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Ristretto MRE: A generalized multi-shot GRE-MRE sequence.

  • Guenthner C Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
  • Sethi S Division of Research Oncology, Guy's and St Thomas' NHS Foundation Trust, London, UK.
  • Troelstra M Division of Imaging Sciences & Biomedical Engineering, King's College London, London, UK.
  • Dokumaci AS Division of Imaging Sciences & Biomedical Engineering, King's College London, London, UK.
  • Sinkus R Division of Imaging Sciences & Biomedical Engineering, King's College London, London, UK.
  • Kozerke S Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
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  • 2019-01-31
Published in:
  • NMR in biomedicine. - 2019
GRE-MRE
MR elastography
eXpresso
interleaved acquisition
multi-shot
multi-slice
Elasticity Imaging Techniques
Female
Humans
Magnetic Resonance Imaging
Phantoms, Imaging
Signal-To-Noise Ratio
Time Factors
English In order to acquire consistent k-space data in MR elastography, a fixed temporal relationship between the MRI sequence and the underlying period of the wave needs to be ensured. To this end, conventional GRE-MRE enforces synchronization through repeated triggering of the transducer and forcing the sequence repetition time to be equal to an integer multiple of the wave period. For wave frequencies below 100 Hz, however, this leads to prolonged acquisition times, as the repetition time scales inversely with frequency. A previously developed multi-shot approach (eXpresso MRE) to multi-slice GRE-MRE tackles this issue by acquiring an integer number of slices per wave period, which allows acquisition to be accelerated in typical scenarios by a factor of two or three. In this work, it is demonstrated that the constraints imposed by the eXpresso scheme are overly restrictive. We propose a generalization of the sequence in three steps by incorporating sequence delays into imaging shots and allowing for interleaved wave-phase acquisition. The Ristretto scheme is compared in terms of imaging shot and total scan duration relative to eXpresso and conventional GRE-MRE and is validated in three different phantom studies. First, the agreement of measured displacement fields in different stages of the sequence generalization is shown. Second, performance is compared for 25, 36, 40, and 60 Hz actuation frequencies. Third, the performance is assessed for the acquisition of different numbers of slices (13 to 17). In vivo feasibility is demonstrated in the liver and the breast. Here, Ristretto is compared with an optimized eXpresso sequence, leading to scan accelerations of 15% and 5%, respectively, without compromising displacement field and stiffness estimates in general. The Ristretto concept allows us to choose imaging shot durations on a fine grid independent of the number of slices and the wave frequency, permitting 2- to 4.5-fold acceleration of conventional GRE-MRE acquisitions.
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  • English
Open access status
hybrid
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https://sonar.ch/global/documents/109354
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