The future of cardiovascular magnetic resonance imaging in thoracic aortopathy: blueprint for the paradigm shift to improve management

Figures

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  Fig. 1. Mechanism underlying the development of thoracic aortic aneurysms. TGFβ transforming growth factor beta 1, VSMC vascular smooth muscle cells

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  Fig. 2. Key molecular pathway signaling driving extracellular matrix degradation and thoracic aneurysm formation. Transforming growth factor beta 1 (TGFβ) signaling plays a crucial role in the development of thoracic aortic aneurysms. Within the extracellular matrix (ECM), TGFβ is normally kept in an inactive state, bound to latency-associated peptides and further stabilized by ECM components. Various proteases including matrix metalloproteinases (MMP), thrombospondin (TSP1), and fibrillin (FBN) fragments can cleave latent TGFβ complexes, releasing active TGFβ into the ECM to bind with its subunits (TGFβR1 and TGFβR2). Binding of TGFβ results in Smad protein phosphorylation and nuclear translocation of Smad complexes, driving gene activation and MMP release. Within the ECM, MMPs cause proteolysis and resultant pathological degradation of the ECM, as well as further release of active TGFβ through direct (cleavage of latent TGFβ complexes) and indirect (MMP-associated fragmentation of fibrillin) pathways. MMP matrix metalloproteinase

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  Fig. 3. AI segmentation of the aorta. Axial views of the ascending and descending aorta at the right pulmonary artery using bright (A) and dark (B) blood sequences. Corresponding AI segmentation of the lumen (A) and aortic wall (B) is displayed in red and purple circles. A 3D image of the aorta can be extracted based on the segmentation in (A), as shown in (C), which can then be applied to determine aortic length, degree of tortuosity, and quantify volume. 3D three-dimensional, AI artificial intelligence

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  Fig. 4. Workflow of wall shear stress acquisition by 4D flow CMR. Following 4D flow sequence acquisition, the aorta can be segmented and computational fluid dynamics (CFD) applied. An automated registered mesh of the aorta can be derived and applied by CFD, following which spatial coordinates (in the x, y, z planes) of each mesh node can be used to calculate velocity and wall shear stress maps in 3D and as 2D flatmaps. Though CFD is not required for velocity mapping, which can be performed in real-time and is therefore more time efficient, it may lack resolution, noise control, and predictive capabilities in which case CFD can be complementary. 2D two-dimensional, 3D three-dimensional, 4D four-dimensional, CMR cardiovascular magnetic resonance, WSS wall shear stress

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  Fig. 5. iT2Prep-BOOST sequence in thoracic aortopathy. Simultaneous bright (A and B) and dark (C and D) blood imaging using the iT2Prep-BOOST sequence in the coronal and sagittal planes in a patient with fusiform aneurysm of the thoracic ascending aorta. This single sequence can be utilized to determine the presence and degree of aneurysmal dilatation on the bright-blood imaging as well as identify underlying pathological processes involving the aortic wall using dark blood imaging. BOOST Bright-blood and black-blOOd phase SensiTive inversion recovery