Robust Cardiac Function Assessment in 4D PC‐MRI Data of the Aorta and Pulmonary Artery

Abstract

Four-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) allows the non-invasive acquisition of timeresolved, 3D blood flow information. Stroke volumes (SVs) and regurgitation fractions (RFs) are two of the main measures to assess the cardiac function and severity of valvular pathologies. The flow rates in forward and backward direction through a plane above the aortic or pulmonary valve are required for their quantification. Unfortunately, the calculations are highly sensitive towards the plane's angulation since orthogonally passing flow is considered. This often leads to physiologically implausible results. In this work, a robust quantification method is introduced to overcome this problem. Collaborating radiologists and cardiologists were carefully observed while estimating SVs and RFs in various healthy volunteer and patient 4D PC-MRI data sets with conventional quantification methods, that is, using a single plane above the valve that is freely movable along the centerline. By default it is aligned perpendicular to the vessel's centerline, but free angulation (rotation) is possible. This facilitated the automation of their approach which, in turn, allows to derive statistical information about the plane angulation sensitivity. Moreover, the experts expect a continuous decrease of the blood flow volume along the vessel course. Conventional methods are often unable to produce this behaviour. Thus, we present a procedure to fit a monotonous function that ensures such physiologically plausible results. In addition, this technique was adapted for the usage in branching vessels such as the pulmonary artery. The performed informal evaluation shows the capability of our method to support diagnosis; a parameter evaluation confirms the robustness. Vortex flow was identified as one of the main causes for quantification uncertainties.

Motion-aware stroke volume quantification in 4D PC-MRI data of the human aorta

“…This coincides with the findings from Köhler et al [19]. The differences between the 2D PC-MRI simulation D2 and S were, on average, smaller than the differences between S and D-especially if there was just a moderate movement of the dynamic centerline.…”

“…The limited improvements imply that it is reasonable to employ static 3D vessel approximations to quantify stroke volumes. Yet, the use of robust methods [19] is recommended due to the calculations' high sensitivity to the measuring plane angulation.…”

“…In the following, we explain selected valvular and vascular pathologies that promote the formation of vortex flow. Köhler et al [19] pointed out the high susceptibility of stroke volume quantification to such complex flow patterns.…”

“…Based on [19], a measuring plane is characterized by a grid size g = g x , g y with 50 × 50 as default, a center position c ∈ R 3 , a normal vector n ∈ R 3 that describes the plane's orientation, a scale s = s x , s y per grid element and two vectors n x , n y that form a local orthonormal system with n.…”

Generation and Visual Exploration of Medical Flow Data: Survey, Research Trends and Future Challenges

“…watershed transformation on a PC‐MRA image [HFS*11], graph‐based, e.g. graph cuts on temporal maximum intensity projection images [KPG*16b], and model based, e.g. active surface models on temporal maximum intensity projection images [vPNtHRV12].…”