Feasibility of 3D Printing Full Endovascular Models for Planning Image-Guided Neuro-Vascular TreatmentsR. O’Hara1, M. Russ1, S.V. Setlur Nagesh1, M. Mokin1, C. Jimenez1,2, A. Siddiqui1, D. Bednarek1, S. Rudin1, C. Ionita1

Toshiba Stroke and Vascular Research Center, University of Buffalo, Buffalo, NY1

University of Antioquia-GIB-Eafit, Medellin, Colombia2

The purpose of this study is to evaluate the feasibility of using 3D printedphantoms of patient vasculatures in order to increase the benefits ofendovascular therapies through treatment planning and reduce the high costsof device research. We used de-identified Computed Tomographic Angiography(CTA) data from stroke patients and segmented vessel geometries asstereolithography (STL) files using a Toshiba Vitrea 3D station. Mesh-editingsoftware and a 3D printer were used to generate the individual structures. A fullvascular model of the endovascular treatment process was manufactured usingCTA image data from the Circle of Willis, coronary arteries, aorta, and femoralarteries. Endovascular interventionists have reported positive feedback aboutthe full model’s similarity to patients after performing mock procedures. Fullvascular replicas of patient-specific vascular anatomy allow interventionists theability to efficiently train and determine treatment solutions, such as stents orcoiling, before operating on patients with complex vascular anatomies.

ABSTRACT

BACKGROUND

METHODS & MATERIALS

RESULTS

CONCLUSIONS

ACKNOWLEDGMENTS

Cardiac and cerebral endovascular procedures are challenging in patients withcomplex vascular anatomies, leading to a greater likelihood of adverse effects.Cardiovascular disease, including stroke, is the leading cause of death in theworld. The associated costs represented 15% of the total health expenditures inthe US in 2009, more than any other major diagnostic group.

During an endovascular intervention, a catheter is guided using x-ray imagingto implement one of many available devices based on a particular patient’svascular anatomy and complications. These devices, including stents, coils, andballoons, are fairly rudimentary and rely on distal actuation. Difficult vasculatureincreases the risk of inaccurate device placement, inability to perform theprocedure, prolonged surgical time and increased dose, and vessel injury.

Full-model, patient-specific vascular phantoms offer a new solution tocomplex patient anatomies. These phantoms allow pre-operative training anddevice testing with models of varying tortuosity and geometry. Neurosurgeonsthat have used these models in a clinical setting have affirmed that themanufactured models offer the most realistic catheter feedback and interactionamong other training methods.

Model-to-Model ConnectionEach model is designed with male and female transitions so that the flow andendovascular devices are not impeded. These connections fit smoothly into oneanother and are sealed using silicone. Printing separate patient vasculargeometries is a result of the limiting size of the printer volume, but allows fordifferent vascular models to be inserted for particular operations.

Geometry AcquisitionThe desired vessel anatomy data is taken from3D reconstructed CT, MRI, and CBCT volumes ofpatients from an ongoing stroke study. Thereconstructed volumes are edited using ToshibaVitrea software, which is used to manuallysegment vessel geometries, remove bone and

tissue, and export the geometry as a high-definition stereolithography (STL) file.

Vessel ManipulationMeshMixer, a mesh-manipulationsoftware, is used to smoothinconsistencies of the continuousvessel surface, to alter the numberof inlets and outlets, wall thicknessand vessel diameters, and to addsupport and connecting structures.

3D PrintingThe STL file of each vessel segment is printed using a Stratasys Objet Eden 260V,a high resolution 3D printer. Specifications for each model include:

• Technology: Inkjet, stereolithography (photo-solidification)• Resolution: < 32 μm in the z-axis, < 200 μm in the xy-plane• Volume: 255 x 252 x 200 mm• Material: TangoPlus – A semi-transparent and elastic

photopolymer resin• Support: SUP705 – A water-soluble, acrylic photopolymer

The assembled full model contains the majorvascular structures commonly involved incardiovascular and neurovascular surgeries.Several printed phantoms connected togetherbetter simulate the traversal of a catheter fromthe femoral arteries to the treatment site.CBCT Imaging is used to analyze the accuracyof the phantoms, observe the flow through thevessels, and test endovascular devices.

The full model is printed with a uniform2.0 mm thickness. This provides themost accurate structural propertiescompared to actual arteries. Failures inthe structure during mock proceduresindicate possible perforations that couldoccur under the same catheter pressurewithin a patient.

The major vascular segments include:

• Left and right external iliac arteries

• Abdominal Aorta

• Descending Thoracic Aorta

• Aortic Arch, including the subclavian,brachiocephalic, and carotid arteries

• Coronary Arteries (not shown)

• Circle of Willis, including the carotidand vertebral arteries

Procedural Phantom ResultsThe patient-specific phantom segments were successfully implemented indiverse mock procedures, including comparing clot retrieval methods, devicedevelopment, and angiographic image acquisition.

Phantom Testing

Phantom Manufacturing

Additional Features for Clinical Testing- To make mock interventional procedures more realistic, several segments ofpatient-specific vasculature were printed to model the navigation of a catheterfrom the femoral artery to the treatment site.- A Circle of Willis phantom with five aneurysms at different locations withdifferent geometries was printed for use as an extensive training tool. Left –Geometry of the model in MeshMixer. Middle – 3D printed model of TangoPlus.Right – Digital subtraction angiography (DSA) of the 3D printed model injectedwith contrast to measure patient-to-phantom accuracy

Cardiac Phantom Example: A coronary phantom was used toacquire angiographic images to verify vessel patency andaccuracy. A catheter was inserted through the aortic arch andcontrast was deployed. (a) Result of averaged DSA sequence.(b) Sequence of DSA frames showing contrast flow. A cardiacphantom diversifies the suite of phantoms, which can beapplied to a wider range of cardiovascular interventions.

Aneurysm Coiling Example: (a) Afluoroscopic snapshot of the initialpart of the procedure. (b) Detail ofthe micro-catheter placed in theaneurysm. (c) Final fluoroscopicsnapshot of a coil mass placed in the

Portions of this on-going research has been made possible as a result of funding from the following sources:• NIH Grant R01-EB002873• CURCA Student Grant

aneurysm dome. (d)DSA showing initialarrival of the boluscontrast.

There is a need for safer and more reliable vascular procedures than theresults of conventional open surgeries currently provide. Endovascularinterventions provide this security, but accrue higher financial costs fromresearch and device development.

Patient-specific vascular phantoms provide a standardized experimentalplatform for device-testing trials, and can be used for familiarizing physicianswith complex patient anatomies to anticipate changes in therapies, pre-operatively. This may shorten the duration of the procedure, which will reducedose to the patient, as well as reduce the risk of thrombolytic events, pre-procedural complications, and the number of devices wasted on failedattempts. Patient-specific phantoms were successfully used in mock, image-guided endovascular procedures with positive feedback from multipleinterventionists. They are a versatile and powerful tool, and offer a uniquelearning opportunity for neurosurgeons, their successors, and the endovascularfield.

Asymmetric Flow Diverter:A deployment study was performed

using the new aneurysm phantom. Thepurpose of this treatment was toreduce blood flow in an aneurysm, butnot in the anterior communicatingartery. By examining bolus arrival timein pre- vs. post-treatment DSA runs,the change in flow to the treatedregion can be seen.

(b)