(Vienna, March 21, 2024) In a joint project between the MedUni Vienna and the TU Vienna, the world’s first 3D printed “brain phantom” was developed, which is modeled 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 MedUni Vienna and TU Vienna has now shown in a study, 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 Medical University of Vienna and the TU 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. Already in 2017, a two-photon polymerization printer was developed at the TU Vienna that enables upscaled printing. In the course of this, we also worked on brain phantoms as an application together with the Medical University of Vienna and the University of Zurich. 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 is primarily used for printing microstructures in the nanometer and micrometer range – not for printing 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 the way a cell phone camera works: “We see the greatest progress in photography with cell phone cameras not necessarily in new, better lenses, but in the software that improves the images captured.” The situation is similar “It’s about 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.”
Brain phantom train analysis software
The authentic reproduction of characteristic nerve structures in the brain is therefore important for “training” the dMRI analysis software. The use of 3D printing enables the creation of diverse and complex designs that can be modified and customized. The brain phantoms therefore represent areas in the brain that generate particularly complex signals and are therefore difficult to analyze, such as crossing nerve pathways. In order to calibrate the analysis software, the brain phantom is examined using dMRI and the measurement data is analyzed as in a real brain. Thanks to 3D printing, the design of the phantoms is precisely known and the results of the analysis can be checked. MedUni Vienna and TU Vienna were able to show that this works as part of their joint research work. The developed phantoms can be used to improve dMRI, which can benefit surgical planning and research into neurodegenerative diseases such as Alzheimer’s, Parkinson’s and multiple sclerosis.
Despite the proof of concept, the team still faces challenges. The biggest challenge currently lies in scaling the method: “The high resolution of two-photon polymerization enables the printing of details in the micro- and nanometer range and is therefore very suitable for imaging cranial nerves.” “It takes a correspondingly long time “We used this technology to print a cube several cubic centimeters in size,” explains Chalupa-Gantner. “Our goal is therefore not only to develop even more complex designs, but also to further optimize the printing process itself.”
Publication: Advanced Materials Technologies
Towards Printing the Brain: A Ground Truth Microstructural Phantom for MRI;
Michael Woletz, Franziska Chalupa-Gantner, Benedikt Hager, Alexander Ricke, Siawoosh Mohammadi, Stefan Binder, Stefan Baudis, Aleksandr Ovsianikov, Christian Windischberger, Zoltan Nagy;
https://doi.org/10.1002/admt.202300176
