University of pittsburgh 3d printing

The widespread use of advanced imaging in radiology has become a key factor in diagnosis and communication between physicians. While these visualizations have traditionally been used in the 2D plane as CT or MRI scans as DICOM files, software developers have recently created tools to reconstruct diagnostic images as 3D anatomical imaging.

3D printed models are a natural extension of these various 3D rendering options and offer many additional benefits such as tactile feedback and other tangible information that visualizations cannot provide. nine0036

When a patient's severe foot deformity could not be fully represented with 2D images, surgeons used a 3D printed model to plan how to correct gait with preoperative equipment and work with clinical staff and receptionists.

For example, research on a custom 3D printed model allowed a UK orthopedic surgeon to find a solution with a lower risk of abnormal injury to a boy's forearm

“Access to the model has changed standard CT therapy from a four-hour complex osteotomy to a simple, much less invasive 30-minute soft tissue procedure,” says Dr. Michael Eames

A successful operation was completed in just 30 minutes — reduction of more than three hours from the originally scheduled time in the operating room, saving the hospital an estimated $5,500. Subsequently, the patient spent less time on post-operative care and recovered more quickly

Workflows from scan to 3D model

Creating 3D printed files and 3D printed models requires special considerations and minor changes to the medical imaging workflow

The tailored workflow can be divided into three steps: image acquisition, image segmentation and 3D printing

IMAGE ACQUISITION

Image acquisition is the first step and is already integrated into the workflow. The most common imaging techniques suitable for 3D printing are CT and MRI. In general, 3D models can be printed from any volumetric image dataset (slices) with sufficient contrast to differentiate tissues. nine0036

Cone beam CT is also widely used for dental and otolaryngological imaging of teeth, but contrast can be worse than conventional CT, making segmentation more difficult. See recommendations for setting up patient scans for 3D models in the second part of this booklet

IMAGE SEGMENTATION

The main goal of this step is to reduce the complexity of the original image while leaving the necessary characteristics unchanged and isolated. Once the radiographer has received the DICOM, they must perform Regions of Interest (ROI) processing, which will be rendered as a 3D printed object. The process of identifying and separating tissues and other areas of interest is called segmentation. Depending on the complexity of the model, it is performed by a radiologist-technician under the guidance of a radiologist or directly by a radiologist. Once the segmentation is completed, it is reviewed by the surgeon for final approval13

A number of commercial and open source software products can be used for the segmentation process (see the list at the end of this section). Before choosing a software solution, consider your intended use, regulatory requirements in your area, and recommendations at your institution.

ROI segmentation steps can include automatic methods (eg thresholding, edge detection and region enlargement) or manual selection and adjustments. Thresholding uses parameters that can be identified and associated with a particular ROI, such as bones with higher Hounsfield values ​​relative to their surroundings. nine0036

Thresholds may need to be dynamic and include more sophisticated algorithms to account for factors such as CT noise and beam hardening that can create artifacts and other unwanted results.

Another option is to use a growth region to automate segmentation, where the algorithm assigns voxels as belonging to one part or another based on similarity or difference to surrounding voxels. This may require additional adjustments and clarifications. nine0036

After segmentation is complete, convert the segmented objects to a file type that can be used by the 3D printer. This file type is usually an STL or OBJ file format.

After conversion, make any necessary physical adjustments that are more common in 3D modeling, such as smoothing surfaces, filling holes, and fixing other minor features. These adjustments can be made by a specialist in various CAD or CAM programs and should always include review by a physician to ensure that the result is clinically useful. nine0036

Once the radiographer has received DICOM, they must determine the regions of interest (ROI) that will be displayed as a 3D printed object. Source: ITK-Snap

In-house 3D printing enables healthcare providers to quickly create high resolution medical models.

3D PRINT

Once the final file is ready, it can be exported and sent to a 3D printer for production. There are several key factors to consider when choosing the right 3D printing technology, including: the cost of the printer, software, and materials; print speed, accuracy and resolution; ease of use and access to customer service; the type of printed materials, including biocompatibility and sterilization for certain uses. nine0036

After printing, parts should be rinsed with isopropyl alcohol (IPA) to remove excess resin and, depending on the material and application, post-cured in a curing chamber. All biocompatible resins require post-cure prior to use, while standard Formlabs resins such as White and Clear Resin increase post-cure strength and stability.

