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Advanced intraoperative MR images (ioMRI) acquired during the resection of pediatric brain tumors could offer additional physiological information to preserve healthy tissue. With this work, we aimed to develop a protocol for ioMRI with increased sensitivity for arterial spin labeling (ASL) and diffusion MRI (dMRI), optimized for patient positioning regularly used in the pediatric neurosurgery setting. For ethical reasons, ASL images were acquired in healthy adult subjects that were imaged in the prone and supine position. After this, the ASL cerebral blood flow (CBF) was quantified and compared between both positions. To evaluate the impact of the RF coils setups on image quality, we compared different setups (two vs. four RF coils) by looking at T1-weighted (T1w) signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), as well as undertaking a qualitative evaluation of T1w, T2w, ASL, and dMR images. Mean ASL CBF did not differ between the surgical prone and supine positions in any of the investigated regions of interest or the whole brain. T1w SNR (gray matter: p = 0.016, 34% increase; white matter: p = 0.016, 32% increase) and CNR were higher (p = 0.016) in the four versus two RF coils setups (18.0 ± 1.8 vs. 13.9 ± 1.8). Qualitative evaluation of T1w, T2w, ASL, and dMR images resulted in acceptable to good image quality and did not differ statistically significantly between setups. Only the nonweighted diffusion image maps and corticospinal tract reconstructions yielded higher image quality and reduced susceptibility artifacts with four RF coils. Advanced ioMRI metrics were more precise with four RF coils as the standard deviation decreased. Taken together, we have investigated the practical use of advanced ioMRI during pediatric neurosurgery. We conclude that ASL CBF quantification in the surgical prone position is valid and that ASL and dMRI acquisition with two RF coils can be performed adequately for clinical use. With four versus two RF coils, the SNR of the images increases, and the sensitivity to artifacts reduces.
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Imagen por Resonancia Magnética , Procedimientos Neuroquirúrgicos , Relación Señal-Ruido , Humanos , Masculino , Femenino , Imagen por Resonancia Magnética/métodos , Niño , Adulto , Circulación Cerebrovascular/fisiología , Marcadores de Spin , Imagen de Difusión por Resonancia Magnética , Encéfalo/diagnóstico por imagen , Encéfalo/cirugíaRESUMEN
The YOUth cohort study is a unique longitudinal study on brain development in the general population. As part of the YOUth study, 2000 children will be included at 8, 9 or 10 years of age and planned to return every three years during adolescence. Magnetic resonance imaging (MRI) brain scans are collected, including structural T1-weighted imaging, diffusion-weighted imaging (DWI), resting-state functional MRI and task-based functional MRI. Here, we provide a comprehensive report of the MR acquisition in YOUth Child & Adolescent including the test-retest reliability of brain measures derived from each type of scan. To measure test-retest reliability, 17 adults were scanned twice with a week between sessions using the full YOUth MRI protocol. Intraclass correlation coefficients were calculated to quantify reliability. Global brain measures derived from structural T1-weighted and DWI scans were reliable. Resting-state functional connectivity was moderately reliable, as well as functional brain measures for both the inhibition task (stop versus go) and the emotion task (face versus house). Our results complement previous studies by presenting reliability results of regional brain measures collected with different MRI modalities. YOUth facilitates data sharing and aims for reliable and high-quality data. Here we show that using the state-of-the art YOUth MRI protocol brain measures can be estimated reliably.
