Date Published: December 6, 2017
Publisher: Springer International Publishing
Author(s): Leonid Chepelev, Carolina Souza, Waleed Althobaity, Olivier Miguel, Satheesh Krishna, Ekin Akyuz, Taryn Hodgdon, Carlos Torres, Nicole Wake, Amy Alexander, Elizabeth George, Anji Tang, Peter Liacouras, Jane Matsumoto, Jonathan Morris, Andy Christensen, Dimitrios Mitsouras, Frank Rybicki, Adnan Sheikh.
In this work, we provide specific clinical examples to demonstrate basic practical techniques involved in image segmentation, computer-aided design, and 3D printing. A step-by-step approach using United States Food and Drug Administration cleared software is provided to enhance surgical intervention in a patient with a complex superior sulcus tumor. Furthermore, patient-specific device creation is demonstrated using dedicated computer-aided design software. Relevant anatomy for these tasks is obtained from CT Digital Imaging and Communications in Medicine images, leading to the generation of 3D printable files and delivery of these files to a 3D printer.
Segmentation separates the voxels of interest using a range of properties, such as their HU values, presence within a specific predefined bounding box ranging from the entire study volume to a limited region of interest, or a degree of contiguity to define a single continuous structure such as a rib or a vessel. The files included with this work in supporting documentation can be opened by double-clicking after the installation of the inPrint software, or from within the inPrint software using the File menu on systems where this software is installed. The main program window contains the toolbox on the left as well as project visualization with the three orthogonal visualization planes and the 3D rendering window (Fig. 2). DICOM images may be imported and loaded into a project file, using a similar intuitive wizard from the File menu as well. Before progressing further, please take a moment to familiarize yourself with the software shortcuts and anatomy (Table 1).Fig. 2Layout of the inPrint software graphical user interface. On the top left, the menu toolbar with File, Edit, View, and Help menus. Below this, menu toolbar with segmentation and model editing menus. The operation toolbar (titled Guided Segmentation on this view) contains the available operations and operation settings. Below this, the ROI and Part lists can be found. Top right, the three orthogonal planes and the 3D visualizations are shown. Finally, the lower right is reserved for software logs and various HU distribution and window/level visualizationsTable 1Selected software shortcuts in the in Print softwareShortcutActionScroll wheel (center mouse)OR Shift right click + dragPan: Move the mouse while keeping the center click pressedRight click + drag (2D Views)Zoom: Move the mouse vertically while keeping the button pressedCTRL + right click + drag (3D View)Zoom: Move the mouse vertically while keeping the buttons pressedArrow Up/Scroll wheel upGo to next sliceArrow Down/Scroll wheel downGo to previous slicePage UpSkip 10 slices upwardPage DownSkip 10 slices downwardCTRL + LMake slice indicators visible/invisibleSPACEZoom the chosen view to full screen and backBackspaceSwitch between two window statesCTRL + ZUndo the previous action.CTRL + Right click + Drag (2D Views)Adjusts window/level in 2D images
In this part, we demonstrate the techniques involved in the generation of hollow and solid printable models using the 3-Matic CAD software. To begin, review the anatomy of the software (Fig. 18).Fig. 18Graphical user interface of the 3-matic software. Top left, the menu and tabbed menu toolbars. Center, work area with the visualization of the current model. Right upper corner, the Object Tree with all the involved objects. Right lower corner, the Operations tab, with all operation parameters. Bottom left, the Logger which logs the current actions. Note the Expert Mode at the bottom of the window. This expert mode allows control of additional parameters, some of which are used in this work
While model post-processing is quite useful in optimizing models for printing, the role of Computer-aided design (CAD) is better exemplified by demonstrating an approach for the creation of a customized tracheal stent for a simulated case of significant tracheal stenosis secondary to mass effect from an adjacent mediastinal tumor (included in Additional files 1, 2 and 3).
In principle, the process of submitting a model to a 3D printer is highly variable, and ranges from placement of a model onto an external storage device which is then inserted into the printer to using a graphical user interface to submit a model to a printer connected to the computer directly or through a network. The end result, however, is the translation of the 3D geometry stored within STL or similar files into a set of printer instructions, such as movement paths for the printer head, print bed movement, and a range of instructions that are highly dependent on the printer used.
As applications of 3D printing in medicine continue to expand, familiarity with the basic software operations and tasks becomes increasingly important. This technical note presented at the 2017 annual meeting of the RSNA expands on our earlier teaching sessions to include segmentation and printing of a Pancoast tumor. Finally, the application of patient-specific airway stent design with CAD demonstrates some of the basic techniques involved in clinical applications of 3D printing.