3D printed ventricular septal defect patch: a primer for the 2015 Radiological Society of North America (RSNA) hands-on course in 3D printing
D Printing in Medicine
3D printed ventricular septal defect patch: a primer for the 2015 Radiological Society of North America (RSNA) hands-on course in 3D printing
Andreas A. Giannopoulos 0 1 4
Leonid Chepelev 0 3
Adnan Sheikh 3
Aili Wang 3
Wilfred Dang 3
Ekin Akyuz 3
Chris Hong 3
Nicole Wake
Todd Pietila 2
Philip B. Dydynski
Dimitrios Mitsouras 1 4
Frank J. Rybicki 3
0 Equal contributors
1 Applied Imaging Science Lab, Department of Radiology, Brigham and Women's Hospital , Boston, MA , USA
2 Biomedical Engineering , Materialise, Plymouth, MI , USA
3 The Ottawa Hospital Research Institute and the Department of Radiology, University of Ottawa , Ottawa, ON , Canada
4 Applied Imaging Science Lab, Department of Radiology, Brigham and Women's Hospital , Boston, MA , USA
Hand-held three dimensional models of the human anatomy and pathology, tailored-made protheses, and custom-designed implants can be derived from imaging modalities, most commonly Computed Tomography (CT). However, standard DICOM format images cannot be 3D printed; instead, additional image post-processing is required to transform the anatomy of interest into Standard Tessellation Language (STL) format is needed. This conversion, and the subsequent 3D printing of the STL file, requires a series of steps. Initial post-processing involves the segmentation-demarcation of the desired for 3D printing parts and creating of an initial STL file. Then, Computer Aided Design (CAD) software is used, particularly for wrapping, smoothing and trimming. Devices and implants that can also be 3D printed, can be designed using this software environment. The purpose of this article is to provide a tutorial on 3D Printing with the test case of complex congenital heart disease (CHD). While the infant was born with double outlet right ventricle (DORV), this hands-on guide to be featured at the 2015 annual meeting of the Radiological Society of North America Hands-on Course in 3D Printing focused on the additional finding of a ventricular septal defect (VSD). The process of segmenting the heart chambers and the great vessels will be followed by optimization of the model using CAD software. A virtual patch that accurately matches the patient's VSD will be designed and both models will be prepared for 3D printing.
3D Printing; Congenital heart disease; Ventricular septal defect; Segmentation; Computed-aided design; Patch; Radiological Society of North America; Hands-on Course; Medical education; Precision medicine
Introduction
3D printing refers to the fabrication of a tangible object
from a digital file by a 3D printer. Materials are commonly
deposited layer-by-layer and then fused to form the final
three dimensional object. Additive Manufacturing (AM),
Rapid Prototyping (RP), and Additive Fabrication (AF) are
synonyms for 3D printing. According to the most recent
classification by American Society of Testing and
Materials (ASTM), there are seven major types of 3D printing
technology. Although these technologies share similarities,
they differ in speed, cost, and resolution of the product.
Moreover, a variety of materials can be used to fabricate
the model.
A handheld printed model derived from Digital Imaging
and Communications in Medicine (DICOM) images
represents a natural progression from 3D visualization [1].
DICOM image files cannot be used directly for 3D
printing; further steps are necessary to make them readable by
3D printers. The purpose of this hands-on course is to
convert a set of DICOM files into a 3D printed model
through a series of simple steps. Some of the initial
postprocessing steps may be familiar to the radiologist, as they
share common features with 3D visualization tools that
are used for image post-processing tasks such as 3D
volume rendering.
Most 3D printed models are derived from DICOM
images generated from CT scanners. Images can be
reconstructed from isotropic voxels with slice thickness
less than or equal to 1.25 mm. For 3D printing, image
post-processing has both similarities to and substantial
differences from methods used by radiologists for 3D
visualization. As in 3D visualization, specific software
packages enable segmentation of DICOM images using
semi-automated and manual segmentation algorithms,
allowing the user to demarcate desired parts. The most
commonly used tools are thresholding, region growing,
and manual sculpting.
The segmented data are then exported in a file format
that can be recognized by 3D printers. In essence, this
process is conversion of 2D images to 3D triangular
facets that compose a mesh surface. To date, the most
widely used format is Standard Tessellation Language
(denoted by the file extension “STL”). In most cases, the
STL output is not optimized for printing and further
refinement is required. This refining step may be
unfamiliar even to radiologists versed in 3D visualization;
Computer Aided Design (CAD) software is used to
perform steps such as “wrapping” and “smoothing” to make
the model more (...truncated)