3D Lab in a Hospital Environment

3D Lab in a Hospital Environment 3 key reasons why a professional desktop printer is a great fit By Xavier Mottart & Pieter Slagmolen Materialise NV - Leuven, Belgium

3D printing technology has been rapidly gaining momentum as a recognized and beneficial contributor to healthcare. Patient-specific devices, surgical tools, the virtual planning of complex procedures, enhanced educational tools and improved patient communication are all positive outcomes of 3D printing technologies. These benefits have made 3D Printing popular, and its own popularity has made it more and more accessible. So much so, that an increasing number of hospitals want a 3D printing lab in-house, to build up a knowledge base and to shorten the time between ordering a model and holding it [1]. In 2010, three hospitals in the U.S. had a centralized 3D printing facility using Mimics technology, and this number had already increased by a factor of 33 by 2016. Nowadays, more than 200 hospitals around the world have access to 3D printers [3]. In the near future, an exponential growth is expected in the use of 3D-printed models [2]. A soaring rise in the number of facilities using 3D Printing, and high expectations for the use of 3D-printed models for medical purposes, show that 3D labs in hospitals are truly helping medical professionals to provide patient-specific care. As with any innovation, there are challenges to overcome and lessons to be learned while setting up a lab. How can 3D Printing be optimized and integrated into a hospital workflow? What components are needed? Which printer is appropriate and can a professional 3D desktop printer be used to get started? Which people do you need to develop and run a 3D lab? These are essential questions that this white paper will touch upon. 100 99 78 75 50 50 28 25 14 7 3 0 2010 2011 2012 2013 2014 2015 2016 Figure 1 - Hospitals in the U.S. with a centralized 3D printing facility using Materialise Mimics technology 2 By Xavier Mottart & Pieter Slagmolen I Materialise NV - Leuven, Belgium

LEARNING OBJECTIVES First, this paper provides a general overview on optimizing a workflow from image acquisition to 3D-printed model and talks about integrating this workflow on all levels in a hospital infrastructure. Next, it summarizes the resources needed to develop this workflow, including software and hardware requirements. Further, a validation test with a representative setup demonstrates the three key reasons for setting up a lab with a professional desktop 3D printer. Finally, it shows that a passionate and highly skilled team will make any 3D lab an effective 3D printing hub. This white paper should thereby enable healthcare professionals to identify the right steps that will ensure a smooth transition from a 3D printing dream to an achievable reality. 1. THE WORKFLOW: FROM IMAGE TO 3D PRINTING There s no shortage of arguments to start a 3D printing lab. Experts and pioneers in the introduction of 3D printing in radiology are convinced that while use of advanced visualization in radiology is instrumental in diagnosis and communication with referring clinicians, there is an unmet need to render Digital Imaging and Communications in Medicine (DICOM) images as three-dimensional (3D) printed models capable of providing both tactile feedback and tangible depth information about anatomic and pathologic states [2]. However, not all hospitals have the expertise and resources to regularly use 3D medical image post processing. To ensure that 3D anatomical models will enhance the hospital environment with better patient-specific data, improve patient communication and educate through a tangible representation of the anatomy, a dedicated workflow is essential. This workflow is composed of a series of sequential steps: medical imaging, 3D modeling and 3D Printing. These steps are ideally fully integrated at all levels of the hospital infrastructure to optimize the workflow from medical image acquisition to the 3D printer. A recognized and smooth workflow will allow good interaction between all the stakeholders and ensure a useful model for the physician. 3

Figure 2 - Integrated workflow DICOM integration STL integration Image Acquisition PACS Medica Device Software SLA 3D Desktop Printer 3D-Printed Anatomical Model INTEGRATED WORKFLOW 2. ESSENTIAL COMPONENTS OF A 3D LAB To build the optimized workflow and integrate it at all levels in the hospital infrastructure, three components are essential and will be discussed further: 1. Acquiring medical images for 3D Printing 2. Mastering 3D modeling 3. Matching 3D printing technology with the applications The following sections provide detailed guidelines to set up those three considerations into your hospital workflow. Furthermore, the sections highlight specific features that those three essential components should have, to ensure a smooth and optimized process. 2.1 ACQUIRING MEDICAL IMAGES FOR 3D PRINTING: GET IT RIGHT FROM THE START High-quality medical imaging is a prerequisite for 3D Printing. Several authors have described imaging recommendations for 3D Printing [2, 10]. Some companies provide recommendations based on specific applications [7]. Most commonly, CT and MR imaging is used. Imaging protocols aim to ensure an isotropic resolution below 1 mm and strong contrast between the anatomies to print and the background. These are essential for easy segmentation and high-quality 3D modeling. A close collaboration between radiologists, technical 3D specialists and physicians is required to attain optimal medical images that will be used in your 3D printing software. 4

