Tom W.J. Scheenen^1,2, Stephan Orzada^2,3, Thiele Kobus¹, Miriam W Lagemaat¹, Marnix C Maas¹, Oliver Kraff², Stefan Maderwald², Irina Brote^2,3, Mark E Ladd^2,3, and Andreas K Bitz^2,3
1Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Gelderland, Netherlands, ²Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, Germany,³Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany

MRI of the prostate with an 8-channel multi TxRx body array coil at 7T was explored in four healthy volunteers. With a multiple spin echo pulse sequence with prolonged 180 degree pulses, images of 7 separate echoes were used to calculate T2 values of peripheral zone and transition zone tissue in the prostate. Small but significant differences in T2 demand long echo times for T2 weighted contrast. Moreover, the large radiofrequency power deposition of multi spin echo pulse sequences point to the need for alternatives for anatomical imaging, which is explored with true balanced gradient echo imaging.

Xiufeng Li¹, Pierre-Francois Van de Moortele¹, Kamil Ugurbil¹, and Greg Metzger^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

The destructive interference of RF pulses is one well-known challenge for ultrahigh field MR imaging. B1+ shimming for the target anatomy alone is not sufficient for ASL, where each RF pulse in the sequence has varying requirements with respect to B1+ amplitude, homogeneity, location and spatial coverage. To optimally use the RF power available and simultaneously manage the RF deposition in the body, different RF optimization solutions were applied dynamically during an ASL sequence. Preliminary results show that optimization of B1+ for each RF pulse in a sequence and applying those solutions dynamically during imaging acquisition appear to improve ASL perfusion results in the prostate at 7T.

Stephan Orzada^1,2, Sören Johst^1,2, Andreas K. Bitz^1,2, Oliver Kraff^1,3, Irina Brote^1,2, Susanne C. Ladd^1,2, Mark E. Ladd^1,2, and Stefan Maderwald^1,3
1Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, NRW, Germany, ²Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, NRW, Germany, ³University of Duisburg-Essen, Essen, NRW, Germany

With increasing field strength, the wavelength of the B1 field is shortened, making abdominal imaging at 7 Tesla and above very challenging due to the severe B1 inhomogeneities. Recently, Time Interleaved Acquisition of Modes (TIAMO) has been proposed as an easy and robust scheme for mitigating these inhomogeneity effects. In this work, we present first abdominal images acquired with TIAMO at 7 Tesla. The results appear to render promising contrasts and homogeneous images. Abdominal imaging at 7 Tesla seems feasible with TIAMO, since images without signal dropouts can be acquired within a reasonable acquisition time.

Fabian Hezel¹, Peter Kellman², Christof Thalhammer¹, Celal Özerdem¹, Wolfgang Renz³, and Thoralf Niendorf^4
1Berlin Ultrahigh Field Facility, Max Delbrueck Center for Molecular Medicine, Berlin, Germany, ²Laboratory of Cardiac Energetics, National Institutes of Health/NHLBI, Bethesda, MD, United States, ³Siemens Medical Systems, Erlangen, Germany, ⁴Berlin Ultrahigh Field Facility, Max Delbrueck Center for Molecular Medicine, Berlin, Berlin, Germany

This pilot study examines the feasibility of abdominal imaging at 7.0 T using (i) in-phase and out-of-phase imaging, (ii) high spatial resolution T1-weighted imaging, (iii) fat/water imaging and (iv) T2* mapping in conjunction with a 16 channel torso TX/RX coil array. Despite the observed non-uniformities of the RF field distribution, our initial results suggest that high spatial resolution anatomic details accomplished at 7.0 T can be considered to be beneficial in future clinical liver imaging.

Lance DelaBarre¹, J. Thomas Vaughan¹, Carl Snyder¹, and Pierre-Francois van de Moortele^1
1CMRR - Dept. of Radiology, University of Minnesota, Minneapolis, MN, United States

The challenges of balanced steady-state free precession (bSSFP) cardiac cine increase with field strength. The effect static field inhomogeneities and RF efficiency are explored for 7T, and 7T bSSFP cines are presented.

Peter Kellman¹, Fabian Hezel², Saurabh Shah³, Wolfgang Renz⁴, Christof Thalhammer², Jeanette Schulz-Menger^2,5, and Thoralf Niendorf^2,6
1NIH, Bethesda, MD, United States, ²Berlin Ultrahigh Field Facility, Max-Delbrueck-Center for Molecular Medicine, Berlin, Germany, ³Siemens Medical Solutions, USA, Chicago, IL, United States, ⁴Siemens Healthcare, Erlangen, Germany, ⁵Charité Campus Buch, Helios Klinkum, Berlin, Germany, ⁶Experimental and Clinical Research Center, Charité Campus Buch, Humboldt-University, Berlin, Germany

Fat-water separated imaging has been demonstrated at 7T for cardiac imaging application using a multi-echo Dixon approach. This approach overcomes limitations of conventional chemical shift fat suppression which is difficult at high field strength. Fat-water separated imaging is an important tool for characterizing tissue and providing fat suppression.

Sebastian Schmitter¹, Edward J Auerbach¹, Gregor Adriany¹, Kamil Ugurbil¹, and Pierre-Francois Van de Moortele^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

It has been shown that time-of-flight (TOF) cerebral angiography can be obtained at 7T. However, because of SAR limitations additional techniques like standard Saturation pulses (SAT) to target veins, and Magnetization Transfer (MT) to target background tissues cannot be applied. The goal of this work is to demonstrate 7T-TOF contrast enhancement using MT and/or SAT without exceeding SAR limitations. For this purpose, VERSE was applied on excitation and SAT pulses, MT was only applied during a subset of k-space lines. Our results indicate that VERSE SAT and sparse MT pulses successfully increase TOF contrast at 7T without exceeding SAR limits.

K A Danishad¹, Niravkumar Darji¹, and Oliver Speck^1
1Department of Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Saxony Anhalt, Germany

High RF power deposition caused by multiple 180⁰ refocusing pulses is a major limitation of TSE sequences in ultra high field MR imaging. In this study, the flip angle variation of the hyper-TSE sequence was optimized to further reduce SAR. T₂-contrast and image artifacts of the modified hyper-TSE sequence were compared with standard TSE and hyper-TSE sequences. Our results indicate that the hyper-TSE sequence with further reduced FA can be used in high-field systems without compromising the T₂-contrast and SNR and with the benefit of increased coverage or reduced SAR.

Irene Maria Louise van Kalleveen¹, Vincent O. Boer¹, Peter Luijten¹, Jaco J.M. Zwanenburg¹, and Dennis W.J. Klomp^1
1Radiology, UMC Utrecht, Utrecht, Netherlands

Limitations and potentials of adiabatic TSE for human application at 7T have been demonstrated. The limitations of the adiabatic regime, when going to lower B₁ fields, are discussed and the importance of correct k-space sampling has been shown. Furthermore, compared to a conventional TSE, an adiabatic TSE improves the homogeneity of the image. This is simulated and confirmed in phantom measurements as well as in vivo, on the primary visual cortex and the left carotid artery, using a transmit and receive surface coil.