The new approach is both fast and accurate – thanks to the use of “dithered bitmaps”, which is a file format in which grayscale pixels are converted into black and white pixels of different densities to create shades of gray and black – quite similar to “half-tones” used to print pictures on paper in newspapers and magazines.

Converting differently-shaded pixels into a mix of black or white pixels with different densities lets 3D printers use two different materials to make the model and preserve subtle detail.


"Our approach not only allows for high levels of detail to be preserved and printed into medical models, but it also saves a tremendous amount of time and money," said James Weaver, Ph.D., Senior Research Scientist at the Wyss Institute and corresponding author of the paper. “Manually segmenting a CT scan of a healthy human foot, with all its internal bone structure, bone marrow, tendons, muscles, soft tissue, and skin, for example, can take more than 30 hours, even by a trained professional – we were able to do it in less than an hour."

The new approach could help push 3D printing into even routine exams and diagnoses, and patient education.

"I imagine that sometime within the next 5 years, the day could come when any patient that goes into a doctor's office for a routine or non-routine CT or MR scan will be able to get a 3D-printed model of their patient-specific data within a few days," said Weaver.

Of additional interest is that the methods for the preparation of the bitmap input files described here were all performed with open-source software using existing image-processing algorithms, noted the researchers, emphasizing that this will permit “for the unconstrained widespread adoption of this approach.”

In May, NHS surgeons used 3D printing to perform a lifesaving kidney transplant on two-year-old Dexter Clark.

They used Stratasys’ multi-material 3D printing technology plan their procedure prior to implanting a kidney from Dexter’s father into the young infant’s abdomen. The hospital is the first of any to use this technology to map out a successful transplant of an adult kidney into a small child with anatomical complexities.

“The ability to print a 3D model of the patient’s anatomy in varying textures, with the intricacies of the blood vessels clearly visible within it, enables us to differentiate critical anatomical relations between structures,” Pankaj Chandak, the transplant registrar at Guy’s and St Thomas’ NHS Foundation Trust, told HCB News. “The flexible materials also allowed us to better mimic the flexibility of organs within the abdomen for simulation of the surgical environment.”


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