Segmented TOF at 7 T MRI: Technique and clinical applications

Zhang, Zihao; Deng, Xiaofeng; Weng, Dehe; An, Jing; Zuo, Zhentao; Wang, Bo; Wei, Ning; Zhao, Jizong; Xue, Rong

doi:10.1016/j.mri.2015.07.002

Cited by 16 publications

(7 citation statements)

References 20 publications

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“…The main reason underlying this neglect may be the small size of hippocampal vessels, with the diameter of hippocampal arteries ranging from 0.2 to 0.8 mm (mean 0.5 mm). Today, 7 Tesla (7 T) time-of-flight magnetic resonance (TOF MR) angiography allows imaging of these small vessels and provides a time-efficient method to achieve high-resolution angiograms without venous contamination ( Heverhagen et al, 2008 ; Zang et al, 2015 ).…”

Section: Introductionmentioning

confidence: 99%

Hippocampal vascularization patterns: A high-resolution 7 Tesla time-of-flight magnetic resonance angiography study

Spallazzi

Dobisch

Becke

et al. 2019

NeuroImage: Clinical

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Considerable evidence suggests a close relationship between vascular and degenerative pathology in the human hippocampus. Due to the intrinsic fragility of its vascular network, the hippocampus appears less able to cope with hypoperfusion and anoxia than other cortical areas. Although hippocampal blood supply is generally provided by the collateral branches of the posterior cerebral artery (PCA) and the anterior choroidal artery (AChA), different vascularization patterns have been detected postmortem. To date, a methodology that enables the classification of individual hippocampal vascularization patterns in vivo has not been established. In this study, using high-resolution 7 Tesla time-of-flight angiography data (0.3 mm isotropic resolution) in young adults, we classified individual variability in hippocampal vascularization patterns involved in medial temporal lobe blood supply in vivo. A strong concordance between our classification and previous autopsy findings was found, along with interesting anatomical observations, such as the variable contribution of the AChA to hippocampal supply, the relationships between hippocampal and PCA patterns, and the different distribution patterns of the right and left hemispheres. The approach presented here for determining hippocampal vascularization patterns in vivo may provide new insights into not only the vulnerability of the hippocampus to vascular and neurodegenerative diseases but also hippocampal vascular plasticity after exercise training.

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Section: Introductionmentioning

confidence: 99%

Hippocampal vascularization patterns: A high-resolution 7 Tesla time-of-flight magnetic resonance angiography study

Spallazzi

Dobisch

Becke

et al. 2019

NeuroImage: Clinical

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“…Protocol modifications are still introduced in order to overcome acquisition time and specific absorption rate (SAR) limitations. Despite the report that longer repetition time (TR) and larger flip angle (FA) had better visualization for small vessels with slow-flowing blood [12], Zhang et al chose TR = 20 ms and FA = 188 in order to limit the total acquisition time to 10 min and avoid motion artifacts in clinical scans [40].…”

Section: Discussionmentioning

confidence: 99%

Ultra high field TOF-MRA: A method to visualize small cerebral vessels. 7 T TOF-MRA sequence parameters on different MRI scanners – Literature review

Grochowski

Staśkiewicz²

2017

Neurologia i Neurochirurgia Polska

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“…For an improved appreciation of the TOF angiograms acquired with 3 slabs, a saturation band upstream each slab would have eased the suppression of the venous residual signal. This would imply to take special care of the SAR limitations as proposed in different studies [4,7,55] since, at 7T, conventional 90° saturation is hard to implement at high repetition rate given the increased SAR.…”

Section: Ramp Slopes Are Hard To Calibratementioning

confidence: 99%

Time-of-flight angiography at 7T using TONE double spokes with parallel transmission

Saïb

Gras

Mauconduit

et al. 2019

Magnetic Resonance Imaging

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Purpose: To demonstrate that fast-kz spokes can be used in parallel transmission to homogenize flip angle ramp profiles (known as TONE) in slab selections, and thereby improve Time-Of-Flight angiography of the whole human brain at 7T. Methods: 1 + and 0 maps were measured on seven human brains with a z-segmented coil connected to an 8-channel pTx system. Tailored two-spoke pulses were designed under strict hardware and SAR constraints for uniform slab profile before transforming their subpulse waveforms for linearly-increasing flip-angle ramps. Increasing angulations along the feethead direction were prescribed in 2-slab and 3-slab TOF acquisitions. Excitation patterns were simulated and compared with RF-shimmed (single spoke) ramp pulses. Excitation performances were assessed in ~10-min TOF acquisitions by visually inspecting Maximal Intensity Projections angiograms. Results: The flip-angle ramp fidelity achieved by double spokes inside slabs of interest was improved by 30-40 % compared to RF-shimmed ramps. This allowed better homogenizing signal along arteries, and depicting small vessels in distal areas of the brain, in comparison with RF-shimmed ramp pulses or double-spoke uniform excitation. Conclusion: Ramp double spokes used in conjunction with parallel transmission yield better blood saturation compensation and more finely resolved TOF angiograms than mere double spokes or ramp single spokes at 7 T.

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Segmented TOF at 7 T MRI: Technique and clinical applications

Cited by 16 publications

References 20 publications

Hippocampal vascularization patterns: A high-resolution 7 Tesla time-of-flight magnetic resonance angiography study

Hippocampal vascularization patterns: A high-resolution 7 Tesla time-of-flight magnetic resonance angiography study

Ultra high field TOF-MRA: A method to visualize small cerebral vessels. 7 T TOF-MRA sequence parameters on different MRI scanners – Literature review

Time-of-flight angiography at 7T using TONE double spokes with parallel transmission

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