KEYWORDS: 3D printing, 3D image processing, Image segmentation, 3D modeling, Printing, Image processing, Visualization, Picture Archiving and Communication System, Imaging informatics, Medicine, Cardiology, Heart, Angiography, Fluoroscopy, Imaging systems
3D printing an anatomically accurate, functional flow loop phantom of a patient’s cardiac vasculature was used to assist
in the surgical planning of one of the first native transcatheter mitral valve replacement (TMVR) procedures. CTA scans
were acquired from a patient about to undergo the first minimally-invasive native TMVR procedure at the Gates Vascular
Institute in Buffalo, NY. A python scripting library, the Vascular Modeling Toolkit (VMTK), was used to segment the 3D
geometry of the patient’s cardiac chambers and mitral valve with severe stenosis, calcific in nature. A stereolithographic
(STL) mesh was generated and AutoDesk Meshmixer was used to transform the vascular surface into a functioning closed
flow loop. A Stratasys Objet 500 Connex3 multi-material printer was used to fabricate the phantom with distinguishable
material features of the vasculature and calcified valve. The interventional team performed a mock procedure on the
phantom, embedding valve cages in the model and imaging the phantom with a Toshiba Infinix INFX-8000V 5-axis Carm
bi-Plane angiography system.
Results: After performing the mock-procedure on the cardiac phantom, the cardiologists optimized their transapical
surgical approach. The mitral valve stenosis and calcification were clearly visible. The phantom was used to inform the
sizing of the valve to be implanted.
Conclusion: With advances in image processing and 3D printing technology, it is possible to create realistic patientspecific
phantoms which can act as a guide for the interventional team. Using 3D printed phantoms as a valve sizing
method shows potential as a more informative technique than typical CTA reconstruction alone.
KEYWORDS: 3D printing, Surgery, Sodium, Manufacturing, 3D modeling, 3D image processing, Medical devices, Medical research, Image segmentation, Arteries, Neodymium, Printing, Medical imaging
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.
Minimally invasive endovascular image-guided interventions (EIGIs) are the preferred procedures for treatment of a wide range of vascular disorders. Despite benefits including reduced trauma and recovery time, EIGIs have their own challenges. Remote catheter actuation and challenging anatomical morphology may lead to erroneous endovascular device selections, delays or even complications such as vessel injury. EIGI planning using 3D phantoms would allow interventionists to become familiarized with the patient vessel anatomy by first performing the planned treatment on a phantom under standard operating protocols. In this study the optimal workflow to obtain such phantoms from 3D data for interventionist to practice on prior to an actual procedure was investigated. Patientspecific phantoms and phantoms presenting a wide range of challenging geometries were created. Computed Tomographic Angiography (CTA) data was uploaded into a Vitrea 3D station which allows segmentation and resulting stereo-lithographic files to be exported. The files were uploaded using processing software where preloaded vessel structures were included to create a closed-flow vasculature having structural support. The final file was printed, cleaned, connected to a flow loop and placed in an angiographic room for EIGI practice. Various Circle of Willis and cardiac arterial geometries were used. The phantoms were tested for ischemic stroke treatment, distal catheter navigation, aneurysm stenting and cardiac imaging under angiographic guidance. This method should allow for adjustments to treatment plans to be made before the patient is actually in the procedure room and enabling reduced risk of peri-operative complications or delays.
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