Ultra-fast and accurate assessment of cardiac function in rats using accelerated MRI at 9.4 Tesla

MRI can accurately and reproducibly assess cardiac function in rodents but requires relatively long imaging times. Therefore, parallel imaging techniques using a 4-element RF-coil array and MR sequences for cardiac MRI in rats were implemented at ultra-high magnetic fields (9.4 Tesla [T]). The hypothesis that these developments would result in a major reduction in imaging time without loss of accuracy was tested on female Wistar rats under isoflurane anesthesia. High-resolution, contiguous short-axis slices (thickness 1.5 mm) were acquired covering the entire heart. Two interleaved data sets (i) with the volume coil (eight averages) and (ii) with the four-element coil array (one average) were obtained. In addition, two-, three-, and fourfold accelerated data sets were generated through postprocessing of the coil array data, followed by a TGRAPPA reconstruction, resulting in five data sets per rat (in-plane voxel size 100 x 100 microm). Using a single blinded operator, excellent agreement was obtained between volume coil (acquisition time: 88 min) and the fourfold accelerated (<3 min) data sets (e.g., LV mass 436 +/- 21 mg vs 433 +/- 19 mg; ejection fraction 74 +/- 5% vs 75 +/- 4%). This finding demonstrates that it is possible to complete a rat cine-MRI study under 3 min with low variability and without losing temporal or spatial resolution, making high throughput screening programs feasible.