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1. Efficient solution of large-scale algebraic Riccati equations associated with index-2 DAEs via the inexact low-rank Newton-ADI method

   https://doi.org/10.1016/j.apnum.2019.11.016  

   Benner, Peter ; Heinkenschloss, Matthias ; Saak, Jens ; Weichelt, Heiko K. ( June 2020 , Applied Numerical Mathematics)

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2. Simultaneous multislice cardiac magnetic resonance fingerprinting using low rank reconstruction

   https://doi.org/10.1002/nbm.4041  

   Hamilton, Jesse I. ; Jiang, Yun ; Ma, Dan ; Chen, Yong ; Lo, Wei‐Ching ; Griswold, Mark ; Seiberlich, Nicole ( December 2018 , NMR in Biomedicine)

   This study introduces a technique for simultaneous multislice (SMS) cardiac magnetic resonance fingerprinting (cMRF), which improves the slice coverage when quantifying myocardialT_1,T₂, andM₀. The single‐slice cMRF pulse sequence was modified to use multiband (MB) RF pulses for SMS imaging. Different RF phase schedules were used to excite each slice, similar to POMP or CAIPIRINHA, which imparts tissues with a distinguishable and slice‐specific magnetization evolution over time. Because of the high net acceleration factor (R = 48 in plane combined with the slice acceleration), images were first reconstructed with a low rank technique before matching data to a dictionary of signal timecourses generated by a Bloch equation simulation. The proposed method was tested in simulations with a numerical relaxation phantom. Phantom and in vivo cardiac scans of 10 healthy volunteers were also performed at 3 T. With single‐slice acquisitions, the mean relaxation times obtained using the low rank cMRF reconstruction agree with reference values. The low rank method improves the precision inT₁andT₂for both single‐slice and SMS cMRF, and it enables the acquisition of maps with fewer artifacts when using SMS cMRF at higher MB factors. With this technique, in vivo cardiac maps were acquired from three slices simultaneously during a breathhold lasting 16 heartbeats. SMS cMRF improves the efficiency and slice coverage of myocardialT₁andT₂mapping compared with both single‐slice cMRF and conventional cardiac mapping sequences. Thus, this technique is a first step toward whole‐heart simultaneousT₁andT₂quantification with cMRF.

    

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3. Time efficient whole-brain coverage with MR Fingerprinting using slice-interleaved echo-planar-imaging

   https://doi.org/10.1038/s41598-018-24920-z  

   Rieger, Benedikt ; Akçakaya, Mehmet ; Pariente, José C. ; Llufriu, Sara ; Martinez-Heras, Eloy ; Weingärtner, Sebastian ; Schad, Lothar R. ( December 2018 , Scientific Reports)
4. Parameter map error due to normal noise and aliasing artifacts in MR fingerprinting

   https://doi.org/10.1002/mrm.27638  

   Kara, Danielle ; Fan, Mingdong ; Hamilton, Jesse ; Griswold, Mark ; Seiberlich, Nicole ; Brown, Robert ( January 2019 , Magnetic Resonance in Medicine)

   To introduce a quantitative tool that enables rapid forecasting of T₁and T₂parameter map errors due to normal and aliasing noise as a function of the MR fingerprinting (MRF) sequence, which can be used in sequence optimization.

   The variances of normal noise and aliasing artifacts in the collected signal are related to the variances in T₁and T₂maps through derived quality factors. This analytical result is tested against the results of a Monte‐Carlo approach for analyzing MRF sequence encoding capability in the presence of aliasing noise, and verified with phantom experiments at 3 T. To further show the utility of our approach, our quality factors are used to find efficient MRF sequences for fewer repetitions.

   Experimental results verify the ability of our quality factors to rapidly assess the efficiency of an MRF sequence in the presence of both normal and aliasing noise. Quality factor assessment of MRF sequences is in agreement with the results of a Monte‐Carlo approach. Analysis of MRF parameter map errors from phantom experiments is consistent with the derived quality factors, with T₁(T₂) data yielding goodness of fit R²≥ 0.92 (0.80). In phantom and in vivo experiments, the efficient pulse sequence, determined through quality factor maximization, led to comparable or improved accuracy and precision relative to a longer sequence, demonstrating quality factor utility in MRF sequence design.

   The here introduced quality factor framework allows for rapid analysis and optimization of MRF sequence design through T₁and T₂error forecasting.

    

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5. Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T

   https://doi.org/10.1002/mrm.28404  

   Liu, Yuchi ; Hamilton, Jesse ; Eck, Brendan ; Griswold, Mark ; Seiberlich, Nicole ( July 2020 , Magnetic Resonance in Medicine)

   This work aims to develop an approach for simultaneous water–fat separation and myocardial T₁and T₂quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T.

   Two 15‐heartbeat cMRF sequences with different rosette trajectories designed for water–fat separation at 3T and 1.5T were implemented. Water T₁and T₂maps, water image, and fat image were generated with B₀inhomogeneity correction using a B₀map derived from the cMRF data themselves. The proposed water–fat separation rosette cMRF approach was validated in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and water/oil phantoms. It was also applied for myocardial tissue mapping of healthy subjects at both 3T and 1.5T.

   Water T₁and T₂values measured using rosette cMRF in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom agreed well with the reference values. In the water/oil phantom, oil was well suppressed in the water images and vice versa. Rosette cMRF yielded comparable T₁but 2~3 ms higher T₂values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images.

   Rosette cMRF provides fat images along with myocardial T₁and T₂maps with significant fat suppression. This technique may improve visualization of the anatomical structure of the heart by separating water and fat and could provide value in diagnosing cardiac diseases associated with fibrofatty infiltration or epicardial fat accumulation. It also paves the way toward comprehensive myocardial tissue characterization in a single scan.

    

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