Communication3D printing of MRI compatible components: Why every MRI research group should have a low-budget 3D printer
Introduction
Commercial clinical MRI systems are usually equipped with a variety of MR-compatible accessories, for instance to provide positioning support and comfort for patients and staff. However, during research and initial sequence testing custom-made phantoms are frequently used, which may not fit into the standard fixation accessories. Make-shift arrangement solutions to fixate and position phantoms using cushions and sandbags are often sub-optimal, particularly as these items can, in our experience, slowly move or shift under their own load and under the influence of scanner vibrations during the experiments. Small animal MRI is another application increasingly performed on clinical scanners [1], [2], which requires, apart from using special dedicated animal coils, sufficient yet careful immobilization of the animals [3], [4]. Specifically, due to the required sub-millimeter imaging resolution, even small motions can result in imaging artifacts [5], [6].
Several of these limitations could be overcome by specially designed appliances, which exactly fit the experimental setup. However, special unique fixation devices or holders frequently require individual manufacturing and the production with turning lathes or CNC lathes is usually time consuming and expensive as this manufacturing process is not well suited to produce unique specimen. For this reason, rapid prototyping has become an integral part in research and development departments where the recent advances in 3D printing technology [7], [8] enable direct manufacturing of functional, detailed and complex prototypes in a fast and efficient way.
Recent hard- and software developments have led to a range of designs for 3D printers using fused deposition modeling (FDM) [7], which are meanwhile available as self-assembly kits in the price range of 500–2000 € [9], [10]. The design of these 3D printers is based on a print head that acts like an x–y–z plotter. The raw material, most often acrylonitrile butadiene styrene (ABS) or biodegradable polylactic acid (PLA), is molten in the print head and deposited layer by layer on the build table, creating the 3D object [7], [8].
The aim of this work was to design, create and test MRI compatible holders as well as a fixation device for mouse imaging on a clinical MRI system by using a low budget 3D printer [11], [12]. The process from the digital representation to the final printed object is described and illustrated.
Section snippets
Materials and methods
The main steps in creating a 3D printed object are to design and define the object with the aid of computer aided design (CAD) software prior to conversion into a toolpath description for the 3D printer, which is accomplished by so called slicer programs.
Results
All designed parts were successfully printed on the Ultimaker 3D printer. The loop coil platform (Fig. 4) was designed and printed overnight, demonstrating one major advantage of having a 3D printer available in the lab. The more complex mouse bed (Fig. 5) took longer to design and to print. A summary of all the parts, their weight and print time is given in Table 1.
Discussion
The possibilities of current 3D printers using FDM print technology [10] are quite intriguing, especially with respect to MRI as the materials used are inherently MR compatible. The versatility of the 3D printing process enables a wide variety of applications, from holders and appliances, as shown here, to phantoms [25] and even printing of implantable scaffolds for tissue regeneration [26]. Simple geometries, like the loop coil platform, can be quickly designed and printed overnight. More
Conflict of interest statement
All authors declare that they have no competing interests.
Ethical approval
This work did not involve any humans, so no ethical approval is required. All animal experiments were performed in accordance to the European “Convention for Animal Care and Use of Laboratory Animals” and with approval of the local animal welfare commitee and the “Thüringer Landesamt für Verbraucherschutz”.
Acknowledgment
This work was financially supported by the Carl Zeiss Foundation with a dissertation fellowship (MK).
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Editor's Comment: Reports on medical and clinically related applications of additive manufacturing techniques appear regularly in the Journal. In this Communication by Herrmann and colleagues, the authors present their experiences of using a fused-deposition technique to fabricate MRI compatible plastic components. The article details the design and fabrication of a small-animal fixation device for use in a clinical MRI scanner. In the on-line supplement to this article, the authors provide the CAD datasets on which their models were based for readers to download (in the industry standard STL format). With additive manufacturing systems becoming more readily available, and at relatively low cost, the technology is likely to find ever increasing application in biomedical engineering research.