Indirect 1H-[13C] MRS of the human brain at 7 T using a 13C-birdcage coil and eight transmit-receive 1H-dipole antennas with a 32-channel 1H-receive array.

The neuronal tricarboxylic acid and glutamate/glutamine (Glu/Gln) cycles play important roles in brain function. These processes can be measured in vivo using dynamic 1H-[13C] MRS during administration of 13C-labeled glucose. Proton-observed carbon-edited (POCE) MRS enhances the signal-to-noise ratio (SNR) compared with direct 13C-MRS. Ultra-high field further boosts the SNR and increases spectral dispersion; however, even at 7 T, Glu and Gln 1H-resonances may overlap. Further gain can be obtained with selective POCE (selPOCE). Our aim was to create a setup for indirect dynamic 1H-[13C] MRS in the human brain at 7 T. A home-built non-shielded transmit-receive 13C-birdcage head coil with eight transmit-receive 1H-dipole antennas was used together with a 32-channel 1H-receive array. Electromagnetic simulations were carried out to ensure that acquisitions remained within local and global head SAR limits. POCE-MRS was performed using slice-selective excitation with semi-localization by adiabatic selective refocusing (sLASER) and stimulated echo acquisition mode (STEAM) localization, and selPOCE-MRS using STEAM. Sequences were tested in a phantom containing non-enriched Glu and Gln, and in three healthy volunteers during uniformly labeled 13C-glucose infusions. In one subject the voxel position was alternated between bi-frontal and bi-occipital placement within one session. [4-13C]Glu-H4 and [4-13C]Gln-H4 signals could be separately detected using both STEAM-POCE and STEAM-selPOCE in the phantom. In vivo, [4,5-13C]Glx could be detected using both sLASER-POCE and STEAM-POCE, with similar sensitivities, but [4,5-13C]Glu and [4,5-13C]Gln signals could not be completely resolved. STEAM-POCE was alternately performed bi-frontal and bi-occipital within a single session without repositioning of the subject, yielding similar results. With STEAM-selPOCE, [4,5-13C]Glu and [4,5-13C]Gln could be clearly separated. We have shown that with our setup indirect dynamic 1H-[13C] MRS at 7 T is feasible in different locations in the brain within one session, and by using STEAM-selPOCE it is possible to separate Glu from Gln in vivo while obtaining high quality spectra.

Improving the lesion appearance on FLAIR images synthetized from quantitative MRI: a fast, hybrid approach.

OBJECTIVE: The image quality of synthetized FLAIR (fluid attenuated inversion recovery) images is generally inferior to its conventional counterpart, especially regarding the lesion contrast mismatch. This work aimed to improve the lesion appearance through a hybrid methodology. MATERIALS AND METHODS: We combined a full brain 5-min MR-STAT acquisition followed by FLAIR synthetization step with an ultra-under sampled conventional FLAIR sequence and performed the retrospective and prospective analysis of the proposed method on the patient datasets and a healthy volunteer. RESULTS: All performance metrics of the proposed hybrid FLAIR images on patient datasets were significantly higher than those of the physics-based FLAIR images (p < 0.005), and comparable to those of conventional FLAIR images. The small difference between prospective and retrospective analysis on a healthy volunteer demonstrated the validity of the retrospective analysis of the hybrid method as presented for the patient datasets. DISCUSSION: The proposed hybrid FLAIR achieved an improved lesion appearance in the clinical cases with neurological diseases compared to the physics-based FLAIR images, Future prospective work on patient data will address the validation of the method from a diagnostic perspective by radiological inspection of the new images over a larger patient cohort.

Synthetic MRI with Magnetic Resonance Spin TomogrAphy in Time-Domain (MR-STAT): Results from a Prospective Cross-Sectional Clinical Trial.