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Imagen por Resonancia Magnética/métodos , Reproducibilidad de los Resultados , Niño , Estudios de Cohortes , Femenino , Humanos , Estudios Longitudinales , MasculinoRESUMEN
BACKGROUND: Ultra-high-field magnetic resonance imaging (MRI) of the brain is attractive for image guidance during neurosurgery because of its high tissue contrast and detailed vessel visualization. However, high-field MRI is prone to distortion artifacts, which may compromise image guidance. Here we investigate intra- and extracranial distortions in 7-T MRI scans. METHODS: Five patients with and 5 patients without skin-adhesive fiducials received magnetization-prepared T1-weighted 7-T MRI and standard 3-T MRI scans. The 7- and 3-T images were rigidly coregistered and compared. Intracranial distortions were evaluated qualitatively, whereas shifts at the skin surface and shifts of the center positions of skin-adhesive fiducials were measured quantitatively. Moreover, we present an illustrative case of an ultra-high-field image-guided skull base meningioma resection. RESULTS: We found excellent intracranial correspondence between 3- and 7-T MRI scans. However, the average maximum skin shift was 6.8 ± 2.0 mm in group A and 5.2 ± 0.9 mm in group B. The average maximum difference between the skin-adhesive fiducial positions was 5.6 ± 3.1 mm in group B. In our tumor resection case, the meningioma blood supply could be targeted early thanks to 7-T image guidance, which made subsequent tumor removal straightforward. CONCLUSIONS: There are no visible intracranial distortions in magnetization-prepared T1-weighted 7-T MRI cranial images. However, we found considerable extracranial shifts. These shifts render 7-T images unreliable for patient-to-image registration. We recommend performing patient-to-image registration on a routine (computed tomography scan or 3-T magnetic resonance) image and subsequently fusing the 7-T magnetic resonance image with the routine image on the image guidance machine, until this issue is resolved.
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Imagen por Resonancia Magnética/métodos , Procedimientos Neuroquirúrgicos/métodos , Cirugía Asistida por Computador/métodos , Adhesivos , Adulto , Anciano , Anciano de 80 o más Años , Artefactos , Campos Electromagnéticos , Femenino , Humanos , Masculino , Meningioma/irrigación sanguínea , Meningioma/diagnóstico por imagen , Meningioma/cirugía , Fantasmas de Imagen , Reproducibilidad de los Resultados , Neoplasias de la Base del Cráneo/irrigación sanguínea , Neoplasias de la Base del Cráneo/diagnóstico por imagen , Neoplasias de la Base del Cráneo/cirugíaRESUMEN
Objective: The aim of this study is to determine whether the use of 7 tesla (T) MRI in clinical practice leads to higher detection rates of focal cortical dysplasias in possible candidates for epilepsy surgery. Methods: In our center patients are referred for 7 T MRI if lesional focal epilepsy is suspected, but no abnormalities are detected at one or more previous, sufficient-quality lower-field MRI scans, acquired with a dedicated epilepsy protocol, or when concealed pathology is suspected in combination with MR-visible mesiotemporal sclerosis-dual pathology. We assessed 40 epilepsy patients who underwent 7 T MRI for presurgical evaluation and whose scans (both 7 T and lower field) were discussed during multidisciplinary epilepsy surgery meetings that included a dedicated epilepsy neuroradiologist. We compared the conclusions of the multidisciplinary visual assessments of 7 T and lower-field MRI scans. Results: In our series of 40 patients, multidisciplinary evaluation of 7 T MRI identified additional lesions not seen on lower-field MRI in 9 patients (23%). These findings were guiding in surgical planning. So far, 6 patients underwent surgery, with histological confirmation of focal cortical dysplasia or mild malformation of cortical development. Significance: Seven T MRI improves detection of subtle focal cortical dysplasia and mild malformations of cortical development in patients with intractable epilepsy and may therefore contribute to identification of surgical candidates and complete resection of the epileptogenic lesion, and thus to postoperative seizure freedom.
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Measurement of Chemical Exchange Saturation Transfer (CEST) is providing tissue physiology dependent contrast, e.g. by looking at Amide and NOE (Nuclear Overhauser Enhancement) effects. CEST is unique in providing quantitative metabolite information at high imaging resolution. However, direct comparison of Amide and NOE effects between different tissues may result in wrong conclusions on the metabolite concentration due to the additional contributors to the observed CEST contrast, such as water content (WC) and water T1 relaxation (T1w). For instance, there are multiple contradictory reports in the literature on Amide and NOE effects in white matter (WM) and gray matter (GM) at 7T. This study shows that at 7T, tissue water T1 relaxation is a stronger contributor to CEST contrasts than WC. After water T1 correction, there was no difference in Amide effects between WM and GM, whereas WM/GM contrast was enhanced for NOE effects.
