Future imaging techniques in aortic pathologies and clinical implications.

Future imaging techniques in aortic pathology will be used to detect early subclinical pathological changes and to identify patients who would benefit from early surgical intervention. Current imaging for aortic pathology is mainly computed tomography (CT). This modality produces static images which are used as the basis to decide which patients require intervention. Subclinical disease can be detected experimentally by novel magnetic resonance (MR) techniques such as molecular imaging: measurement of the amount of elastin in the aortic wall has the potential to identify patients with low levels of elastin at risk of aortic dilatation. These patients could then be monitored in a more intensive aneurysm surveillance programme. Endothelial dysfunction can also be detected experimentally by MR techniques. Measurement of endothelial permeability will be used to tailor preventative medical treatment to individual patients. Aortic diameter is the main indication for treatment in both aortic aneurysms and chronic aortic dissection but may be prone to error. False lumen thrombosis detected on first-pass imaging is used as an outcome measure in randomized controlled trials. Blood pool contrast agent imaging is flow independent and is not subject to the significant error associated with current imaging methods. Four-dimensional phase contrast magnetic resonance (4D PC-MR) imaging can quantify flow in both the true and false lumens of aortic dissection. The amount and pattern of flow in the false lumen is related to the rate of aortic expansion. 4D PC-MR can demonstrate entry tears between the true and false lumens and this information can be used to guide endovascular treatment. Hybrid imaging techniques such as positron emission tomography (PET) combined with CT (PET-CT) can give information about the degree of inflammation in the aortic wall, and preliminary studies have shown that a positive scan can predict patients with dissection who are likely to have a poor outcome. These new techniques combine anatomical and functional data in a single acquisition. The richness of the data allows a greater understanding of the pathophysiology in each individual patient which will result in improved clinical outcomes.