Borjan Gagoski¹, Berkin Bilgic², Cornelius Eichner², Himanshu Bhat³, P. Ellen Grant¹, Lawrence L Wald², and Kawin Setsompop^2
1Boston Children's Hospital, Boston, MA, United States, ²Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ³Siemens Medical Solutions, Charlestown, MA, United States

The acquisition of RARE imaging, which is the most commonly used clinical sequence, can be lengthy particularly if high isotropic resolution is desired. RARE can be accelerated using Simultaneous MultiSlice (SMS) imaging, which enables acceleration without reducing the number of k-space lines, and hence without √R penalty. Recently, MB=8 acceleration in SMS-RARE imaging at 2mm slice resolution has been achieved by Norris et al., through a combination of low-SAR PINS refocusing pulse and blipped-CAIPI parallel imaging method which limits g-factor noise amplification. In this work, we push further in this direction to achieve MB=15 acceleration to allow high quality 1mm isotropic resolution whole-brain T2-weighted RARE imaging to be performed in just 70s. This acceleration level was achieved through a combination of i) MultiPINS RF pulse which reduces SAR of SMS refocusing pulse further by another 2 fold and ii) Wave-CAIPI parallel imaging method which enables MB=15 acceleration at very minor g-factor penalty (gmax=1.41 and gavg=1.12). This highly accelerated RARE sequence can accelerate clinical imaging to increase patient throughput while achieving high quality, high isotropic resolution data.

Alessandro Sbrizzi¹, Benedikt Poser², Desmond H Y Tse², Hans Hoogduin³, Peter R Luijten³, and Cornelis A van den Berg^3
1UMC Utrecht, Utrecht, Utrecht, Netherlands, ²Faculty of Psychology and Neuroscience, Maastricht University, Limburg, Netherlands, ³UMC Utrecht, Utrecht, Netherlands

Multi-slice excitation schemes are based upon the superposition of single-band RF waveforms. Through inter-slice phase relaxation, it is possible to minimize the constructive interference and thus to obtain lower peak amplitude RF pulses. We cast the problem as a linear objective function with quadratic equality and inequality constraints. This can be solved very quickly. The achieved peak power is lower than the existing phase relaxation method and control of RF peak power over the whole CAIPIRINHA excitation scheme and/or a whole pTx system with channel/slice dependent amplitude/phase shimming settings is obtained.

Ziyue Wu¹, Michael C.K. Khoo¹, and Krishna S. Nayak^1
1University of Southern California, Los Angeles, CA, United States

We present a method for simultaneous multi-slice compliance measurement based on sparse golden-angle radial CAIPIRINHA, with acceleration factor up to 33.3. We present data from patients with obstructive sleep apnea and normal controls. One interesting finding is that a narrower airway site does not always correspond to higher compliance or higher Pcrit.

Sjoerd Crijns¹, Alessandro Sbrizzi¹, Bjorn Stemkens¹, Cornelis van den Berg¹, Peter Luijten¹, Jan Lagendijk¹, and Anna Andreychenko^1
1UMC Utrecht, Utrecht, Utrecht, Netherlands

Simultaneous multi-slice imaging combined with CAIPIRINHA has the potential to significantly accelerate MR imaging. So far, these techniques have focused on acceleration in the spatial domain. In this study we show a method to acquire signal from multiple chemical shifts in multiple slices simultaneously, which are subsequently separated into individual slice/chemical shift images.

Huihui Ye^1,2, Borjan Gagoski³, Berkin Bilgic¹, Stephen F Cauley¹, Dan Ma⁴, Yiping Du², Lawrence L Wald¹, Mark A Griswold⁴, and Kawin Setsompop^1
1MGH/HST Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ²Zhejaing University, Hangzhou, Zhangjiang, China, ³Boston Children’s Hospital, MA, United States, ⁴Case Western Reserve University, Ohio, United States

To separate the signal from simultaneously acquired slices using simultaneous-multislice magnetic resonance fingerprinting (SMS-MRF) acquisition, we have proposed t-blipped SMS-MRF method which uses Gz blips to create TR dependent phase differences between SMS slices and RF encoding patterns, which utilizes different flip angle train for the different SMS slices. In this work, we propose to complement these SMS signal encoding techniques with GROG+slice-GRAPPA (GsG) reconstruction, a novel k-space parallel imaging approach that can provide good unaliasing performance in the slice direction for the highly undersampled MRF signal. We demonstrate the performance of GROG+GRAPPA in conjunction with t-blipped SMS-MRF at MB=3 with in vivo experiment.

