Development of radiopaque FFF filaments for bone and teeth representation in 3D printed radiological objects

Matheus Savi,Daniel Villani,Marco Antônio Bertoncini Andrade,Orlando Rodrigues Jr,Maria da Penha Albuquerque Potiens

doi:10.15392/bjrs.v10i1.1739

Abstract

The use of 3D printing technologies is growing widely, including the possibility of design phantoms for imaging and dosimetry. For that, high attenuation tissues such as cortical bone, dentin and enamel need to be mimicked to accurately produce 3D printed phantoms, especially for Fused Filament Fabrication (FFF) printing technology. A Radiopaque FFF filament commercially available had been hard to be found; and this study aims to report, step-by-step, the development of a radiopaque FFF filament. A combination of radiopaque substances (Barium Sulfate - BaSO4 and Calcium Carbonate - CaCO3) was selected using the National Institute of Standards and Technology (NIST) XCOM tool theoretical data and added as filler in an Acrylonitrile Butadiene Styrene (ABS) matrix. The filament was homogenized and gone under first characterizations by analyzing its density, Scanning Electron Microscopy (SEM), Computed Tomography (CT) and micro-CT (µCT) scans. Three filaments were produced with different Hounsfield Units (HU) equivalences: XCT-A (1607HU), XCT-B (1965HU) and XCT-C (2624HU) with respective densities of 1.166(6) g/cm³, 1.211(2) g/cm³ and 1.271(3) g/cm³. With these values, high attenuation tissues, such as bones, dentine and enamel, can now be mimicked with FFF 3D printing technology, at a low cost of production.

Highlights

There are many techniques to 3D print an object, such as Stereolithography (SLA), Fused Filament Fabrication (FFF), Selective Laser Sintering (SLS) and Polyjet
The recent work of Price et al [23] proposed a filament based on an Acrylonitrile Butadiene Styrene (ABS) matrix doped with calcium titanate (CaTiO3) that was homogenous and suitable for bone representation. Considering this area is still underdeveloped and a documented step-by-step process could be useful to the scientific community, this paper aims to report the creation of a radiopaque filament to be used in FFF 3D printing technology testing a variety of dopant materials
The process involved in combining the binder to the elected filler occurs in the filament extruder, in a molten section, where ABS pellets are melted between 215 oC to 230 °C while the BaSO4 is added as a fine powder and carried by a thread

Summary

Introduction

There are many techniques to 3D print an object, such as Stereolithography (SLA), Fused Filament Fabrication (FFF), Selective Laser Sintering (SLS) and Polyjet. Commercially available FFF filament materials capable of simulating tissues that exhibit high density and attenuation, compatible with bone, dentin and enamel, are hard to find. Iron and other ferromagnetic materials have been used to simulate these tissues [10,11,12]; they have the intrinsic limitations of not being compatible with Magnetic Resonance (MRI) equipment if needed. For CT scans, HU values inside a given ROI could show high standard deviation, especially with high printing layer heights or narrow CT slices (under 2 mm thickness). This is caused by the difference of attenuation coefficients between adjacent tissues or materials, which could provoke heterogeneity and measurement uncertainties. The high attenuation Fe filament could result in image artifacts similar to metallic implants

Objectives

Methods

Results

Conclusion