Volume 04 / Issue 03 / September 2016
From CT scan of a bone to 3D printed model, using Open Source software and a desktop printer Boyd Goldie
Although commercial 3D models can be made from a patient’s CT scan, this is usually reserved for special cases, such as neurosurgical skull reconstruction or planning correction of malunion in the extremity. These models are produced by commercial companies, take as long as two weeks to produce and are costly. A distal radius might cost in the region of £250. However, 3D printers are becoming affordable for either an individual or a small department. This article details a low cost and speedy alternative utilising open source (free) software and a desktop printer.
how to make something. It instructs the machine tool where, how fast and through what path to move. For 3D printing, this software is referred to as slicing software. Cura is open source slicing software, which has been developed by Ultimaker and converts .STL into G-Code. Cura is reputed to be the fastest slicing software currently available. Using an Ultimaker2 printer I have made models that have subsequently helped plan surgery and inform patients.
How to convert DICOM to G-Code
Material and method Digital Imaging and Communications in Medicine (DICOM) is the standard for handling, storing, printing and transmitting information in medical imaging1,3. Many PACS software programs can produce on-screen volume or 3D images, but they generally cannot export the information in the file format required for a 3D printer. STL (STereoLithography) is a file format native to the stereolithography CAD software created by 3D Systems. STL is also known as Standard Tessellation Language2. Boyd Goldie
Some software to convert DICOM to STL is commercially
available, although it is costly and presumably aimed at institutions. By contrast, 3D Slicer is a free, open source software package for visualisation and image analysis. 3D Slicer is designed to function on multiple platforms, including Windows, Linux and Mac Os X1. It is very powerful and has the capacity to create a 3D model from either a CT or MRI scan. The model can then be exported in a .STL file. In order to print a .STL file, it has to be converted by software into G-Code. G-Code is a programming language used in computer-aided manufacture to tell computerised machine tools
Most radiology departments are able to produce a CD/ DVD that contains the DICOM files of a patient’s CT scan. It is best to copy and paste the folder containing all the DICOM subfolders and files to a new folder on your computer. Rename the folder something other than just DICOM. The 3D Slicer software can be downloaded from www.slicer.org. The software is not particularly intuitive. However, a good tutorial for using it is available on YouTube at http://youtu.be/ MKLWzD0PiIc. The technique for selecting the part of a bone to be printed differs from how most PACS software makes a volume on screen. With PACS software, one
Volume 4 / Issue 3