2.2 MASTERING 3D MODELING: THE IMPORTANCE OF DEDICATED SOFTWARE By using high-quality medical images and the right tools, image segmentation can be done efficiently. A combination of automated and manual segmentation functionality allows users to cope with the most complex anatomical anomalies. A 3D model can be generated after segmentation, for the purpose of the 3D print. Further preparations and augmentations of the segmented anatomy are thus needed. This process may include features such as cleaning and smoothing to remove artifacts, adding thickness to represent vessel walls, cutting the model to achieve optimal visualization, etc. [1]. The preparation of the 3D model will determine the applications it can be used for. When Figure 3 Congenital heart disease view in software expert users perform this step, they can positively influence the print technology that can be used to create a suitable model, and optimize the time and material that will be required to build the part. Also, they can ensure the feasibility of printing, and minimize the post-process cleaning of the eventual model. After completing the segmentation and modeling work, the accuracy of the final file should always be verified against the original DICOM imaging, e.g. by overlaying the contours of the 3D virtual model over the medical images (as shown in Figure 3). Additional recommendations for the workflow can be found in other publications [1]. 5

2.3 SELECTING A 3D PRINTER: MATCHING TECHNOLOGY WITH REQUIREMENTS There is a wide range of available 3D printing technologies suited for anatomical printing. These include material extrusion (FDM PLA, ABS), VAT photo-polymerization (SLA UV light-cured liquid resin), powder-bed fusion (SLS - powder), binder jetting (ColorJet - Gypsum) and material jetting (PolyJet UV light-cured liquid resin). Each of these has its own characteristics and applications and is available in different sizes, with different capabilities and in various price ranges. Studying the various options for 3D printers thoroughly in light of the specific requirements for each institution, will help create a high-quality and cost-effective solution. An extensive analysis of the various options is outside the scope of this paper as it mostly aims to illustrate the potential of a representative desktop solution. Some additional information on 3D printing technologies and their general pros and cons, can already be found in 3D Printing Techniques for Anatomical Printing. 6

The role of desktop printers What holds for 3D printers in general is equally true for desktop printers. A wide variety of choices are available out there, each with its advantages and disadvantages. In general, they have the benefit of being convenient, cost-effective and scalable with respect to industrial scale 3D printers. Most common methods are based on material extrusion (FDM) or VAT polymerization. While the former is typically clean and has a very low running cost, the latter is accurate, robust and can be used with medical-grade materials. While both technologies hold value, VAT polymerization, also known as SLA (Stereolithography Apparatus), is thus a sensible solution for getting started with a 3D lab in a hospital framework. What is SLA? SLA (Stereolithography Apparatus) belongs to a family of additive manufacturing technologies known as VAT photopolymerization. These machines are all built around the same principle, using a light source a UV laser or projector to cure liquid resin into hardened plastic. The main physical differentiation lies in the arrangement of the core components, such as the light source, the build platform, and the resin tank. [5]. See how the 3D virtual model becomes a finished part: The 3D model A laser hardens UV curable liquid The platform adjusts its height gradually while the laser selectively hardens the material to form the part and its support The excess liquid is washed away and the support is removed The part is finished Benefits Considerations Suggested applications Desktop printer format Postprocessing station with chemicals CMF, orthopaedic and cardiovascular applications Material : Transparent / Rigid Color options : 2 7

3. EVALUATION OF A DESKTOP 3D PRINTER The aim of this section is to investigate the expected quality of a desktop-driven 3D lab setup, to evaluate the economic aspects of such a setup and look at operational characteristics. For this, we identified a representative test setup, in line with the workflow of Figure 2, which is composed of these elements: Materialise software (for segmentation and modeling) Fomlabs PreForm software (to prepare files for the final print) Formlabs Form 2 (SLA professional 3D desktop printer) We chose to assess this particular setup for a few reasons. The segmentation, modeling and verification are addressed within a single software. The printer, the Formlabs Form 2, is considered a high-quality SLA 3D desktop printer that is easy to use and implement in a medical environment, at a fraction of the cost of traditional industrial-grade 3D printers. It uses medicalgrade resins that enable high precision, repeatability and low-cost digital production of a large range of in-house products, such as orthodontic and anatomical models [5]. To evaluate the performance of this test setup, we printed two anatomical models representing relevant use cases: Hollow model of a congenital heart disease Heart model based on CT images, least accurate part (0.6 mm) Hollow model with variable wall thickness (1.5mm, 1.75mm, 4mm,...) Small details in model Mandible with surgery planning (cutting planes) Bone model based on CT images, least accurate part (1 mm) Teeth based on optical scan of plaster model (highly detailed 10-50 µm) 8

