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Cardiac Magnetic Resonance Imaging at 7 Tesla
Published on: January 6, 2019
Adiabatic turbo spin echo in human applications at 7 T
Irene M L van Kalleveen1, Wouter Koning, Vincent O Boer
1Department of Radiology, UMC Utrecht, Utrecht, The Netherlands. I.M.L.vanKalleveen@umcutrecht.nl
Magnetic Resonance in Medicine
|January 4, 2012
Summary
Adiabatic turbo spin echo (TSE) sequences overcome B(1) field nonuniformity in ultrahigh-field MRI. This study shows improved image quality with adiabatic TSE at 7 T, even with surface coils, benefiting brain, neck, and pelvic imaging.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Radiofrequency (RF) Pulse Technology
- Biomedical Engineering
Background:
- Nonuniform B(1) fields in ultrahigh-field MRI cause significant artifacts with conventional radiofrequency (RF) pulses.
- Turbo spin echo (TSE) sequences are particularly susceptible to signal loss in areas of B(1) field inhomogeneity, especially when using surface coils.
- Adiabatic TSE sequences offer a potential solution due to their inherent insensitivity to B(1) nonuniformity.
Purpose of the Study:
- To investigate the efficacy of adiabatic TSE sequences at 7 Tesla (T) using surface coil transceivers for human imaging.
- To assess the limitations and benefits of adiabatic RF pulses under B(1) strength and RF power deposition constraints.
- To evaluate the potential for improved image quality in challenging anatomical regions.
Main Methods:
- Development and tuning of adiabatic RF pulses for 7 T MRI, operating in the superadiabatic regime.
- Multidimensional Bloch simulations to model the behavior of RF pulses over the echo train.
- Phantom measurements and in vivo imaging of the brain, neck (carotid artery), and pelvis (prostate) at 7 T.
- Comparison of adiabatic TSE with conventional TSE sequences, employing proper k-space sampling.
Main Results:
- Adiabatic RF pulses were tuned to accommodate B(1) constraints, though this resulted in a compromised dynamic range and signal modulation.
- Bloch simulations and phantom data confirmed these limitations.
- Despite compromises, adiabatic TSE demonstrated superior image quality compared to conventional TSE in the brain, neck, and pelvis at 7 T.
Conclusions:
- Adiabatic TSE sequences are a viable alternative to conventional TSE for ultrahigh-field MRI at 7 T, particularly when using surface coils.
- While B(1) dynamic range is compromised, proper k-space sampling enables improved image quality, mitigating artifacts caused by B(1) nonuniformity.
- This technique holds promise for enhanced diagnostic imaging in various human anatomical regions at 7 T.
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