There’s no question that computer modeling, simulation, and additive manufacturing have transformed clinical medicine around the world. What’s always fascinated me, though, is the variety of ways these technologies have been implemented in different hospitals and even different departments within the same hospital. As a prototyping fellow at Sinai BioDesign, a design and prototyping group within the Mount Sinai Hospital in New York, I’ve seen firsthand almost all of the ways 3D printing, and more broadly, 3D data can be leveraged within a health system. Like many other tools and data streams, there’s no single way 3D medical data is acquired or used within the health system. In each case, though, these printing, scanning, and rendering applications are crucial to clinical care and research. For part 1 of this Expert Corner blog, I’ll be focusing on use cases for 3D modeling and printing and in next week’s part 2 , I’ll be discussing clinical applications of 3D scanning technologies, the other side of the medical 3D coin.

At Sinai BioDesign, a large portion of our 3D modeling and printing work is focused on pre- and peri-operative applications; providing models of patients’ anatomy for crucial guidance before and during surgical procedures. It often comes as a surprise to people, though, to learn how often we never produce a printed model from the data we acquire. No matter the surgical plan, a 3D model (typically an STL file) is produced from medical imaging data (usually CT and MRI scans). Printing that 3D model, however, is not always the next step in the process.

At Mount Sinai, the decision on whether or not to print a model often falls along surgical departmental lines, with rationales rooted in the nature of different surgeries. Our Department of Neurosurgery, for example, rarely leverages 3D printing in their pre- and peri-operative surgical guidance, opting instead to render the data with a variety of VR and AR tools. For pre-surgical planning, technologies like the Surgical Theater platform are used to produce 3D models of patients’ anatomy, which the surgeon can then manipulate on interactive displays and even “walk” through using VR headsets. While a 3D printed copy of a patient’s anatomy is easier to probe, manipulate, and analyze than the actual patient’s anatomy in the OR, it often doesn’t afford the kind of perspectives and spatial understanding that can be achieved through a VR rendering. Any view that would be blocked by actual anatomies, such as the skull, is also frequently blocked by the printed anatomy. In VR you can shift the transparency of different tissues in much the same way you can adjust the transparency of layers in Photoshop, but you can adjust colors and transparency in a 3D printed model.

Furthermore, the tissues neurosurgeons operate on – mostly brain, blood vessels, and tumors located in and around brain and blood vessels – are very soft and materials with accurate mechanical properties cannot be produced through existing 3D printing technologies. As such, there is little to no tactile information gained through a printed anatomical model and the visual/spatial information is at best as good as what can be obtained through rendering the 3D models in VR. Lastly, Mount Sinai’s Neurosurgery Department frequently employs AR, heads-up display technologies as a means of peri-operatively visualizing anatomical data. This ability to overlay and highlight important anatomical information (say the location of a brain tumor, or important blood vessels that should be avoided) on the live visuals being captured in the OR is arguably even more useful than looking back and forth between a printed model and the patient (at least in the case of neurosurgery).

Although, as the neurosurgery examples show, the lifecycle of an STL in a hospital doesn’t always lead to a 3D printer, there are many cases in which it does, and many departments that almost always print anatomical models for surgical guidance. For purposes of surgical planning, the Ear, Nose, and Throat (ENT) department at Mount Sinai is one of the most avid users of printed anatomical models. Many ENT procedures require the use of endoscopic cameras and surgical tools, typically inserted via the nostrils. Unlike neurosurgery, the tissues involved in ENT procedures are bony and cartilaginous, much stiffer and more reasonably approximated by the thermoplastics and ceramic powders our anatomical models are printed out of. As such, performing a dry run of a planned ENT procedure on the printed copy of a patient’s anatomy comes much closer to approximating the conditions that will be experienced in the OR. Very often, this means using the same types of endoscopes as catheters on the printed model as would be used on the patient while evaluating maneuverability, fit, and overall strategy.