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Sustancia Gris/diagnóstico por imagen , Imagen por Resonancia Magnética , Sustancia Blanca/diagnóstico por imagen , Algoritmos , Amidas , Encéfalo/diagnóstico por imagen , HumanosRESUMEN
In this article we report the complete data obtained in-vivo for the paper: "Lines of Baillarger in vivo and ex-vivo: myelin contrast across lamina at 7T MRI and histology" (Fracasso et al., 2015) [1]. Single participant data (4 participants) from the occipital lobe acquisition are reported for axial, coronal and sagittal slices; early visual area functional localization and laminar profiles are reported. Data from whole brain images are reported and described (5 participants), for axial, coronal and sagittal slices. Laminar profiles from occipital, parietal and frontal lobes are reported. The data reported in this manuscript complements the paper (Fracasso et al., 2015) [1] by providing the full set of results from the complete pool of participants, on a single-participant basis. Moreover, we provide histological images from the ex-vivo sample reported in Fracasso et al. (2015) [1].
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BACKGROUND: Pre-clinical detection of atherosclerosis enables personalized preventive strategies in asymptomatic individuals. Cardiovascular magnetic resonance (CMR) has evolved as an attractive imaging modality for studying atherosclerosis in vivo. Yet, the majority of aortic CMR studies and proposed sequences to date have been performed at 1.5 tesla using 2D BB techniques and a slice thickness of 4-5 mm. Here, we evaluate for the first time the reproducibility of an isotropic, T1-weighted, three-dimensional, black-blood, CMR VISTA sequence (3D-T1-BB-VISTA) for quantification of aortic wall characteristics in healthy, young adults. METHODS: In 20 healthy, young adults (10 males, mean age 31.3 years) of the AMBITYON cohort study the descending thoracic aorta was imaged with a 3.0 T MR system using the 3D-T1-BB-VISTA sequence. The inter-scan, inter-rater and intra-rater reproducibility of aortic lumen, total vessel and wall area and mean and maximum wall thickness was evaluated using Bland-Altman analyses and Intraclass Correlation Coefficients (ICC). Based on these findings, sample sizes for detecting differences in aortic wall characteristics between groups were calculated. RESULTS: For each studied parameter, the inter-scan, inter-rater and intra-rater reproducibility was excellent as indicated by narrow limits of agreement and high ICCs (ranging from 0.76 to 0.99). Sample sizes required to detect a 5% difference in aortic wall characteristics between two groups were 203, 126, 136, 68 and 153 per group for lumen area, total vessel area and vessel wall area and for mean and maximum vessel wall thickness, respectively. CONCLUSION: The 3D-T1-BB-VISTA sequence provides excellent reproducibility for quantification of aortic wall characteristics and can detect small differences between groups with reasonable sample sizes. Hence, it may be a valuable tool for assessment of the subtle vascular wall changes of early atherosclerosis in asymptomatic populations.
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Aorta Torácica/anatomía & histología , Aortografía/métodos , Ensayos Clínicos como Asunto/métodos , Angiografía por Resonancia Magnética , Tamaño de la Muestra , Adulto , Estudios Transversales , Femenino , Voluntarios Sanos , Humanos , Masculino , Variaciones Dependientes del Observador , Valor Predictivo de las Pruebas , Estudios Prospectivos , Reproducibilidad de los Resultados , Adulto JovenRESUMEN
The human cerebral cortex is characterized by a number of features that are not uniformly distributed, such as the presence of multiple cytoarchitectonic elements and of myelinated layers running tangentially to the cortex surface. The presence and absence of these features are the basis of the parcellation of the cerebral cortex in several areas. A number of areas show myelin increases localized within the cortex, e.g., the stria of Gennari located in layer IV of the primary visual cortex. Sub-millimeter MRI can resolve myelin variations across the human cortex and may allow in vivo parcellation of these brain areas. Here, we image within-area myelination. We modified a T1-weighted (T1-w) MPRAGE sequence to enhance myelin visualization within the cortex. First, we acquired images from an ex vivo sample, and compared MRI laminar profiles from calcarine (corresponding to primary visual cortex) and extra-calcarine areas with histology sections from the same locations. Laminar profiles between myelin stained sections and the T1-w images were similar both in calcarine as well as extra-calcarine cortex. In calcarine cortex, the profile reveals the stria of Gennari. In extra-calcarine cortex, a similar profile exists which we suggest corresponds to the lines of Baillarger. Next, we adapted the same sequence to image within-area myelination in vivo. Also in in vivo data, we discriminated similar laminar profiles in calcarine and extra-calcarine cortex, extending into parietal and frontal lobes. We argue that this myelin pattern outside the calcarine cortex represents the lines of Baillarger.
