Investigation of Three-dimensional Printing Materials for Printing Aorta Model Replicating Type B Aortic Dissection

Abstract

Aim: To determine a printing material that has both elastic property and radiology equivalence close to real aorta for simulation of endovascular stent graft repair of aortic dissection. Background: With the rapid development of three-dimensional (3D) printing technology, a patient-specific 3D printed model is able to help surgeons to make better treatment plan for Type B aortic dissection patients. However, the radiological properties of most 3D printing materials have not been well characterized. This study aims to investigate the appropriate materials for printing human aorta with mechanical and radiological properties similar to the real aortic computed tomography (CT) attenuation. Objective: Quantitative assessment of CT attenuation of different materials used in 3D printed models of aortic dissection for developing patient-specific 3D printed aorta models to simulate type B aortic dissection. Method: A 25-mm length of aorta model was segmented from a patient’s image dataset with diagnosis of type B aortic dissection. Four different elastic commercial 3D printing materials, namely Agilus A40 and A50, Visijet CE-NT A30 and A70 were selected and printed with different hardness. Totally four models were printed out and conducted CT scanned twice on a 192-slice CT scanner using the standard aortic CT angiography protocol, with and without contrast inside the lumen.Five reference points with region of interest (ROI) of 1.77 mm2 were selected at the aortic wall and intimal flap and their Hounsfield units (HU) were measured and compared with the CT attenuation of original CT images. The comparison between the patient’s aorta and models was performed through a paired-sample t-test to determine if there is any significant difference. Result: The mean CT attenuation of aortic wall of the original CT images was 80.7 HU. Analysis of images without using contrast medium showed that the material of Agilus A50 produced the mean CT attenuation of 82.6 HU, which is similar to that of original CT images. The CT attenuation measured at images acquired with other three materials was significantly lower than that of original images (p<0.05). After adding contrast medium, Visijet CE-NT A30 had an average CT attenuation of 90.6 HU, which is close to that of the original images with statistically significant difference (p>0.05). In contrast, the CT attenuation measured at images acquired with other three materials (Agilus A40, A50 and Visiject CE-NT A70) was 129 HU, 135 HU and 129.6 HU, respectively, which is significantly higher than that of original CT images (p<0.05). Conclusion: Both Visijet CE-NT and Agilus have tensile strength and elongation close to real patient’s tissue properties producing similar CT attenuation. Visijet CE-NT A30 is considered the appropriate material for printing aorta to simulate contrast-enhanced CT imaging of type B aortic dissection. Due to lack of body phantom in the experiments, further research with simulation of realistic anatomical body environment should be conducted.

Optimization of Computed Tomography Angiography Protocols for Follow-Up Type B Aortic Dissection Patients by Using 3D Printed Model

“…Third, the Visijet CE-NT material has two different hardnesses, A30 and A70, with A30 having a tensile strength between 0.2 and 0.4, which is close to elderly cardiovascular tissue properties. Finally, our recent study confirms that Visijet CE-NT A30 is the most appropriate material for printing aorta models because its CT attenuation is similar to that of the contrast-enhanced CT images of aortic dissection [22].…”

“…Patient-specific 3D printed phantoms have been proven to be valuable in multiple medical applications [16][17][18][19][20][21]. In our previous study, we described how we developed a patient-specific 3D printed TBAD aortic model, and confirmed its accuracy in resembling the mechanical and radiological properties of in vivo imaging under CT scanning modalities [22]. In this study, we extended our application of a 3D printed aorta model to focus on the study of optimal CT protocols by deploying a bespoke stent graft inside the true lumen of the AD aorta model to simulate the TEVAR process, and then scanning the model with different CT protocols.…”

“…Based on our previous study, we chose four different 3D printing materials that had mechanical properties close to that of patients with aortic dissection [22]. In terms of transparency, a completely transparent model would enhance stent graft deployment without the need for imaging and contrast.…”

“…However, a transparent elastomer printing material was not available from commercial companies, therefore, a translucent material was the next best option. After scanning samples of several available materials with the current clinical thoracic CTA protocol, one of the materials, Visijet CE-NT (3D systems Inc., Wilsonville, OR, USA), was selected as it had the same radiological properties to in vivo aorta [22]. The reason for choosing Visijet CE-NT is due to the following reasons: first, it is a rubber-like material suitable for printing aorta-like models.…”

3D-Printed Coronary Plaques to Simulate High Calcification in the Coronary Arteries for Investigation of Blooming Artifacts

“…The 3D-printed coronary artery models are advantageous to a simple tube model, which does not replicate realistic coronary anatomy [ 40 , 41 ], while 3D printing allows for creation of individual anatomy and simulation of disease. Three-dimensional-printed personalised aorta, pulmonary, and coronary artery models created from CT angiographic images replicate realistic anatomy and pathology, thus serving as an excellent tool for studying optimal CT scanning protocols [ 42 , 43 , 44 , 45 ]. In our previous reports, we simulated pulmonary embolism in the main and side pulmonary artery branches using patient-specific 3D-printed pulmonary artery model and tested different CT pulmonary angiography (CTPA) protocols consisting of a range of kV and pitch values.…”