BACKGROUND: Magnetic Resonance Spin TomogrAphy in Time-domain (MR-STAT) can reconstruct whole-brain multi-parametric quantitative maps (eg, T1 , T2 ) from a 5-minute MR acquisition. These quantitative maps can be leveraged for synthetization of clinical image contrasts. PURPOSE: The objective was to assess image quality and overall diagnostic accuracy of synthetic MR-STAT contrasts compared to conventional contrast-weighted images. STUDY TYPE: Prospective cross-sectional clinical trial. POPULATION: Fifty participants with a median age of 45 years (range: 21-79 years) consisting of 10 healthy participants and 40 patients with neurological diseases (brain tumor, epilepsy, multiple sclerosis or stroke). FIELD STRENGTH/SEQUENCE: 3T/Conventional contrast-weighted imaging (T1 /T2 weighted, proton density [PD] weighted, and fluid-attenuated inversion recovery [FLAIR]) and a MR-STAT acquisition (2D Cartesian spoiled gradient echo with varying flip angle preceded by a non-selective inversion pulse). ASSESSMENT: Quantitative T1 , T2 , and PD maps were computed from the MR-STAT acquisition, from which synthetic contrasts were generated. Three neuroradiologists blinded for image type and disease randomly and independently evaluated synthetic and conventional datasets for image quality and diagnostic accuracy, which was assessed by comparison with the clinically confirmed diagnosis. STATISTICAL TESTS: Image quality and consequent acceptability for diagnostic use was assessed with a McNemar's test (one-sided α = 0.025). Wilcoxon signed rank test with a one-sided α = 0.025 and a margin of Δ = 0.5 on the 5-level Likert scale was used to assess non-inferiority. RESULTS: All data sets were similar in acceptability for diagnostic use (≥3 Likert-scale) between techniques (T1 w:P = 0.105, PDw:P = 1.000, FLAIR:P = 0.564). However, only the synthetic MR-STAT T2 weighted images were significantly non-inferior to their conventional counterpart; all other synthetic datasets were inferior (T1 w:P = 0.260, PDw:P = 1.000, FLAIR:P = 1.000). Moreover, true positive/negative rates were similar between techniques (conventional: 88%, MR-STAT: 84%). DATA CONCLUSION: MR-STAT is a quantitative technique that may provide radiologists with clinically useful synthetic contrast images within substantially reduced scan time. EVIDENCE LEVEL: 1 Technical Efficacy: Stage 2.

A vision of 14 T MR for fundamental and clinical science.

OBJECTIVE: We outline our vision for a 14 Tesla MR system. This comprises a novel whole-body magnet design utilizing high temperature superconductor; a console and associated electronic equipment; an optimized radiofrequency coil setup for proton measurement in the brain, which also has a local shim capability; and a high-performance gradient set. RESEARCH FIELDS: The 14 Tesla system can be considered a 'mesocope': a device capable of measuring on biologically relevant scales. In neuroscience the increased spatial resolution will anatomically resolve all layers of the cortex, cerebellum, subcortical structures, and inner nuclei. Spectroscopic imaging will simultaneously measure excitatory and inhibitory activity, characterizing the excitation/inhibition balance of neural circuits. In medical research (including brain disorders) we will visualize fine-grained patterns of structural abnormalities and relate these changes to functional and molecular changes. The significantly increased spectral resolution will make it possible to detect (dynamic changes in) individual metabolites associated with pathological pathways including molecular interactions and dynamic disease processes. CONCLUSIONS: The 14 Tesla system will offer new perspectives in neuroscience and fundamental research. We anticipate that this initiative will usher in a new era of ultra-high-field MR.

Sex Differences in Plaque Composition and Morphology Among Symptomatic Patients With Mild-to-Moderate Carotid Artery Stenosis.

