Measurement of systolic and diastolic arterial wall shear stress in the ascending aorta

Efstathopoulos, Efstathios P.; Patatoukas, George; Pantos, Ioannis; Benekos, Odysseas; Katritsis, Demosthenes; Kelekis, Nikolaos L.

doi:10.1016/j.ejmp.2008.02.001

« Previous Next »Physica Medica: European Journal of Medical Physics
Volume 24, Issue 4 , Pages 196-203, December 2008

Measurement of systolic and diastolic arterial wall shear stress in the ascending aorta

Efstathios P. Efstathopoulos
- Second Department of Radiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
- Corresponding author. Second Department of Radiology, General University Hospital “ATTIKON” Rimini 1 Street, Chaidari GR 124 62, Athens, Greece. Tel.: +30 210 5831 827; fax: +30 210 5326 418.
George Patatoukas
- Second Department of Radiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
Ioannis Pantos
- Second Department of Radiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
- Department of Cardiology, Athens Euroclinic, Athens, Greece
Odysseas Benekos
- Second Department of Radiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
Demosthenes Katritsis
- Department of Cardiology, Athens Euroclinic, Athens, Greece
Nikolaos L. Kelekis
- Second Department of Radiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece

Received 3 September 2007; received in revised form 1 February 2008; accepted 2 February 2008. published online 17 March 2008.

Abstract

Purpose

Wall shear stress (WSS) appears to contribute significantly in the initiation and progression of atherosclerotic disease. The purpose of this work is to present in vivo systolic and diastolic WSS calculations in the human ascending aorta by the application of three straightforward methodologies based on Poiseuille's theory of flow.

Materials and methods

Blood flow measurements were performed retrospectively in the ascending aorta of 20 non-atherosclerotic patients using phase-contrast MRI. WSS calculations were performed assuming Poiseuille's theory of flow based on average flow volume, average flow velocity and maximum flow velocity. Systolic and diastolic WSS values were calculated and compared with the calculated maximum and minimum values of WSS throughout the cardiac cycle.

Results

Systolic WSS values calculated by average flow volume, average flow velocity and maximum flow velocity were similar (0.4±0.2N/m², 0.4±0.3N/m²and 0.4±0.2N/m², respectively). Diastolic WSS values calculated by maximum flow velocity were significantly higher (11.6±7.0×10⁻²N/m²) compared to values calculated by average flow volume (0.3±0.9×10⁻²N/m²) and average flow velocity (0.3±1.0×10⁻²N/m²). Comparison of systolic and diastolic WSS values with maximum and minimum WSS values showed that time instances of maximum and minimum blood flow velocities do not coincide with time instances of maximum and minimum blood flow volume.

Conclusion

In vivo calculation of WSS in the ascending aorta is feasible by phase-contrast MRI flow measurements and straightforward methodologies based on Poiseuille's theory of flow. However, measurements based on maximum flow velocity show larger deviations compared to measurements based on mean flow volume or mean flow velocity.

Keywords: Wall shear stress, Phase-contrast MRI