Improved fat water separation with water selective inversion pulse for inversion recovery imaging in cardiac MRI

Abstract

To develop an improved chemical shift-based water-fat separation sequence using a water-selective inversion pulse for inversion recovery 3D contrast-enhanced cardiac magnetic resonance imaging (MRI). In inversion recovery sequences the fat signal is substantially reduced due to the application of a nonselective inversion pulse. Therefore, for simultaneous visualization of water, fat, and myocardial enhancement in inversion recovery-based sequences such as late gadolinium enhancement imaging, two separate scans are used. To overcome this, the nonselective inversion pulse is replaced with a water-selective inversion pulse. Imaging was performed in phantoms, nine healthy subjects, and nine patients with suspected arrhythmogenic right ventricular cardiomyopathy plus one patient for tumor/mass imaging. In patients, images with conventional turbo-spin echo (TSE) with and without fat saturation were acquired prior to contrast injection for fat assessment. Subjective image scores (1 = poor, 4 = excellent) were used for image assessment. Phantom experiments showed a fat signal-to-noise ratio (SNR) increase between 1.7 to 5.9 times for inversion times of 150 and 300 msec, respectively. The water-selective inversion pulse retains the fat signal in contrast-enhanced cardiac MR, allowing improved visualization of fat in the water-fat separated images of healthy subjects with a score of 3.7 ± 0.6. Patient images acquired with the proposed sequence were scored higher when compared with a TSE sequence (3.5 ± 0.7 vs. 2.2 ± 0.5, P < 0.05). The water-selective inversion pulse retains the fat signal in inversion recovery-based contrast-enhanced cardiac MR, allowing simultaneous visualization of water and fat.