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3D Printing has emerged as a disruptive technology in the healthcare field. Over the past 20 years, it has been leveraged with great success to plan complex medical procedures, produce custom devices and instruments, and to better train future clinicians. As the accessibility to the technology increases, many hospitals are beginning to adopt 3D printing labs or service lines to support the growing level of interest from physicians. By bringing the technology in house, it supports a reduction in 3D printing lead times compared to outsourcing methods, and helps to build knowledge and drive innovation within the hospital.
Equal to the tremendous potential of 3D Printing, there are also significant challenges to its widespread adoption. Reimbursement challenges, lack of robust evidence proving efficacy, and technical difficulties all contribute to this. One of the largest barriers to overcome is the technical know-how to implement a new disruptive technology in the existing clinical workflow.
So where to start when considering the implementation of a 3D printing program, large or small? What does the entirety of the 3D printing process look like in a medical center? Some questions to ask and considerations to take into account when setting out to start your own 3D printing core lab.
Departmental or Institutional?
Is your goal to support a single medical discipline with 3D Printing? Or to provide a large-scale service institution-wide? The answer to this question will determine not only the resources needed to run the lab, but also the appropriate software and hardware necessary to optimally support specific medical disciplines with 3D printed models. Understand the modeling requirements for each discipline you are seeking to serve prior to making significant investments. Your workflow will look very different if you are building models to support congenital heart surgery as opposed to bone models for complex cranio-maxillofacial reconstructions. By increasing the scope of the lab and servicing a larger pool of clinicians, it will also help to justify the significant capital and operational costs to acquire equipment and run a quality service. Higher volumes of model requests will result in greater economies of scale for your organization.
Figure 1- 3D printed skull defect and custom cranio-plate (Image courtesy Materialise)
Imaging Is Everything
When building patient-specific models or medical devices, great imaging is the precursor for accurate 3D models and an efficient process. CT or MRI? Contrast-enhanced or non-contrast? Each modeling application will have unique imaging requirements, so a close collaboration with your imaging departments is key. It is also important to define the appropriate protocols for imaging and to educate surgeons on the importance of this for model making. This preparation will avoid the need to re-scan a patient or to work with less than optimal imaging to create a 3D model. In general terms, it is best to acquire high resolution, both spatial and temporal, images to achieve the best 3D printing results (thin-slice, gated imaging). Lean on the expertise of your radiology colleagues to assist in optimal protocol definition or reach out to the industry experts for recommendations.
Ordering and Communication
How does a surgeon indicate when he/she would like a model to support a procedure? Do they send an email or walk to the lab to discuss in person? When does it make sense to implement a more sophisticated ordering system? There is no clear answer for this. I wouldn’t let this hinder your ability to get started. Start simple and develop close working relationships with your surgeons before building a more robust ordering system into the clinical workflow. Be prepared to handle this challenge as the operation is scaled to handle greater volumes of cases.
Software for the 3D Printing Workflow
Appropriate processing of your medical imaging data for 3D Printing is often an overlooked part of the workflow. To optimize your workflow from Dicom imaging to the 3D printer, it is best to find a single software solution that addresses each step of the workflow. This will save you time and reduce headaches and errors that can arise when linking steps between software programs licensed by different vendors. Considering that the results of your modeling will be used to supplement clinical decision-making, it is also imperative to use software tools that are cleared for medical use and have been cleared through the FDA 510k pathway. This was also referenced in a recent paper published by researchers at the FDA in May 2016. Although they determine that cleared software should be used to process the patient imaging, they state that the 3D printer is outside the scope of regulation similar to a traditional desktop laser printer (Di Prima et al, 2016).
As a general rule, start first by fully understanding the needs of the clinician for a specific use case. Will the model be used as a pre-surgical planning tool? Or for education or training? Understand the necessary anatomy and additional landmarks needed in the model in order to work most efficiently. By fully understanding the scope of the project from the beginning, it will ensure a useful model for the surgeon, save time in the segmentation/modeling process, and often lead to a faster build using less material.
The considerations for preparing CT, MRI, or 3D ultrasound data for 3D printing are very different from traditional image post-processing and 3D volume rendering techniques. Choose an appropriate software tool that has a strong combination of automated and manual segmentation functionality. Often the cases that will most benefit most from 3D printing are also the most complex in terms of anatomical anomalies. This can challenge even the most sophisticated segmentation algorithms, so also find a tool that enables efficient manual intervention during segmentation when necessary. In addition, it is useful to have a tool that can reconstruct and render your STL files within the software instead of a simple STL export option. This gives you the advantage of seeing and verifying what you have created prior to 3D printing.
Figure 2- Congenital heart anatomy segmented with Mimics Innovation Suite software
Segmenting the medical imaging is only half of the 3D modeling battle. Often, the more determinative and labor-intensive part of the 3D printing process is the further preparation and augmentation of your segmented anatomy prior to 3D printing. This can include features such as cleaning and smoothing to remove artifacts, adding connecting geometries to hold anatomy in the proper anatomical positions, adding thickness to represent vessel walls, cutting of the model to achieve optimal visualization, and indicating color or multiple materials. The considerations are many. How you prepare the 3D model will determine how useful the print will be clinically, how much time and material will be required to build the part, and the feasibility of printing and cleaning the eventual model. A robust toolset and a ‘design for 3D printing’ mindset must be adopted to achieve success.
For example, if your surgeon requests a model to plan a repair of facial trauma, he/she may also want to understand the optimal outcome to restore cosmetics and function. For this, it would be helpful to provide a second model of the patient’s anatomy mirrored across the midface to understand what the optimal reconstruction outcome would look like. For a complex heart procedure, the surgeon will want to understand the intricacies of the intra-cardiac anatomy or landmarks for a specific valve or vessel. This will require you to prepare the heart model with windows or cut along a split line to achieve this visualization and separate components to identify another color in the model. Each application of 3D printing will have very different 3D modeling requirements.