Short-T2 MRI: Principles and recent advances

Weiger, Markus; Pruessmann, Klaas P.

doi:10.1016/j.pnmrs.2019.07.001

Cited by 57 publications

(56 citation statements)

References 319 publications

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“…This effect is already visible in XI for an acquisition time of 4 ms. Previously explored alternatives to short-T imaging 23 are the acquisition of a second gradient echo by flipping the gradient polarity 17 , or the reduction of the number of single points by means of a ramped hybrid encoding 24 . However, they both lead to artifacts in our setup due to eddy currents induced during gradient switching.…”

Section: Resultsmentioning

confidence: 99%

Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner

Algarin

Caballero²,

Borreguero

et al. 2020

Sci Rep

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Magnetic Resonance Imaging (MRI) of hard biological tissues is challenging due to the fleeting lifetime and low strength of their response to resonant stimuli, especially at low magnetic fields. Consequently, the impact of MRI on some medical applications, such as dentistry, continues to be limited. Here, we present three-dimensional reconstructions of ex-vivo human teeth, as well as a rabbit head and part of a cow femur, all obtained at a field strength of 260 mT. These images are the first featuring soft and hard tissues simultaneously at sub-Tesla fields, and they have been acquired in a home-made, special-purpose, pre-medical MRI scanner designed with the goal of demonstrating dental imaging at low field settings. We encode spatial information with two pulse sequences: Pointwise-Encoding Time reduction with Radial Acquisition and a new sequence we have called Double Radial Non-Stop Spin Echo, which we find to perform better than the former. For image reconstruction we employ Algebraic Reconstruction Techniques (ART) as well as standard Fourier methods. An analysis of the resulting images shows that ART reconstructions exhibit a higher signal-to-noise ratio with a more homogeneous noise distribution.

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Section: Resultsmentioning

confidence: 99%

Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner

Algarin

Caballero²,

Borreguero

et al. 2020

Sci Rep

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“…For the head sample the issue was avoided altogether since no comparison of different gradient strength images was performed, and for the foot sample the sweep pulse was largely spectrally uniform, producing images free of pulse‐induced weighting. Another potential image bias may arise from the spectral response of the RF coil, 24 as suggested by the limited bandwidth of the solenoid coil of 0.67 MHz. In analogy with the pulse, the effect of the associated weighing of the individual projections for the 3D radial data is relatively benign, and no related intensity variation was apparent in the images.…”

Section: Discussionmentioning

confidence: 99%

High‐resolution MRI of mummified tissues using advanced short‐T₂ methodology and hardware

Baadsvik

Weiger

Froidevaux

et al. 2020

Magnetic Resonance in Med

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Evolutionary medicine aims to study disease development from a longterm perspective, and through the analysis of mummified tissue, timescales of several thousand years are unlocked. Due to the status of mummies as ancient relics, noninvasive techniques are preferable, and, currently, CT imaging is the most widespread method. However, CT images lack soft-tissue contrast, making complementary MRI data desirable. Unfortunately, the dehydrated nature and short T 2 times of mummified tissues render them practically invisible to standard MRI techniques. Specialized short-T 2 approaches have therefore been used, but currently suffer severe resolution limitations. The purpose of the present study is to improve resolution in MRI of mummified tissues. Methods: The zero-TE-based hybrid filling technique, together with a high-performance magnetic field gradient, was used to image three ancient Egyptian mummified human body parts: a hand, a foot, and a head. A similar pairing has already been shown to increase resolution and image quality in MRI of short-T 2 tissues. Results: MRI images of yet unparalleled image quality were obtained for all samples, reaching isotropic resolutions of 0.6 mm and SNR values above 100. The same general features as present in CT images were depicted but with different contrast, particularly for regions containing embalming substances. Conclusion: Mummy MRI is a potentially valuable tool for (paleo)pathological studies, as well as for investigations into ancient mummification processes. The results presented here show sufficient improvement in the depiction of mummified tissues to clear new paths for the exploration of this field.

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“…The images were then reconstructed using 2 different trajectories: the nominal-and the GIRF-corrected trajectory. The employed sequence parameters were TE 0.14 ms/ 2.2 ms, TR 7.6 ms, flip angle 5°, in-plane resolution 0.6 × 0.6 mm 2 , slice thickness 1 mm, FOV 210 × 210 × 100 mm 3 , dwell time 1.84 μs, ramp length 0.15 ms, maximum gradient strength 30.36 mT/m, acquisition window 0.72 ms, 704 spokes, 393 samples, scan time of 6.15 min, and SENSE acceleration factor of 2 in the Cartesian-sampled dimension.…”

Section: Phantom Measurementsmentioning

confidence: 99%

“…For the spine measurements, a single UTE was acquired using the built-in-table 16-channel posterior coil and the following parameters: TE 0.14 ms, TR 6.3 ms, flip angle 5°, in-plane resolution 0.45 × 0.45 mm 2 , slice thickness 3 mm, FOV 250 × 250 × 279 mm 3 , ramp length 0.08 ms, maximum gradient strength 15.04 mT/m, dwell time 3.12 μs, acquisition window 1.77 ms, 945 spokes, 568 samples, radial percentage of 85%, half-scan factor of 0.6 in slice direction, and scan time of 6.3 min.…”

Section: In Vivo Measurementsmentioning

confidence: 99%

“…1,2 In conventional MRI, short-T 2 tissues appear as signal voids and are not directly visible. 3 UTE imaging is an approach that allows the detection of such short-T 2 signal components. UTE sequences have received increasing interest, especially in studies of the musculoskeletal (MSK) system, thanks to their ability to visualize short-T 2 tissue components such as those within cartilage, 4 knee menisci, 5 ligaments, 6 tendons, cortical bone, 7 and other similar examples.…”

Section: Introductionmentioning

confidence: 99%

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Trajectory correction based on the gradient impulse response function improves high‐resolution UTE imaging of the musculoskeletal system

Kronthaler

Rahmer

Börnert

et al. 2020

Magnetic Resonance in Med

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Short-T2 MRI: Principles and recent advances

Cited by 57 publications

References 319 publications

Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner

Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner

High‐resolution MRI of mummified tissues using advanced short‐T₂ methodology and hardware

Trajectory correction based on the gradient impulse response function improves high‐resolution UTE imaging of the musculoskeletal system

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Short-T2 MRI: Principles and recent advances

Cited by 57 publications

References 319 publications

Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner

Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner

High‐resolution MRI of mummified tissues using advanced short‐T2 methodology and hardware

Trajectory correction based on the gradient impulse response function improves high‐resolution UTE imaging of the musculoskeletal system

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High‐resolution MRI of mummified tissues using advanced short‐T₂ methodology and hardware