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Background: Displacement Encoding with Stimulated Echoes (DENSE) encodes displacement into the phase of the magnetic resonance signal. The encoding frequency (ke) maps the measured phase to tissue displacement while the strength of the encoding gradients affects image quality. 2D cine DENSE studies have used a ke of 0.10 cycles/mm, which is high enough to remove an artifact-generating echo from k-space, provide high sensitivity to tissue displacements, and dephase the blood pool. However, through-plane dephasing can remove the unwanted echo and dephase the blood pool without relying on high ke. Additionally, the high sensitivity comes with the costs of increased phase wrapping and intra-voxel dephasing. We hypothesized that ke below 0.10 cycles/mm can be used to improve image characteristics and provide accurate measures of cardiac mechanics. Methods: Spiral cine DENSE images were obtained for 10 healthy subjects and 10 patients with a history of heart disease on a 3 T Siemens Trio. A mid-ventricular short-axis image was acquired with different ke: 0.02, 0.04, 0.06, 0.08, and 0.10 cycles/mm. Peak twist, circumferential strain, and radial strain were compared between acquisitions employing different ke using Bland-Altman analyses and coefficients of variation. The percentage of wrapped pixels in the phase images at end-systole was calculated for each ke. The dephasing of the blood signal and signal to noise ratio (SNR) were also calculated and compared. Results: Negligible differences were seen in strains and twist for all ke between 0.04 and 0.10 cycles/mm. These differences were of the same magnitude as inter-test differences. Specifically, the acquisitions with 0.04 cycles/mm accurately quantified cardiac mechanics and had zero phase wrapping. Compared to 0.10 cycles/mm, the acquisitions with 0.04 cycles/mm had 9 % greater SNR and negligible differences in blood pool dephasing. Conclusions: For 2D cine DENSE with through-plane dephasing, the encoding frequency can be lowered to 0.04 cycles/mm without compromising the quantification of twist or strain. The amount of wrapping can be reduced with this lower value to greatly simplify the input to unwrapping algorithms. The strain and twist results from studies using different encoding frequencies can be directly compared. [ABSTRACT FROM AUTHOR]

Although the grey Verhulst model has been widely adopted in many fields and demonstrated satisfactory results, literatures show its performance still could be enhanced. For this purpose, on the basis of modeling mechanism of grey Verhulst model, this paper proposes a novel grey Verhulst model considering related factors influencing the prediction accuracy of systems. In this proposed model, this work provides an algorithm for computing the modeling parameters of this novel grey model and obtains the time response equation of this proposed model by employing a differential equation as a reasoning tool. Finally, a case example is adopted for demonstration. Case analysis shows that compared with the original grey Verhulst model, the novel model has higher performances on model forecasting. [ABSTRACT FROM AUTHOR]

Ultrafine sub-5 nm magnetic iron oxide nanoparticles coated with oligosaccharides (SIO) with dual T1-T2 weighted contrast enhancing effects and fast clearance have been developed as magnetic resonance imaging (MRI) contrast agents. Excellent water solubility, biocompatibility and high stability of such sub-5 nm SIO nanoparticles were achieved by using the "in situ polymerization" coating method, which enables glucose to form oligosaccharides directly on the surface of hydrophobic iron oxide nanocrystals. Reported ultrafine SIO nanoparticles exhibit a longitudinal relaxivity (r1) of 4.1 mM-1 s-1 and a r1/r2 ratio of 0.25 at 3 T (clinical field strength), rendering improved T1 or "brighter" contrast enhancement in T1-weighted MRI in addition to typical T2 or "darkening" contrast of conventional iron oxide nanoparticles. Such dual contrast effects can be demonstrated by liver imaging with T1 "darkening" contrast in the liver parenchyma but T1 "bright" contrast in the hepatic vasculature. More importantly, this new class of ultrafine sub-5 nm iron oxide nanoparticles showed much faster body clearance than those with larger sizes, promising better safety for clinical applications. [ABSTRACT FROM AUTHOR]

