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OK! Rendering of a customizable phantom holder design. The structure consists of a larger spherical shell (pink), into which a constellation of smaller capsules can be inserted in one layer (green). The layer can be easily adjusted to vary the number and position of capsules (red/blue), and although only one of these layers is shown, more can be inserted if necessary. Photo credit: Advanced Materials Technologies (2024). DOI: 10.1002/admt.202300176
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Rendering of a customizable phantom holder design. The structure consists of a larger spherical shell (pink), into which a constellation of smaller capsules can be inserted in one layer (green). The layer can be easily adjusted to vary the number and position of capsules (red/blue), and although only one of these layers is shown, more can be inserted if necessary. Photo credit: Advanced Materials Technologies (2024). DOI: 10.1002/admt.202300176
In a joint project between the TU Vienna and MedUni Vienna, the world’s first 3D printed “brain phantom” was developed, which is based on the structure of brain fibers and can be imaged using a special variant of magnetic resonance imaging (dMRI).
As a scientific team led by the TU Vienna and MedUni Vienna has now shown, these brain models can be used to advance research into neurodegenerative diseases such as Alzheimer’s, Parkinson’s and multiple sclerosis. The research was published in the journal Advanced Materials Technologies.
Magnetic resonance imaging (MRI) is a widely used diagnostic imaging procedure that is primarily used to examine the brain. MRI can be used to examine the structure and function of the brain without the use of ionizing radiation. With a special variant of MRI, diffusion-weighted MRI (dMRI), the direction of the nerve fibers in the brain can also be determined. However, it is very difficult to correctly determine the direction of nerve fibers at the crossing points of nerve fiber bundles because nerve fibers with different directions overlap there.
In order to further improve the process and test analysis and evaluation methods, an international team, in collaboration with the TU Vienna and the Medical University of Vienna, developed a so-called “brain phantom” that was produced using a high-resolution 3D printing process.
Tiny cube with micro channels
Researchers from the Medical University of Vienna as MRI experts and the TU Vienna as 3D printing experts worked closely with colleagues from the University of Zurich and the University Hospital Hamburg-Eppendorf. In 2017, a two-photon polymerization printer was developed at TU Vienna that enables upscaled printing. The resulting patent forms the basis for the brain phantom that has now been developed and is maintained by the research and transfer support team at TU Vienna.
Visually, this phantom doesn’t have much in common with a real brain. It is much smaller and shaped like a cube. Inside there are extremely fine, water-filled microchannels the size of individual cranial nerves. The diameter of these channels is five times thinner than a human hair.
In order to imitate the fine network of nerve cells in the brain, the research team led by the first authors Michael Woletz (Center for Medical Physics and Biomedical Engineering, MedUni Vienna) and Franziska Chalupa-Gantner (3D Printing and Biofabrication Research Group, TU Vienna) used a rather unusual 3D printing process: two-photon polymerization. This high-resolution process primarily prints microstructures in the nanometer and micrometer range, but not three-dimensional structures in the cubic millimeter range.
In order to produce phantoms of a suitable size for dMRI, researchers at TU Vienna are working on scaling the 3D printing process and enabling the printing of larger objects with high-resolution details. The upscaled 3D printing provides the researchers with very good models that, when viewed in dMRI, enable different nerve structures to be assigned.
Michael Woletz compares this approach to improving the diagnostic capabilities of dMRI with how a cell phone camera works. “We see the biggest advances in phone camera photography not necessarily in new, better lenses, but in the software that improves the images captured.”
“The situation is similar with dMRI: With the newly developed brain phantom, we can adapt the analysis software much more precisely and thus improve the quality of the measurement data and reconstruct the neural architecture of the brain more precisely,” says Woletz.
More information:
Michael Woletz et al., Toward Printing the Brain: A Microstructural Ground Truth Phantom for MRI, Advanced Materials Technologies (2024). DOI: 10.1002/admt.202300176
Magazine information:
Advanced material technologies