BACKGROUND AND PURPOSE: Incidence of ischemic stroke differs between men and women, with substantially higher rates in men. The underlying mechanism of this difference remains poorly understood but may be because of differences in carotid atherosclerosis. Using an in-depth imaging-based approach, we investigated differences between carotid plaque composition and morphology in male and female patients with stroke, taking into account differences in total plaque burden. Additionally, we investigated all possible within-artery combinations of plaque characteristics to explore differences between various plaque phenotypes. METHODS: We included 156 men and 68 women from the PARISK (Plaque At Risk) study, a prospective cohort study of patients with recent ischemic cerebrovascular symptoms and <70% ipsilateral carotid stenosis. Plaque characteristics (intraplaque hemorrhage [IPH], lipid-rich necrotic core [LRNC], calcifications, thin-or-ruptured fibrous cap, ulcerations, total plaque volume) were assessed with magnetic resonance imaging and multidetector-row computed tomography angiography. We used multivariable logistic and linear regression analyses to assess sex differences in plaque characteristics. RESULTS: We found significant difference in total plaque volume between men and women (ß=22.9 mm3 [95% CI, 15.4-30.5]; mean volume in men 1399±425 mm3, in women 1011±242 mm3). Additionally, men were more likely to have IPH (odds ratio [OR]=2.8 [95% CI, 1.3-6.3]; IPH proportion in men 49%, in women 16%) and LRNC (OR=2.4 [95% CI, 1.2-4.7]; LRNC proportion in men 73%, in women 41%) even after adjustment for total plaque volume. We found no sex-specific differences in plaque volume-corrected volumes of IPH, LRNC, and calcifications. In terms of coexistence of plaque characteristics, we found that men had more often a plaque with coexistence of calcifications, LRNC, and IPH (OR=2.7 [95% CI, 1.2-7.0]), with coexistence of thin-or-ruptured fibrous cap/ulcerations, LRNC, and IPH (OR=2.4 [95% CI, 1.1-5.9]), and with coexistence of all plaque characteristics (OR=3.0 [95% CI, 1.2-8.6]). CONCLUSIONS: In symptomatic patients with mild-to-moderate carotid stenosis, men are more likely to have a high-risk carotid plaque with IPH and LRNC than women, regardless of total plaque burden. Men also have more often a plaque with multiple vulnerable plaque components, which could comprise an even higher stroke risk. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01208025.

CXCR4 expression in glioblastoma tissue and the potential for PET imaging and treatment with [68Ga]Ga-Pentixafor /[177Lu]Lu-Pentixather.

PURPOSE: CXCR4 (over)expression is found in multiple human cancer types, while expression is low or absent in healthy tissue. In glioblastoma it is associated with a poor prognosis and more extensive infiltrative phenotype. CXCR4 can be targeted by the diagnostic PET agent [68Ga]Ga-Pentixafor and its therapeutic counterpart [177Lu]Lu-Pentixather. We aimed to investigate the expression of CXCR4 in glioblastoma tissue to further examine the potential of these PET agents. METHODS: CXCR4 mRNA expression was examined using the R2 genomics platform. Glioblastoma tissue cores were stained for CXCR4. CXCR4 staining in tumor cells was scored. Stained tissue components (cytoplasm and/or nuclei of the tumor cells and blood vessels) were documented. Clinical characteristics and information on IDH and MGMT promoter methylation status were collected. Seven pilot patients with recurrent glioblastoma underwent [68Ga]Ga-Pentixafor PET; residual resected tissue was stained for CXCR4. RESULTS: Two large mRNA datasets (N = 284; N = 540) were assesed. Of the 191 glioblastomas, 426 cores were analyzed using immunohistochemistry. Seventy-eight cores (23 tumors) were CXCR4 negative, while 18 cores (5 tumors) had both strong and extensive staining. The remaining 330 cores (163 tumors) showed a large inter- and intra-tumor variation for CXCR4 expression; also seen in the resected tissue of the seven pilot patients-not directly translatable to [68Ga]Ga-Pentixafor PET results. Both mRNA and immunohistochemical analysis showed CXCR4 negative normal brain tissue and no significant correlation between CXCR4 expression and IDH or MGMT status or survival. CONCLUSION: Using immunohistochemistry, high CXCR4 expression was found in a subset of glioblastomas as well as a large inter- and intra-tumor variation. Caution should be exercised in directly translating ex vivo CXCR4 expression to PET agent uptake. However, when high CXCR4 expression can be identified with [68Ga]Ga-Pentixafor, these patients might be good candidates for targeted radionuclide therapy with [177Lu]Lu-Pentixather in the future.

Dolichoarteriopathies of the extracranial internal carotid artery: The Plaque At RISK study.

