Utmaningar och förbättringsmöjligheter för MR-faskontrast vid diagnostik av kronisk aortainsufficiens

Abstract

Aortic valve regurgitation (AR) occurs when the valve fails to close properly, allowing blood to flow back into the left ventricle during diastole. This puts extra strain on the heart and, over time, can lead to damage and reduced heart function. Phase contrast magnetic resonance imaging (PC-MRI) is considered an accurate method to assess the AR severity. In some cases, though, complex blood flow, through-plane heart motion, and the presence of metal implants may affect the diagnostic certainty. This thesis aims to determine if and how these factors influence the assessment of AR severity and to develop new potential biomarkers for AR patients using PC-MRI.

In Paper I, the blood flow was characterized in detail in patients with chronic AR using PC-MRI. The results showed that patients with larger aortas and greater AR displayed more skewed and complex flow in the ascending aorta. Paper II determines the influence of complex blood flow on PC-MRI in the ascending aorta of patients with chronic AR. The results showed that flow complexity varied with (measurement) position and that a more complex flow was associated with lower measurement repeatability. Paper III determines the influence of through-plane heart motion on the PC-MRI in the ascending aorta in patients with chronic AR. The results showed that such motion errors can lead to underestimation of AR severity, particularly in patients with large aortas. Paper IV evaluates the potential of assessing AR severity using PC-based biomarkers in the descending aorta of patients with chronic AR. With such vi biomarkers, significant and non-significant AR could be separated with high diagnostic certainty. Paper V uses a flow phantom to evaluate the effect of dynamic susceptibility changes due to the movement of metallic aortic valve protheses during the PC-MRI acquisition. The results showed that such effects can further lead to underestimation of the AR severity.

In summary, this thesis shows that complex flow, through-plane heart motion, and dynamic susceptibility changes can affect the assessment of AR severity using PC-MRI, particularly in patients with dilated aortas. Furthermore, PC-MRI biomarkers in the descending aorta can be used as a supportive reference and thereby improve the diagnostic certainty for patients with chronic AR.