Features
Nanyang Technological University
Singapore
http://media.ntu.edu.sg

Scientists from Nanyang Technological University (NTU), Singapore, have developed an ultrasound device that produces sharper images through the use of 3D printed lenses. With clearer images, doctors and surgeons can have greater control and precision when performing noninvasive diagnostic procedures and medical surgeries.

A new ultrasound device produces sharper images through 3D printed lenses. (Credit: Nanyang Technological University)

The innovative ultrasound device is equipped with superior resin lenses that have been 3D printed. The new device will allow for more accurate medical procedures that involve the use of ultrasound to kill tumors, loosen blood clots, and deliver drugs into targeted cells.

In current ultrasound machines, the lenses that focus the ultrasound waves are limited to cylindrical or spherical shapes, restricting the clarity of the images. With 3D printing, complex lens shapes can be made, resulting in sharper images. The 3D printed lenses allow ultrasound waves to be focused at multiple sites, or the lenses can shape the focus specifically to suit a target, which current ultrasound machines are unable to do.

The novel ultrasound device was developed by a multidisciplinary team of scientists, led by Claus-Dieter Ohl, an associate professor in NTU’s School of Physical and Mathematical Sciences. The ultrasound device has undergone rigorous testing, and the findings have been published in a paper titled, “Laser-Generated focused Ultrasound for Arbitrary Waveforms,” in Applied Physics Letters, a peer-reviewed journal published by the American Institute of Physics.

How it Works

In the paper, the researchers describe how transducers for laser-generated focused ultrasound can achieve photoacoustic waves with several hundred bars positive pressure in water, whereas previous designs have employed concave glass substrates decorated with catalytically grown carbon nanotubes. The paper discusses how their process shows that arbitrarily shaped surfaces made of polymers and printed with 3D printers allow the generation of waveforms with complex temporal and spatial shapes.

They present three different polymer materials together with a simplified deposition technique, which was achieved by “painting layers of carbon-nanotube powder and polydimethylsiloxane.” Using a clear resin, the researchers obtained pressure amplitudes of 300 bar peak positive. The researchers note that the flexibility of polymer substrates enabled complex waveforms to be generated. The researchers say that this is demonstrated with a stepped surface, which launches two waves separated by 0.8 μs. In the paper, detailed pressure measurements are supported with shadowgraph images and simulations of the wave.

Overcoming Current Limitations

Ultrasound waves are produced by firing sound waves at a glass surface or “lens” to create high-frequency vibrations. In conventional ultrasound machines, the resulting heat causes the lens to expand rapidly, generating high-frequency vibrations that produce ultrasound waves.

With lenses that are 3D printed, the new ultrasound device overcomes the limitations of glass. Customized and complex 3D printed lenses can be made for different targets, which results in better imaging. In addition, the 3D printed lenses are cheaper and easier to produce than conventional glass lenses.

“3D printing reinvents the manufacturing process, enabling the creation of unique and complex devices. In turn, the way medical devices are created needs to be rethought. This is an exciting discovery for the scientific community as it opens new doors for research and medical surgery,” said Ohl.

With this breakthrough, the NTU team has begun discussions with various industry and healthcare partners looking to develop prototypes for medical and research applications.

“In most medical surgeries, precision and noninvasive diagnosis methods are crucial. This novel device not only determines the focus of the wave but also its shape, granting greater accuracy and control to medical practitioners,” said Ohl.

This breakthrough taps into an ultrasound market that is expected to grow to about US $6.9 billion by 2020. The research is also expected to promote new medical techniques and research opportunities in health sciences such as surgery and biotechnology. Researchers could use the sound waves to measure elastic properties of cells in a petri dish, seeing how they respond to forces. This would be useful, for example, to distinguish between harmful and benign tumor cells.

“This is a very promising breakthrough, potentially offering significant clinical benefits to the field of cancer imaging. This technology has the potential to reduce image distortions and more accurately differentiate cancerous from noncancerous soft tissue,” said Tan Cher Heng, adjunct assistant professor, LKC medicine lead for anatomy and radiology, and senior consultant with the Department of Diagnostic Radiology at Tan Tock Seng Hospital.