BACKGROUND AND PURPOSE: Dolichoarteriopathies of the extracranial part of the internal carotid artery (ICA) are associated with cerebrovascular events, yet information on their prevalence and risk factors remains limited. The aim of the present study therefore was to study the prevalence and risk factors of dolichoarteriopathies in a sample of patients with cerebrovascular symptoms from the Plaque At RISK (PARISK) study. METHODS: In a random sample of 100 patients from the PARISK study, multidetector computed tomography angiography (MDCTA) was performed as part of clinical workup. On MDCTA, we evaluated the extracranial trajectory of the ICA by measuring the length (in millimeters), the tortuosity index (TI; defined as the ICA length divided by the shortest possible distance from bifurcation to skull base), and dolichoarteriopathy type (tortuosity, coiling or kinking). Next, we investigated the association between cardiovascular risk factors and these measurements using linear and logistic regression analyses. RESULTS: The mean (standard deviation) length of the ICA was 93 (± 14) mm, with a median (interquartile range) TI of 1.2 (1.1-1.3). The overall prevalence of dolichoarteriopathies was 69%, with tortuosity being the most common (72%), followed by coiling (20%), and kinking (8%). We found that age and obesity were associated with a higher TI: difference per 10-year increase in age: 0.05 (95% confidence interval [CI] 0.02-0.08) and 0.16 (95% CI 0.07-0.25) for obesity. Obesity and hypercholesterolemia were associated with a more severe type of dolichoarteriopathy (odds ratio [OR] 2.07 [95% CI 1.04-4.12] and OR 2.17 [95% CI 1.02-4.63], respectively). CONCLUSION: Dolichoarteriopathies in the extracranial ICA are common in patients with cerebrovascular symptoms, and age, obesity and hypercholesterolemia may play an important role in the pathophysiology of these abnormalities.

Intracranial Atherosclerosis Assessed with 7-T MRI: Evaluation of Patients with Ischemic Stroke or Transient Ischemic Attack.

Background Intracranial atherosclerosis is an important cause of ischemic stroke and is associated with several vascular risk factors. Current imaging is mainly based on the assessment of luminal narrowing rather than abnormalities in the vessel wall. Purpose To investigate the relationship between vascular risk factors and atherosclerotic lesion burden of intracranial arteries assessed with vessel wall MRI at 7 T in participants with ischemic stroke or transient ischemic attack (TIA). Materials and Methods In this prospective study (trial identification number: NTR2119; www.trialregister.nl), study participants who presented with ischemic stroke or TIA of the anterior circulation between December 2009 and September 2017 underwent pre- and postcontrast 7-T vessel wall MRI within 3 months of symptom onset. All large arteries of the intracranial circulation were assessed for number, location, and enhancement of vessel wall lesions. Generalized estimating equations for Poisson regression were used to investigate the relationship between vascular risk factors and number or enhancement of vessel wall lesions. Results Ninety participants (52 men; mean age, 60 years) were evaluated. Increasing age (relative risk [RR], 1.02; 95% confidence interval [CI]: 1.01, 1.03), hypertension (RR, 1.46; 95% CI: 1.06, 2.02), diabetes mellitus (RR, 1.67; 95% CI: 1.20, 2.33), and a higher multivariable vascular risk score (Second Manifestations of Arterial Disease risk score) (RR, 1.01; 95% CI: 1.00, 1.02) were associated with a higher number of vessel wall lesions in the anterior circulation. Contrast material-enhancing vessel wall lesions were associated only with increasing age (RR, 1.03; 95% CI: 1.01, 1.05). No association was found between smoking and the number of vessel wall lesions. Conclusion Except for smoking, traditional common cardiovascular risk factors were associated with a higher number and enhancement of intracranial vessel wall lesions at 7-T MRI in individuals evaluated after ischemic stroke or transient ischemic attack. Published under a CC BY 4.0 license. Online supplemental material is available for this article.

Intracranial Vessel Wall Lesions on 7T MRI (Magnetic Resonance Imaging).