More information about print options

Visit our Software Support and Resources pages for more information on how to set up files for printing and learn more about specifications such as internal supports and minimum wall thickness

POTENTIAL FIELD 3D PRINTING SOFTWARE AND HARDWARE

Note: Each section requires only one kind of software that completes the workflow steps. This list is for ease of reference and research and does not constitute an endorsement of any particular software or vendor. If you require anatomical models without segmentation or printing in situ, specialized service providers offer conversion, segmentation and/or printing services for a fee (e.g. Anatomage, Armor Bionics, Axial3D and Materialize)

Check your local regulations and intended use before choosing a software solution.

Transform + Segmentation

Preparation for editing + File management, smoothing and identification

Support Generation + Print Orientation

Printer

Post-print

Formlabs finishing kit	Form Wash and Form Cure 9029eight
Ultrasonic cleaner (e. g. GT Sonic)	CUREBox CB-4051

* Formlabs and Materialize have partnered to offer a comprehensive package of services in the US, Europe and Japan. Mimics inPrint is a specialized software solution for creating accurate virtual anatomical models from medical images and preparing files for 3D printing. Integrated into Clinical Environments (PACS), Mimics inPrint includes predefined workflows with direct link to Formlabs 3D printers. nine0036

Patient Scan Setup for 3D Models

Some traditional medical imaging scans cannot be converted to high quality 3D models for clear and accurate anatomical structures. Plain radiographs (X-rays) and ultrasounds are not commonly used for 3D printing and these imaging techniques are not recommended.

The most commonly used imaging modalities for evaluating internal structures are computed tomography and MRI imaging. These rendering methods generate a DICOM file. DICOM is a standard for storing and transmitting medical images and can be thought of as a series of slices. nine0036

DICOM images cannot be edited in 3D design software or sent directly to a printer. To convert a DICOM file to a format suitable for 3D printing, such as an STL or OBJ file, separate software is required to calculate the surface area of ​​interest. This surface will become a 3D model.

Almost any DICOM file with sufficiently fine detail (such as thin slices) can be converted to a format that supports 3D printing of the structure of interest. nine0036

The following articles may be helpful in the preparation, printing and post-processing of anatomy models:

Design models for print support

Design features and geometry recommendations 9

Post-curing printing

Post-processing basics

Criteria for creating a printable scan

The first consideration when converting a CT or MRI to a 3D model is what needs to be shown; bones, vessels, and whole organs are all modeled differently. A model with outdated structures not only detracts from the focus of the model, but it will also be harder to produce. Scanning at the right specifications makes it easy to create a 3D printable model. The main features are intravenous contrast and slice thickness.

For 3D bone models, low contrast images are likely to be sufficient for accurate and detailed printing. Models containing solid organs, tumors, or vascular structures almost always require contrast magnification scans

Introductory contrast information

CT brightness variation allows the segmentation software to highlight different structures, allowing you to print an area or organ of interest. Some structures, such as bones, are inherently bright on CT scans. This makes it easier to 3D print when started from a non-contrast CT. However, intravenous

(IV) contrast is needed when you want to 3D print a blood vessel, tumor, or most organs. A contrast agent is injected into the patient just before the scan. With IV contrast, blood vessels (arteries and veins) and solid organs (such as the liver, kidneys, spleen, heart, and brain) become brighter when scanned, allowing the segmentation software to accurately separate them from surrounding tissues. See images below for a comparison of non-contrast and contrast-enhanced CT scans of the abdomen. nine0036

The effect of intravenous contrast is shown with two axial (transverse) CT scans of the upper abdomen. On a right scan, the aorta is enhanced, whereas on a left scan, the aorta appears very similar to the adjacent soft tissue. The contrast allows you to isolate the desired structures in post-processing. Source: Embodi 3D

In addition to enhancing contrast, slice thickness and resolution are equally important for planning when creating a 3D model. Most clinically useful scans were obtained at adequate resolution for 3D printing. However, if you try to 3D print an anatomical model while scanning with thick sections, your

model will have a rough surface. According to numerous sources, when creating a model for 3D printing, it is very important to use scans with slices less than 1.25 mm.

