Quantification of Caval contribution to flow in the Right and Left Pulmonary Artery of Fontan patients with 4D Flow MRI

Abstract

Background Knowledge of caval contribution to flow in the Right and Left Pulmonary Artery (RPA and LPA) of Fontan patients is of great interest, because uneven flow distribution to the lungs is associated with pulmonary arteriovenous malformations. However, in Fontan circulation more than 1 source of flow to the RPA and LPA is present, which makes difficult to quantify the flow distribution with standard methods. Although a novel MRI application was developed to quantify caval contribution years ago, it has limitations and it is not applicable to patients with turbulent flow in the Pulmonary Arteries (PA)[1]. We propose a new method to easily quantify the flow distribution in Fontan patients. Methods A 4D Flow sequence was acquired in 12 healthy volunteers and 9 Fontan patients on a 1.5T Philips scan. Flow distribution was quantified with particles traces using the software “GTFlow”. The new method consists of emitting particles from a Region Of Interest (ROI) with a temporal resolution of ~40 ms. Then, we quantified the flow distribution by counting the particles arriving to a different ROI. To validate this method, 2 independent observers compared the flow contribution of the main PA to the RPA and LPA in healthy volunteers. This was done calculating net forward flow, which was used to validate the distribution of flow obtained with our new method. Thereafter, we quantified the flow distribution of the Superior and Inferior Vena Cava (SVC and IVC) to the RPA and LPA in Fontan patients.