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The progression to 7 Tesla (7 T) magnetic resonance imaging (MRI) yields promises of substantial increase in signal-to-noise (SNR) ratio. This increase can be traded off to increase image spatial resolution or to decrease acquisition time. However, renal 7 T MRI remains challenging due to inhomogeneity of the radiofrequency field and due to specific absorption rate (SAR) constraints. A number of studies has been published in the field of renal 7 T imaging. While the focus initially was on anatomic imaging and renal MR angiography, later studies have explored renal functional imaging. Although anatomic imaging remains somewhat limited by inhomogeneous excitation and SAR constraints, functional imaging results are promising. The increased SNR at 7 T has been particularly advantageous for blood oxygen level-dependent and arterial spin labelling MRI, as well as sodium MR imaging, thanks to changes in field-strength-dependent magnetic properties. Here, we provide an overview of the currently available literature on renal 7 T MRI. In addition, we provide a brief overview of challenges and opportunities in renal 7 T MR imaging. [ABSTRACT FROM AUTHOR]

Objectives: Previous studies using intracranial vessel wall MRI techniques showed that over 50 % of patients with ischemic stroke or TIA had one or more intracranial vessel wall lesions. In the current study, we assessed the preferential location of these lesions within the intracranial arterial tree and their potential changes over time in these patient groups. Methods: Forty-nine patients with ischemic stroke ( n = 25) or TIA ( n = 24) of the anterior cerebral circulation underwent 7.0 T MRI, including a T-weighted magnetization-preparation inversion recovery turbo-spin-echo (MPIR-TSE) sequence within one week and approximately one month after symptom onset. Intracranial vessel wall lesions were scored for multiple locations within the arterial tree and differences between one-week and one-month images. Results: At baseline, 132 intracranial vessel wall lesions were found in 41 patients (84 %), located primarily in the anterior cerebral circulation (74 %), with a preferential location in the distal internal carotid artery and M1 and M2 segments of the middle cerebral artery. During follow-up, presence or enhancement patterns changed in 14 lesions (17 %). Conclusions: A large burden of intracranial vessel wall lesions was found in both the anterior and posterior cerebral circulation. Most lesions were found to be relatively stable, possibly indicating a more generalized atherosclerotic process. Key points: • Intracranial vessel wall lesions are present in patients with varying cerebrovascular diseases. • Intracranial vessel wall 7.0 T MRI provides information on preferential location and natural course. • Distal ICA and M1 and M2 segments of MCA are predilection sites. • 83 % of lesions found remained stable, possibly indicating more generalized atherosclerosis. [ABSTRACT FROM AUTHOR]

Background: Detection of cardiac fibrosis based on endogenous magnetic resonance (MR) characteristics of the myocardium would yield a measurement that can provide quantitative information, is independent of contrast agent concentration, renal function and timing. In ex vivo myocardial infarction (MI) tissue, it has been shown that a significantly higher T1ρ is found in the MI region, and studies in animal models of chronic MI showed the first in vivo evidence for the ability to detect myocardial fibrosis with native T1ρ-mapping. In this study we aimed to translate and validate T1ρ-mapping for endogenous detection of chronic MI in patients. Methods: We first performed a study in a porcine animal model of chronic MI to validate the implementation of T1ρ-mapping on a clinical cardiovascular MR scanner and studied the correlation with histology. Subsequently a clinical protocol was developed, to assess the feasibility of scar tissue detection with native T1ρ-mapping in patients (n = 21) with chronic MI, and correlated with gold standard late gadolinium enhancement (LGE) CMR. Four T1ρ-weighted images were acquired using a spin-lock preparation pulse with varying duration (0, 13, 27, 45 ms) and an amplitude of 750 Hz, and a T1ρ-map was calculated. The resulting T1ρ-maps and LGE images were scored qualitatively for the presence and extent of myocardial scarring using the 17-segment AHA model. Results: In the animal model (n = 9) a significantly higher T1ρ relaxation time was found in the infarct region (61 ± 11 ms), compared to healthy remote myocardium (36 ± 4 ms) . In patients a higher T1ρ relaxation time (79 ± 11 ms) was found in the infarct region than in remote myocardium (54 ± 6 ms). Overlap in the scoring of scar tissue on LGE images and T1ρ-maps was 74%. Conclusion: We have shown the feasibility of native T1ρ-mapping for detection of infarct area in patients with a chronic myocardial infarction. In the near future, improvements on the T1ρ -mapping sequence could provide a higher sensitivity and specificity. This endogenous method could be an alternative for LGE imaging, and provide additional quantitative information on myocardial tissue characteristics. [ABSTRACT FROM AUTHOR]

Objectives: Intracranial vessel wall magnetic resonance imaging (MRI) may improve the diagnosis of vessel wall abnormalities. Current methods are hampered by limited coverage and few contrast weightings. We present a multi-sequence protocol with whole-brain coverage for vessel wall imaging on 7.0-T MRI. Methods: A modified magnetisation-preparation inversion recovery turbo-spin-echo (MPIR-TSE) sequence was used to obtain proton density (PD)-, T-, and T-weighting with 190-mm whole-brain coverage. Three observers independently scored the visibility of arterial vessel walls in five healthy volunteers, and compared the conspicuity and image contrast of all sequences. Clinical applicability was demonstrated in 17 patients with cerebrovascular disease. Results: Conspicuity was good for all acquisitions, with best scores for the original limited-coverage sequence, followed by whole-brain coverage T- PD- and T-weighted sequences, respectively. Mean vessel wall/background MR signal intensity ratios for all whole-brain sequences were similar, with higher scores for the limited-coverage MPIR-TSE sequence. Signal intensity ratios were highest in patients, for the whole-brain T-weighted sequence. Conclusions: The whole-brain multi-sequence vessel wall protocol can assess intracranial arterial vessel walls with full brain coverage, for different image contrast weightings. These sequences could eventually characterise intracranial vessel wall abnormalities similar to current techniques for assessing carotid artery plaques. Key points: - Intracranial vessel wall imaging using MRI improves diagnosis of cerebrovascular diseases. - Conventional 7-T MRI sequences cannot image the whole cerebral arterial tree. - New whole-brain 7-T MRI sequences compare favourably with smaller-coverage sequences. - These whole-brain sequences can demonstrate the entire cerebral arterial tree. - These sequences should help in the diagnosis of vessel wall abnormalities. [ABSTRACT FROM AUTHOR]