Two CT scans of the chest. The image on the left shows a frontal view constructed from 5 mm thick slices, while the high resolution scan shows a similar view of the chest using only 1 mm thick slices. Thick slices in the left image create rough textures that will result in a lower quality print. Source: Embodi 3D

The thickness of sections obtained from CT or MRI scans are converted directly into details generated from 3D scans. Depending on the focus object, areas of the image should be reconstructed with isotropic voxels of 1.25 mm or less15. According to a Mayo Clinic presentation in March 2016, 1 to 5 mm slices can be used for large structures, while 0.75 mm can be used for thin bone16. Thicker regions may degrade model accuracy, while very thin regions (e.g. <0.25 mm) may require extensive segmentation and STL enhancement, especially in the presence of image artifact. Cardiac models show sufficient accuracy with 0.5 mm patches, but thinner targets may be required for thin objects such as the inferior wall of the orbit17. Generally, thicker areas can create fuzzy or less accurate prints. However, unnecessarily thin areas can lead to significantly more work in the post-processing step. nine0036

Regulatory Issues

Please check local regulations, material data, patient information, and institutional requirements before 3D printing or using anatomical models. If you work in the US, please refer to the latest FDA presentation which outlines its guidance document18 Please note that these documents and recommendations are subject to change. Make sure you are using the latest guidelines. nine0036

Formlabs is the industry's leading manufacturer of 3D printers and materials used by healthcare providers to support the practice of medicine

Conclusion

Barriers to the transition to personalized precision medicine are fast disappearing. The advent of affordable, professional-grade 3D printers has enabled healthcare providers to produce anatomy models for specific patients and specialties with inspiring results. In some cases, the initial cost of a high quality printer has been covered by the time saved in the operating room after the surgeon used the 3D printed model to prepare for one complex procedure.19

“Medicine is not a one-size-fits-all solution, and when a tool like desktop 3D printing comes along that allows you to create personalized medical solutions, there is no doubt that it needs to be used to its full potential.”

Todd Goldstein

Instructor, Institute for Medical Research. Feinstein Director, 3D Printing Lab, Northwell Ventures, Northwell Health

Understanding the workflow required to integrate 3D printing is key to success. nine0036

This tutorial covers everything you need to get started, popular workflows and tools and methods to ease the transition from patient scanning to 3D printing

Contact us to learn more about 3D printing in Your institution and join the community of innovators in precision medicine

