Endovascular aortic repair (EVAR) is a minimally invasive alternative to open surgery for the treatment of aortic aneurysms (AA). However, standard EVAR is not applicable to complex AA with involvement of vital branches, which could be occluded by the endograft. As an emerging technique, the concept of multiple overlapping uncovered stents (MOUS) have been proposed to manage complex lesions. MOUS was used to modulate the flow pattern inside the aneurysm sac, and promote the thrombus formation followed by the aneurysm shrinkage. In this dissertation, we sought to investigate the mechanism of MOUS-induced flow modulation and key factors associated with the success of this novel technique: - The mechanical behaviour of AA was characterised by uniaxial material tests (Chapter 4). A Bayesian framework was proposed for material constants identification. They were found correlated to the microstructure of tissue fibre network and were capable in differentiating tissue types. - Solid-to-solid interaction and one-way fluid-solid interaction (FSI) analysis was performed based on patient-specific computer tomography angiography (Chapters 5&6). Structural stress concentrations were observed within the landing zones, which increased with the number of stents deployed. In the parameter studies (Chapter 6), the overall porosity was identified as the dominant factor of the flow-diverting outcome, while cross-stent structures of MOUS had limited influence. - The pathological effect of structural stress concentration induced by an implanted device was further studied in rabbit models (Chapter 7). The wall structural stress and fluid shear stress were obtained from FSI analysis based on magnetic resonance imaging (MRI), and correlated to plaque characteristics. Both high structural stress and low fluid shear stress were found correlated to plaque initialisation and increased inflammation. Overall, MOUS modulates the blood flow with robust performance under different overlapping patterns. Image-based biomechanical analysis can optimise MOUS design and can contribute to personalised pre-surgery planning.

在現代外科實務中，我們今天認為是標準作業程序的手術，追溯到初期可能是激進創新。多年來，外科技術雖然已經有頻繁的修改，但往往是漸進式地。心臟和血管外科領域中的大多數創新並沒有導致日常實踐劇變。然而，在過去的幾年中，在我服務的醫院和全世界，我看到了治療腹主動脈瘤 (AAA) 的典範轉移，亦即主動脈腔內修復 (EVAR)。 相對於傳統開腹手術修復 （OSR），主動脈腔內修復較傳統開腹手術修復有顯著較低的手術死亡率。不過，長遠來說，總死亡率或動脈瘤相關死亡率並無差異；而主動脈腔內修復有較高的植入物相關併發症和必須再次手術的機率，且成本更高。然而，主動脈腔內修復還是成為腹主動脈瘤治療的支柱。這是為什麼？ 除了是激進的技術創新，主動脈腔內修復也是技術頓悟。傳統上，醫療服務是典型的技術輔助服務情境，其中包含兩個單獨的、然而是密切相關的溝通系統： 一個是產業與醫師之間，另一個是醫師與病人之間。醫師居於樞紐地位，不僅確保治療之執行，而且還要評估結果。由於現代資訊與通信技術的發達，病人可以方便地搜尋輔助醫療文獻資訊、線上資訊和個人社會網絡的意見。這就像是詮釋者的作用。這詮釋者的解釋對病人、外科醫生、和醫療產業界產生了實質上重大的影響，反之亦然。以前在這服務體系中互相分離的部分現在可以緊密地互相配合了，這與服務導向邏輯中價值共同創造的概念是不謀而合的。 總之，對多重利益相關者之意義提升是臨床醫療服務典範轉移的原因。在醫療行業中引入服務導向邏輯的概念的重要性，不論是在日常實務和創新策略上的意義都是不容忽視的。醫療服務中，多重利益相關者比以前更涉及共同創造價值的過程。未來的創新者除了專注在技術和科技上，更必須考慮該創新對多重利益相關者之意義提升。 / In modern surgical practice, what we consider as standard procedures today may be radical innovations dated back to the early days. Over the years, there has been frequent modification of surgical techniques, often incremental though, and most innovations in the field of cardiac and vascular surgery didn’t result in drastic changes in the daily practice. However, during the past several years, I have been witnessing a paradigm shift in the treatment of abdominal aortic aneurysm (AAA) in my hospital and worldwide towards endovascular aortic repair (EVAR). In comparison to the traditional open surgical repair (OSR), EVAR was associated with a significantly lower operative mortality than OSR. However, no differences were seen in total mortality or aneurysm-related mortality in the long term, and EVAR was associated with increased rates of graft-related complications and reinterventions and was more costly. Nevertheless, EVAR is becoming the mainstay of AAA treatment. Why is this? Except for being a radical technology innovation, EVAR is also a technology epiphany. Traditionally, medical service is a typical technology-assisted service encounter, consisting of two separate, however, closely inter-related communication systems: one between the industry and the physician, and the other one between the physician and the patient. The physician is of the pivot role that not only ensures the execution of treatment but also evaluates the results.With modern information and communication technologies, patients caneasily search information from paramedical literatures, online information, and opinions from personal social network. This serves the emerging role of an interpretor. This interpretors’interpretation has substantial influence on patients, surgeons, industry, and payers and vice versa. Previously separated parts in the service system now can be closely inter-related. This is in concordance with the concept of co-creation of value in service-dominant logic. It is concluded that newly defined meanings to multiple stakeholders are the reasons for paradigm shift in clinical medical service. The importance of introduction of the concept of service-dominant logic into the medical industry, both in daily practice and in innovation strategy can never be over-emphasized. Multiple stakeholders are being involved much more than before in the process of co-creation of value in medical service.Future innovators must concentrate on meanings to multiple stakeholders as well on techniques and technologies.