Objectives: Seven-Tesla MRI demonstrated new pathological features of multiple sclerosis (MS) using T2*-weighted sequences. However, a clinical MRI protocol at 7 T has never been investigated. We evaluated the clinical value of 7-T MRI by investigating the sensitivity of lesion detection compared with 3 T. Methods: Thirty-eight MS patients and eight healthy controls underwent multi-contrast MRI using 3D T1-weighted (3D-T1w), 2D dual-echo T2-weighted (2D-T2w) and 3D fluid-attenuated inversion recovery (3D-FLAIR) at 3 and 7 T. Images were analysed for focal lesions, which were counted and categorised according to anatomical location. The study was approved by the institutional review board. Results: Lesion-wise analysis showed increased lesion counts in cortical grey matter (GM) at 7 T of 91, 75 and 238 % for 3D-T1w, 2D-T2w and FLAIR sequences, respectively. Patient-wise analysis confirmed this for 2D-T2w and FLAIR ( P < 0.023 and P < 0.001). Seven-Tesla white matter (WM) lesion detection was not increased; 3D-FLAIR even detected significantly more WM lesions at 3 T. Conclusions: Using a clinical multi-contrast MRI protocol, increased lesion detection was observed in cortical GM but not in WM. Given the clinical relevance of GM abnormalities, this may have consequences for clinical outcome measures, prognostic classification and future diagnostic criteria incorporating GM abnormalities. Key Points: • Standard multi-contrast 7-T magnetic resonance imaging in multiple sclerosis is feasible. • Seven-Tesla MRI detects more cortical grey matter lesions than 3 T. • Seven-Tesla MRI fares no better than 3 T in detecting white matter lesions. • Grey matter abnormalities have high diagnostic and prognostic relevance in MS. [ABSTRACT FROM AUTHOR]

Background: Risk prediction of rupture of intracranial aneurysms is poor and is based mainly on lumen characteristics. However, characteristics of the aneurysm wall may be more informative predictors. The limited resolution of currently available imaging techniques and the thin aneurysm wall make imaging of wall thickness challenging., Objective: To introduce a novel protocol for imaging wall thickness variation using ultra--high-resolution 7.0-Tesla (7.0-T) magnetic resonance imaging (MRI)., Methods: We studied 33 unruptured intracranial aneurysms in 24 patients with a T1-weighted 3-dimensional magnetization-prepared inversion-recovery turbo-spin-echo whole-brain sequence with a resolution of 0.8 × 0.8 × 0.8 mm. We performed a validation study with a wedge phantom and with 2 aneurysm wall biopsies obtained during aneurysm treatment using ex vivo MRI and histological examination and correlating variations in MRI signal intensity with variations in actual thickness of the aneurysm wall., Results: In vivo, the aneurysm wall was visible in 28 of the 33 aneurysms. Variation in signal intensity was observed in all visible aneurysm walls. Ex vivo MRI showed variation in signal intensity across the wall of the biopsies, similar to that observed on the in vivo images. Signal intensity and actual thickness in both biopsies had a linear correlation, with Pearson correlation coefficients of 0.85 and 0.86., Conclusion: Unruptured intracranial aneurysm wall and its variation in thickness can be visualized with 7.0-T MRI. Aneurysm wall thickness variation can now be further studied as a risk factor for rupture in prospective studies.

Purpose: To develop a magnetic resonance imaging (MRI) protocol that visualizes both the perforating arteries and the related anatomy in a single acquisition at 7 T., Material and Methods: T(1)-weighted magnetization prepared imaging (MPRAGE) was empirically modified for use as angiography method at 7 T. The resulting sequence depicts the vasculature simultaneously with the surrounding anatomical structures, and is referred to as "magnetization prepared anatomical reference MRA" (MPARE-MRA). The method was compared to time-of-flight (TOF) MRA in seven healthy subjects. The conspicuity of the perforating arteries and the contrast between gray and white matter were evaluated both quantitatively by contrast-to-noise (CNR) measurements, and qualitatively by two radiologists who scored the images., Results: The contrast-to-noise ratio (CNR) between blood and background was 28 +/- 9 for MPARE-MRA and 35 +/- 16 for TOF-MRA, indicating good conspicuity of the vessels. CNR values were: internal capsule (IC) vs. caudate head (CH): 4.2 +/- 0.7; IC vs. putamen: 3.5 +/- 0.6; white matter vs. gray matter: 9.7 +/- 2.5., Conclusion: The benefits of ultra-high-field MRI can transform MPRAGE into a new angiography method to image small vessels and associated parenchyma at the same time. This technique can be used to study the correlation between tissue damage and vascular pathology., ((c) 2008 Wiley-Liss, Inc.)