months or even years, during which the flow diverter must be monitored using MRI and angiogram technology,” said the university.
The team is trying to build a suitable sensor into a diverter, and along the way has created a new type of diverter – using a highly-porous thin film nitinol.
The sensor is a membrane hundred nanometers thick made of two metal layers surrounding a dielectric material and encapsulated in a soft elastomer, which wraps around the flow diverter. Transfer printing is among the fabrication techniques used.
“The membrane is deflected by the flow through the diverter, and depending on the strength of the flow, the velocity difference, the amount of deflection changes,” said GaTech researcher Woon-Hong Yeo. “We measure the amount of deflection based on the capacitance change, because the capacitance is inversely proportional to the distance between two metal layers.”
Application in the brain creates significant challenges.
“The sensor has to be compressed for placement, so it must be capable of stretching 300 or 400%,” said Yeo. “The sensor structure has to be able to endure that kind of handling while being conformable and bending to fit inside the blood vessel.”
As well as nitinol (a nickel-titanium alloy), gold and magnesium have been tried. “All can be safely used in the body, but magnesium offers the potential to be dissolved into the bloodstream after it is no longer needed,” said GaTech.
The proof-of-principle sensor was connected to a guide wire for in-vitro testing, and now the team is working on a wireless version that could be implanted in a living animal.
Alongside Georgia Tech, institutions involved included Virginia Commonwealth University, University of Pittsburgh, Korea Advanced Institute of Science and Technology, Chonnam National University and Washington State University.
The work is published as ‘Stretchable, implantable, nanostructured flow-diverter system for quantification of intra-aneurysmal hemodynamics‘ in ACS Nano.