Ola Norbeck¹, Magnus Mårtensson^2,3, Enrico Avventi³, Mathias Engström^1,3, and Stefan Skare^1,3
1Dept. of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden, ²EMEA Research and Collaboration, GE Applied Science Laboratory, GE Healthcare, Stockholm, Sweden, ³Dept. of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden

Simultaneous multi-slice (SMS) MR imaging, sometimes in combination with regular parallel imaging in the phase encoding direction, has led to a dramatic speed up of multi-volume echo-planar imaging (EPI) for fMRI and diffusion MRI. In multi-volume SMS imaging, the first volume can be acquired without acceleration and be used for calibration of the subsequent SMS accelerated volumes.For clinical MRI, most often only involving one volume per scan, one needs to make sure that the SMS calibration does not consume a large fraction of the total scan time. To keep the SMS calibration time short, a low resolution 2D GRE scan may be used. In this work, we have developed SMS RF pulses and applied them to PROPELLER imaging. As PROPELLER uses a large set of blade volumes (~10 per minute), we suggest to perform SMS and regular in-plane GRAPPA calibration on the first propeller blade volume as a part of the scan. With only one blade volume being fully sampled in both the phase encoding direction and the slice direction, and with the remaining blades fully accelerated without any ACS lines, the overall scan time could be kept very short and without needing separate GRE scans. For our accelerated PROPELLER sequence, GRAPPA and split-slice-GRAPPA was used for unfolding, and the GRAPPA kernel was rotated to calculate sets of weights the other blade volumes. The technique was validated with our T1-W SE PROPELLER sequence. Our work shows that PROPELLER scans can be accelerated with SMS in addition to in-plane acceleration, allowing almost 75 % scan time reduction.

Yi Wang¹, Thomas Martin¹, Steen Moeller², Essa Yacoub², and Danny JJ Wang^1
1Neurology, UCLA, Los Angeles, CA, United States, ²Center of Magnetic Resonance Research, University of Minnesota, MN, United States

Balanced SSFP is a widely used fast imaging technique because of its high SNR efficiency and the unique T2/T1 contrast. Its main limitation is the banding artifact resulting from its sensitivity to field inhomogeneity. One common approach for banding reduction is to perform multiple acquisitions with different phase cycling, which inevitably lengthens the total imaging time. In this work, we introduce an efficient approach for rapid banding removal in SSFP by utilizing phase-cycled MB imaging with CAIPIRINHA. Using such technique, multiple phase-cycled images can be obtained within the same imaging time as a conventional single SSFP acquisition.

Huihui Ye^1,2, Dan Ma³, Yun Jiang³, Stephen F Cauley¹, Yiping Du², Lawrence L Wald¹, Mark A Griswold³, and Kawin Setsompop^1
1MGH/HST Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ²Zhejaing University, Hangzhou, Zhangjiang, China, ³Case Western Reserve University, Ohio, United States

Magnetic resonance fingerprinting (MRF) permits non-invasive quantification of multiple important properties simultaneously. In conventional MRF, an acquisition time of approximately 10s is required for each imaging slice. In this work, we developed a new simultaneous multi-slice (SMS) technique to speed up MRF acquisition. Specifically, we proposed t-blipped SMS-MRF method, which utilizes additional Gz blip encodings to provide phase modulation between the signals of simultaneously acquired slices and creates controlled-aliasing in the temporal axis. We demonstrated the ability of t-blipped SMS-MRF technique to accelerate MRF acquisition by 2-fold (MB=2) and provide good parameter mapping at an acquisition time of 5s per slice using both simulation and in vivo acquisition. We find that the t-blipped SMS technique can speed up the MRF acquisition allowing a rapid quantitative parameter mapping in a clinically relevant time frame.

Steen Moeller¹, Edward Auerbach¹, An T Vu¹, Christophe Lenglet¹, Stamatios N Sotiropoulos², Kamil Ugurbil¹, and Essa Yacoub^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States, ²FMRIB-Centre, Oxford, Oxfordshire, United Kingdom

The use of a 2D-EPI ghost correction for Multiband imaging with in-plane undersampling is proposed to address residual ghosting prevalent in low b-value diffusion images at ultra high fields. Integration with the slice-GRAPPA algorithm is demonstrated, with the computational effort only affecting the calibration of the algorithm.

Keren Yang¹, Rosa Sanchez Panchuelo¹, Martin Buehrer², Richard Bowtell¹, and Susan Francis^1
1University of Nottingham, Nottingham, Nottinghamshire, United Kingdom, ²Gyrotools, Zurich, Switzerland

We incorporate a multiband acquisition with DABS ASL to form a MB-DABS sequence to allow simultaneous assessment of ASL and BOLD functional connectivity measures across the whole brain. The use of MB-DABS improves the temporal SNR of both ASL and BOLD data. Using single band DABS ASL, only the visual network can be reliably detected using ASL, whereas with dual slice multiband acquisition ASL, multiple networks are identified, in line with the BOLD measures.