When not intended for patient-specific practice, Sinai BioDesign’s printed anatomical models are frequently used for more generalized practice, especially for neurological procedures such as stereoelectroencephalography (SEEG), which involved the placement of electrodes deep into the brain. As you might imagine, a procedure that involves drilling through the skull and inserting foreign objects into the brain is also a procedure that requires a lot of training and practice. Many of the commercially available practice models do a poor job of replicating actual human anatomy, so we’ve begun producing our own practice models using a combination of 3D printing and casting techniques. The skull and key vasculature to be avoided are printed from a hard, ceramic powder (which happens to feel fairly similar to bone, with respect to drilling) and a cast of a brain (my brain, in fact[1] ) made from a cryogel that replicates the mechanical properties of brain tissue is inserted inside the printed skull. The fully assembled models are then used with the SEEG drilling equipment for training courses for surgeons. These hybrid printed/cast anatomical models have been so successful at replicating human anatomy, at both the physical and mechanical levels, that the production of skulls for SEEG training is likely the single largest application of 3D printing at Mount Sinai.

When considering the impact of 3D printing in medicine, we often primarily consider the impact of printed objects that are directly integrated into the surgical cycle, be they implants, prostheses, or pre-surgical planning models. It is important to remember, though – and I hope my examples from Sinai BioDesign illustrate this – that there are many ways 3D printing (and the 3D files that precede printing) impact clinical care even when not directly integrated into a surgery. Printed models, like our SEEG dummies, are helping democratize training for complex surgical procedures and creating more realistic practice environments. Furthermore, the digital models that produce all of these printed objects don’t even need to be physically manifested to have crucial clinical utility. In cases such as neurosurgery, where a printed model doesn’t necessarily add much to the pre-surgical planning process, VR pre-surgical “walkthroughs” and AR peri-operative guidance can decrease procedure durations and improve outcomes. 3D medical technologies will likely never be used in the same way everywhere, but I think it’s clear all of them will play a crucial role somewhere.

About the Author

Joseph Borrello

Joseph Borrello is currently a biomedical engineer and PhD Candidate at Mount Sinai, working in the labs of Drs. Kevin Costa and Junqian Xu, in addition to managing digital fabrication operations within the Sinai BioDesign innovation team. Previously, he worked at 3D Systems on technical development in the consumer marketing department and as a liaison with engineering project management teams.

He received his bachelors in Biomedical Engineering from Macaulay Honors College at The City College of New York, where he remains active in the Zahn Innovation Center, an on-campus tech startup incubator.

Joseph is also an active member of the New York City startup ecosystem. He is the founder of Proto-Sauce, which is developing new materials for resin-based 3D printing, as well as the CTO of Biosapien, leveraging 3D printing to produce personalized therapeutics. He also tries to summarize as many of the local happenings as he can in his newsletter Magnitude and Direction.

Finally, Joseph is also the editorial assistant for 3DHEALS Lattice newsletter, where he tirelessly curate the best content for healthcare 3D printing and bioprinting community with the 3DHEALS team.

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The post Clinical Applications of Medical Modeling- Part One appeared first on 3DHeals.

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3DHEALS GALICIA 2017

 

Dear colleagues and friends,

 

Additive manufacturing (AM) has become a common technology in many departments, although regulations for its use in healthcare facilities may sometimes not be as clear as we would like. Last year, upon my arrival at the European Face Centre (EFC), Professor Maurice Mommaerts and I considered AM an interesting field for research because of many doubts surrounding its products. Mrs. An Vijverman, a lawyer who specializes in Belgian and European life sciences legislation, shared with us her valuable professional opinion regarding the European Union (EU) and Belgian laws related to medical devices. We hope that an interesting peer-reviewed manuscript with a detailed discussion will soon be accepted for publication, though I would like to share a summary of our conclusions here.

 

Additive manufacturing or three-dimensional (3D) printing, includes techniques used to (re)produce an object from a data set typically in Standard Tessellation Language, allowing us to shift from conventional subtractive- (milling, turning, cutting) or net shaping- (casting, molding, forging, stamping) based manufacturing. Mr. Charles Hull obtained the first approved AM patent in 1986, and in 1989, Stratasys developed the fused deposit filament molding (FDM) printer, now likely the most commonly used type of desktop 3D printer. Other types of AM printers (per the American Society for Testing and Materials) are Stereolithography, Material Jetting, Binder Jetting, Directed Energy Deposition, Powder Bed Fusion and Sheet Lamination that can use various materials, such as paper, wood, polymers, or metals.

