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Stack-of-radial multiecho gradient-echo MRI is promising for free-breathing liverTo validate stack-of-radial MRI with self-gating motion compensation in phantoms, and to evaluate it in children.Prospective.Four vials with differentSixteen pediatric patients with suspected nonalcoholic fatty liver disease or steatohepatitis (five females, 13 ± 4 years, body mass index 29.2 ± 8.6 kg/mStack-of-radial, and 2D and 3D Cartesian multiecho gradient-echo sequences at 3T.Ungated and gated stack-of-radial proton density fat fraction (PDFF) andPhantom results were fitted with a weighted linear model. Demographic differences between excluded and included subjects were tested by multivariate analysis of variance. PDFF andUngated stack-of-radialStack-of-radial MRI with self-gating motion compensation seems to allow free-breathing liver2 TECHNICAL EFFICACY STAGE: 2.

To develop an accurate free-breathing 3D liverA free-breathing multi-echo stack-of-radial sequence was applied in 5 normal subjects and 6 patients at 3 Tesla. Respiratory motion compensation was implemented using the inherent self-gating signal. A breath-hold Cartesian acquisition was the reference standard. Proton density fat fraction andFree-breathing stack-of-radial without self-gating exhibited signal attenuation in echo images and artifactually elevated apparentThe proposed self-gating method corrects the respiratory motion bias and enables accurate free-breathing stack-of-radial quantification of liver

The BOLD signal not only reflects changes in local neural activity, but also exhibits variability from physiological processes like cardiac rhythms and breathing. We investigated how both of these physiological sources are reflected in the pulse oximetry (PO) signal, a direct measure of blood oxygenation, and how this information can be used to account for different types of noise in the BOLD response. Measures of heart rate, respiration and PO were simultaneously recorded while neurologically healthy participants performed an eye-movement task in a 3T MRI. PO exhibited power in frequencies that matched those found in the independently recorded cardiac and respiration signals. Using the phasic and aphasic properties of these signals as nuisance regressors, we found that the different frequency components of the PO signal could be used to identify different types of physiological artifacts in the BOLD response. A comparison of different physiological noise models found that a simple, down-sampled version of the PO signal improves the estimation of task-relevant statistics nearly as well as more established noise models that may run the risk of over-parameterization. These findings suggest that the PO signal captures multiple sources of physiological noise in the BOLD response and provides a simple and efficient way of modeling these noise sources in subsequent analysis.

Conventional x-ray angiography is presently the gold standard for detecting coronary artery disease. This is a highly invasive procedure with a risk of developing potentially serious complications in addition to its drawback of exposure to ionizing radiation. Magnetic resonance imaging (MRI), a noninvasive method with no known adverse effects, offers exciting possibilities with its ability to acquire true three-dimensional (3D) volume information, image double oblique tomographic planes in the body, and generate excellent soft tissue contrast. These advantages have led to the emergence of MRI as one of the important tools for cardiac imaging. There have been significant improvements in MR systems in recent years that allow for higher gradient subsystems and higher slew rates. This has enabled the realization of magnetic resonance (MR) angiography, which now is consistently used for imaging the head, neck, and body vasculature. Despite all these advances, coronary MR angiography remains a challenge due to the small size of the coronary vessels, their tortuous nature, and the sensitivity of MRI to motion. Different methods, such as electrocardiographic gating and breath-holding or free-breathing approaches using navigators, have been investigated to overcome the cardiac and respiratory motion in coronary MR angiography, respectively. Various pulse sequences have been used in conjunction with these strategies. Injection of extravascular contrast agents led to the improvement of angiographic techniques in terms of higher signal-to-noise and contrast-to-noise ratios. The advent of intravascular agents may improve further the quality and reliability of coronary MR angiography. Recently, true fast imaging with steady-state precession (FISP), an imaging technique with an inherently high imaging efficiency, has emerged as a new angiographic technique. Although coronary MR angiography is still not proven clinically, it is a promising modality for detecting coronary artery disease.