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Imagen de Difusión Tensora/métodos , Fibras Nerviosas Mielínicas/ultraestructura , Lóbulo Occipital/citología , Lóbulo Occipital/diagnóstico por imagen , Corteza Visual/citología , Corteza Visual/diagnóstico por imagen , Adulto , Cadáver , Femenino , Humanos , Masculino , Persona de Mediana Edad , Red Nerviosa/citología , Red Nerviosa/diagnóstico por imagen , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
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.
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Riñón/diagnóstico por imagen , Angiografía por Resonancia Magnética , Imagen por Resonancia Magnética , Animales , Humanos , Aumento de la Imagen/métodos , Riñón/patología , Nefronas/diagnóstico por imagen , Nefronas/patología , Oxígeno/sangre , Oxígeno/química , Reproducibilidad de los Resultados , Relación Señal-Ruido , Marcadores de SpinRESUMEN
OBJECTIVES: In this study, we propose a method to acquire high spatial-resolution T1ρ-maps, which allows bright and black-blood imaging, in a single breath-hold. To validate this innovative method, the reproducibility was tested in phantoms and volunteers. Lastly, the sensitivity and specificity for infarct detection was compared with the criterion standard late gadolinium enhancement (LGE). METHODS: T1ρ-mapping was performed using a T1ρ-prepared balanced steady-state free precession sequence at 1.5 T and 3 T. Five images with increasing spin-lock preparation times (spin-lock = 0, 10, 20, 30, 40 milliseconds, amplitude = 500 Hz) were acquired with an interval of 3 beats. Black-blood imaging was performed using a double inversion pulse sequence. The method was tested in 2 times 10 healthy volunteers at 1.5 and 3 T and in 9 myocardial infarction patients at 1.5 T. T1ρ-maps, and LGE images were scored for presence and extent of myocardial scarring. RESULTS: Phantom results show that the proposed T1ρ-mapping method gives accurate T1ρ-values. The mean T1ρ-relaxation time of the myocardium in healthy controls was 52.8 ± 1.8 milliseconds at 1.5 T and 46.4 ± 1.8 milliseconds at 3 T. In patients, the T1ρ of infarcted myocardium was (82.4 ± 5.2 milliseconds), and the T1ρ of remote myocardium was (54.2 ± 2.8 milliseconds; P < 0.0001). Sensitivity of infarct detection on a T1ρ-map was 70%, with a specificity of 94%, compared with LGE. CONCLUSIONS: In this study, we have investigated a method to acquire high spatial-resolution T1ρ-maps of the heart in a single breath-hold. This method proved to be reproducible and had high specificity compared with LGE and can thus be used for the endogenous detection of myocardial fibrosis in patients with ischemic cardiomyopathy.
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Contencion de la Respiración , Imagen por Resonancia Magnética/métodos , Infarto del Miocardio/diagnóstico por imagen , Infarto del Miocardio/patología , Miocardio/patología , Adulto , Femenino , Fibrosis , Gadolinio , Corazón/diagnóstico por imagen , Humanos , Aumento de la Imagen/métodos , Masculino , Fantasmas de Imagen , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
PURPOSE: Aortic vessel wall imaging requires large coverage and a high spatial resolution, which makes it prohibitively time-consuming for clinical use. This work explores the feasibility of imaging the descending aorta in acceptable scan time, using two-dimensional (2D) spatially selective excitation and a new way of inversion recovery for black blood imaging. METHODS: The excitation pattern and field of view in a 3D gradient echo sequence are reduced in two dimensions, following the aorta's anisotropic geometry. Black blood contrast is obtained by partially inverting the blood's magnetization in the heart at the start of the cardiac cycle. Imaging is delayed until the inverted blood has filled the desired part of the aorta. The flip angle and delay are determined such that the blood signal is nulled upon arrival in the aorta. RESULTS: Experiments on eight volunteers showed that the descending aortic vessel wall could be imaged over more than 15 cm at a maximal resolution of 1.5 × 1.5 × 1.5 mm(3) in less than 5 min minimal scan time. CONCLUSION: This feasibility study demonstrates that time-efficient isotropic imaging of the descending aorta is possible by using 2D spatially selective excitation for motion artifact reduction and a new way of inversion recovery for black blood imaging.