 

The EFC runs two FDM printers (MakerBot Replicator 2 and MakerBot Replicator 2X), which provide up to 0.100-mm layer resolution and 7,522 cm3 (25.2 cm L × 19.9 cm W × 15.0 cm H) of building volume using 1.75-mm diameter polylactic acid (PLA) filaments for consistent and environmentally friendly (biodegradable) printing. Such printers should be in a ventilated area to avoid accumulation of toxic fumes released from melted PLA. If the printed product will be in direct contact with a patient, it should comply with the Medical Device Regulations document first published by the EU Council in 1993 (Directive 93/42/EEC) and its latest amendment released in 2016. Broadly defined, a medical device (MD) is an instrument (hardware and software) used for diagnosis, prevention, monitoring, prediction, prognosis, treatment, or alleviation of disease. A custom-made device (CMD) is “any device specifically made in accordance with a written prescription of a doctor of medicine, of a dental practitioner or of any other person authorized by national law by virtue of this person’s professional qualifications which gives, under his responsibility, specific design characteristics, and is intended for the sole use of a particular patient exclusively to meet their individual conditions and needs.” (Directive 93/42/EEC, 2016) Once a product is determined to be an MD or CMD, the device is classified into one of three categories outlined by Directive 93/42/EEC (2016) based on the product’s type and length of body contact. These categories are summarized in Table 1. If the product will not touch a patient (e.g., models used for mock surgery), it is not considered an MD.

Table 1. Medical device (MD) classification criteria according to Annex VII of Directive 93/42/EEC, 2016.

 

Directive 93/42/EEC (2016) includes over 16 annexes that address MD-related issues, such as essential requirements for patient health and safety depending on the MD’s category, materials involved, packaging (sterile or non-sterile), labeling, and waste disposal procedures. Custom-made devices should have a unique identification number with manufacturer details, the doctor’s name with professional qualifications, the patient’s name, and the purpose of the device. This information should be available for 10-15 years if the product is implantable. Biocompatibility is of key importance. The International Standard Organization (ISO) establishes guidelines with which any MD that is meant to be in contact with a patient must comply (ISO 10993-1; 2009). The standards describe the structured biological evaluation of such an MD that must be planned, carried out, and documented by an experienced professional.

 

Summary:

• Models for teaching purposes, studying complex bony structures, performing a mock surgery, for molding a plate or an orbital floor mesh require no special oversight because they will have no direct contact with a patient.
• Custom-made devices that will be in direct contact with a patient, including surgical guides, orthognathic wafers, and facial implants, are classified according to EU Council Directive 93/42/EEC (Table 1) and must adhere to standards described in ISO 10993-1.

Although PLA is widely used in surgeries, FDM printer filaments are not ISO- certified, likely because the material is too porous and its low melting point for conventional sterilization will not guarantee its dimensional stability. Other thermoplastics used for CMD construction, such as acrylonitrile butadiene styrene from Stratasys and polyethylene terephthalate (PET or PETE) and nylon 680 from Taulman 3D, have been granted Class IIa status under ISO 10993. Thus, under specific circumstances, CMDs composed of these materials can be in contact with the patient for up to 30 days. The sterilization process is generally achieved through flash steam or ethylene oxide, depending on the specific product.

If one is manufacturing a CMD within the European Community (CE), one must be aware that:

– CE marking cannot be placed on the CMD unless it is intended for clinical investigation (Articles 17 and 18 of Directive 93/42/EEC, 2016).

– A CMD can be marketed if it complies with Article 42 and Annex XI of Directive 93/42/EEC (2016), which describe a conformity assessment procedure addressing general safety and performance requirements outlined in Annex I and related text. Article 4 of the directive specifies that if the product was manufactured within a health institution, the product shall be considered “in service” and must, therefore, comply with CE regulations. However, an exception to the former rule is outlined in Article 4.4a. If the device is kept at the institution, its manufacture passes appropriate quality management procedures, and the health institution provides information upon request regarding its use to their competent authority, including detailed information about the device and its production, then the device does not need to comply with CE regulations. A device produced in-house is not considered “on the market” if the product is not sold to a third party or to a patient; one such case includes surgical guides and models. Nevertheless, the local regulations in each country should be verified. For example, Belgium institutes a more flexible policy (Koninklijk Besluit van 18 Maart 1999 betreffende de medische hulpmiddelen) under which no clearance from the EU Council is needed for CMDs.Proper standardized regulations for AM are needed. Future changes to Directive 93/42/EEC regarding MDs are likely imminent.

Please comment how you print, sterilize, and market AM devices in your countries!

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