Assesment of 4D aortic strain from 3D time-resolved MRI in aortic aneurysms

Abstract

Aortic aneurysms are a class of frequent cardiovascular disease related to an increased risk of life-threating complications, such as aortic dissection and rupture. These acute events are characterized by a very bad prognosis, with mortality comprised between 60 to 70%. Maximum aortic diameter is the sole established parameter for risk assessment but many acute events happen at a diameter lower than that suggested for preventive substitution of the diseased region. Aortic deformation may be used for better risk stratification. Three-dimensional (3D) time-resolved cine cardiac magnetic resonance images (CMR) allows for the quantification of strain over the totality of the aorta, overcoming many limitations of 2D imaging, such as the predefined location of analysis and through plane deformation. The aim of the present study was to assess 4D strain of the whole thoraco-abdominal aorta during one cardiac cycle. The dataset was provided by Hospital Universitari Vall d’Hebron and consisted on 3D cine CMR and contrast-enhanced 3D angiography (MRA). 3D volume of the whole thoraco-abdominal aorta was obtained from contrast-enhanced 3D angiography and allows to identify the aortic wall and extract deformation values at those points. Volumetric images of the aorta from 3D cine CMR at different cardiac phases were registered and the deformation field at the aortic wall was extracted and analysed. Local strain of the wall was extracted in anatomically-identified regions and was divided into circumferential and radialcomponents. The evaluation of aortic strain may help to monitor and evaluate risk in patients with aortic aneurysms.