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BackgroundLeft atrial volume (LAV) and emptying fraction (LAEF) are phasic during cardiac cycle. Their relationships to left ventricular end diastolic pressure (LVEDP) have not been fully defined.MethodsForty one patients undergoing clinically indicated left heart catheterization were recruited for same day cardiovascular magnetic resonance (CMR). LAV and LAEF were assessed in cine images using biplane area and length method. Three phasic LAV was assessed at LV end systole (LAVmax), LV end diastole (LAVmin) and late LV diastole prior to LA contraction (LAVac). LAEF was assessed as global LAEF (LAEFTotal), passive (LAEFPassive) and active LAEF (LAEFContractile). The relationships of phasic LAV and LAEF to LVEDP were assessed using Receiver operating characteristic comparing areas under the curves (AUC).ResultsThe mean age of the patients was 59 years. A history of heart failure was present in 16 (39%) with NYHA functional class III or IV in 8 (20%) patients. Average LV ejection fraction was 49 ± 16% ranging from 10% to 74% and LVEDP by catheterization 14 ± 8 mmHg ranging from 4 mmHg to 32 mmHg. LAVmin had the strongest association with LVEDP elevation (>12 mmHg) (AUC 0.765, p = 0.002), as compared to LAVmax (AUC 0.677, p = 0.074) and LAVac (AUC 0.735, p = 0.008). Among three phasic LAEF assessed, LAEFTotal had the closest association with LVEDP elevation (AUC 0.780, p = 0.001), followed by LAEFContractile (AUC 0.698, p = 0.022) and LAEFPassive (AUC 0.656, p = 0.077).ConclusionsIncreased LAVmin and decreased LAEFTotal have the best performance in identifying elevated LVEDP among three phasic LAV and LAEF analyzed. Future studies should further characterize LA phasic indices in clinical outcomes.

Lung perfusion imaging using a 2D saturation recovery SSFP perfusion MRI coupled with a model-independent deconvolution algorithm demonstrated physiologically consistent dynamic heterogeneity of lung perfusion distribution.

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This work aims to demonstrate that radial acquisition with k-space variant reduced-FOV reconstruction can enable real-time cardiac MRI with an affordable computation cost. Due to non-uniform sampling, radial imaging requires k-space variant reconstruction for optimal performance. By converting radial parallel imaging reconstruction into the estimation of correlation functions with a previously-developed correlation imaging framework, Cartesian k-space may be reconstructed point-wisely based on parallel imaging relationship between every Cartesian datum and its neighboring radial samples. Furthermore, reduced-FOV correlation functions may be used to calculate a subset of Cartesian k-space data for image reconstruction within a small region of interest, making it possible to run real-time cardiac MRI with an affordable computation cost. In a stress cardiac test where the subject is imaged during biking with a heart rate of >100 bpm, this k-space variant reduced-FOV reconstruction is demonstrated in reference to several radial imaging techniques including gridding, GROG and SPIRiT. It is found that the k-space variant reconstruction outperforms gridding, GROG and SPIRiT in real-time imaging. The computation cost of reduced-FOV reconstruction is ~2 times higher than that of GROG. The presented work provides a practical solution to real-time cardiac MRI with radial acquisition and k-space variant reduced-FOV reconstruction in clinical settings.

Using inversion recovery steady-state free precession segmented k-space imaging for the detection of myocardial infarction, we noticed that some structures appeared in the wrong locations of the image. In this work, the spatial displacement is demonstrated and explained from both theoretical and experimental points of view. The effect is due to a change in phase from segment to segment of the detected magnetization from species with long T 1 's such as cysts, fluid collections, and cerebrospinal fluid. Depending on the number of k-space segments and view ordering, structures can be replicated throughout the image or displaced by half of the phase-encoding field of view. Attempts to reduce acquisition times with short repetition time (TR) techniques have always been limited by signalto-noise constraints. Hence, the strong signal available with short TRs accounts for the increased use of fully refocused gradient-echo techniques (1) (called steady-state free precession (SSFP), fast imaging with steady-state freeprecession, fast imaging employing steady-state excitation, or balanced turbo fast-field-echo). Gradient refocusing increases signal through the reuse of magnetization from repetition time to repetition time and provides images with contrast dependent on the ratio of the T 2 relaxation time to the T 1 relaxation time.With the use of T 1 shortening contrast agents, although T 2 * weighted sequences can be used, one typically chooses a T 1 weighted pulse sequence. To introduce T 1 weighting into an SSFP pulse sequence, a preparatory 90°radiofrequency pulse (saturation) or 180°radiofrequency pulse (inversion) is used prior to the refocused gradient-echo pulse sequence. Applications to date include MR angiography (2), arterial spin-labeling (3), first-pass myocardial perfusion (4), and delayed-hyperenhanced imaging (5).To overcome artifacts associated with physiologic motion or improve the efficiency of preparatory pulses such as saturation or inversion recovery (IR) and chemical fat saturation, a technique termed k-space segmentation is used (6). k-space segmentation introduces a repeated MR pulsed experiment. If full magnetization recovery does not occur between segments as data collection is repeated, the observed signal will be dependent on the magnetization state at the end of the previous segment. When an inversion pulse is used, this incomplete recovery may cause alternating longitudinal magnetization available at the beginning of each segment. A change in phase from segment to segment of the detected magnetization of species with long T 1 's such as cysts, fluid collections, and cerebrospinal fluid will result. Species with shorter T 1 's, such as blood and myocardium, recover longitudinal magnetization more quickly and the detected magnetization remains in phase. This change in phase from segment to segment causes a predictable spatial displacement when an interleaved acquisition is used. In this work, this phenomenon and its effect on the final image are demonstrated and explained from both theoretical...

ObjectiveWe investigated age related remodeling and associated changes in systolic and diastolic function and myocardial mechanics using cardiac MRI and echocardiography.