Session: 06-04-01 Design for Additive Manufacturing I

Paper Number: 71030

Start Time: Friday, 12:05 PM

71030 - Development and Manufacturing of Cervical Stenosis Models for the Integration Into a Neurointerventional Simulation Model 

Ischaemic stroke is one of the main reasons for death and disability worldwide. In this case, the blood vessels in the head are occluded by a blood clot, a so-called thrombus, so that there is a lack of oxygen in a region of the brain. It is important to remove this thrombus as early as possible in order to prevent or minimise permanent damage to the patient. The mechanical removal of a thrombus, the so-called thrombectomy, has become the accepted treatment. In this procedure, a catheter is advanced via the femoral artery to the affected vessel in the brain and the thrombus is removed by means of a wire mesh. Vascular constrictions, so-called stenoses, can make the removal of such a thrombus more difficult by blocking the treatment path or occurring in combination with one. Therefore, it is important to dilate these vessel stenoses during stroke treatment. One of the methods used to treat stenoses is Percutaneous Transluminal Angioplasty (PTA), which uses a balloon attached to a catheter to dilate the vessel. Since stroke treatment is a complicated procedure that is performed under high temporal pressure, training for this procedure is of particular importance.

The aim of this study is the development and manufacturing of cervical stenosis models to simulate the PTA in a physical stroke training and research model to replace training on animal models. For this purpose, an interdisciplinary team of neuroradiologists and engineers worked out the requirements for the stenosis models, developed various concepts, manufactured them and tested their functionality using original treatment instruments. Additive Manufacturing (AM) is used to produce the models, as its geometric freedom makes it possible to produce complicated anatomical shapes.

The development of the models followed the procedure of VDI 2221. The geometric requirements for the stenosis models, such as the degree and position of the stenosis, the functional requirements, such as a realistic opening behaviour after treatment (stenosis dilates and remains open) as well as the use of the models under X-ray radiation (metal-free) were defined with the medical professionals. Based on this, concepts were developed that can be manufactured using AM. These are based on the principle of reproducing a healthy vessel by means of an elastic or flexible material, which is pressed together from the outside by a hard moulded shell and force-applying component, which are also produced by means of AM. The moulded shell has the negative image of a stenosis. The force-applying component compresses the mould shell, creating the stenosis in the vessel model. When the balloon pressure of the balloon catheter is applied, the force in the force-applying component and thus the force acting on the moulded shell is released by the force-applying component. The vessel model can thus return to its original healthy shape. Stereolithography was chosen as the manufacturing process, as preliminary work had shown the suitability of this process for reproducing blood vessel models. In addition, vessel models made of silicone were included in the study as a comparison. In a series of tests in a full physical simulation environment with medical professionals, the concept of an outer shell held together with two snap fasteners or by Dual LockTM velcro was shown to be suitable. For the fabrication of the vascular models, the Formlabs material Flexible 80 A Resin proved to be more promising than the Elastic Resin, as the latter cracked too easily due to the compression in the moulded shell.

Presenting Author: Nadine Wortmann Institute of Product Development and Mechanical Engineering Design - Hamburg University of Technology

Authors:

Nadine Wortmann Hamburg University of Technology
Helena Guerreiro University Medical Center Hamburg-Eppendorf
Anna Kyselyova University Medical Center Hamburg-Eppendorf
Andreas M. Frölich Röntgenpraxis im Tesdorpfhaus
Jens Fiehler University Medical Center Hamburg-Eppendorf
Dieter Krause Hamburg University of Technology