This protocol describes a procedure for creating functional artificial neonatal heart models by utilizing a combination of magnetic resonance imaging, 3D printing, and injection molding. The purpose of these models is for integration into the next generation of neonatal patient simulators and as a tool for physiological and anatomical studies.
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Method Article
Anatomically Realistic Neonatal Heart Model for Use in Neonatal Patient Simulators
In This Article
Summary
Abstract
Neonatal patient simulators (NPS) are artificial patient surrogates used in the context of medical simulation training. Neonatologists and nursing staff practice clinical interventions such as chest compressions to ensure patient survival in the case of bradycardia or cardiac arrest. The simulators used currently are of low physical fidelity and therefore cannot provide qualitative insight into the procedure of chest compressions. The embedding of an anatomically realistic heart model in future simulators enables the detection of cardiac output generated during chest compressions; this can provide clinicians with an output parameter, which can deepen the understanding of the effect of the compressions in relation to the amount of blood flow generated. Before this monitoring can be achieved, an anatomically realistic heart model must be created containing: two atria, two ventricles, four heart valves, pulmonary veins and arteries, and systemic veins and arteries. This protocol describes the procedure for creating such a functional artificial neonatal heart model by utilizing a combination of magnetic resonance imaging (MRI), 3D printing, and casting in the form of cold injection molding. Using this method with flexible 3D printed inner molds in the injection molding process, an anatomically realistic heart model can be obtained.
Introduction
Every year millions of neonates are admitted to neonatal intensive care units (NICU). In NICUs, most emergencies relate to problems in the airway, breathing, and circulation (ABC) and require interventions such as chest compressions. NPS offer a valuable teaching and training tool to practice such interventions. For some NPS, embedded sensors can detect whether performance meets the recommended clinical guidelines1 for depth and speed of chest compressions. The adherence to guidelines can be used to calculate and quantify performance, and in this regard, such state of the art NPS can be viewed as a tangible and white box metric for evaluating p....
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Protocol
All institutional approvals were obtained before patient imaging.
1. Image Acquisition and Segmentation
- Acquire a thoracic MRI scan of a neonate in Digital Imaging and Communications in Medicine (DICOM) format. Capture every slice of the scan in the ventricular diastolic stage of the heart cycle or obtain a thoracic MRI from an autopsy.
NOTE: A visibly clear definition of the heart muscle, as well as atria and ventricles, is essential. - Using processing software (see Table of Materials) import the DICOM file of the thoracic MRI. Using the 'Editing Masks' menu item, select the area of the ....
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Results
This study details a method to create an anatomically realistic neonatal heart model combining MRI imaging, 3D printing, and cold injection molding. The ductus arteriosus as well as foramen ovale were not included in the heart model presented in this paper. The method described in this paper can also be applied to other internal organs, such as lungs, and rib cage structures. Rib cage structures require no molds and can be printed directly using flexible materials. In (
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Discussion
For the model developed in this study, we identified that injection molding over a 3-min period is required to prevent air entering the cast (Figure 5, Figure 6). To ensure that silicone reaches the narrow spaces of the valves, "pre-casting" or "coating" of the valve areas in the mold is essential. Since the inner molds shaping the heart chambers have to exit the final silicone cast through 5 mm openings, multi-material 3D printing for molds is n.......
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Disclosures
The authors declare no potential conflicts of interest concerning research, authorship, and publication of this article. This research received no specific grant from any funding agency in public, commercial, or not-for-profit sectors.
Acknowledgements
This research was performed within the Dutch framework of IMPULS perinatology. The authors would like to thank the Radboud UMCN Museum for Anatomy and Pathology and the Máxima Medical Centre Veldhoven for providing the neonatal MRI scans used for this work. The authors further would like to thank Jasper Sterk, Sanne van der Linden, Frederique de Jongh, Pleun Alkemade, and the D.search lab at the faculty of Industrial Design for their significant contributions to the development of this research. Lastly the authors would like to thank Rohan Joshi for his proof reading of the manuscript.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| Ecoflex 5 | Smooth-on | Silicon casting material | |
| 400ml Static mixers | Smooth-on | Mixing tubes | |
| Manual dispensing gun | Smooth-on | Used for injection molding | |
| 5-56 PTFE spray | CRC | Release agent for the molds | |
| Sodium-hydroxide | N/A | This was purchased as caustic soda at the hardware store, in dry, 99% pure form. As it is widely available, there is no company specified | |
| VeroWhite | Stratasys | The hard material used in the print | |
| TangoBlackPlus | Stratasys | The rubber material used in the print | |
| Support Material | Stratasys | The standard support material used by stratasys | |
| Magill Forceps | GIMA | Infant size. This is for removing the inner molds | |
| Stratasys Connex 350 | Stratasys | If this machine is not owned, another option is to have the parts printed through a third party printing firm such as 3D-hubs to get the parts printed and shipped. | |
| Balco Powerblast (Water Jet) | Stratasys | ||
| Euro 8-24 Set P (Air Compressor) | iSC | 4007292 | |
| Syringe with blunt needle | N/A | A 20ml syringe with a 0.5mm diameter blunt needle. | |
| Mimics 17.0 software | Materialise | This software was used to segment the heart model from the MRI. There are sevaral free MRI imaging software tools available such as InVesalius, or Osirix, although they may prove to provide less functionality. | |
| Magics 9.0 software | Materialise | This was used to repair and smooth the .stl files generated by mimics. This smoothing can also be done in most other 3D modeling freeware. | |
| Solidworks | Software used for editting the heart model. Most other freeware CAD software can be used to perform this stage of processing. |
References
- Wyllie, J., Bruinenberg, J., Roehr, C. C., Rüdiger, M., Trevisanuto, D., Urlesberger, B. European resuscitation council guidelines for resuscitation 2015. Resuscitation. 95, 249-263 (2015).
- Sawyer, T., Strandjord, T. P., Johnson, K., Low, D. Neon....
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