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Aorta/anatomía & histología , Aumento de la Imagen/métodos , Imagenología Tridimensional/métodos , Angiografía por Resonancia Magnética/métodos , Adulto , Anisotropía , Artefactos , Estudios de Factibilidad , Femenino , Voluntarios Sanos , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , MasculinoRESUMEN
The aim of this study was to assess the relation between location and type of intracranial atherosclerosis (ICAS) and cortical microinfarcts (CMIs) and macroinfarcts in 18 patients presenting with ischemic stroke (n = 12) or transient ischemic attack (TIA) (n = 6) using 7 tesla MR imaging. The protocol included: 3D T2-weighted FLAIR and 3D T1-weighted Magnetization-Preparation Inversion Recovery Turbo Spin Echo sequence. ICAS lesions and infarcts were scored by two raters. The relation between ICAS lesions, calculated ratios of ICAS lesion characteristics, location, and infarcts were examined using linear regression analyses. A total number of 75 ICAS lesions (all patients), 101 CMIs (78% of patients), and 31 macroinfarcts (67% of patients) were found. Seventy-six and sixty-five percent of the CMIs and macroinfarcts, respectively, were found in the same vascular territory as the ICAS lesions (p = 0.977, p = 0.167, respectively). A positive correlation existed between the number of macroinfarcts and CMIs (p < 0.05). In patients with macroinfarcts, we found more concentric (p < 0.01) and diffuse (p < 0.05) type of ICAS lesions. A high prevalence of brain tissue lesions, both macroinfarcts and CMIs, were found in patients with ICAS. Macroinfarcts were found to be related to specific ICAS lesion types. The type of ICAS lesion seems to be promising as a marker for ICAS patients at higher risk of future infarcts.
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Encéfalo/irrigación sanguínea , Encéfalo/diagnóstico por imagen , Infarto Cerebral/diagnóstico por imagen , Circulación Cerebrovascular/fisiología , Arteriosclerosis Intracraneal/diagnóstico por imagen , Angiografía por Resonancia Magnética/métodos , Adulto , Anciano , Anciano de 80 o más Años , Infarto Cerebral/etiología , Infarto Cerebral/fisiopatología , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Arteriosclerosis Intracraneal/complicaciones , Arteriosclerosis Intracraneal/fisiopatología , Masculino , Persona de Mediana Edad , Estudios ProspectivosRESUMEN
BACKGROUND: Patients with sickle cell anemia (SCA) are at a high risk to develop cerebral damage. Most common are silent cerebral infarctions (SCIs), visible as white matter hyperintensities (WMHs) on MRI in a patient without neurological deficits. The etiology of SCIs remains largely unclear. In addition, patients are at an increased risk for overt stroke, which is associated with large vessel disease. This classification based on the presence or absence of neurological deficits may not be the most fitting for research purposes, as it does not match the different underlying pathology. A classification based on imaging findings may therefore be a more straightforward approach for research purposes. We explored the feasibility to identify imaging features of SCIs in young, asymptomatic patients with SCA using ultra high-field 7 Tesla (7T) MRI. 7T MRI has a high resolution, which offers a unique chance to investigate small subclinical brain lesions in detail. To explore the superiority of 7T in identifying imaging abnormalities, we compared our results with 3T MRI. METHODS: Ten young, neurologically asymptomatic patients with SCA underwent 7T and 3T MRI; 10 healthy, age-matched controls underwent 7T MRI. We used existing neuroimaging standards to classify the brain lesions. We scored 7T and 3T scans separately, blinded for all other results. RESULTS: Using 7T MRI, we identified more patients with intracerebral lesions (9/10 vs. 5/10), a higher total count of WMHs (203 vs. 190, p = 0.016) and more lacunes (5 vs. 4) compared to 3T MRI. Abnormalities seen on 7T, which could not be identified on 3T, were cortical hyperintensities (in 3/10) and a different aspect of irregular WMHs, closely associated with cortical hyperintensities in a patient with large vessel stenosis. In 7 controls, a total of 13 WMHs were present. CONCLUSION: Using 7T MRI, we identified more intracerebral lesions compared to 3T, and found several abnormalities not visible on 3T. 7T MRI in SCA seems of particular interest to study the cortical involvement and the relation between WMHs and the cortex. We found some imaging features that are thought to be representative for small vessel disease, including WMHs, lacunes and prominent perivascular spaces; to understand whether small vessel disease plays a role in SCA requires further research.
