Visualizing and 3D Printing Dilated Patient Aortas from Echocardiography

Fig 1. Dilated Aortic root

Visualizing and 3D Printing Dilated Patient Aortas from Echocardiography


1,2Azad Mashari, 1Joshua Qua Hiansen, 1,2Massimiliano Meineri

1Department of Anesthesia and Pain Management, Toronto General Hospital; 2University of Toronto Faculty of Medicine


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Background

The main goal of these project pages is to showcase our work and provide people a resource to download the 3D STL files, but also as a resource to get technical information about the process involved and serve as an adjunct to any scientific papers that may use these models.

While these projects may be combined in a formal academic paper and submitted to a journal, the website will allow us to present work and discuss, in detail, things that would otherwise not be of much use to a medical/scientific journal.  As such the following sections are what we’re thinking:

(a) Background

(b) Interactive Materials

(c) Technical Details and Results

Each one of the background, interactive materials, technical details and results pages should be on its own separate page to present as much of the information as possible to the user in one location.


Text here: Please cite this article for use in any research articles etc etc…


Interactive Materials

Unlike a traditional paper, we’re going to be putting interactive content up on our research pages.  Namely (1) download link to the 3D model itself and (2) an interactive 3D model of the project within this window and (3) Links to any academic/scientific papers/posters abstracts that use these models . 

The interactive 3D model will be done via a website, Sketchfab, where we host our 3D models for people to interact with on the internet: For example: https://skfb.ly/TOy8

Fig 3.

Technical Details & Results

Image acquisition

A senior cardiac anesthesiologist with expert knowledge of cardiac echocardiography obtained dilated patient aortic root/valve image data via transesophageal echocardiography (TEE).

 

Image segmentation

Obtained TEE image dataset was anonymized and imported into image segmentation program Mimics (Materialise, Belgium).  Several temporal phases were recorded during the TEE exam.  For the purposes of this project, a time series at end systole was chosen as the image series of choice.

Due to the speckled nature of images captured via echocardiography, standard image segmentation techniques such as thresholding were too inaccurate.  To generate a voxel model of the aortic root/valve, a fully manual segmentation approach was used.

Manual segmentation required the operator to label several anatomical features by grouping specific pixels together by painting on different label-mask layers per anatomic feature.  These features were: left ventricular outflow tract (LVOT), aortic leaflets, aortic root, sinotubular junction (STJ) and ascending aorta.  Labeling was done on every image within the selected image series for this particular aortic root/valve.

Following, each label-mask was exported as a separate 3D model written as a stereolithography (stl) file.  Doing so provided the flexibility to reconstruct the aortic root model with a different combinations of anatomic features.  For this particular project, the aortic root and leaflets were selected anatomic regions to be 3D printed.

 

3D model editing

The 3D model of the aortic root and leaflets were imported into 3D modeling editing software Meshmixer (Autodesk, CA).  Within Meshmixer, the root and leaflet models were combined into one solid 3D object.  After, a smoothing function was applied to decrease the stratified appearance of the model.  Lastly, the model was inspected within Meshmixer for any errors that may hinder 3D printing.

 

3D printing

Once 3D editing was complete, the now combined 3D aortic root/leaflet model was imported into 3D printing slicing software Pre-Form (Formlabs, MA) to prepare for fabrication on the Form 2 desktop stereolithography (SLA) 3D printer.  The following printing settings were used:

 

Table 1.  Settings used to 3D print the dilated aortic root/leaflet model on the Form 2 3D printer

Resin Type Layer Height Supports Part Orientation
Clear 0.1 mm Yes Automatic

The dilated patient aortic root/leaflet model was printed in 2 hours and 25 mins requiring 20 mL of clear resin.

 

Post-processing

The process of printing with an SLA 3D printer necessitates the use of post-processing techniques to remove uncured resin from the printed object and to obtain a high degree of surface quality.

Removal of uncured resin was done by placing the printed aortic root/leaflet model into a 99% isopropyl alcohol (IPA) bath.  First, the print was agitated while submerged in the IPA.  Following, the print was allowed to stay at rest, fully submerged in the IPA, for approximately 15 minutes.

The aortic root/valve model was then removed from the IPA bath, rinsed with clean water and support structures were removed.  Next, the model underwent aggressive sanding to polish its surface.  Sanding was done with a series of wet sandpaper steadily increasing in grit (200, 600, 800, 1000 and 1500).  Finally, the aortic root/leaflet model was coated with a thin layer of clear-coat spray paint to protect from environmental UV and to maintain a clear surface finish.

 

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