Background The most time consuming and limiting step in three dimensional (3D) cine displacement encoding with stimulated echoes (DENSE) MR image analysis is the demarcation of the left ventricle (LV) from its surrounding anatomical structures. The aim of this study is to implement a semi-automated segmentation algorithm for 3D cine DENSE CMR using a guide point model approach. Methods A 3D mathematical model is fitted to guide points which were interactively placed along the LV borders at a single time frame. An algorithm is presented to robustly propagate LV epicardial and endocardial surfaces of the model using the displacement information encoded in the phase images of DENSE data. The accuracy, precision and efficiency of the algorithm are tested. Results The model-defined contours show good accuracy when compared to the corresponding manually defined contours as similarity coefficients Dice and Jaccard consist of values above 0.7, while false positive and false negative measures show low percentage values. This is based on a measure of segmentation error on intra- and inter-observer spatial overlap variability. The segmentation algorithm offers a 10-fold reduction in the time required to identify LV epicardial and endocardial borders for a single 3D DENSE data set. Conclusion A semi-automated segmentation method has been developed for 3D cine DENSE CMR. The algorithm allows for contouring of the first cardiac frame where blood-myocardium contrast is almost nonexistent and reduces the time required to segment a 3D DENSE data set significantly. [ABSTRACT FROM AUTHOR]

Within cardiomyocytes, endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) are thought to modulate L-type calcium channel (LTCC) function and sarcoplasmic reticulum calcium cycling, respectively. However, divergent results from mostly invasive prior studies suggest more complex roles. To elucidate the roles of nNOS and eNOS in vivo, we applied noninvasive cardiac MRI to study wild-type (WT), eNOS-/-, and nNOS-/- mice. An in vivo index of LTCC flux (LTCCI) was measured at baseline (Bsl), dobutamine (Dob), and dobutamine + carbacholamine (Dob + CCh) using manganese-enhanced MRI. Displacement-encoded MRI assessed contractile function by measuring circumferential strain (Ecc) and systolic (dEcc/dt) and diastolic (dEcc/dtdiastolic) strain rates at Bsl, Dob, and Dob + CCh. Bsl LTCCI was highest in nNOS-/- mice (P < 0.05 vs. WT and eNOS-/-) and increased only in WT and eNOS-/- mice with Dob (P < 0.05 vs. Bsl). LTCCI decreased significantly from Dob levels with Dob + CCh in all mice. Contractile function, as assessed by Ecc, was similar in all mice at Bsl. With Dob, Ecc increased significantly in WT and eNOS-/- but not nNOS-/- mice (P < 0.05 vs. WT and eNOS-/-). With Dob + CCh, Ecc returned to baseline levels in all mice. Systolic blood pressure, measured via tail plethysmography, was highest in eNOS-/- mice (P < 0.05 vs. WT and nNOS-/-). Mice deficient in nNOS demonstrate increased Bsl LTCC function and an attenuated contractile reserve to Dob, whereas eNOS-/- mice demonstrate normal LTCC and contractile function under all conditions. These results suggest that nNOS, not eNOS, plays the dominant role in modulating Ca2+ cycling in the heart. [ABSTRACT FROM AUTHOR]

Cardiac-synchronized brain motion is well documented, but the accurate measurement of such motion on the pixel-by-pixel basis has been hampered by the lack of proper imaging technique. In this article, the authors present the implementation of an autotracking spiral cine displacement-encoded stimulation echo (DENSE) magnetic resonance imaging (MRI) technique for the measurement of pulsatile brain motion during the cardiac cycle. Displacement-encoded dynamic MR images of three healthy volunteers were acquired throughout the cardiac cycle using the spiral cine-DENSE pulse sequence gated to the R wave of an electrocardiogram. Pixelwise Lagrangian displacement maps were computed, and 2D displacement as a function of time was determined for selected regions of interests. Different intracranial structures exhibited characteristic motion amplitude, direction, and pattern throughout the cardiac cycle. Time-resolved displacement curves revealed the pathway of pulsatile motion from brain stem to peripheral brain lobes. These preliminary results demonstrated that the spiral cine-DENSE MRI technique can be used to measure cardiac-synchronized pulsatile brain motion on the pixel-by-pixel basis with high temporal/spatial resolution and sensitivity. [ABSTRACT FROM AUTHOR]

An abstract of the paper "Comparison of SNR Efficiencies and Strain for Cine DENSE Using Conventional EPI, Flyback EPI and Spiral K-space Trajectories," by Xiaodong Zhong and colleagues, from the 2011 SCMR/Euro CMR Joint Scientific Sessions, held in Nice, France, from February 3-6, 2011, is presented.

An abstract of the paper "Quantifying Right Ventricular Motion and Strain Using 3D Cine DENSE MRI," by Daniel A. Auger and colleagues is presented.