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Verification and Labeling
After completing your segmentation and modeling work, you may be in a hurry to get your part on the 3D printer. However, there is an opportunity to unintentionally introduce errors in the above steps. Prior to printing, the accuracy of your final file should be verified against the original DICOM imaging. Did you take liberties and over-smooth or remove a key feature from the model? Did you cut away a structure that would be an important landmark for the surgeon? I would highly recommend a software solution that allows the user to overlay the STL surfaces back on the Dicom data. This will allow you to verify accuracy (and establish credibility with your surgical colleagues) as well as make subtle adjustments or refinements to the model.
Figure 4- Contour verification of prepared heart model demonstrated in Mimics Innovation Suite
Ensuring traceability of your 3D prints will also reduce the opportunity for making errors with your 3D printing program. As you scale your operation and build greater volumes of models, it is critical to understand what models are coming off the printer and what case they each belong to. To reduce the chance of mixing models or providing the wrong model to a surgeon, each anatomical model should be pre-labeled with software prior to printing. Use a requisition number that will trace back to the medical records to ensure traceability of your 3D models. You will also want to use labels if you create mirror images or want to clearly indicate what side of the patient the model was derived from. This will reduce the chance for operator confusion and eliminate the chance they may operate on the wrong side of the body.
Figure 5- Applying a text label to a heart model using Mimics Innovation Suite
Close collaboration between personnel is key in this process. It is necessary to define the scope and use of the model with the surgeon or interventionist prior to starting the process in addition to verification near the end. This can be facilitated through web meetings or face-to-face discussion. It can also help to have a software solution capable of exporting a file format which can be interrogated by the surgeon. It is highly unlikely that your surgeon will be able to open an STL file! Exports such as 3D PDFs can be an excellent tool for this purpose allowing efficient transfer and sharing of data within an environment of a simple PDF reader.
Figure 6- 3D PDF communication tool exported from Mimics Innovation Suite
The STL file format is the universal digital 3D modeling format for 3D printing. This is the file that will be fed to the 3D printer to slice and build the part. Not all STL files are created equal. The number and quality of the triangle facets will determine the eventual quality of your printed part. You may also find very thin walls in the model that fall under the minimum resolution of your printer or that will be very brittle and tear-sensitive. It is imperative to have a robust STL diagnostic and fixing tool to ensure a successful and quality build. Nothing is more frustrating that build failures attributed to errors in the digital file. This is an area where significant time and money can be lost.
Figure 7- File fixing in preparation for 3D printing in Mimics Innovation Suite
3D Printing: How to Choose?
Insource or outsource? This is the first question you should ask. Outsourcing will allow you to minimize your upfront capital investment but is typically associated with longer lead times. Outsourcing can also be advantageous in the rapidly evolving market of 3D printers. What equipment you buy today could soon be obsolete with better and lower-cost technology being brought to market. From a purely economic standpoint, outsourcing is often the best strategy to get started.
If you decide to invest in a printer, where should you start? 3D printers come in many different technologies which all have their advantages. FDM, PolyJet, laser sintering, stereolithography, and binder jetting all have unique advantages for certain applications. Resolution, speed, materials, color and of course cost, are key factors you should consider. Leverage experts in the industry to understand what technology makes the most sense given your use case and budget.
In addition to understanding the best 3D printer for your program, you’ll also need to understand the space required to house it. Certain printing technologies take up a very small footprint while others may require dedicated facilities. Some machines require additional equipment to clean the models after printing or will have greater maintenance associated. Fully understand all of these considerations before making your choice.
Figure 8- Example of flexible 3D printed heart model (Image courtesy Materialise)
Personnel and Training
You will need specific skill sets to run an effective 3D printing service. Knowledge in imaging and anatomy/pathology is required for accurate segmentation. A level of engineering skill is needed to prepare your 3D models in the best way for printing. Additional resources may be needed to clean models and maintain machines. The scale of your operation will determine the resources needed. Start small and lay out a plan for organic growth. By starting at a small scale, it will help to build momentum with clinicians and administrators to support the activity. If you build it, they will come! Make sure to learn from and be trained by experts in the field. Master the process from image acquisition through 3D printing. This will ensure that you avoid common pitfalls and are operating in the most efficient way possible.
Figure 9- Example of multi-material 3D printed model of heart and airway anomaly (Image courtesy Materialise)
Although 3D printing as a core service in a hospital is still in its infancy, many innovative institutions have been blazing a path. Leverage the experts both in industry and among your peers who have developed similar programs. This might mean working collaboratively on a few cases as a service or visiting other established medical 3D printing facilities. Establishing a new technology such as 3D printing can seem like an overwhelming endeavor. However, by taking into account the many considerations and requirements from the beginning, it will help you to develop a plan to start and grow a successful service for your institution.
Sr. Business Development Manager – Materialise
Di Prima, M., Coburn, J., Hwang, D. et al. 3D Print Med (2015) 2: 1. doi:10.1186/s41205-016-0005-9