Project of Imaging

Peri-Operative Risk Assessment of Abdominal Aortic Aneurysms Using 4D and Multi-Perspective Ultrasound

To improve the risk assessment in patients with abdominal aortic aneurysms (AAAs), an ultrasound based method has been developed to estimate the stiffness and wall stress in AAAs. Current research focuses on improving and extending this method using more advanced imaging techniques (giving better image quality) and more sophisticated mechanical models.

An abdominal aortic aneurysm (AAA) is a local enlargement of the abdominal aorta. Aneurysms are mostly asymptomatic, but are at the risk of rupturing, causing a life-threatening hemorrhage. Surgical intervention to prevent rupture is performed when the risk of rupture is expected to be greater than the risk of the surgery. Currently, the risk of rupture is assessed by monitoring the diameter and growth of the AAA using ultrasound. Thresholds for both diameter and growth are based on population data and are not tailored for the individual patient. In some patients the AAA ruptures before the threshold diameter is reached, while other patients have a very large AAA which has not ruptured. These findings highlight the need for a better prediction of rupture risk. Our research focuses on the biomechanics of AAAs, as rupture will occur when the stresses acting on the wall exceed the strength of the wall.

In previous work, a method is developed to estimate the stress and stiffness of the AAA wall. 3D+t ultrasound data is used to obtain a patient-specific geometry and wall motion. From this data a patient-specific finite element model is created, in which the stiffness is tuned to match the wall motion. This model gives insight into patient-specific stress and stiffness of the AAA. Ongoing research aims to relate these parameters to the risk of rupture for a better, patient-tailored clinical decision support for endovascular surgery.

Surgical treatment consists of placing a stent-graft in the aorta, which is also not without risk. After the EndoVascular Aneurysm Repair (EVAR) procedure, the aneurysm will respond to the inserted stent-graft, which may lead to stent migration, leakages, or aneurysm growth. For optimal surgical repair and post-EVAR treatment, mechanical quantification of the wall-stent interaction is necessary. The model used to determine patient-specific stress and stiffness will be extended for post-EVAR applications to predict and quantify mechanical wall-stent interactions.

Projects for bachelor-end projects, internships and MSc projects are available.

  • Ultrasound simulations of AAAs for verification and validation of FE inverse methods
  • Improving ultrasound acquisition techniques for improved contrast and resolution
  • Image processing for automation of segmentation and registration of ultrasound images.
  • Refining FE models for the estimation of local stiffness measures
  • Extending modeling framework with sophisticated boundary conditions
  • Multi-perspective ultrasound imaging

Other projects can be designed with the supervisors (Niels Petterson (PhD), Esther Maas (PhD), Larissa Jansen (PhD) & Richard Lopata).