Automatic realignment of myocardial first-pass MR perfusion images

Magnetic resonance first-pass imaging of a bolus of contrast agent is well adapted to distinguish normal and hypoperfused areas of the myocardium. In most cases, the signal intensity-time curves in user defined regions of interest (ROI) are studied. As image acquisition is ECG-gated, the images are acquired at the same moment in the cardiac cycle, and the basic shape of the heart is similar from one view to the next. However, superficial respiratory motion can displace the heart in the short-axis plane. The aim of this study is to correct for the respiratory motion of the heart by performing an automatic realignment of the myocardial ROI based on a method tracking the movement of the lung-myocardium interface. Visual and quantitative analyses performed on 120 curves show a very good concordance between the automatic methods and the manual one.

1. Introduction

Magnetic Resonance first-pass imaging of a bolus of contrast agent is well adapted to distinguish normal and hypoperfused areas of the myocardium. In most cases, the signal intensity-time curves in user defined regions of interest (ROI) are studied [1], [2]. The ROI is usually delimited by the left ventricular epicardial and endocardial borders. In our case, 1t is traced manually on an image with sufficient contrast between the blood pool and the myocardium. This ROI is then divided into eight segments (figure 1). As in the method presented by Penzkofer et al. [3], a centreline equidistant to the epicardial and the endocardial borders of the LV is traced automatically (figure 1). For each segment of the ROI, a corresponding signal intensity-time curve is obtained.