Sandrine Debecker October 27, 2016

Catheter-based interventions are often the therapy of choice when treating the cardiovascular system of fragile and weak patients. Though often much less invasive than alternative treatments, this technique has its own limitations: it risks dislodging plaque or calcium into the circulatory system as well as potentially damaging, rupturing or penetrating the arterial walls. Also, imaging and the extensive use of contrast agent are not without risk.

With a catheter that tracks and senses the middle of the channel, avoids artery walls and notifies the interventionalist of danger, many of these complications could be avoided. Developing this type of “intelligent” catheter was the goal of the EU-funded CASCADE Project.

CASCADE: the added value of realistic benchtop models

The European research project “CASCADE", acronym for Cognitive AutonomouS CAtheter operating in Dynamic Environments, was set up to advance the treatment of cardiovascular diseases by providing a new dexterous and intelligent robotic catheter. The researchers have focused on endovascular aortic valve replacements, like transcatheter aortic valve implantation (TAVI), as catheters are used for these specific procedures.

Various tests are required during the consecutive stages of device development. Given the advanced and experimental nature of the CASCADE project, having realistic testing environments was key for the success of the project. Depending on which individual aspect of the catheter they wanted to test (IVUS, automatic steering, flow sensing, etc.), specific benchtop models were needed to ensure optimal testing.

Materialise designed and manufactured these test beds in different materials, resulting in a variety of rigid and flexible models. The researchers could then evaluate their suitability for use in both a development and a testing environment for robotic catheterization devices.

Patient-specific silicon benchtop model - CASCADE Project

Patient-specific silicon benchtop model manufactured by a hybrid method

Creating 3D-printed patient-specific benchtop models

First, the patient’s CT images were imported, segmented and converted in Materialise Mimics software to create a 3D digital model of the patient’s anatomy. The printed models were then used to simulate the entire transfemoral approach from the groin through the aorta and up to the aortic valve.

One of the benchtop models was printed using a proprietary process called Materialise HeartPrint Flex. This technology has been validated to conform with the distensibility of arterial vessels and is thereby ideally suited for this purpose. The material gives the model a natural feel while realistically pulsing when attached to a blood flow simulation pump.

The IVUS probe is inserted in the HeartPrint Flex model attached to the pumping circuit. The blue elements closed the openings of all side branches, while the black tubes made the connections with the pumping circuit. The black line within the model was the IVUS probe, held by the hand on the right side of the picture. © Imperial College, London

CASCADE Project - HeartPrint Flex model

According to the researchers, the patient-specific benchtop models provided a good representation of clinical reality. Also, the models offered a suitable testing environment during different stages of the development process. Each model had its own unique features necessitated by specific tests. The rigid 3D-printed model offered high transparency and robustness. The material characteristics of both deformable models were close to that of vascular tissue. The research team concluded that

“using a realistic testing environment in the early stages of development can reduce the time and efforts necessary to move the device to further stages”.

With the development of smart catheters, interventionalists could operate better in complex and deformable environments. In the long-term, CASCADE technology could be used in TAVI, abdominal aortic aneurysms, mitral valve repair, and the treatment of cardiac arrhythmia.

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