## 5 So, How Can We Take It to the Skies?
### A Model-Based System Engineering Design (MBSE) Approach  
The design and development process for medical devices has traditionally followed a linear waterfall approach (Figure 5) [32]. It is a basic logical sequential design process, usually starting with capturing the requirements (users, products, regulatory, etc.), and each phase must be reviewed, verified, and completed before the next phase can begin. The waterfall linear approach has limitations such as the fact that each phase of development proceeds in a strict order, which makes it hard to accommodate change requirements throughout the product lifecycle management (PLM) phases, and it is not suitable for complex designs.  
In recent years, collaborative and concurrent design together with realistic engineering and manufacturability considerations have attracted the interest of many researchers. To ensure that the medical devices can be tested faster and more reliably, and to accelerate their time from concept to market, efforts must be directed towards fulfilling regulatory requirements and pushing innovation in a sustainable way.  
Furthermore, the design, development, and dissemination of medical devices are regulated by regulatory bodies around the world such as the FDA in the USA, the Therapeutic Goods Administration (TGA) in Australia, and the European Medicines Agency in the European Union to ensure the safety and efficacy of the products. Through a complex system of legislation, the time from concept to market for medical devices, which includes the review and approval processes that meet requirements for conformity, can be lengthy and costly [33].  
Hence, to realize such a vision to transform ideas from industry-academia collaboration, we proposed a new approach that complements the 'V' model (Figure 6). It is a direct approach of integrating collaborative and concurrent product design on a single virtual design platform with model-based system engineering (MBSE).  
Figure 5: The traditional linear waterfall approach for the design and development process.  
Figure 6: Proposed MBSE “Diamond” modified from Boeing: approved for public release (RROI 19-00155-BDS).  
In reducing the weight and size of a complex CT scanner to retrofit into a search and rescue helicopter, an appropriate framework is required to assist in designing and testing medical devices virtually before introducing them into the physical world. As the project involved multiple stakeholders, the effectiveness and efficiency of the proposed design required input and effort from people of multiple disciplines including engineering, medicine, legal, technical, etc.  
Through the proposed MBSE diamond approach, we would develop a digital twin of CT scanner and aircraft. Digital twin is commonly known as a digital or virtual representation of a physical entity, and a bidirectional connection of data between them for the purpose of improving the performance of the physical part using computational modelling and simulations [34]. The key feature of the MBSE diamond approach is the creation of digital models to design and optimize systems before the first physical item is built. It also allowed continuous improvement and enabled scope flexibility, team input, and the delivery of a quality product that emphasized verification and validation with the use of test cases to ensure adherence to which the product should be built as-designed data and vice versa [33].  
The design process for modifying and retrofitting a CT scanner can be classified into three steps: (1) default structure reduction, (2) support structure design, and (3) integration onto mobile interior (Agusta Westland AW189). CATIA (Dassault Systemes, Velizy-Villacoublay, France), three-dimensional computer-aided design software, was used to model both the CT scanner model and the cabin interior of AW189.