Using high-frequency ultrasound waves to treat deep brain conditions is a relatively new idea, but it’s one with huge potential. However, getting sound waves through the skull, which is between 2mm and 8mm thick, is tricky.
“When you're generating sound waves and trying to penetrate sound waves through structures, these sound waves can be dispersed through a process called attenuation,” explained Andrew Feeney, a research fellow at Warwick University’s Centre for Industrial Ultrasonics. “Bone has quite a high attenuation factor, which means that it disperses sound waves in a particular way compared to the media surrounding it.”
To tackle that problem, researchers from the University of California, Riverside have developed a ceramic skull implant that will allow doctors to deliver ultrasound treatments on demand, and on a recurring basis.
The group, which was part of the international ‘Window to the Brain’ project, created and tested a transparent, ceramic material that could be used to replace a portion of the skull. The material is a variation of the ceramic material Yttria Stabilized Zirconia (YSZ), that is sometimes called the ‘steel of ceramics’ because of its versatility.
Ceramics are promising because they don’t disturb human tissue, and they’re hard and shatter-resistant. An existing ceramic cranial implant for laser-based therapies is already in clinical trials. "These materials are already being used in dental crowns and hip replacements, and our team is working to extend their application to the diagnosis and treatment of a wide variety of brain pathologies and neurological disorders," said Guillermo Aguilar, a professor of mechanical engineering at UC Riverside.
The ceramic window will make it easier to focus ultrasound on a particular area of the brain. “Because they're treating a certain part of the brain they want to be able to focus all that energy onto one point,” Feeney told Professional Engineering. “if you have a barrier like the skull in-between, you're not going to be able to control that in any way. By replacing it with something that they know the physical properties of, they can then concentrate on trying to focus the energy.”
According to the researchers, it could also open up new types of treatment. “Developing an optically and radio-frequency transparent cranial implant was already an exciting accomplishment, and we continue to work to make this implant a reality,” said Aguilar. “Now, proving that ultrasound could be transmitted through the implant could expand its therapeutic capabilities even further.”
The research was published in the journal Advanced Healthcare Materials.