LINKS

1. Chepelev, Leonid, Andreas Giannopoulos, Anji Tan, Dimitrios Mitsouras, and Frank J. Rybicki Medical 3D Printing: Terminology Standardization Techniques and Report Trends 3D- printing in medicine 3, no. 1 (2017) doi:101186/s41205-017-0012-5
2. Mitsworth, Dimitris, Peter Lakouras, Amir Imanzadeh, Andreas A Giannopoulos, Tianrun Kai, Kanako K. Kumamaru, Elizabeth George, et al. "3D Medical Printing for the Radiologist" RadioGraphics 35, no. 7 (November 2015): 1965–88 https ://doi.org/101148/rg2015140320
3. Kerr, William, Philip Rowe, and Steven Gareth Pierce "Accurate 3D Bone Reconstruction Using Ultrasonic Synthetic Aperture Techniques for Robotic Knee Arthroplasty" Computerized Medical Imaging and Graphics 58 (June 2017): 23–32 https://doi org/101016/j compmedimag 201703 002
4. Chen, Xing, Jesse K Possel, Katherine Waconne, Ann F van Ham, P. Christian Klink, and Peter R. Roelfsema "3D printing and modeling of customized implants and surgical guides for lower primates" Journal of Neuroscience Methods 286 (July 2017 ): 38–55 https://doi org/101016/jjneumeth 201705 013
5. Wong, K. S., S.M. Kumta, N. V. Geel and J. Demol "One-stage reconstruction with a 3D printed, biomechanically assessed custom implant after complex resection of pelvic tumors" Computer Surgery 20, no. 1 (January 2, 2015): 14–23 https:// doi org/10 3109/1092908820151076039
6. Tan, Eddie T.W., Ji Ming Lin, and Shri Kumar Dinesh “Creating Acrylic Patient Cranioplasty Implants with an Inexpensive 3D Printer” Journal of Neurosurgery 124, no. 5 (May 2016): 1531–37 https://doi org/10 3171/2015 5 jns15119
7. Tan, Eddie T.W., Ji Ming Lin, and Shri Kumar Dinesh “Creating Acrylic Patient Cranioplasty Implants with an Inexpensive 3D Printer” Journal of Neurosurgery 124, no. 5 (May 2016): 1531–37 https://doi org/10 3171/2015 5 jns15119
8. Abdel Hey, Joe, Tarek Smyra, and Ronald Moussa "Customized Implants with PMMA Cranioplasty Using 3D Polylactic Acid Printing Plates: Technical Note with 2 Illustrative Examples" World Neurosurgery 105 (September 2017): 971–979 e1 https http://doi.org/101016/j wneu 201705 00
9. Keith, Jelleten, Gerwin Smith, and Paul Bredveld, 3D Printed Upper Limb Prosthesis: An Overview of Disability and Rehabilitation: Rehabilitation Techniques 12, no. 3 (February 2, 2017): 300–314 https://doi org/ 101080/1748310720161253117
10. Azer, Sami A. and Sara Azer “3D Anatomical Models and Impact on Learning: A Review of Quality in the Literature” Health Professions Education 2, no. 2 (December 2016): 80–98 https://doi org/101016 /j hpe 2016 05 002
11. Preoperative-planning-with-custom-3d-printed-surgical-model-reduces-theater-time by 88 percent Formlabs Accessed November 22, 2017 https://formlabs com/preoperative-planning-with-custom-3d-printed-surgical-model-reduces-theater-time/
nine0003 Christensen, Andy "Medical Imaging Software" 3D printing | Wohlers Associates Accessed November 22, 2017 http://www.wohlersassociates com/
12. Matsumoto, Jane S., Jonathan M. Morris, Thomas Foley, Eric E. Williamson, Shuai Leng, Ciarán P McGay, Joel L. Kuhlmann, Linda E. Nesberg, and Terry J. Vrtiska 3D Physical Modeling: Applications and Experiences in Mayo Clinic RadioGraphics 35, No. 7 (2015): 1989-2006 doi:101148/rg 2015140260
13. Kikinis R, Piper SD, Vosburg K. (2014) 3D Slicer: a platform for subject image analysis, visualization and clinical support. Intraoperative image processing. Imaging Therapy, Ferenc A. Jolez, Editor 3 (19): 277-289 ISBN : 978-1-4614-7656-6 (Print) 978-1-4614-7657-3 (Online) https://www slicerorg/wiki/ CitingSlicer
14. Mitsworth, Dimitris, Peter Lakouras, Amir Imanzadeh, Andreas A Giannopoulos, Tianrun Kai, Kanako K. Kumamaru, Elizabeth George, et al. "3D Medical Printing for the Radiologist" RadioGraphics 35, no. 7 (November 2015): 1965–88 https ://doi.org/101148/rg2015140320
15. T. J. Vrtiska, MD, Jane Matsumoto, MD, Jay Morris, MD, Imaging: The Role of the Radiologist. A Key First Step” Mayo Clinic (March 4, 2016)
16. Mitsworth, Dimitris, Peter Lakouras, Amir Imanzadeh, Andreas A Giannopoulos, Tianrun Kai, Kanako K. Kumamaru, Elizabeth George, et al. "3D Medical Printing for the Radiologist" RadioGraphics 35, no. 7 (November 2015): 1965–88 https ://doi.org/101148/rg2015140320
17. Nooshin Kiarashi, Ph. D., FDA/CDRH/Department of Radiological Medicine, "FDA Current Practice and Regulations, FDA/CDRH-RSNA SIG Joint Meeting on Customized 3D Printed Anatomical Models", excerpt from https://www fda gov/ downloads/MedicalDevices/NewsEvents/WorkshopsConferences/ UCM575723 pdf
18. Preoperative-planning-with-custom-3d-printed-surgical-model-reduces-theater-time by 88 percent Formlabs Accessed November 22, 2017

ADDITIONAL RESOURCES AND LINKS

1531–37 https://doi org/10 3171/2015 5 jns15119 Kikinis R., Pieper S. D., Vosburg K. (2014) 3D Slicer: A Platform for Objective Image Analysis , imaging and clinical support. Intraoperative image processing. Imaging Therapy, Ferenc A. Jolez, Editor 3 (19): 277-289 ISBN : 978-1-4614-7656-6 (Print) 978-1-4614-7657-3 (Online)

Rybicki F. Christensen, A. (05/12/2017) Recommendations for Medical 3D print: Patient safety. Retrieved Nov 03, 2017 from https://www 3printrcom/ guidelines-medical-3d-printing-patient- safety-3345869/ (n d ) http://www conceptualiz com/resources html

Biomedical Modeling, Inc Materials (16.

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