For patients with impaired breath-hold capacity and/or arrhythmias, real-time cine MRI may be more clinically useful than breath-hold cine MRI. However, commercially available real-time cine MRI methods using parallel imaging typically yield relatively poor spatio-temporal resolution due to their low image acquisition speed. We sought to achieve relatively high spatial resolution (~2.5mm × 2.5mm) and temporal resolution (~40ms), to produce high-quality real-time cine MR images that could be applied clinically for wall motion assessment and measurement of left ventricular (LV) function. In this work, we present an 8-fold accelerated real-time cardiac cine MRI pulse sequence using a combination of compressed sensing and parallel imaging (k-t SPARSE-SENSE). Compared with reference, breath-hold cine MRI, our 8-fold accelerated real-time cine MRI produced significantly worse qualitative grades (1–5 scale), but its image quality and temporal fidelity scores were above 3.0 (adequate) and artifacts and noise scores were below 3.0 (moderate), suggesting that acceptable diagnostic image quality can be achieved. Additionally, both 8-fold accelerated real-time cine and breath-hold cine MRI yielded comparable LV function measurements, with coefficient of variation < 10% for LV volumes. Our proposed 8-fold accelerated real-time cine MRI with k-t SPARSE-SENSE is a promising modality for rapid imaging of myocardial function.

Purpose: To improve myocardial perfusion magnetic resonance imaging (MRI) by reconstructing undersampled radial data with a spatiotemporal constrained reconstruction method (STCR). Materials and Methods:The STCR method jointly reconstructs all of the time-frames for each slice. In 7 subjects at rest, on a 3-T scanner, the method was compared with a conventional (GRAPPA) Cartesian approach.Results: Increased slice coverage was obtained, as compared with Cartesian acquisitions. On average, 10 slices were obtained per heartbeat for radial acquisitions (8 of which are suitable for visual analysis with the remaining 2 slices, in theory, usable for quantitative purposes), whereas 4 slices were obtained for the conventional Cartesian acquisitions. The new method was robust to interframe motion, unlike using Cartesian undersampling and STCR. STCR produced images with an image quality rating (1 for best and 5 for worst) of 1.7 Ϯ 0.5; the Cartesian images were rated 2.6 Ϯ 0.4 (P ϭ 0.0006). A mean improvement of 44 (Ϯ17) in signal-to-noise (SNR) ratio and 46 (ϩ22) in contrast-to-noise ratio (CNR) was observed for STCR. Conclusion:The new radial data acquisition and reconstruction scheme for dynamic myocardial perfusion imaging is a promising approach for obtaining significantly higher coverage and improved SNR ratios. Further testing of this approach is warranted during vasodilation in patients with coronary artery disease.

Dynamic contrast-enhanced (DCE) MRI is a powerful technique to probe an area of interest in the body. Here a temporally constrained reconstruction (TCR) technique that requires less k-space data over time to obtain good-quality reconstructed images is proposed. This approach can be used to improve the spatial or temporal resolution, or increase the coverage of the object of interest. The method jointly reconstructs the space-time data iteratively with a temporal constraint in order to resolve aliasing. The method was implemented and its feasibility tested on DCE myocardial perfusion data with little or no motion. The results obtained from sparse k-space data using the TCR method were compared with results obtained with a sliding-window (SW) method and from full data using the standard inverse Fourier transform (IFT) reconstruction. Acceleration factors of 5 (R ‫؍‬ 5) were achieved without a significant loss in image quality. Mean improvements of 28 ؎ 4% in the signal-to-noise ratio (SNR) and 14 ؎ 4% in the contrast-to-noise ratio (CNR) were observed in the images reconstructed using the TCR method on sparse data (R ‫؍‬ 5) compared to the standard IFT reconstructions from full data for the perfusion datasets. Dynamic contrast-enhanced (DCE) MRI is used to track changes over time in an object of interest by acquiring a series of images. A contrast agent is injected and the data are acquired in k-space for each time frame. Rapid acquisitions are required to track the quickly changing contrast in the object. One application of DCE-MRI is myocardial perfusion, which is an important tool for assessing coronary artery disease. In DCE-MRI for myocardial perfusion, contrast agents such as gadolinium (Gd)-DTPA are injected and images are acquired using ECG-gated sequences to track the uptake of the contrast agent by the myocardium at high temporal resolution.To reduce the data acquisition time of dynamic MRI, a number of techniques have been developed. These methods acquire a fraction of k-space in each time frame and reconstruct images based on a priori information about the dynamic data. Methods such as keyhole imaging (1,2) and reduced-encoding MR imaging with generalized-series reconstruction (RIGR) (3Ϫ5) assume that in a dynamic sequence only the low-frequency data change and the high-frequency data remain static. Thus full data can be acquired for a single frame in the sequence and only lowfrequency data need to be acquired for the remaining frames. This assumption of static high frequencies is not always accurate.View-sharing-type methods (6 -9) assume that the dynamics in an image sequence change only by a small amount from frame to frame. Thus only a fraction of data can be acquired for each frame and the missing data can be obtained from the adjacent frames. Such data-sharing is equivalent to linear interpolation in time and can reduce temporal resolution.More recently, Madore et al. (10) proposed the unaliasing by Fourier-encoding the overlaps using the temporal dimension (UNFOLD) method for cardiac cine imagin...