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Anemia de Células Falciformes/patología , Encéfalo/patología , Imagen por Resonancia Magnética , Neuroimagen , Adolescente , Adulto , Anemia de Células Falciformes/diagnóstico , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Neuroimagen/métodos , Accidente Cerebrovascular/patología , Adulto JovenRESUMEN
OBJECTIVE: The implementation of 7T magnetic resonance imaging for human use has the potential to further advance spatial resolution beyond that of 3T. This could result in potential advantages in the depiction of the membranous structures of the inner ear. The inner ear is particularly challenging to visualize at 7T because of its anatomic location, which can lead to susceptibility banding artifacts and signal loss. STUDY DESIGN: Three healthy volunteers underwent magnetic resonance imaging at 3T and 7T scanner. At 7T, a unilateral dielectric pad was used for image optimization. Scan duration therefore doubled to a total of 15 minutes at 7T. METHODS: The depiction of 10 anatomic parts of the inner ear was evaluated by two independent readers using a four-point grading scale. RESULTS: The interscalar septum, utricular macula, and the nerve bundles in the internal auditory canal were visualized more clearly at 7T. CONCLUSION: Although reduction of image artifacts remains challenging, especially at 7T, all structures depicted at 3T could be depicted at 7T. Image quality for some anatomic structures was superior at 7T. Further improvement of image quality could be achieved by developing dedicated surface coils and by technical advancement in B1 shimming and dedicated radiofrequency pulses.
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Oído Interno/anatomía & histología , Imagen por Resonancia Magnética/métodos , Adulto , Artefactos , Humanos , Procesamiento de Imagen Asistido por ComputadorRESUMEN
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.
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Arterias Cerebrales/patología , Ataque Isquémico Transitorio/patología , Imagen por Resonancia Magnética/métodos , Accidente Cerebrovascular/patología , Adulto , Anciano , Anciano de 80 o más Años , Circulación Cerebrovascular , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Arteria Cerebral Media/patologíaRESUMEN
OBJECTIVES: Fluid-attenuated inversion recovery (FLAIR) imaging is an important clinical 'work horse' for brain MRI and has proven to facilitate imaging of both intracortical lesions as well as cortical layers at 7T MRI. A prominent observation on 7T FLAIR images is a hyperintense rim at the cortical surface and around the ventricles. We aimed to clarify the anatomical correlates and underlying contrast mechanisms of this hyperintense rim. MATERIALS AND METHODS: Two experiments with post-mortem human brain tissue were performed. FLAIR and T2-weighted images were obtained at typical in vivo (0.8mm isotropic) and high resolution (0.25mm isotropic). At one location the cortical surface was partly removed, and scanned again. Imaging was followed by histological and immunohistochemical analysis. Additionally, several simulations were performed to evaluate the potential contribution from an artifact due to water diffusion. RESULTS: The hyperintense rim corresponded to the outer - glia rich - layer of the cortex and disappeared upon removal of that layer. At the ventricles, the rim corresponded to the ependymal layer, and was not present at white matter/fluid borders at an artificial cut. The simulations supported the hypothesis that the hyperintense rim reflects the tissue properties in the outer cortical layers (or ependymal layer for the ventricles), and is not merely an artifact, although not all observations were explained by the simulated model of the contrast mechanism. CONCLUSIONS: 7T FLAIR seems to amplify the signal from layers I-III of the cortex and the ependyma around the ventricles. Although diffusion of water from layer I into CSF does contribute to this effect, a long T2 relaxation time constant in layer I, and probably also layer II-III, is most likely the major contributor, since the rim disappears upon removal of that layer. This knowledge can help the interpretation of imaging results in cortical development and in patients with cortical pathology.