Figure 4 Congenital heart disease and planned mandible 3D models printed with the Formlabs Form 2 (respectively dental model resin and dental SG resin) The test setup was evaluated on three different grounds: Quality of the 3D-printed models in reference to the ground truth Economic aspects related to investment and running costs Operational aspects and versatility of the applications 4. KEY FINDINGS FROM TESTING A REFERENCE SETUP 4.1 REASON #1 IT S A HIGH-QUALITY SOLUTION After evaluating the test results, we highlighted three key reasons why a professional SLA desktop printer can be a good choice for setting up a 3D lab in-house. The two models shown above (Figure 4) were first segmented, designed and prepared for 3D Printing, using Materialise software. Next, the files were 3D-printed with the Formlabs Form 2. Afterwards, the 3D-printed models were post-processed and cleaned, and the supports were removed. To evaluate the accuracy of the print, the physical 3D models were scanned in 3D using an optical scanner. Finally, a surface comparison was performed between the original 3D file and the optically scanned 3D file using Materialise software. A visual inspection of the prints showed that after careful postprocessing, no support structures remained which could be wrongly identified as anatomical features. Also, visual inspection did not show any missing features compared to the virtual models. Between three printed versions of each model, the median of the surface distance was 0.12mm for the planned mandible and 0.14mm for the congenital heart model. The surface comparison between the original 3D file and the optically scanned 3D file is shown below using a color scale. If you take a look at the mapping between the two, note that despite the steady increase in optical scanning accuracy, low light reflection on steep slopes creates artifacts that leave some holes in the scanned surfaces. 9

Figure 5 Part Comparison analysis congenital heart and mandible This confirms that 3D Printing with the test setup is more accurate than the recommended image resolution for the highlighted medical applications [2, 6, 7, 8, 9]. This illustrates that the technology is suited to obtain an accurate representation of the anatomy. 4.2 REASON #2 IT S COST-EFFECTIVE Another advantage of setting up a 3D lab in-house with a solution that includes an SLA desktop printer is the low investment. Below, we analyze the cost per model associated with different ways of implementing 3D printing technologies (including the Formlabs Form 2). In the analysis, we include the prices of the software, the consumables and printer depreciation. We compare a desktopbased setup with full outsourcing of 3D production and with a representative high-end setup that is based on an industrial-grade 3D printer. Figure 6 Cost analysis comparison between industrial-grade 3D printer, Formlabs Form 2 desktop printer and outsourcing 10

The above analysis shows that about 20 models per year is the tipping point where it can become more cost-effective to insource using a desktop printer, than outsourcing the printing to a service bureau. A big difference can be seen between a desktop-based setup and a setup based on an industrial 3D printer. This is due to a low initial investment and a low material cost per print. Obviously, this analysis is a simplification and each institution s individual situation should be looked at in more detail. Besides economic aspects, considerations such as resource availability, operational aspects, servable applications, communication and others should be made before deciding to insource and how. 4.3 REASON #3 THE APPLICATIONS AND MATERIALS AVAILABLE ARE MANY 3D anatomical models can be used for a broad range of applications in the specialties of orthopedics, maxillofacial surgery, cardiovascular disease, oncology, pediatric and many more. Some of the applications are listed by field below. Cardiology: Congenital heart disease (DORV, DAA, ASD,...) Structural heart diseases such as Left Atrial Appendage (LAA) or mitral disease. Orthopedics: Scolioses Complex fractures such as tibia plateau, acetabulum or calcaneus. Hip dysplasia Maxillofacial applications Facial trauma Orthognatic surgery And many more Facial trauma: Provide a second model of the patient s anatomy mirrored across the midface to understand the optimal outcome for restoring cosmetics and function [1]. 11 Complex heart procedure: Provide a heart model cut along a split line with magnets to close it or with windows to highlight the intricacies of the intra-cardiac anatomy [1].

