The Design and Development of an Anthropomorphic Coronary Artery Network Phantom

Abstract

Percutaneous coronary intervention (PCI) is one of the main medical procedures employed for the treatment of coronary artery disease. During this procedure, the coronary arteries are visualized using X-ray imaging. However, it only generates 2D images which can complicate several tasks, including assessing the lesion and correctly placing a stent. To overcome this limitation, researchers of Philips Research are developing technologies that allow the implementation of 3D imaging data derived from coronary CT angiography in the catheterization laboratory. Throughout the development, a coronary artery network phantom could serve as a beneficial tool. Such a phantom should be anthropomorphic and have realistic imaging and mechanical properties. Additionally, it should serve as a platform on which a basic PCI procedure can be performed. No commercially or academically developed phantom satisfies these criteria, thus the objective for this project was to design and develop an anthropomorphic coronary artery network phantom with realistic imaging and mechanical properties, which can be used to mimic both healthy and atherosclerotic human coronary arteries.
A material study was initially conducted to find the most suitable materials for the development of the phantom. During the first stage, the radiodensity of several materials was measured. Based on those results, and other factors such as safety, usability and durability, it was concluded that PlatSil Gel 25 would be used for the development of the arterial wall. Additionally, the heart and non-calcified lesions were to be made from VytaFlex 20 in combination with BaSO4. The calcified lesions were to be made from PlatSil Gel 25 and also required the addition of BaSO4 to increase their radiodensity. After the imaging tests, uniaxial tensile tests were conducted to measure the stiffness of PlatSil Gel 25 samples with different concentrations of PlatSil hardener. These results demonstrated that PlatSil Gel 25 has a comparable stiffness to that of healthy human coronary arteries in the longitudinal direction. When combined with the hardener, it can also mimic the stiffness of atherosclerotic coronary arteries.
After the material study, the coronary artery network phantom was designed and developed. The design comprises a simplified representation of the heart, and an arterial network that consists of the coronary artery network and a simplified representation of the arterial pathway distal to the aortic root. To manufacture the arterial network, a water-soluble 3D-printed mould was manually coated with PlatSil Gel 25 and subsequently dissolved in water. Due to the solubility of the mould, it was possible to manufacture a geometrically complex and hollow arterial network as a single part. Additionally, it was demonstrated that this manufacturing method can be used to include lesions within the arterial wall, and that its stiffness can be locally changed.
During the evaluation of the final phantom, its geometrical, imaging and mechanical properties were assessed and compared with the formulated requirements. Based on the results it can be concluded that the phantom meets many of the requirements. Furthermore, it was demonstrated that a guidewire can be inserted into the arterial network and manipulated up to the end of the left circumflex artery. Nevertheless, the evaluation also revealed some areas of improvement. Most notable are the improvements related to the imaging properties of the phantom. For example, the radiodensity of the arterial wall was slightly too high. In addition, the attenuation was not uniform throughout the parts of the phantom that contained BaSO4, as was evident from X-ray and CT images.
In conclusion, this project demonstrated that the utilized manufacturing method and materials can be used to develop a healthy and atherosclerotic coronary artery network phantom, that possesses realistic geometrical, imaging and mechanical properties. Additionally, it has the potential to serve as a platform on which a basic PCI procedure can be performed. Nevertheless, several areas of improvement related to both the manufacturing method and phantom remain, which might form the foundation for a future project.