Chinese Team Develops Low-Cost, Highly Accurate Method for 3D Printing Patient-Specific Liver Models
3D printed medical models are making their way into hospitals around the world as medical professionals recognize their value. Patient-specific anatomical models offer physicians the opportunity to physically touch and examine complicated internal structures, understanding the extent and precise locations of issues to be addressed through medical procedures. Patients also benefit from the models, which can be used to inform them of specifics of both condition and treatment. Research performed worldwide is building upon knowledge to create ever-better models and systems for creating patient-specific models, such as was recently seen in Minnesota. While in that case, better models referred to their lifelike textures, other improvements have been in focus for research in China, as a team of researchers led by Professor Cheng Shujie from the Affiliated Hospital of Hebei University are now introducing precise 3D printed liver models that reproduce complex anatomies at a much lower cost than had been previously available.
Hepatic surgeries can be complex and confusing for surgeons working without predetermined pathways and plans from a 1:1 exact model, and livers have proven a viable target for 3D printing medical models. Building upon work done in China’s Zhujiang Hospital, led by Fang Chihua, as well as research from Japan’s Tsukuba University and Poland’s Jagiellonian University, the Hebei-based team set out to develop their own method to 3D print liver models, after, as surgeon Ke Zhang of the Affiliated Hospital of Hubei University notes in a manuscript shared with us, “innovative optimizations and accuracy controls of almost every step.”
“Professor Shujie Cheng is the master of our hospital and the leader of our research team. I am a surgeon and also a committee member of [the] Chinese Medical Doctor Association,” Zhang tells us of the complicated research, to which the team dedicated almost 10 months of work.
The work from the other research institutions all shared a common focus in creating low-cost, accurate 3D printed liver models, and Professor Cheng’s team sought to reduce costs and enhance precision even further.
“The achievements of the three teams mentioned above are very enlightening to the research of the Affiliated Hospital of Hebei University. Meanwhile the Cheng Shujie team hopes the method can provide a reliable alternative for the hepatic surgeons during the long process of the multi-nozzles technology popularization as well as its price dropping and inspire more subject applications,” Zhang explained in the manuscript.
To combat costs and obtain high resolution in their medical models, the team turned to stereolithography. Zhang explains in the manuscript for the project:
“At the first time in the world, the team led by Professor Cheng Shujie from the Affiliated Hospital of Hebei University spent less than 4 hours on parallel printing of the entire internal structure and the surface of the liver under the layer thickness of 0.1mm with high speed photosensitive resin by using two high speed LCD-SLA 3D printers equipped with liquid cooling system. Then after one precise match by applying the improved traditional transfer molding technology, they completed the manufacturing process of patient-specific medical models with high transparent resin. As the internal structure of the liver was printed at once, malignant tumors can be seen clearly in the model. Compared with the measured distance from the 3D computer model, the errors of the measured distance of the printed model and its adjacent blood vessels are all less than 0.7 mm in every direction. With the premise of decreasing printing time drastically and improving the printing accuracy, it has further lowered the cost of model production, which has greatly increased the surgery efficiency and accuracy.”
This method can create a detailed, life-sized liver model for approximately $80-$90. Accuracy and resolution come from the use of SLA 3D printing technology, which has lower capital and material costs than industrial multi-material technologies, while requiring only one assembly step that the team notes has a low error rate, precluding the need for multiple steps and points of assembly for an FFF-based print job.
The method isn’t perfect, as the team are immediately willing to admit. One of two primary shortcomings that Professor Cheng pointed out lies in post-processing, as each model currently requires approximately 30 hours of work following completion of the print job and resin. The other drawback lies in more complex models, as an “extremely complicated exterior” sees “the time cost of the method [increase] profoundly, thus [losing] the producing advantages and [callling] for support of multi-nozzle printing technology.” Still, at what the manuscript describes as a conservative estimate, approximately 80% of complex hepatic surgery needs are met through this production method.
“The greatest significance of the method probably is lowering the cost considerably while keeping the accuracy to the maximum and enhancing the printing speed, which enables the broad applications of the 3D printing in the hepatic surgery field,” Zhang’s manuscript explains.
Finished models created using the team’s method include precise reproduction of the liver itself, “including the precise surface and the high transparent liver parenchyma,” the patient’s exact tumor, and complete three-system level 5-6 vascular net, where the main vessel is level 1. Vessel end diameters “have reached the limit of CT slice resolution,” offering sub-millimeter precision.
“After repeated and thorough verifications, Professor Cheng Shujie considers that the manufacturing method, currently developed by the Affiliated Hospital of Hebei University, of transparent, full colored and high accuracy pre-surgery planning liver model is qualified in aiding a series of extremely difficult, accurate and personalized hepatic surgeries,” Zhang writes. “And it could be used for producing more complicated models after improved by the current methods which will turn most of complex and difficult surgeries that surgeons thought impossible to perform into possibilities.”
In addition to use in hepatic surgery, this method can potentially make its way to other areas of medical care, including the many that are already incorporating 3D printing at an accelerating rate. Orthopedics, neurosurgery, obstetrics and gynecology, cosmetic surgery, and stomatology are among the areas the Hebei team notes. 3D printed models allow medical care providers a literal hands-on approach to healthcare to directly and personallly understand anatomies and prepare for procedures.
More details regarding this work will be published in the near future, including accuracy control and measurement data; further discussion can be had with the team via email.[All images provided by Affiliated Hospital of Hebei University]
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