Revolutionizing airborne medicine: designing a helicopter-integrated head CT scanner
Creators: name: Kwok, Jun Sheng
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400308
subject: Medical devices

description: Stroke is a global health challenge and is a leading cause of mortality and chronic disability, with ischemic stroke accounting for around 80% of all strokes. Due to its highly time-sensitive nature, earlier stroke treatments should be enforced for improved recovery rate, where ideally treatment should be administered within the first hour after onset of stroke symptoms – ‘golden hour’ for the best recovery result. Recombinant tissue plasminogen activator (r-tPA) is a thrombolytic drug which was approved by the Food and Drug Administration (FDA) in treating patients with acute ischemic stroke (AIS), where its efficacy was proven over decades clinical practice and applications. However, the applicability of the administration of r-tPA is limited to three hours of stroke onset, and that a prior head computed tomography (CT) scan is required from the stroke patient to determine the nature of the stroke. To achieve this, the mobile stroke unit (MSU) was conceptualized and implemented to deliver the diagnosis and treatment to a stroke patient.

However, due to geographical challenges, most rural communities were still unable to receive a timely stroke intervention, where in fact access to specialized stroke facilities for proper stroke treatment poses a challenge. Therefore, the aircraft counterpart (Air-MSU) of the conventional road MSU poses as a plausible solution to this shortcoming by expanding the catchment area for regional locations in Australia. Air-MSUs often operate in challenging conditions, requiring medical equipment that is lightweight, portable, and robust. A key piece of equipment is the CT scanner, an essential diagnostic tool in critical care. However, current CT scanners are not designed with the unique constraints of the Air-MSU in mind, such as limited space and weight restrictions. Therefore, this research arises from the need to optimize the design of the CT scanner for use in the Air-MSU. It aims to design, develop, and validate a lightweight, structurally robust CT scanner that can be retrofitted into a helicopter.

In collaboration with Australian Stroke Alliance and Melbourne Brain Centre, research presented in this thesis aims to explore the possibilities and methodologies in reducing the weight and effectively, the size of an existing portable head CT scanner – CereTom by Neurologica, such that it can be retrofitted into the proposed search and rescue (SAR) helicopter – AgustaWestland AW189. A novel framework was developed and implemented in place encompassing the conceptualization to physical validation design phase with the integration of a digital twin concept, to demonstrate the mechanical design of fitting a portable head CT scanner into a search and rescue helicopter. This framework was then used to initiate the conceptualization of a newly modified 3D CT scanner model through the project specifications and requirements. Where the components of the nominated CT scanner were assessed and removed or replaced where applicable for further weight and size reduction. Consequently, a new support structure was designed in place to house the newly replaced components, and a robust material selection process was developed utilizing Ashby plots to select on the most optimum material for the newly designed support structure according design criteria and requirements, which turned out to be carbon fibre reinforced polymer (epoxy with 55% long carbon fibre strands). Next, the new support structure underwent topology optimization to further reduce its mass while optimizing its structural integrity. Finally, finite element analysis (FEA) was carried out to verify the newly topology optimized structure under specified loads. Through the replacement and removal of default components, and the utilization of topology optimization technique, a new weight-optimized and structurally verified support structure for the CT scanner was proposed, and can be retrofitted into AW189, where a total of 91.81 kg was reduced from the default CereTom model. This research contributes to a better understanding of how to create optimized designs for medical equipment, advancing topology optimization techniques, and streamlining the product design process; providing fundamental insights for the future of technical development and implementation of the Air-MSU concept.