Mario O. Malavé¹, Nii Okai Addy¹, R. Reeve Ingle¹, Joseph Y. Cheng¹, and Dwight G. Nishimura^1
1Electrical Engineering, Stanford University, Stanford, California, United States

For whole-heart coronary MRA, we are developing a sequence based on alternating-TR SSFP and 3D cones k-space sampling. For SSFP imaging, the order in which each readout is acquired must be carefully chosen to avoid eddy current effects. In this work, multidimensional golden means and phyllotaxis designs were developed for the 3D cones trajectory to sample a more distributed region of k-space during each heartbeat without introducing eddy current artifacts. For verification of signal quality and eddy current reduction, these methods were compared to the default sequential ordering.

Manojkumar Saranathan¹ and Brian K. Rutt^1
1Dept. of Radiology, Stanford University, Stanford, CA, United States

MPRAGE imaging conventionally nulls CSF but other tissues of interest like WM, GM can also be nulled and are of clinical interest. We developed a novel fast Cartesian undersampling and view sharing strategy for multi-contrast 3D MPRAGE imaging in short scan times. The technique called McMPRAGE was tested on patients and healthy subjects at 7T.

Saikat Sengupta^1,2, David S. Smith^1,2, and E. Brian Welch^1,2
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, United States, ²Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, United States

In this work, we demonstrate whole-body fat/water separation at 3 Tesla using a 90 second multiecho Continuously Moving Table (CMT) MRI scan based on a golden angle (GA) radial sampling pattern. GA sampling allows retrospective profile binning for arbitrary slice thickness reconstructions and high degrees of radial under-sampling without coherent image artifacts. This allows the collection of 4 echoes per TR for accurate fat/water separation, as well as whole-body ΔB0 and R2* mapping. We demonstrate high-quality whole-body (1.8 m Z direction coverage) fat/water separation with this technique in a rapid 90-second scan.

Andreia C. Freitas^1,2, Marzena Wylezinska^1,2, Malcolm J Birch², Steffen E. Petersen¹, and Marc E. Miquel^1,2
1William Harvey Research Institute, Queen Mary University of London, London, United Kingdom, ²Clinical Physics, Barts Health NHS Trust, London, United Kingdom

Real-time MRI is a promising tool to dynamically image the vocal tract during speech. However, obtaining the required temporal resolution while maintaining image quality is still a major challenge. While Cartesian sequences are widely available and easy to implement, non-Cartesian sequences have been suggested to improve spatial-temporal resolution. This study provides a comparison of non-Cartesian (radial and spiral) and Cartesian real-time sequences in velopharyngeal closure assessment. At higher frame rates, spiral acquisition provided a 25%-60% superior SNR than radial and Cartesian sequences. Spiral sequences also showed superior image quality scoring (32% classified “Excellent”) and improved temporal fidelity at higher frame rates.

Haifeng Wang¹, Leo Tam¹, Emre Kopanoglu¹, Dana Peters¹, Gigi Galiana¹, and R. Todd Constable^1
1Department of Diagnostic Radiology, Yale University, New Haven, CT, United States

O-Space has been proved to outperform Cartesian SENSE when the effective acceleration factor approaches, equals, or exceeds the number of radiofrequency (RF) coils. However, the advantages over radial imaging (which is the linear trajectory underlying O-Space) have been less clear. In this study, we show that increasing readout sampling, which carries essentially zero time cost, produces high-resolution O-Space images that are clearly superior, with sharper features and fewer artifacts. Increased resolution in the readout has little effect on radial image quality. The experimental results illustrate that the addition of nonlinear gradients can improve image quality and surpass conventional radial imaging in accelerated data acquisitions.

Naoharu Kobayashi¹, Djaudat Idiyatullin¹, Curtis A Corum¹, and Michael Garwood^1
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States

A 3D radial MRI method tolerant to off-resonance blurring, which combines linogram k-space sampling, Hermitian extrapolation and a 3D ultra-short echo time sequence known as SWIFT, is introduced. The off-resonance tolerance was tested by simulation and in vivo human dental imaging at 4T. The proposed method removed off-resonance blurring that is common in radial MRI sequences; the off-resonance artifacts became displacement/distortion of images, which is similar to Cartesian MRI.

Yuval Zur¹ and Weitian Chen^2
1GE Healthcare, Tirat Carmel, Israel, ²Applied Science Lab, GE Healthcare, Menlo Park, CA, United States

3D Fast Spin Echo with flip angle modulation is used for high resolution T2 weighted imaging due to high T2 contrast and the ability to reformat the data in any desirable plane. Unavoidable violations of the CPMG condition due to system imperfections generate artifacts. Previously we presented a method to overcome this problem with a two excitations approach where two data sets are combined, such that scan time is twice as long. In this work we present a new stable parallel imaging method to synthesize the second data set from the first thereby reducing scan time to a single excitation.

Konrad Schieban¹, Markus Weiger¹, Franciszek Hennel², Andreas Boss³, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, ETH Zurich, Zurich, Switzerland, ²Bruker BioSpin MRI GmbH, Ettlingen, Germany, ³Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland

Zero Echo Time (ZTE) MRI is a 3D radial projection technique dedicated to imaging tissues with rapid transverse relaxation. In ZTE imaging, RF excitation is typically performed with short, block-shaped pulses of limited flip angle, thus restricting T1-weighting and possibly SNR. To overcome these limitations, it is proposed here to replace the block pulse with frequency- and amplitude modulated RF pulses. These are optimized with respect to flip angle amplitude and uniformity over the bandwidth spanned by the frequency encoding gradients. The enhanced flip angle performance achieved in this way is demonstrated experimentally in phantoms and a tissue sample.

Hyungseok Jang^1,2, Curtis N Wiens¹, and Alan B McMillan^1
1Radiology, University of Wisconsin, Madison, WI, United States, ²Electrical and Computer Engineering, University of Wisconsin, Madison, WI, United States

In UTE imaging, achieving short encoding time is one of the most important and challenging tasks to reduce the impact of T2* decay and realize high spatial resolution. In this study, we propose a ramped hybrid encoding (RHE) scheme that realizes the best encoding time for high spatial resolution UTE imaging.