Evaluation of MR angiography at 7.0 Tesla MRI using birdcage radio frequency coils with end caps

Kang, Chang-Ki; Hong, Seok-In; Han, Juhee; Kim, Kyoung Nam; Kim, Sang-Hoon; Kim, Young-Bo; Cho, Zang-Hee

doi:10.1002/mrm.21472

Cited by 12 publications

(7 citation statements)

References 22 publications

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“…The increase of the magnetic field strength from 1.5 Tesla to 3 Tesla has been proven beneficial for clinical neuroimaging and feasible for ultra-high-field 7 Tesla MRI, facilitating a significant increase in spatial resolution [4], [8], [9], [15]–[17], [33], [34]. M oenninghoff et al presented a high-resolution 7 Tesla TOF MRA protocol for clinical application including venous saturation pulses.…”

Section: Discussionmentioning

confidence: 99%

Improved Cerebral Time-of-Flight Magnetic Resonance Angiography at 7 Tesla – Feasibility Study and Preliminary Results Using Optimized Venous Saturation Pulses

et al. 2014

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PurposeConventional saturation pulses cannot be used for 7 Tesla ultra-high-resolution time-of-flight magnetic resonance angiography (TOF MRA) due to specific absorption rate (SAR) limitations. We overcome these limitations by utilizing low flip angle, variable rate selective excitation (VERSE) algorithm saturation pulses.Material and MethodsTwenty-five neurosurgical patients (male n = 8, female n = 17; average age 49.64 years; range 26–70 years) with different intracranial vascular pathologies were enrolled in this trial. All patients were examined with a 7 Tesla (Magnetom 7 T, Siemens) whole body scanner system utilizing a dedicated 32-channel head coil. For venous saturation pulses a 35° flip angle was applied. Two neuroradiologists evaluated the delineation of arterial vessels in the Circle of Willis, delineation of vascular pathologies, presence of artifacts, vessel-tissue contrast and overall image quality of TOF MRA scans in consensus on a five-point scale. Normalized signal intensities in the confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter were measured and vessel-tissue contrasts were calculated.ResultsRatings for the majority of patients ranged between good and excellent for most of the evaluated features. Venous saturation was sufficient for all cases with minor artifacts in arteriovenous malformations and arteriovenous fistulas. Quantitative signal intensity measurements showed high vessel-tissue contrast for confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter.ConclusionThe use of novel low flip angle VERSE algorithm pulses for saturation of venous vessels can overcome SAR limitations in 7 Tesla ultra-high-resolution TOF MRA. Our protocol is suitable for clinical application with excellent image quality for delineation of various intracranial vascular pathologies.

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Section: Discussionmentioning

confidence: 99%

Improved Cerebral Time-of-Flight Magnetic Resonance Angiography at 7 Tesla – Feasibility Study and Preliminary Results Using Optimized Venous Saturation Pulses

et al. 2014

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“…With increasing field strength, proton T 1 relaxation times are prolonged, which is anticipated to benefit time‐of‐flight (TOF) angiography. Combined with the much higher spatial resolution, which can be implemented as a result of enhanced sensitivity, the depiction of much finer vessel branches is achievable . With this technique, it is possible to depict very small blood vessels, such as the lenticulostriate arteries .…”

Section: Brain Imaging At 7 Tmentioning

confidence: 99%

7‐T MR—from research to clinical applications?

et al. 2011

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Over 20,000 MR systems are currently installed worldwide and, although the majority operate at magnetic fields of 1.5 T and below (i.e. about 70%), experience with 3-T (in high-field clinical diagnostic imaging and research) and 7-T (research only) human MR scanners points to a future in functional and metabolic MR diagnostics. Complementary to previous studies, this review attempts to provide an overview of ultrahigh-field MR research with special emphasis on emerging clinical applications at 7 T. We provide a short summary of the technical development and the current status of installed MR systems. The advantages and challenges of ultrahigh-field MRI and MRS are discussed with special emphasis on radiofrequency inhomogeneity, relaxation times, signal-to-noise improvements, susceptibility effects, chemical shifts, specific absorption rate and other safety issues. In terms of applications, we focus on the topics most likely to gain significantly from 7-T MR, i.e. brain imaging and spectroscopy and musculoskeletal imaging, but also body imaging, which is particularly challenging. Examples are given to demonstrate the advantages of susceptibility-weighted imaging, time-of-flight MR angiography, high-resolution functional MRI, (1)H and (31)P MRSI in the human brain, sodium and functional imaging of cartilage and the first results (and artefacts) using an eight-channel body array, suggesting future areas of research that should be intensified in order to fully explore the potential of 7-T MR systems for use in clinical diagnosis.

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“…However, since the Specific Absorption Rate (SAR) increases with B 0 , TOF-MRA at 7T cannot use normal large-FA saturation band in the protocol as in the lower field MR system. Consequently, TOF angiograms at 7T were often obtained without venous saturation [3,9], or with compromised thickness of saturation band [10]. Some studies used the variable-rate selective excitation (VERSE) pulse instead of sinc pulses for venous saturation, meanwhile, small-FA pulse was used for saturation to reduce SAR in TOF-MRA at 7T [11,12].…”

Section: Introductionmentioning

confidence: 99%