Transcatheter Treatment of "Complex" Aortic Coarctation Guided by Printed 3D Model

Clinical situations for which 3D Printing is considered an appropriate representation or extension of data contained in a medical imaging examination: vascular conditions

BACKGROUND

Medical three-dimensional (3D) printing has demonstrated utility and value in anatomic models for vascular conditions. A writing group composed of the Radiological Society of North America (RSNA) Special Interest Group on 3D Printing (3DPSIG) provides appropriateness recommendations for vascular 3D printing indications.

METHODS

A structured literature search was conducted to identify all relevant articles using 3D printing technology associated with vascular indications. Each study was vetted by the authors and strength of evidence was assessed according to published appropriateness ratings.

RESULTS

Evidence-based recommendations for when 3D printing is appropriate are provided for the following areas: aneurysm, dissection, extremity vascular disease, other arterial diseases, acute venous thromboembolic disease, venous disorders, lymphedema, congenital vascular malformations, vascular trauma, vascular tumors, visceral vasculature for surgical planning, dialysis access, vascular research/development and modeling, and other vasculopathy. Recommendations are provided in accordance with strength of evidence of publications corresponding to each vascular condition combined with expert opinion from members of the 3DPSIG.

CONCLUSION

This consensus appropriateness ratings document, created by the members of the 3DPSIG, provides an updated reference for clinical standards of 3D printing for the care of patients with vascular conditions.

Fabrication of deformable patient-specific AAA models by material casting techniques

Background

Abdominal Aortic Aneurysm (AAA) is a balloon-like dilatation that can be life-threatening if not treated. Fabricating patient-specific AAA models can be beneficial for in-vitro investigations of hemodynamics, as well as for pre-surgical planning and training, testing the effectiveness of different interventions, or developing new surgical procedures. The current direct additive manufacturing techniques cannot simultaneously ensure the flexibility and transparency of models required by some applications. Therefore, casting techniques are presented to overcome these limitations and make the manufactured models suitable for in-vitro hemodynamic investigations, such as particle image velocimetry (PIV) measurements or medical imaging.

Methods

Two complex patient-specific AAA geometries were considered, and the related 3D models were fabricated through material casting. In particular, two casting approaches, i.e. lost molds and lost core casting, were investigated and tested to manufacture the deformable AAA models. The manufactured models were acquired by magnetic resonance, computed tomography (CT), ultrasound imaging, and PIV. In particular, CT scans were segmented to generate a volumetric reconstruction for each manufactured model that was compared to a reference model to assess the accuracy of the manufacturing process.

Results

Both lost molds and lost core casting techniques were successful in the manufacturing of the models. The lost molds casting allowed a high-level surface finish in the final 3D model. In this first case, the average signed distance between the manufactured model and the reference was (- 0.2 ± 0.2 ) mm. However, this approach was more expensive and time-consuming. On the other hand, the lost core casting was more affordable and allowed the reuse of the external molds to fabricate multiple copies of the same AAA model. In this second case, the average signed distance between the manufactured model and the reference was (0.1 ± 0.6 ) mm. However, the final model's surface finish quality was poorer compared to the model obtained by lost molds casting as the sealing of the outer molds was not as firm as the other casting technique.

Conclusions

Both lost molds and lost core casting techniques can be used for manufacturing patient-specific deformable AAA models suitable for hemodynamic investigations, including medical imaging and PIV.

Enabling supra-aortic vessels inclusion in statistical shape models of the aorta: a novel non-rigid registration method

Statistical Shape Models (SSMs) are well-established tools for assessing the variability of 3D geometry and for broadening a limited set of shapes. They are widely used in medical imaging due to their ability to model complex geometries and their high efficiency as generative models. The principal step behind these techniques is a registration phase, which, in the case of complex geometries, can be a critical issue due to the correspondence problem, as it necessitates the development of correspondence mapping between shapes. The thoracic aorta, with its high level of morphological complexity, poses a multi-scale deformation problem due to the presence of several branch vessels with varying diameters. Moreover, branch vessels exhibit significant variability in shape, making the correspondence optimization even more challenging. Consequently, existing studies have focused on developing SSMs based only on the main body of the aorta, excluding the supra-aortic vessels from the analysis. In this work, we present a novel non-rigid registration algorithm based on optimizing a differentiable distance function through a modified gradient descent approach. This strategy enables the inclusion of custom, domain-specific constraints in the objective function, which act as landmarks during the registration phase. The algorithm's registration performance was tested and compared to an alternative Statistical Shape modeling framework, and subsequently used for the development of a comprehensive SSM of the thoracic aorta, including the supra-aortic vessels. The developed SSM was further evaluated against the alternative framework in terms of generalisation, specificity, and compactness to assess its effectiveness.

Virtual simulations in planning intravascular treatment of aortic coarctation - a retrospective analysis

Introduction

A number of studies on using both three-dimensional printing and virtual models in assessment of aortic coarctation have been published, yet none of them uses virtual modelling as a planning tool in a blind retrospective analysis.

Aim

Assessment of virtual modelling and virtual reality in planning interventional treatment of aortic coarctation.

Material and methods

The study involved computed tomography scans of 20 patients performed prior to interventional treatment of aortic coarctation, which were used to create a virtual three-dimensional model of the aorta in Materialise Mimics. A group of potential stents was modelled in Materialise 3-Matic and complete simulations were assessed in Mimics Viewer using a virtual reality headset in order to choose an optimal stent, which was later compared with the implanted one.

Results

In 5 cases identical or very similar stents were proposed, in 12 cases simulations had slight, potentially avoidable misestimations either in stent length or diameter, and in 3 cases differences were more considerable. Overall, in 14 cases the location of the stent was concordant between the simulation and reality and in the remaining 6 cases the simulated stent was located lower than the actual one.

Conclusions

The method of computer modelling provided a satisfactory success rate of predicting the possible stents to use during the procedure. Differences in chosen stents may have been caused by individual experience in interventional cardiology, the lack of availability of certain stents in the heart catheterization laboratory, the lack of information about the diameter of the vascular access and differences in dimensions measured on the model, tomography and angiography.

3D model-guided transcatheter closure of ascending aorta pseudoaneurysm with the novel Amplatzer Trevisio intravascular delivery system

Ascending aorta pseudoaneurysm (AAP) is a rare but life-threatening complication of atherosclerosis, endocarditis, chest trauma, transcatheter or cardio-thoracic procedures. Since surgical repair is burdened by high morbidity and mortality, percutaneous closure is nowadays considered a valuable cost-effective therapeutic alternative. Due to unpredictability and complexity of local anatomy, no standardized technique and device are advised. In this setting, 3D printing technology could significantly help in planning trans-catheter approach. This article reports on a 3D printed model-guided percutaneous closure of a huge AAP using an Amplatzer Septal Occluder (Abbott, Plymouth MN) implanted by the recently commercialized Amplatzer Trevisio Intravascular Delivery System.