Advanced 3D Mesh Manipulation in Stereolithographic Files and Post-Print Processing for the Manufacturing of Patient-Specific Vascular Flow Phantoms

Abstract

Complex vascular anatomies can cause the failure of image-guided endovascular procedures. 3D printed patient-specific vascular phantoms provide clinicians and medical device companies the ability to preemptively plan surgical treatments, test the likelihood of device success, and determine potential operative setbacks. This research aims to present advanced mesh manipulation techniques of stereolithographic (STL) files segmented from medical imaging and post-print surface optimization to match physiological vascular flow resistance. For phantom design, we developed three mesh manipulation techniques. The first method allows outlet 3D mesh manipulations to merge superfluous vessels into a single junction, decreasing the number of flow outlets and making it feasible to include smaller vessels. Next we introduced Boolean operations to eliminate the need to manually merge mesh layers and eliminate errors of mesh self-intersections that previously occurred. Finally we optimize support addition to preserve the patient anatomical geometry. For post-print surface optimization, we investigated various solutions and methods to remove support material and smooth the inner vessel surface. Solutions of chloroform, alcohol and sodium hydroxide were used to process various phantoms and hydraulic resistance was measured and compared with values reported in literature. The newly mesh manipulation methods decrease the phantom design time by 30 - 80% and allow for rapid development of accurate vascular models. We have created 3D printed vascular models with vessel diameters less than 0.5 mm. The methods presented in this work could lead to shorter design time for patient specific phantoms and better physiological simulations.

Keywords: 3D Printing; Aneurysms; CTA Segmentation; Patient-Specific; Vascular Phantoms.

Figure 1

Flow chart showing the manufacturing process for 3D printing patient-specific phantoms (Left Internal Carotid Artery shown above).

Figure 2

(A) The unedited STL file of a left internal carotid artery. (B) ‘Add tube’ function for merging vessels. (C) A completed flow outlet. (D) The edited mesh before adding a thickness and support.

Figure 3

The before (left) and after (right) result of using a Boolean union for adjoining the outer layer of the vascular mesh to the support structure. The Boolean union smoothly combines the two meshes without affecting the inner layer of the vascular mesh.

Figure 4

Setup for acquiring the hydraulic resistances of three coronary phantom replicas.

Figure 5

Closed flow loop setup for acquiring DSA images of the patient-specific vascular flow phantom.

Figure 6

(A) Single layer mesh geometry (B) Vessel wall thickness and the inlet and outlets (C) Addition of the support structure (D) Printed and cleaned phantom

Figure 7

The SEM images of a TangoPlus slice flushed with sodium hydroxide after (A) 1 minute (B) 2 minutes and (C) 3 minutes

Figure 8

Average DSA of the contrast bolus release in a 3D printed model of the left internal carotid artery. Inner vessel diameters as small as 0.45–0.50 mm were measured. Some of the support material in the distal regions could not be removed, blocking the flow of contrast. The circular marker has a diameter of 4.76 mm.

Figure 9

DSA showing the arrival and dissipation of the contrast bolus. The circular marker has a diameter of 4.76 mm.