At the Toshiba Stroke and Vascular Research Center in Buffalo NY, Dr. Ciprian Ionita and his team have developed a novel method to create 3D-printed vascular models (or "phantoms") using Polyjet printing technology from Stratasys. These models of the brains vasculature (blood vessels) are being used for surgical training and planning. Dr. Ionita collaborates with Dr. Adnan H. Siddiqui, Chief Medical Officer of The Jacobs Institute, who is using the phantoms when planning complex neurosurgery procedures such as repair of brain aneurysms.
|This is a 3D-printed vascular phantom, which approximates the brain blood-vessel network of a patient. The white regions are flexible and simulate the feel of real blood vessels, while the pink region provides a rigid support structure (Image Credit: Jacobs Institute)|
The process of creating a vascular phantom begons with a CT scan of the patient's brain. The volumetric scan data is imported into Vital Images' Vitrea software, a tool for exploring and segmenting medical data. Biomedical engineers extract the critical regions of the vascular (blood vessel) network as 3D surfaces, and export the result as a standard triangle mesh. This mesh is then imported into Autodesk Meshmixer. In Meshmixer, the raw vessel meshes are cleaned up - holes are filled, tiny unprintable vessels are removed, and so on. Then, the vessel walls are thickened and combined with a supporting structure, so that they can be printed. Dr. Ionita's team has published several papers about their workflow  .
|Overview of the process of designing a 3D-printable vascular phantom in Autodesk Meshmixer, based on an initial CT scan. This figure is reproduced from publication , see full citation below (Copyright: Proc SPIE Int Soc Opt Eng)|
Once the phantom has been designed, it needs to be fabricated. Ultimately the goal is to produce a physical model that is as close to the "feel" of real tissue as possible. The Buffalo team relies on Stratasys' multi-material Polyjet printers, which can combine translucent flexible regions and rigid plastic regions in the same print, as shown in the image above. In some cases the model is used primarily for inspection - it is much easier for a surgeon to understand the spatial configuration of the blood vessel network when looking at a physical model, compared to a 3D rendering.
The Buffalo team has taken 3D-printed patient models a step further, and is using the phantoms in a surgery simulator. This allows the neurosurgeon to directly practice a procedure, such as an aneurysm repair or clot removal. The simulator setup is shown in the image below. Fluid is pumped through the phantom, simulating blood flow. The surgeon does not directly look at the print, instead they look through a live X-ray feed, which is what they will have during the operation. The procedures involve feeding a catheter (think long, flexible wire) up through the body into the brain - the inlet labeled "9F Sheath" is where this would happen.
|The setup for a brain clot removal simulation using a 3D-printed vascular phantom. Fluid is pumped through the phantom, and the surgeon feeds a catheter up through the blood vessel network while looking through the X-ray screen. This figure is reproduced from publication , see full citation below (Copyright: Journal of Neurointerventional Surgery)|
As you might imagine, operating on the brain with a flexible wire that is winding through the patients blood vessel network is not easy. Last fall I visited Dr. Ionita's group to help them improve their Meshmixer workflows. While I was there I had a chance to try out one of these simulators. It felt a bit like a video game, but of course I did not have anyone's life in my hands. And it was extremely difficult! The Buffalo team had another visitor more recently, who you might recognize:
|Hillary Clinton examining 3D-printed vascular model designed in Autodesk Meshmixer, with Dr. Adnan H. Siddiqui, Chief Medical Officer, The Jacobs Institute (Image Credit: Derek Gee/Buffalo News)|
For neurosurgeons like Dr. Siddiqui, being able to practice procedures can literally save lives. In the video below, Dr. Siddiqui explains a case where the simulator allowed him to identify an issue with a surgical plan. As a result, potentially life-threatening complications were identified before the patient was on the operating table.
 Ionita CN, Mokin M, Varble N, Bednarek DR, Xiang J, Snyder KV, Siddiqui AH, Levy EI, Meng H, Rudin S: Challenges and Limitations of Patient-Specific Vascular Phantom Fabrication Using 3D Polyjet Printing. Proc Soc Photo Opt Instrum Eng 9038:90380M, March 13, 2014. PMID 25300886 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4188370/
 Russ M, O’Hara R, Setlur Nagesh SV, Mokin M, Jimenez C, Siddiqui A, Bednarek D, Rudin S, Ionita C: Treatment Planning for Image-Guided Neuro-Vascular Interventions Using Patient-Specific 3D Printed Phantoms. Proc SPIE Int Soc Opt Eng 9417:941726-1—941726-11, March 19, 2015 (DOI 10.1117/12.2081997). PMID 26778878. http://spie.org/Publications/Proceedings/Paper/10.1117/12.2081997
 Mokin M, Ionita CN, Setlur Nagesh SV, Rudin S, Levy EI, Siddiqui AH: Primary Stentriever Versus Combined Stentriever Plus Aspiration Thrombectomy Approaches: In Vitro Stroke Model Comparison. J Neurointerv Surg 7:453-457, June 2015 (epub April 30, 2014 DOI: 10.1136/neurintsurg-2014-011148). PMID: 24789594 http://www.ncbi.nlm.nih.gov/pubmed/24789594
In the video below, Dr. Adnan H. Siddiqui from the Jacobs Institute describes how a 3D-printed vascular phantom helped to save a patient's life. This video was produced by Stratasys Corporation.