Comparison between prospective and retrospective triggering for mouse cardiac MRI

Abstract

High-resolution magnetic resonance imaging (MRI) has evolved into one of the major non-invasive tools to study the healthy and diseased mouse heart. This study presents a Cartesian CINE MRI protocol based on a fast low-angle shot sequence with a navigator echo to generate cardiac triggering and respiratory gating signals retrospectively, making the use of ECG leads and respiratory motion sensors obsolete. MRI of the in vivo mouse heart using this sequence resulted in CINE images with no detectable cardiac and respiratory motion artefacts. The retrospective method allows for steady-state imaging of the mouse heart, which is essential for quantitative contrast-enhanced MRI studies. A comparison was made between prospective and retrospective methods in terms of the signal-to-noise ratio and the contrast-to-noise ratio between blood and myocardial wall, as well as global cardiac functional indices: end-diastolic volume, end-systolic volume, stroke volume and ejection fraction. The retrospective method resulted in almost constant left-ventricle wall signal intensity throughout the cardiac cycle, at the expense of a decrease in the signal-to-noise ratio and the contrast-to-noise ratio between blood and myocardial wall as compared with the prospective method. Prospective and retrospective sequences yielded comparable global cardiac functional indices. The largest mean relative difference found was 8% for the end-systolic volume.

Evaluation of manual and automatic segmentation of the mouse heart from CINE MR images

“…The SNR and CNR values in Table 1 were comparable with values found in a previous study (5) and are representative for high-quality mouse cardiac MR images. It is likely that the CNR is important for the end results of the global functional parameters for the automatic as well as for the manual segmentation.…”

“…These short-axis slices minimize partial volume effects and are largely perpendicular to the direction of wall motion and wall thickening. At each slice position a series of cinematographic (CINE) MR images is collected, which can be done by ECG triggering (4) or retrospective reconstruction (5). The myocardial wall and cavity volumes of the left or right ventricle of the heart are found by segmentation of the epicardial and endocardial borders within each slice and timeframe.…”

Magnetic resonance imaging of the regenerating neonatal mouse heart

“…Analysis of the navigator echo was performed as described previously 24 to yield k-space signals for 20 frames per slice, which were then subjected to CS-reconstruction as reported previously 25 , followed by isotropic zerofilling (factor of two), filtering (modified third-order Butterworth filter), and Fourier transformation. Examples for respiratory and cardiac traces obtained from the navigator signal are shown in Fig.…”

Long-term effects of hepatocyte growth factor gene therapy in rat myocardial infarct model

“…Incoherent gradient-echo fast low-angle shot sequence-based cardiac cine MRI (IntraGate; Bruker Biospin) was performed using respiratory and cardiac gating with the following parameters: TR ¼ 34.8 ms, TE ¼ 3.0 ms, FA ¼ 101, matrix size ¼ 128 Â 128, FOV ¼ 60 Â 60 mm 2 , ST¼ 1 mm, number of slices ¼ 6, NA ¼ 300, cardiac frames ¼ 10 and total scan time ¼ 22 min 16 s. The nominal voxel resolution was 469 Â 469 Â 1000 mm 3 . 32 Ten frame sets of 2D, multislice, short-axis cardiac images were obtained. Image reconstruction and analysis were performed using ParaVision (Bruker Biospin) and MRVision (MRVision, Winchester, MA, USA).…”

“…The LV cavity was manually delineated on short-axis images because of the unclear automatic separation of the papillary muscles from the myocardial wall. 32 EDV and end-systolic volume (ESV) were measured, and ejection fraction (%) was calculated as (EDVÀESV)/EDV Â 100.…”