Health monitoring of fistulas for dialysis patients using ultrasound scans 1=Biomaterials and tissue engineering 2=Healthcare technologies

慢性肾脏疾病影响着英国约300万人，目前有超过30，000人接受血液透析。透析是肾功能下降的严重慢性肾病患者除移植外的唯一选择。为了建立透析的血管通路，您需要创建动静脉（AV）瘘。动静脉瘘是通过外科手术将手臂中的静脉改道至动脉，绕过小血管（毛细血管）。瘘管手术后，静脉随着时间的推移发生了巨大的变化：静脉壁被拉伸，血管腔增加，使血流超过500 ml/min。静脉变得更大和更强，以便于使用针头进行透析。成熟时，动静脉瘘提供了一个长期的接入点，将患者连接到透析机。不幸的是，AV瘘不会永远持续下去。它的功能会随着时间的推移而恶化，最终会在某个时候失败。瘘失败的根本原因仍然没有很好地理解，新的动静脉瘘的平均时间跨度约为5年。瘘管是否会失败的不可预测性可能会导致透析患者的高度焦虑。例如，瘘管可能会出现狭窄并突然凝块。当瘘管不再充分发挥功能时，必须通过手术创建新的瘘管，这可能对透析患者的身体健康和心理健康产生不利影响。在这个项目中，我们提出了一种新的健康监测瘘管使用超声扫描。我们在皇家伯克希尔医院（RBH）跟踪了一小群透析患者。在定期医院透析期间，患者将使用超声扫描。瘘管健康监测需要对AV瘘管进行重复医学扫描。与超声扫描相关的低风险使这种方法成为可能。否则，这既不安全（在CT的情况下），也不经济可行（在MRI的情况下）。由于健康风险和成本，我们不能为每个人使用CT扫描仪。产生瘘管模型的手持式超声技术是创建个体3D瘘管成像模型的实用替代方案。由于瘘管功能与瘘管的血流动力学密切相关，计算流体动力学（CFD）模拟可以帮助我们了解瘘管的基本血流动力学特征，从而监测瘘管功能。根据超声扫描构建的3D瘘管模型将用于瘘管患者的CFD建模。患者特定的瘘管血流CFD建模将告知我们瘘管失败的早期迹象，并深入了解这些失败的原因。通过了解瘘管的流动动力学，我们可以预测哪个瘘管会起作用。我们还可以识别出由于其血流动力学而更容易发生狭窄的瘘管，我们可以通过早期干预使其持续更长时间。这是一个雄心勃勃的项目，旨在开发一种可靠而实用的超声图像采集技术，用于瘘管患者的CFD建模，并建立一种可用于未来纵向研究的稳健方案。我们将与行业合作伙伴（飞利浦）合作，利用他们在图像采集方面的专业知识。该项目将有助于更好地了解瘘管病健康监测和早期干预。数据分析将被简化，使其成为一种临床工具，而不是拥有数据并等待几天才得到答案。

Chronic kidney disease affects about 3 million people in the UK and currently over 30,000 people are on haemodialysis. Dialysis is the only option apart from a transplant for severe chronic kidney disease patients with reduced kidney function. To establish vascular access for dialysis, you need to create arteriovenous (AV) fistula. AV fistula is the surgical re-routing of a vein in the arm to an artery, bypassing small blood vessels (capillaries). After the fistula surgery, the vein undergoes dramatic changes over time: the wall of the vein is stretched and the vessel lumen increases to enable blood flow over 500 ml/minute. The vein becomes larger and stronger to allow easy access with needles for dialysis. At maturation, AV fistula provides a long-term access point to connect the patient to the dialysis machine. Unfortunately, AV fistula does not last forever. Its function can deteriorate over time, and it will ultimately fail at some point. The underlying causes for fistula failure are still not very well understood and the average time span for a new AV fistula is about 5 years. Unpredictability of whether the fistula will fail or not can cause high levels of anxiety among dialysis patients. For example, a fistula can develop stenosis and suddenly clot up. When a fistula no longer functions adequately, a new fistula has to be created surgically and this can have a detrimental impact on physical wellbeing and mental health of dialysis patients. In this project, we propose a novel health monitoring of fistulas using ultrasound scanning. We follow a small group of dialysis patients at Royal Berkshire Hospital (RBH). During their regular hospital visit for dialysis, patients will be scanned using ultrasound. Fistula health monitoring requires repeat medical scans of AV fistulas. The low risks associated with ultrasound scanning makes this approach possible. Otherwise, this would not be safe (in case of CT) nor economically feasible (in case of MRI). We cannot use a CT scanner for everyone due to health risks and cost. Handheld ultrasound technique producing a fistula model is a practical alternative to create individual 3D fistula imaging models. As fistula function is closely related to the blood flow dynamics of the fistula, computational fluid dynamics (CFD) simulations can help us understand the underlying haemodynamic characteristics in the fistula and thus monitor the fistula function. The 3D fistula models constructed from ultrasound scans will be used for CFD modelling in fistula patients. Patient-specific CFD modelling of fistula blood flow will inform us of early signs of fistula failure and also shed insights into the causes of these failures. By understanding the flow dynamics of fistula, we can predict which fistula is going to work. We can also identify fistulas which are more likely to develop stenosis because of their flow dynamics, and we may be able to keep them going longer through early intervention. This is an ambitious project to develop a reliable and practical technique for ultrasound image acquisition for CFD modelling in fistula patients and to establish a robust protocol which can be used in future longitudinal studies. We will work alongside an industry partner (Philips), leveraging their expertise on image acquisition. This project will lead to a better understanding on fistula health monitoring and early intervention. The data analysis will be streamlined, so that it becomes a clinical tool rather than having the data and waiting for several days before you have an answer.