Abstract
Three-dimensional (3D) printing has been widely used and grown rapidly through the last decades, it addresses the challenges of traditional moulding and subtractive manufacturing. In the context of cardiovascular disease (CVD), patient-specific cardiac phantoms can play an important role for interventional cardiology procedures. The emergence of 3D printing and 3D printable soft materials provide the opportunity to produce anthropomorphic phantoms with complex geometries and realistic properties for applications in cardiology. This thesis presents novel work in this field of research, focusing on the use of two soft materials: Layfomm40 and silicone. Both materials complement each other based on their strengths and weaknesses for different cardiac phantom fabrication. Several different phantoms were designed and constructed, and the functionality was demonstrated and analysed.Chapter 1 introduces 3D printing and soft materials, as well as how 3D printing contributes to the healthcare field. Chapter 2 summarizes the state-of-art literature about 3D printed cardiac phantoms, atrial models, and various valve or aorta model manufacturing. Chapter 3 elaborates the material preparation and characterisation. The characterisation involved: 1) mechanical property testing; 2) ultrasound acoustic property testing; 3) optical microscopy; 4) thermal & electrical conductivity testing; and 5) rheological characterisation. Chapter 4 to 6 present three different cardiac models for applications in simulations. The key material used in chapters 4 & 5 was Layfomm40, while silicone was mainly utilised in chapter 6.
Chapter 4 describes the production and evaluation of a patient-specific multi-modal imaging compatible whole heart phantom using Layfomm40. The material and imaging properties of the Layfomm40 phantom were evaluated and compared to commonly used Tango Plus. The results showed that the Layfomm40 phantom had favourable tissue- mimicking material properties and was compatible with multiple imaging modalities. Layfomm40 phantoms have great potential for cardiac interventional procedure simulation and testing of novel technologies. This work was published in the Journal of 3D Printing & Additive Manufacturing.
Cardiac ablation therapy is a common technique used for the treatment of arrythmias. In Chapter 5, a novel bi-atrial phantom was constructed and evaluated for simulation of atrial radiofrequency ablation (RFA). Based on the microscopy and conductivity characterisation results in chapter 3, Layfomm40 was evaluated as a suitable material for compatibility with RFA and electroanatomic mapping systems (EAMSs), which are used for guidance during cardiac RFA procedures. The irreversible thermochromic paint was also investigated to allow visualisation of ablation points. The printed Layfomm40 atrial model was coated with this thermochromic paint, placed in a custom enclosure and evaluated for simulation of cardiac ablation procedures in the cardiac catheterisation laboratory using fluoroscopy and the CARTO3 EAMS. The thermochromic paint allowed realistic visualisation of the ablated areas and the bi-atrial phantom performed well as an interventional procedure simulator. This work was published in Applied Sciences: Emerging Techniques in Imaging, Modelling and Visualization for Cardiovascular Diagnosis and Therapy.
Aortic stenosis is one of the most common cardiac pathologies and there are many open questions regarding its optimal management. There is an emerging demand for aorta and valve phantoms to study aortic stenosis. Although Layfomm40 has been proved to be suitable for creating static cardiac phantoms, it is prone to delamination and therefore it would be challenging to construct dynamic phantoms that can withstand physiological flow conditions or have functional components, such as valves. However, silicone is a resilient soft tissue-mimicking material used commonly to make anthropomorphic phantoms. In Chapter 6, silicone aorta and aortic valve phantoms were constructed and evaluated. Initially, 3D-printed two-part moulds were used to make the phantoms, with the internal mould printed in water-soluble material. Different diseased valves were manufactured with Ecoflex silicone and then attached to a durable aorta model fabricated using Dragonskin silicone. The phantoms were evaluated using a physiological flow circuit and imaged using ultrasound and magnetic resonance imaging (MRI), showing realistic anatomical appearance and physiologically plausible function. Then, for comparison, another aortic valve model was fabricated using direct silicone printing with modified silicone inks. The printed silicone valve also survived in the flow test, demonstrating an alternative and viable new solution for silicone model manufacturing. The valve manufacturing work using the two-part mould technique was published in the MICCAI-STACOM Conference, and the physiological pressure analysis of the silicone valves was accepted in the Journal of Cardiovascular Translational Research.
In conclusion, the work presented in this thesis expands the knowledge and understanding in the domain of using soft materials for construction of cardiac anthropomorphic phantoms. This will have a significant impact for the training of healthcare professionals, testing of novel devices and imaging technologies, and the progression of research for the treatment of CVD.
| Date of Award | 1 May 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Kawal Rhode (Supervisor) & Ronak Rajani (Supervisor) |