Background and Purpose- Intracranial vessel wall lesions are a novel imaging marker of intracranial atherosclerosis (ICAS), but data on their occurrence and risk factors are lacking. Our aim was to study the frequency, distribution, and risk factors of intracranial vessel wall lesions on 7T magnetic resonance imaging in patients with a history of vascular disease. Methods- Within the SMART-MR study (Second Manifestations of Arterial Disease-Magnetic Resonance), cross-sectional analyses were performed in 130 patients (68±9 years) with assessable 7T intracranial vessel wall-magnetic resonance imaging data. Associations between vascular risk factors and ICAS burden, defined as the total number of vessel wall lesions, were estimated using linear regression analyses with ICAS burden as the dependent variable, adjusted for age and sex. Results- Ninety-six percent of patients had ≥1 vessel wall lesion. The mean±SD (range) ICAS burden was 8.5±5.7 (0-32) lesions. Significant associations were found between ICAS burden and age ( b=2.0 per +10 years; 95% CI, 0.81- 3.10), systolic blood pressure ( b=0.9 per +10 mm Hg; 95% CI, 0.27-1.42), diabetes mellitus ( b=3.2 for presence of diabetes mellitus; 95% CI, 0.79-5.72), hemoglobin A1c level ( b=1.2 per +1%; 95% CI, 0.19-2.26), apoB (apolipoprotein-B) ( b=4.7 per +1 g/L; 95% CI, 0.07-9.35), and hs-CRP (high-sensitivity C-reactive protein) level ( b=2.7 for hs-CRP >3 mg/L; 95% CI, 0.22-5.11). No significant associations were found with sex, smoking, and other lipid-factors. Conclusions- Vessel wall lesions are a novel and direct magnetic resonance imaging marker of ICAS. In this cohort, 96% of patients had at least 1 lesion on 7T vessel wall-magnetic resonance imaging. More lesions were found with older age, higher systolic blood pressure, diabetes mellitus, and higher levels of hemoglobin A1c, apoB, and hs-CRP.

Clinical vascular imaging in the brain at 7T.

Stroke and related cerebrovascular diseases are a major cause of mortality and disability. Even at standard-field-strengths (1.5T), MRI is by far the most sensitive imaging technique to detect acute brain infarctions and to characterize incidental cerebrovascular lesions, such as white matter hyperintensities, lacunes and microbleeds. Arterial time-of-flight (TOF) MR angiography (MRA) can depict luminal narrowing or occlusion of the major brain feeding arteries, and this without the need for contrast administration. Compared to 1.5T MRA, the use of high-field strength (3T) and even more so ultra-high-field strengths (7T), enables the visualization of the lumen of much smaller intracranial vessels, while adding a contrast agent to TOF MRA at 7T may enable the visualization of even more distal arteries in addition to veins and venules. Moreover, with 3T and 7T, the arterial vessel walls beyond the circle of Willis become visible with high-resolution vessel wall imaging. In addition, with 7T MRI, the brain parenchyma can now be visualized on a submillimeter scale. As a result, high-resolution imaging studies of the brain and its blood supply at 7T have generated new concepts of different cerebrovascular diseases. In the current article, we will discuss emerging clinical applications and future directions of vascular imaging in the brain at 7T MRI.

The Use and Pitfalls of Intracranial Vessel Wall Imaging: How We Do It.

Intracranial vessel wall magnetic resonance (MR) imaging has gained much attention in the past decade and has become part of state-of-the-art MR imaging protocols to assist in diagnosing the cause of ischemic stroke. With intracranial vessel wall imaging, vessel wall characteristics have tentatively been described for atherosclerosis, vasculitis, dissections, Moyamoya disease, and aneurysms. With the increasing demand and subsequently increased use of intracranial vessel wall imaging in clinical practice, radiologists should be aware of the choices in imaging parameters and how they affect image quality, the clinical indications, methods of assessment, and limitations in the interpretation of these images. In this How I do It article, the authors will discuss the technical requirements and considerations for vessel wall image acquisition in general, describe their own vessel wall imaging protocol at 3 T and 7 T, show a step-by-step basic assessment of intracranial vessel wall imaging as performed at their institution-including commonly encountered artifacts and pitfalls-and summarize the commonly reported imaging characteristics of various intracranial vessel wall diseases for direct clinical applicability. Finally, future technical and clinical considerations for full implementation of intracranial vessel wall imaging in clinical practice, including the need for histologic validation and acquisition time reduction, will be discussed.

Detecting Intracranial Vessel Wall Lesions With 7T-Magnetic Resonance Imaging: Patients With Posterior Circulation Ischemia Versus Healthy Controls.

