To call the human brain complex would be an understatement, with its system of billions upon billions of neurons, contained within the grey matter, firing the information required to run the body. What relays and coordinates that information is white matter: tendrils of myelinated axons and glial cells that transmits signals around the brain.
In the average 20-year-old male brain, there are some 176,000km of myelinated axons. As you can therefore imagine, creating an accurate 3D model of the brain's white matter would be no mean feat -- and the execution of a new model for the Franklin Institute's current exhibition, Your Brain, posed a series of challenges.
Dr Henning U Voss, Associate Professor of Physics in Radiology at Weill Cornell Medical College, who has conducted a decade of research into neuron mapping, headed up the project.
"The human brain consists of white and gray matter. The white matter of the brain contains fibres that connect grey matter areas of the brain with each other," Dr Voss explained. "Using an MRI scan of a 40-year-old man, we calculated diffusion tensors, and then created the white matter fibre tracts from them. We handed a surface model of the fibre tracts to Direct Dimensions for processing."
The resultant file was so large that even opening it was a challenge, the team said -- never mind printing it. Several 3D printing companies rejected the commission, with over 2000 strands, as too complicated. Direct Dimensions of Owing Mills, Maryland, finally accepted the project, breaking down the model into parts that could be printed separately and then assembled.
"Fortunately Dr Voss provided an amazing data set for us to start with. In order to print this at large scale, each of the thousands of strand models would have to be fused to create a single brain model that could then be sliced into printable parts that fit in the build envelope," Direct Dimensions art director Harry Abramson explained. "The whole model would then need engineering and design modifications to ensure that it could be assembled precisely and support itself on its custom mount."
This process took several weeks, packaging separate files that were then sent to American Precision Printing to be printed on a 3D Systems SLS printer. Each of the 10 separate pieces took around 20-22 hours to print.
"It has really become one of the iconic pieces of the exhibit. Its sheer aesthetic beauty takes your breath away and transforms the exhibit space," said Franklin Institute chief bioscientist and lead exhibit developer Dr Jayatri Das. "The fact that it comes from real data adds a level of authenticity to the science that we are presenting. But even if you don't quite understand what it shows, it captures a sense of delicate complexity that evokes a sense of wonder about the brain."