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Purpose To integrate, optimize, and evaluate a three-dimensional (3D) contrast-enhanced sparse MRA technique with iterative reconstruction on a standard clinical MR system. Methods Data were acquired using a highly undersampled Cartesian spiral phyllotaxis sampling pattern and reconstructed directly on the MR system with an iterative SENSE technique. Undersampling, regularization, and number of iterations of the reconstruction were optimized and validated based on phantom experiments and patient data. Sparse MRA of the whole head (field of view: 265 × 232 × 179 mm3) was investigated in 10 patient examinations. Results High-quality images with 30-fold undersampling, resulting in 0.7 mm isotropic resolution within 10 s acquisition, were obtained. After optimization of the regularization factor and of the number of iterations of the reconstruction, it was possible to reconstruct images with excellent quality within six minutes per 3D volume. Initial results of sparse contrast-enhanced MRA (CEMRA) in 10 patients demonstrated high-quality whole-head first-pass MRA for both the arterial and venous contrast phases. Conclusion While sparse MRI techniques have not yet reached clinical routine, this study demonstrates the technical feasibility of high-quality sparse CEMRA of the whole head in a clinical setting. Sparse CEMRA has the potential to become a viable alternative where conventional CEMRA is too slow or does not provide sufficient spatial resolution. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.

Purpose Use repeated stress paradigms and an approach taken from neurological blood oxygen level dependent (BOLD) functional MRI (fMRI) to derive robust cardiac BOLD measurements. Methods Multiple-repetition, single-shot, electrocardiograph-triggered, T2-prepared BOLD balanced steady-state free precession was performed during repeated long breath-holds in 13 volunteers. Nonrigid motion correction was applied to the continuously acquired data and it was analyzed with a general linear model (GLM) taking into account the effects of the breath-hold duration, RR interval, motion, and baseline variations. Both voxel- and region of interest-based analyses were performed. Results The GLM model was able to isolate the component of the BOLD signal arising from the breath-holds and separate it from the background effects due to the changing heart rate and motion. A significant (P

PURPOSE To evaluate the clinical benefit of using a new iterative reconstruction technique fully integrated on a standard clinical scanner and reconstruction system using a TWIST acquisition for high-resolution dynamic three-dimensional contrast-enhanced MR angiography (CE-MRA). METHODS Low-dose, high-resolution TWIST datasets of 11 patients were reconstructed using both standard GRAPPA-based reconstruction for reference and iterative reconstruction, which reduces the temporal footprint of reconstructed images. Image quality of both techniques was assessed by two experienced readers, as well as quantitatively evaluated using a time-signal curve analysis. RESULTS Image quality scores consistently and significantly improved by using iterative reconstruction compared with the standard approach. Most notably, the delineation of small to mid-size vasculature improved from a mean Likert score between "nondiagnostic" and "poor" for standard to between "good" and "excellent" for iterative reconstruction. The full width at half maximum of the contrast agent bolus computed from the time-signal curve was also reduced by iterative reconstruction, allowing for more precise bolus timing. CONCLUSION Iterative reconstruction can substantially improve high-resolution dynamic CE-MRA image quality, most notably in small to mid-size vasculature. Dynamic CE-MRA with iterative reconstruction could become an alternative to conventional static 3D CE-MRA, thus simplifying the clinical workflow. Magn Reson Med 77:833-840, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

To integrate, optimize, and evaluate a three-dimensional (3D) contrast-enhanced sparse MRA technique with iterative reconstruction on a standard clinical MR system.Data were acquired using a highly undersampled Cartesian spiral phyllotaxis sampling pattern and reconstructed directly on the MR system with an iterative SENSE technique. Undersampling, regularization, and number of iterations of the reconstruction were optimized and validated based on phantom experiments and patient data. Sparse MRA of the whole head (field of view: 265 × 232 × 179 mm(3) ) was investigated in 10 patient examinations.High-quality images with 30-fold undersampling, resulting in 0.7 mm isotropic resolution within 10 s acquisition, were obtained. After optimization of the regularization factor and of the number of iterations of the reconstruction, it was possible to reconstruct images with excellent quality within six minutes per 3D volume. Initial results of sparse contrast-enhanced MRA (CEMRA) in 10 patients demonstrated high-quality whole-head first-pass MRA for both the arterial and venous contrast phases.While sparse MRI techniques have not yet reached clinical routine, this study demonstrates the technical feasibility of high-quality sparse CEMRA of the whole head in a clinical setting. Sparse CEMRA has the potential to become a viable alternative where conventional CEMRA is too slow or does not provide sufficient spatial resolution.

Use repeated stress paradigms and an approach taken from neurological blood oxygen level dependent (BOLD) functional MRI (fMRI) to derive robust cardiac BOLD measurements.Multiple-repetition, single-shot, electrocardiograph-triggered, T2-prepared BOLD balanced steady-state free precession was performed during repeated long breath-holds in 13 volunteers. Nonrigid motion correction was applied to the continuously acquired data and it was analyzed with a general linear model (GLM) taking into account the effects of the breath-hold duration, RR interval, motion, and baseline variations. Both voxel- and region of interest-based analyses were performed.The GLM model was able to isolate the component of the BOLD signal arising from the breath-holds and separate it from the background effects due to the changing heart rate and motion. A significant (P0.05) BOLD signal increase was observed in the myocardium of healthy volunteers.Using a recent elastic motion correction algorithm and adapted acquisition techniques, it was possible to apply fMRI-like strategies for cardiac BOLD MRI in volunteers and derive robust BOLD measurements. The observed slight but significant oxygenation increase in the myocardium of volunteers might be explained by the vasodilator effect of increased CO2 concentration under apnea. Detection of such small physiological changes in volunteers performing breath-holds demonstrates that the method could have potential in identifying low oxygenation regions in the myocardium of patients during stress tests.