Bio-dynamic monitoring, diagnosis and follow-up of Abdominal Aortic Aneurysms using optical imaging techniques

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Abdominal aortic aneurisms (AAA) is a localized balloon-like dilation of the abdominal aorta. It accounts for the death of at least 45 individuals per 100,000 population and is a serious threat to aging people. Nowadays, endovascular aortic repair (EVAR) is the most common treatment for AAA. It is a minimally invasive treatment in which an expandable stent graft (endoprosthesis) is placed within the aorta. Major problems of endoprostheses are leakage (endoleak) and migration. Due to endoleaks, the aneurysm sac comes back under systemic blood pressure, which can cause rupture. The pressure inside the aneurism sac is nearly impossible to measure. Such a measurement, together with other indicators (ultrasound or CT scan), would greatly help determining the need for a reintervention. In the past, it has been shown that measurement of the mechanical wave forming on the abdomen due to the heart beat can be an indirect indication of the sac pressure and has the potential to be used as a diagnostics and monitoring signal before and after EVAR. In the previous pre-study of one of the applicants, a laser-vibrometer was used to measure the vibration of the abdomen surface. The procedure was rather cumbersome and also no thorough tests on patients were undertaken. In this project, we want to investigate several optical techniques to indirectly monitor the change of the AAA sac pressure. In particular, Digital Image Correlation (DIC) techniques seem promising for this application. DIC is a rather simple technique based on stereo video images to measure 3D motion of a surface (nowadays used in engineering applications). Such optical techniques are not yet used in medical imaging. Optical techniques such as DIC have not yet been tried to monitor medical conditions although they have the potential to open a whole new field for medical applications such as AAA monitoring and diagnosis. The project is a cooperation between the faculty of Mechanical Engineering and the School of medicine of TUM.