For applications in medicine where the anatomical interpretation of complex cases based on the model is aimed for, some important characteristics that will determine whether a technology is suitable are its ability to create color(s), transparency and flexibility. In general, a desktop SLA is suitable to create models for cases where a single color is sufficient and where the mechanical characteristics of the material are of secondary importance. In our test setup, the Formlabs Form 2 allows the use of a variety of materials for medical models. Matching the printing technology with the application can be challenging. By taking advantage of a versatile software solution for data preparation, the amount of applications that can be served may be expanded. As an example of the material options one can expect from a professional desktop printer, these materials, which can be matched to useful applications in healthcare, are available for the Form 2: Standard resins: These are either opaque white or clear, and their material properties make them suitable for a wide range of applications, mostly in bone tissue or for soft-tissue models where multiple colors and flexibility are not required. Functional flexible resin: This type allows the creation of parts that are bendable and compressible. However, unlike some other materials [10], the flexibility of the material has not yet been demonstrated in relation to real tissue. SG dental resin: This resin is designed to create orthodontic and anatomical models. For more information about its biocompatible properties and sterilization possibilities, please visit the Formlabs Website. 12

On Material usage Consumables are an important cost for 3D Printing. Also, 3D Printing is still a relatively slow process and the amount of time it takes to build a certain part may be useful information in specific scenarios. Therefore, we analyzed the amount of resin that is required for 3D Printing some medical models, including the necessary support structures. The table below illustrates how much resin is needed to print a model and how long will it take. Also, it illustrates the raw material cost for these models (in contrast to the overall cost including all workflow components in the previous graph). Table 1 Printing figures with Formlabs Form 2 This table shows that printing is still a lengthy process and can slightly be regulated (at the expense of geometric accuracy) by working with the layer thickness. It also shows the variability in printing cost when working with more specialized materials. 13

5. GETTING THE RIGHT PEOPLE To obtain the results shown above, not only essential key components and a fully integrated workflow are needed. A highly skilled team will make any 3D lab an effective 3D printing hub and ensure a smooth process, from image acquisition to 3D Printing. Expertise in imaging, anatomy and pathology is needed for the segmentation step, and engineering know-how is useful in preparing the models for the final printing stage [1]. Passionate and driven physicians play an instrumental role in the conception of the lab. 3D Printing can be a powerful educational tool, and can be used to better communicate complicated procedures to patients and families. Communicating these benefits is a must. Acquiring solid 3D printing experience empowers the team to take part in identifying cases for which 3D Printing would be beneficial. Communicating successes with colleagues can open the door for new possible 3D printing applications in other departments, and convince other physicians to consider 3D Printing for challenging cases and education. Over time, gathering concrete data from these successes and making it known to hospital administrators could even perpetuate the financial sustainability of the lab. 6. CONCLUSION There is an increasing demand for more medical 3D printing applications, as their benefits are becoming increasingly obvious. Improved patient-clinician communication, sophisticated educational tools, better planning of complex procedures, patientspecific treatment and tools, and more, are all positive outcomes that only reinforce the power of 3D technology. This white paper illustrates that a 3D lab may very well benefit from a desktopprinter based setup, supported by a passionate team operating on dedicated software. Achieving a smooth workflow that is economically viable and still versatile in the applications it can serve is a real possibility. Don t hesitate to lean on the expertise of the hospital or even reach out to the 3D printing community for recommendations on how to define the optimal set-up and integrate key components at all levels of the hospital structure. 14

7. LEARN MORE ABOUT THE AUTHORS Xavier Mottart received his MSc in Biomedical Engineering at the Université de Liège and completed his master thesis at the Ecole Polytechnique Fédérale de Lausanne. After graduation, he started working at Materialise as a Medical Application Engineer for Materialise amace Acetabular Revision, helping patients with severe hip interventions to achieve better outcomes with patient-specific 3D-printed implants. He designs and performs quality checks for hip implants, including complex development cases which require innovative solutions. He recently shifted his focus to product engineering projects, using his years of experience in the field of Medical 3D Printing to compile whitepapers aimed at informing and aiding hospitals interested in 3D printing technology. Pieter Slagmolen received his MSc in Electromechanical Engineering at the University of Leuven in 2005. He obtained his PhD in medical image processing from the University of Leuven in 2010, focusing on medical imaging for novel radiation therapy techniques. Afterwards he became a research manager at the Medical Imaging Research Center and Flemish Innovation Center iminds, leading innovation projects as well as valorization and (inter) national research collaboration. He has (co-)authored over 20 peerreviewed publications in the field. In 2015, Pieter joined the product management organization of Materialise with the intent of using his scientific experience to improve Materialise Medical software products, in order to support the Materialise vision towards a better and healthier world. 15

