3D printing offers significant benefits for preoperative planning in the medical field. However, due to the high cost of industrial-grade printers, not to mention the difficulty in acquiring the software, it has not been widely adopted.
Jan Witowski, along with a research team from Jagiellonian University, developed a method to use a desktop 3D printer to create human liver models for complex surgical planning. Preoperative models (or known as preoperative guides) are particularly useful in surgeries that require accurate anatomical visualization.
They believe that these models offer several advantages over standard imaging techniques, such as shorter surgery and recovery times, reduced blood loss, and better resection margins.
Challenges Faced by Doctors
When performing laparoscopic resections on the liver, it is crucial to clearly see the tumor's location and the surrounding blood vessels. This reduces the risk of excessive blood loss during surgery.
This is a minimally invasive procedure, and surgeons are keen to explore new ways to improve surgical preparation. However, according to the latest literature, only 10 cases worldwide involve doctors using 3D printing as part of their preparation process. The biggest question is, what is preventing them from using this technology?
As Witowski points out in his paper, the primary factor traditionally preventing surgeons from using 3D printing is cost.
Industrial-grade 3D printers can cost over $200,000, and few medical institutions have professionals who use them.
Additionally, the segmentation software costs thousands of dollars, and these are all costs that few practitioners are willing to bear. Until recently, most liver models were created using material jetting (Polyjet / Multijet), with each model costing up to $5,000.
Another significant factor preventing surgeons from embracing 3D printing technology is time. Developing models using industrial-grade 3D printers takes four to seven days.
Outsourcing takes even longer.
Witowski also emphasized that SLA and SLS are not suitable because surgeons would lose the ability to visualize the parenchyma (the external shape of the liver). His goal is to provide an alternative using FDM printers and silicone, which would significantly reduce manufacturing costs while retaining all the details needed to improve the surgical process.
Using Ultimaker 3D Printers to Create Liver Models
3D printing liver models using desktop 3D printers reduces the overall time by approximately 60-100 hours. The price is also considerably lower. Witowski illustrates how it works with a diagram.
The 52-year-old female patient first underwent laparoscopic colorectal resection, and two years later, laparoscopic right hemihepatectomy (secondary hepatectomy) after a CT scan revealed a solitary metachronous metastasis.
Her CT scans clearly showed the cross-sectional structure, which was then converted into STL files and 3D printed.
For 3D printing, Witowski used Blender, Meshmixer, and Ultimaker Cura, along with an Ultimaker 2+ 3D printer.
Model Development Phase
Model development consists of four key stages: object segmentation, common 3D model computer processing, slicing and printing, and finally, silicone curing, finishing, and assembly.
The total print time ranges from 60 to 100 hours, depending on the model's size, number of parts, print precision, and printer type. In this case, 72 hours of printing were required, and due to material interchangeability and print bed size, it had to be executed in six print jobs.
Post-processing is important to maximize the smooth quality of the silicone surface and prevent haziness. The model is sanded with 100-300 grit sandpaper, then washed with water and dried. It is then coated with self-leveling resin XTC-3D, allowed to cure for about 3 hours until the resin is dry, and then this process is repeated to ensure the surface is smooth enough for silicone casting.
Multi-part structures are bonded together using common cyanoacrylate-based adhesive, then protected at the connection areas with insulating tape and putty to prevent silicone leakage during the casting stage.
Results
Thanks to Ultimaker, Witowski was able to create a transparent, full-sized liver model, showing blood vessels and malignant colorectal cancer metastases, for less than $150. This was achieved using a combination of 3D printed models and molds for silicone casting.
Desktop 3D printers like Ultimaker can be placed immediately in the hospital, and produce physical models of patient anatomy in a matter of hours or days.
This allows surgeons to touch and feel the model, making the process of planning the surgery more realistic.
Jan concludes: “I chose Ultimaker because of its reliability. I need to have a printer that won’t fail me when I am printing several 20+ hour print jobs day after day. I truly believe that using low-cost printing is a huge step towards personalized medicine. I’ll definitely continue using Ultimaker, especially for high-impact projects where I need to be sure to provide results on time.”
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