Retrospective CINE MRI of the mouse heart

E. Heijman, W. de Graaf, C. Diekmann, A. Nauerth, G. Strijkers, K. Nicolay Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, Bruker BioSpin MRI GmbH, Ettlingen, Germany Introduction In cardiac research in vivo studies of mice are indispensable to gain an improved understanding of cardiovascular disease mechanisms and to develop novel diagnostic tools as well as surgical and therapeutic interventions. MRI plays an important role in measuring the global functional parameters of the mouse heart, including end diastolic volume, end systolic volume and ejection fraction (1). These parameters can be determined from triggered cinematographic (CINE) MR images. Without any respiratory gating strategy these images have considerable motion artifacts due to the strong gradient fields of the CINE sequence (2). This can be solved by respiratory gating, at the expense of a fluctuating longitudinal magnetization induced by an idle time between the end of the CINE series and the next trigger event (3). This results in a poorly defined contrast, which makes automatic segmentation difficult and seriously limits the use of contrast agents. To solve this problem we propose a retrospective method for cardiac triggering and respiratory gating, which uses a navigator echo to derive heart and respiratory cycles retrospectively.