8. LEARN MORE ABOUT MATERIALISE Materialise is a global 3D printing software and services company whose medical division is dedicated to enabling researchers, engineers and clinicians revolutionize patient-specific treatment that improves and saves lives. With over 27 years of excellence, our open and flexible platform enables players in healthcare to build innovative and groundbreaking 3D printing applications that make the world a better and healthier place. Reach out to learn more about Materialise solutions and to set up a 3D lab in your hospital. For additional information, please visit materialise.com As was shown in this white paper, the presented test setup is high-quality, cost-effective and can be integrated at all levels in your hospital s infrastructure. A passionate team supported by a well-defined workflow operating on dedicated software, and a professional 3D desktop printer, are all it takes to get your 3D lab up and running. Just start! Your initiative can open doors for more collaboration, innovation and new applications that will make the world a better and healthier place. Materialise provides a complete and accessible turnkey solution that fits your needs. Just get in touch with us to find out how we can support your hospital. 16

9. REFERENCES [1] Six Considerations for Implementing a 3D Printing Core Service in Your Hospital. By Todd Pietila [2] Mitsouras et al, Medical 3D Printing for the Radiologist, RadioGraphics 2015; 35:1965 1988 [3] How a 3-D-printer changed a 4-year-old s heart and life. By Carina Storrs, Special to CNN. October 6, 2015 [4] Implementing Preoperative Surgical Planning Using 3D Printing. Pamela Marcucci, Michael Springer [5] https://formlabs.com/ [6] George et al, Measuring and Establishing the Accuracy and Reproducibility of 3D Printed Medical Models., Radiographics. 2017 Sep-Oct;37(5):1424-1450 [7] Materialise scan protocol, http://www.materialise.com/en/ resources/all/scan-protocols [8] Boston Children s recommendations for optimal image specifications by anatomy for 3D printing -- http:// zew1k2c4b1iul8c3siwdzu5n.wpengine.netdna-cdn.com/wp- content/uploads/2015/07/simpeds3d-print-modality-and- Thickness.pdf [9] Friedman et al, 3D printing from diagnostic images: a radiologist s primer with an emphasis on musculoskeletal imaging putting the 3D printing of pathology into the hands of every physician, Skeletal Radiol (2016) 45:307-321 [10] Material characterization of Materialise HeartPrint models and comparison with arterial tissue properties, Materialise, Katrien Baeck, Patricia Lopes, Peter Verschueren, Materialise, 2017 17

10. APPENDIX TIPS ANAD TRICKS TO GET OPTIMAL RESULTS WITH FORMLABS FORM 2 The statistical analysis presented in this white paper has shown that Formlabs Form 2 is a high-quality SLA 3D printer and can be used to print 3D models in hospital environments. Here are some tips that will help you optimize the quality of the print, the building time and the amount of material that will be used. Quality considerations for file preparation This section contains some tips that will help optimize the quality of the print, the building time and the amount of material that will be used. How should you position your build on the building platform? Make sure the resin can flow out of the objects to avoid dragging and bad quality layers Print objects with large surface area at an angle and not parallel to the build platform. This will reduce the surface that remains in contact with the resin and will make it easier to print Do not always use the same location on the build platform for printing. Print on different areas of the build platform to increase the resin tank s lifetime and the quality of the print as shown below. 18

How can you use supports for your print? It is recommended to always use supports for your build; they will increase the quality of the print. PreForm is the build preparation software by Formlabs that comes with the printer. The software is convenient and easy to understand. It allows either an automatic ( magic button : one click print) or manual support generation. PreForm offers a few control parameters for its support generation module. The default values are safe and reliable for initial use but still not optimal for all parts. With some experience, it is easy to generate or edit the support to optimize it for a specific part. How to post-process your parts? An IPA bath is needed to remove residual resin (2 x 10 minutes) An UV post-curing solution is needed to achieve the final material properties (10 minutes 60 C 108 W with UV-A and UV-B) Formlabs Form 2: The build volume of the Form 2 is limited by the size of the building plate. To print a large model, either scaling or cutting the part in two can be a solution. 19