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Corteza Cerebral/anatomía & histología , Epéndimo/anatomía & histología , Imagen por Resonancia Magnética/métodos , Artefactos , Cadáver , Ventrículos Cerebrales/anatomía & histología , Simulación por Computador , Humanos , Procesamiento de Imagen Asistido por Computador , Inmunohistoquímica , Neuroglía/fisiología , Cambios Post MortemRESUMEN
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 T(1ρ) 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 T(1ρ)-mapping. In this study we aimed to translate and validate T(1ρ)-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 T(1ρ)-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 T(1ρ)-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 T(1ρ)-map was calculated. The resulting T(1ρ)-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 T(1ρ) relaxation time was found in the infarct region (61 ± 11 ms), compared to healthy remote myocardium (36 ± 4 ms) . In patients a higher T(1ρ) 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 T(1ρ)-maps was 74%. CONCLUSION: We have shown the feasibility of native T(1ρ)-mapping for detection of infarct area in patients with a chronic myocardial infarction. In the near future, improvements on the T(1ρ)-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.
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Imagen por Resonancia Magnética/métodos , Infarto del Miocardio/diagnóstico , Miocardio/patología , Adulto , Animales , Estudios de Casos y Controles , Medios de Contraste , Modelos Animales de Enfermedad , Estudios de Factibilidad , Femenino , Fibrosis , Humanos , Masculino , Persona de Mediana Edad , Infarto del Miocardio/patología , Infarto del Miocardio/fisiopatología , Compuestos Organometálicos , Valor Predictivo de las Pruebas , Reproducibilidad de los Resultados , Volumen Sistólico , Porcinos , Función Ventricular Izquierda , Adulto JovenRESUMEN
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.
Asunto(s)
Aneurisma Intracraneal/patología , Imagen por Resonancia Magnética/métodos , Neuroimagen/métodos , Adulto , Femenino , Humanos , Interpretación de Imagen Asistida por Computador , Masculino , Persona de Mediana Edad , Estudios ProspectivosRESUMEN
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.
Asunto(s)
Imagen por Resonancia Magnética/métodos , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/diagnóstico , Imagen de Cuerpo Entero/métodos , Adulto , Estudios de Factibilidad , Femenino , Voluntarios Sanos , Humanos , Masculino , Estudios Prospectivos , Reproducibilidad de los Resultados , Adulto JovenRESUMEN
HYPOTHESIS: The implementation of 7.0 Tesla magnetic resonance imaging (MRI) for human use has the potential to further advance spatial resolution beyond that of 1.5T and 3T. This could result in potential advantages in the depiction of the membranous structures of the inner ear. BACKGROUND: The inner ear is particularly challenging to visualize at 7T. Where the signal-to-noise ratio will scale linear with the field strength, the proximity of the inner ear to the cerebrospinal fluid, nerves, and bone can lead to susceptibility banding artifacts and signal loss at the interface between the inner ear and its surroundings. METHODS: A human head specimen as well as 2 healthy volunteers underwent MRI at a 7 Tesla scanner. First aim was to scan with ultrahigh resolution, independent of scan duration. Second aim was to reduce scan duration. The final step was to develop a scanning protocol suitable for clinical practice, based on previous information from ex vivo imaging. RESULTS: Both in and ex vivo, large objects like the cochlear basal turn, vestibule, and semicircular canals were visualized clearly. The nerves were depicted in more detail in vivo. The interscalar septum was visible in all images. A prolonged acquisition time ex vivo showed more detail of the scala tympani and vestibuli. However, the scala media was never visible, even with maximal resolution. CONCLUSION: Although inhomogeneities remain present, maximum resolution scanning ex vivo as well as scanning in vivo at 7T MRI resulted in clear depiction of the major membranous structures of the inner ear.