BACKGROUND AND PURPOSE: Vessel wall magnetic resonance imaging sequences have been developed to directly visualize the intracranial vessel wall, enabling detection of vessel wall changes, including those that have not yet caused luminal narrowing. In this study, vessel wall lesion burden was assessed in patients with recent posterior circulation ischemia using 7T-magnetic resonance imaging and compared with matched healthy controls. METHODS: Fifty subjects (25 patients and 25 matched healthy controls) underwent 7T-magnetic resonance imaging with an intracranial vessel wall sequence before and after contrast administration. Two raters scored the presence and contrast enhancement of arterial wall lesions in individual segments of the circle of Willis and its primary branches. Total burden and distribution of vessel wall lesions and lesion characteristics (configuration, thickening pattern, and contrast enhancement) were compared both between and within both groups. RESULTS: Overall, vessel wall lesion burden and distribution were comparable between patients and controls. Regarding individual arterial segments, only vessel wall lesions in the posterior cerebral artery were more frequently observed in patients (18.0%) than in controls (5.4%; P=0.003). Many of these lesions showed enhancement, both in patients (48.9%) and in controls (43.5%; P=0.41). In patients, the proportion of enhancing lesions was higher in the posterior circulation (53.3%) than in the anterior circulation (20.6%; P=0.008). CONCLUSIONS: Although overall intracranial vessel wall lesion burden and contrast enhancement were comparable between patients with recent posterior circulation ischemia and healthy controls, this study also revealed significant differences between the 2 groups, suggesting an association between posterior circulation lesion burden/enhancement and ischemic events. CLINICAL TRIAL REGISTRATION: URL: http://www.trialregister.nl. Unique identifier: NTR5688.

High-resolution intracranial vessel wall MRI in an elderly asymptomatic population: comparison of 3T and 7T.

OBJECTIVES: Several intracranial vessel wall sequences have been described in recent literature, with either 3-T or 7-T magnetic resonance imaging (MRI). In the current study, we compared 3-T and 7-T MRI in visualising both the intracranial arterial vessel wall and vessel wall lesions. METHODS: Twenty-one elderly asymptomatic volunteers were scanned by 3-T and 7-T MRI with an intracranial vessel wall sequence, both before and after contrast administration. Two raters scored image quality, and presence and characteristics of vessel wall lesions. RESULTS: Vessel wall visibility was equal or significantly better at 7 T for the studied arterial segments, even though there were more artefacts hampering assessment. The better visualisation of the vessel wall at 7 T was most prominent in the proximal anterior cerebral circulation and the posterior cerebral artery. In the studied elderly asymptomatic population, 48 vessel-wall lesions were identified at 3 T, of which 7 showed enhancement. At 7 T, 79 lesions were identified, of which 29 showed enhancement. Seventy-one percent of all 3-T lesions and 59 % of all 7-T lesions were also seen at the other field strength. CONCLUSIONS: Despite the large variability in detected lesions at both field strengths, we believe 7-T MRI has the highest potential to identify the total burden of intracranial vessel wall lesions. KEY POINTS: • Intracranial vessel wall visibility was equal or significantly better at 7-T MRI • Most vessel wall lesions in the cerebral arteries were found at 7-T MRI • Many intracranial vessel wall lesions showed enhancement after contrast administration • Large variability in detected intracranial vessel wall lesions at both field strengths • Seven-tesla MRI has the highest potential to identify total burden of intracranial atherosclerosis.

Magnetic Resonance Imaging of Plaque Morphology, Burden, and Distribution in Patients With Symptomatic Middle Cerebral Artery Stenosis.

BACKGROUND AND PURPOSE: Intracranial atherosclerosis is a major cause of ischemic stroke worldwide. Intracranial vessel wall imaging is an upcoming field of interest to assess intracranial atherosclerosis. In this study, we investigated total intracranial plaque burden in patients with symptomatic middle cerebral artery stenosis, assessed plaque morphological features, and compared features of symptomatic and asymptomatic lesions using a 3T vessel wall sequence. METHODS: Nineteen consecutive Chinese patients with ischemic stroke and transient ischemic attack (mean age: 67 years; 7 females) with a middle cerebral artery stenosis were scanned at 3T magnetic resonance imaging; the protocol included a time-of-flight magnetic resonance angiography and the T1-weighted volumetric isotropically reconstructed turbo spin echo acquisition sequence before and after (83%) contrast administration. Chi-square tests were used to assess associations between different plaque features. Statistical significance was set at P<0.05. RESULTS: Vessel wall lesions were identified in 18 patients (95%), totaling 57 lesions in 494 segments (12% of segments). Lesions were located primarily in the anterior circulation (82%). Eccentric lesions were associated with a focal thickening pattern and concentric lesions with a diffuse thickening pattern (P<0.001). When differentiating between asymptomatic and symptomatic lesions, an association (P<0.05) was found between eccentricity and asymptomatic lesions, but not for enhancement or a specific thickening pattern. Symptomatic lesions did not have any specific morphological features. CONCLUSIONS: Our results lead to a 2-fold conclusion: (1) The classification system of both thickening pattern and distribution of the lesion can be simplified by using distribution pattern only and (2) differentiation between symptomatic and asymptomatic atherosclerotic lesions was possible using intracranial vessel wall imaging.

Plaque components in symptomatic moderately stenosed carotid arteries related to cerebral infarcts: the plaque at RISK study.

BACKGROUND AND PURPOSE: Carotid plaque composition is a major determinant of cerebrovascular events. In the present analysis, we evaluated the relationship between intraplaque hemorrhage (IPH) and a thin/ruptured fibrous cap (TRFC) in moderately stenosed carotid arteries and cerebral infarcts on MRI in the ipsilateral hemisphere. METHODS: A total of 101 patients with a symptomatic 30% to 69% carotid artery stenosis underwent MRI of the carotid arteries and the brain, within a median time of 45 days from onset of symptoms. The presence of ipsilateral infarcts in patients with and without IPH and TRFC was evaluated. RESULTS: IPH was seen in 40 of 101 plaques. TRFC was seen in 49 of 86 plaques (postcontrast series were not obtained in 15 patients). In total, 51 infarcts in the flow territory of the symptomatic carotid artery were found in 47 patients. Twenty nine of these infarcts, found in 24 patients, were cortical infarcts. No significant relationship was found between IPH or TRFC and the presence of ipsilateral infarcts. CONCLUSIONS: MRI detected IPH and TRFC are not related to the presence of old and recent cortical and subcortical infarcts ipsilateral to a symptomatic carotid artery stenosis of 30% to 69%. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT01208025.

Distribution and natural course of intracranial vessel wall lesions in patients with ischemic stroke or TIA at 7.0 Tesla MRI.

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 T1-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.

Feasibility of high-resolution pituitary MRI at 7.0 tesla.

OBJECTIVES: Since the pituitary gland measures 3-8 mm, imaging with the highest possible spatial resolution is important for the detection of even smaller lesions such as those seen in Cushing's disease. In the current feasibility study, we tested a multi-sequence MRI protocol to visualize the pituitary gland in high resolution at 7.0 Tesla (7.0 T). METHODS: Ten healthy volunteers were examined with a 7.0 T pituitary gland protocol. The protocol consisted of a T1-weighted magnetization-prepared inversion recovery (MPIR) turbo spin-echo (TSE) sequence and a T2-weighted TSE sequence. Additionally, this protocol was tested in five patients with clinical and biochemical suspicion of a microadenoma. RESULTS: The dedicated protocol was successful in visualizing normal pituitary anatomy. At 7.0 T compared to 1.5 T, four times as many slices covered the pituitary gland in sagittal and coronal direction. In three patients, a lesion was diagnosed at 7.0 T, and was confirmed by histopathology to be a microadenoma. CONCLUSION: Head-to-head comparisons of 7.0 T with 1.5 T and 3.0 T are needed with larger samples of patients and with imaging times feasible for clinical settings. However, the current study suggests that high-resolution 7.0 T MRI of the pituitary gland may provide new perspectives when used as a second-line diagnostic examination in the specific context of Cushing's disease. KEY POINTS: • 7.0 T MRI enables ultra-high-resolution imaging of the pituitary gland. • 7.0 T MRI is appropriate to visualize normal pituitary gland anatomy. • The pituitary protocol consists of a T 1 -MPIR-TSE and a T 2 -TSE sequence. • In four patients, a suspected ACTH-producing microadenoma was visualized at 7.0 T. • Histopathology confirmed three of four lesions to be ACTH-producing microadenomas.

High resolution imaging of cerebral small vessel disease with 7 T MRI.

Small vessel disease (SVD) refers to all pathological processes that affect the small vessels of the brain. SVD is an important cause of acute stroke, but is also a leading cause of aging-related cognitive decline and dementia, due to more insidious brain parenchymal damage. The introduction of high field strength MRI (7 T) is likely to offer important new perspectives on the role of SVD in these disorders. In this overview we illustrate the opportunities that 7 T MRI offers in high resolution vascular imaging. In particular, we will show the capability of 7 T MRI to depict the small arteries and veins in the brain, the vascular wall of intracranial arteries, perivascular spaces, and microvascular parenchymal lesions, including microbleeds and microinfarcts.

Quantification of perineural satellitosis in pretreatment glioblastoma with structural MRI and a diffusion tensor imaging template.

Background: Survival outcomes for glioblastoma (GBM) patients remain unfavorable, and tumor recurrence is often observed. Understanding the radiological growth patterns of GBM could aid in improving outcomes. This study aimed to examine the relationship between contrast-enhancing tumor growth direction and white matter, using an image registration and deformation strategy. Methods: In GBM patients 2 pretreatment scans (diagnostic and neuronavigation) were gathered retrospectively, and coregistered to a template and diffusion tensor imaging (DTI) atlas. The GBM lesions were segmented and coregistered to the same space. Growth vectors were derived and divided into vector populations parallel (Φ = 0-20°) and perpendicular (Φ = 70-90°) to white matter. To test for statistical significance between parallel and perpendicular groups, a paired samples Student's t-test was performed. O6-methylguanine-DNA methyltransferase (MGMT) methylation status and its correlation to growth rate were also tested using a one-way ANOVA test. Results: For 78 GBM patients (mean age 61 years ±â€…13 SD, 32 men), the included GBM lesions showed a predominant preference for perineural satellitosis (P < .001), with a mean percentile growth of 30.8% (95% CI: 29.6-32.0%) parallel (0°â€…< |Φ| < 20°) to white matter. Perpendicular tumor growth with respect to white matter microstructure (70°â€…< |Φ| < 90°) showed to be 22.7% (95% CI: 21.3-24.1%) of total tumor growth direction. Conclusions: The presented strategy showed that tumor growth direction in pretreatment GBM patients correlated with white matter architecture. Future studies with patient-specific DTI data are required to verify the accuracy of this method prospectively to identify its usefulness as a clinical metric in pre and posttreatment settings.

Imaging of intracranial arterial disease: a comparison between MRI and unenhanced CT.

Background and purpose: Arterial calcifications on unenhanced CT scans and vessel wall lesions on MRI are often used interchangeably to portray intracranial arterial disease. However, the extent of pathology depicted with each technique is unclear. We investigated the presence and distribution of these two imaging findings in patients with a history of cerebrovascular disease. Materials and methods: We analyzed CT and MRI data from 78 patients admitted for stroke or TIA at our institution. Vessel wall lesions were assessed on 7 T MRI sequences, while arterial calcifications were assessed on CT scans. The number of vessel wall lesions, severity of intracranial internal carotid artery (iICA) calcifications, and overall presence and distribution of the two imaging findings were visually assessed in the intracranial arteries. Results: At least one vessel wall lesion or arterial calcification was assessed in 69 (88%) patients. Only the iICA and vertebral arteries (VA) showed a substantial number of both calcifications and vessel wall lesions. The other vessels showed almost exclusively vessel wall lesions. The number of vessel wall lesions was associated with the severity of iICA calcification (p = 0.013). Conclusions: The number of vessel wall lesions increases with the severity of iICA calcifications. Nonetheless, the distribution of vessel wall lesions on MRI and arterial calcifications on CT shows remarkable differences. These findings support the need for a combined approach to examine intracranial arterial disease.