IBISSA

IBISSA: Image Based mrI Shear Stress Assessment

Summary

The endothelium, a first-line defence mechanism against atherogenesis, produces a wide array of homeostatic mediators. A key stimulus to maintain the protective status of the endothelial lining at the inner vessel wall is the wall shear stress (WSS). WSS is the tangential force that blood flow exerts on the endothelium. To quantify WSS, three dimensional (3D) blood flow patterns need to be measured in vivo, which has been a challenge in medical imaging for many years. Although recent preclinical data of 3D ultrasound studies for general flow visualizations in the left ventricle are promising, at present magnetic resonance imaging (MRI) is the only non invasive imaging modality that can measure 3D blood velocity in a standardized fashion. Although MRI resolution and acquisition speed have increased over the past decades, assessment of WSS is still challenging in complex flow geometries. The main challenge lies in the development and validation of advanced image processing that is needed to reliably derive local WSS. In addition, for acceptance of this novel WSS measurement by the clinical community, WSS values need to be validated and successfully utilized in various patient populations. In this project we aim to develop advanced image processing methods to determine and validate WSS based on MR phase contrast (PC) measurements. We will study complex arterial flow systems such as the carotid bifurcation, intracranial aneurysms and the cavopulmonary connection and pulmonary arteries in patients who have undergone a total cavopulmonary connection operation (Fontan procedure). Initially these diseases will be studied in flow phantoms that mimic the vascular layout. PC MRI will be used to measure blood velocities and flow in those phantoms containing complex flow geometries. In addition both particle imaging velocimetry (PIV) and computational fluid dynamics (CFD) will be performed to validate the experimentally measured velocity data. WSS will be quantified by calculating velocity derivatives at the location of the vessel wall. In our approach high-resolution velocity measurements in phantoms (0.2 mm isotropic resolution) give us the capability to fine-tune the WSS algorithm and carefully study its accuracy compared to CFD based WSS values. We will utilize the newly developed WSS algorithm in various patient populations, namely patients with atherosclerotic disease, patients with unruptured aneurysms, and patients with congenital heart defects. Completion of this study will result in technically and clinically validated technology to quantify the WSS in complex flow geometries.

 

Wall shear stress (WSS) magnitude (colored surface), direction (black arrows) visualized on the vessel wall of a portion of the common carotid artery (CCA) in a healthy volunteer. The gray arrows illustrate the direction and magnitude of the velocity in the vessel. The diameter of this CCA is approximately 6 mm.

 

 

 

 

 

 

Project Team:

  • Dr. ir. A.J. Nederveen (projectleader) , a.j.nederveen@amc.nl - Project Leader
  •  Dr. ir. J.J. Wentzel, j.wentzel@erasmusmc.nl - Project Leader
  •  W.V. Potters MSc , w.v.potters@amc.nl - PhD Student
  •  Ir. M. Cibis, m.cibis@erasmusmc.nl - PhD Student

Publications: