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OBJECTIVE: Repetitive head trauma is common in high-contact sports. Cerebral blood flow (CBF) can measure changes in brain perfusion that could indicate injury. Longitudinal studies with a control group are necessary to account for interindividual and developmental effects. We investigated whether exposure to head impacts causes longitudinal CBF changes. METHODS: We prospectively studied 63 American football (high-contact cohort) and 34 volleyball (low-contact controls) male collegiate athletes, tracking CBF using 3D pseudocontinuous arterial spin labeling magnetic resonance imaging for up to 4 years. Regional relative CBF (rCBF, normalized to cerebellar CBF) was computed after co-registering to T1-weighted images. A linear mixed effects model assessed the relationship of rCBF to sport, time, and their interaction. Within football players, we modeled rCBF against position-based head impact risk and baseline Standardized Concussion Assessment Tool score. Additionally, we evaluated early (1-5 days) and delayed (3-6 months) post-concussion rCBF changes (in-study concussion). RESULTS: Supratentorial gray matter rCBF declined in football compared with volleyball (sport-time interaction p = 0.012), with a strong effect in the parietal lobe (p = 0.002). Football players with higher position-based impact-risk had lower occipital rCBF over time (interaction p = 0.005), whereas players with lower baseline Standardized Concussion Assessment Tool score (worse performance) had relatively decreased rCBF in the cingulate-insula over time (interaction effect p = 0.007). Both cohorts showed a left-right rCBF asymmetry that decreased over time. Football players with an in-study concussion showed an early increase in occipital lobe rCBF (p = 0.0166). INTERPRETATION: These results suggest head impacts may result in an early increase in rCBF, but cumulatively a long-term decrease in rCBF. ANN NEUROL 2023;94:457-469.
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Concussão Encefálica , Futebol Americano , Humanos , Masculino , Concussão Encefálica/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Futebol Americano/lesões , Imageamento por Ressonância Magnética , Circulação Cerebrovascular/fisiologiaRESUMO
Cerebral blood flow (CBF) is an important hemodynamic parameter to evaluate brain health. It can be obtained quantitatively using medical imaging modalities such as magnetic resonance imaging and positron emission tomography (PET). Although CBF in adults has been widely studied and linked with cerebrovascular and neurodegenerative diseases, CBF data in healthy children are sparse due to the challenges in pediatric neuroimaging. An understanding of the factors affecting pediatric CBF and its normal range is crucial to determine the optimal CBF measuring techniques in pediatric neuroradiology. This review focuses on pediatric CBF studies using neuroimaging techniques in 32 articles including 2668 normal subjects ranging from birth to 18 years old. A systematic literature search was conducted in PubMed, Embase, and Scopus and reported following the preferred reporting items for systematic reviews and meta-analyses (PRISMA). We identified factors (such as age, gender, mood, sedation, and fitness) that have significant effects on pediatric CBF quantification. We also investigated factors influencing the CBF measurements in infants. Based on this review, we recommend best practices to improve CBF measurements in pediatric neuroimaging. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 2.
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Imageamento por Ressonância Magnética , Neuroimagem , Adulto , Lactente , Humanos , Criança , Neuroimagem/métodos , Imageamento por Ressonância Magnética/métodos , Tomografia por Emissão de Pósitrons/métodos , Encéfalo/diagnóstico por imagem , Circulação Cerebrovascular/fisiologia , Marcadores de SpinRESUMO
OBJECTIVES: Treatment and outcomes of acute stroke have been revolutionised by mechanical thrombectomy. Deep learning has shown great promise in diagnostics but applications in video and interventional radiology lag behind. We aimed to develop a model that takes as input digital subtraction angiography (DSA) videos and classifies the video according to (1) the presence of large vessel occlusion (LVO), (2) the location of the occlusion, and (3) the efficacy of reperfusion. METHODS: All patients who underwent DSA for anterior circulation acute ischaemic stroke between 2012 and 2019 were included. Consecutive normal studies were included to balance classes. An external validation (EV) dataset was collected from another institution. The trained model was also used on DSA videos post mechanical thrombectomy to assess thrombectomy efficacy. RESULTS: In total, 1024 videos comprising 287 patients were included (44 for EV). Occlusion identification was achieved with 100% sensitivity and 91.67% specificity (EV 91.30% and 81.82%). Accuracy of location classification was 71% for ICA, 84% for M1, and 78% for M2 occlusions (EV 73, 25, and 50%). For post-thrombectomy DSA (n = 194), the model identified successful reperfusion with 100%, 88%, and 35% for ICA, M1, and M2 occlusion (EV 89, 88, and 60%). The model could also perform classification of post-intervention videos as mTICI < 3 with an AUC of 0.71. CONCLUSIONS: Our model can successfully identify normal DSA studies from those with LVO and classify thrombectomy outcome and solve a clinical radiology problem with two temporal elements (dynamic video and pre and post intervention). KEY POINTS: ⢠DEEP MOVEMENT represents a novel application of a model applied to acute stroke imaging to handle two types of temporal complexity, dynamic video and pre and post intervention. ⢠The model takes as an input digital subtraction angiograms of the anterior cerebral circulation and classifies according to (1) the presence or absence of large vessel occlusion, (2) the location of the occlusion, and (3) the efficacy of thrombectomy. ⢠Potential clinical utility lies in providing decision support via rapid interpretation (pre thrombectomy) and automated objective gradation of thrombectomy outcomes (post thrombectomy).
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Isquemia Encefálica , Aprendizado Profundo , Procedimentos Endovasculares , Acidente Vascular Cerebral , Humanos , Acidente Vascular Cerebral/diagnóstico por imagem , Acidente Vascular Cerebral/cirurgia , Filmes Cinematográficos , Estudos Retrospectivos , Trombectomia/métodos , Resultado do Tratamento , Procedimentos Endovasculares/métodosRESUMO
PURPOSE: 3D multi-echo gradient-recalled echo (ME-GRE) can simultaneously generate time-of-flight magnetic resonance angiography (pTOF) in addition to T2*-based susceptibility-weighted images (SWI). We assessed the clinical performance of pTOF generated from a 3D ME-GRE acquisition compared with conventional TOF-MRA (cTOF). METHODS: Eighty consecutive children were retrospectively identified who obtained 3D ME-GRE alongside cTOF. Two blinded readers independently assessed pTOF derived from 3D ME-GRE and compared them with cTOF. A 5-point Likert scale was used to rank lesion conspicuity and to assess for diagnostic confidence. RESULTS: Across 80 pediatric neurovascular pathologies, a similar number of lesions were reported on pTOF and cTOF (43-40%, respectively, p > 0.05). Rating of lesion conspicuity was higher with cTOF (4.5 ± 1.0) as compared with pTOF (4.0 ± 0.7), but this was not significantly different (p = 0.06). Diagnostic confidence was rated higher with cTOF (4.8 ± 0.5) than that of pTOF (3.7 ± 0.6; p < 0.001). Overall, the inter-rater agreement between two readers for lesion count on pTOF was classified as almost perfect (κ = 0.98, 96% CI 0.8-1.0). CONCLUSIONS: In this study, TOF-MRA simultaneously generated in addition to SWI from 3D MR-GRE can serve as a diagnostic adjunct, particularly for proximal vessel disease and when conventional TOF-MRA images are absent.
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Transtornos Cerebrovasculares , Angiografia por Ressonância Magnética , Imageamento por Ressonância Magnética , Transtornos Cerebrovasculares/diagnóstico por imagem , Criança , Humanos , Estudos RetrospectivosRESUMO
Background Iron oxide nanoparticles are an alternative contrast agent for MRI. Gadolinium deposition has raised safety concerns, but it is unknown whether ferumoxytol administration also deposits in the brain. Purpose To investigate whether there are signal intensity changes in the brain at multiecho gradient imaging following ferumoxytol exposure in children and young adults. Materials and Methods This retrospective case-control study included children and young adults, matched for age and sex, with brain arteriovenous malformations who received at least one dose of ferumoxytol from January 2014 to January 2018. In participants who underwent at least two brain MRI examinations (subgroup), the first and last available examinations were analyzed. Regions of interests were placed around deep gray structures on quantitative susceptibility mapping and R2* images. Mean susceptibility and R2* values of regions of interests were recorded. Measurements were assessed by linear regression analyses: a between-group comparison of ferumoxytol-exposed and unexposed participants and a within-group (subgroup) comparison before and after exposure. Results Seventeen participants (mean age ± standard deviation, 13 years ± 5; nine male) were in the ferumoxytol-exposed (case) group, 21 (mean age, 14 years ± 5; 11 male) were in the control group, and nine (mean age, 12 years ± 6; four male) were in the subgroup. The mean number of ferumoxytol administrations was 2 ± 1 (range, one to four). Mean susceptibility (in parts per million [ppm]) and R2* (in inverse seconds [sec-1]) values of the dentate (case participants: 0.06 ppm ± 0.04 and 23.87 sec-1 ± 4.13; control participants: 0.02 ppm ± 0.03 and 21.7 sec-1 ± 5.26), substantia nigrae (case participants: 0.08 ppm ± 0.06 and 27.46 sec-1 ± 5.58; control participants: 0.04 ppm ± 0.05 and 24.96 sec-1 ± 5.3), globus pallidi (case participants: 0.14 ppm ± 0.05 and 30.75 sec-1 ± 5.14; control participants: 0.08 ppm ± 0.07 and 28.82 sec-1 ± 6.62), putamina (case participants: 0.03 ppm ± 0.02 and 20.63 sec-1 ± 2.44; control participants: 0.02 ppm ± 0.02 and 19.65 sec-1 ± 3.6), caudate (case participants: -0.1 ppm ± 0.04 and 18.21 sec-1 ± 3.1; control participants: -0.06 ppm ± 0.05 and 18.83 sec-1 ± 3.32), and thalami (case participants: 0 ppm ± 0.03 and 16.49 sec-1 ± 3.6; control participants: 0.02 ppm ± 0.02 and 18.38 sec-1 ± 2.09) did not differ between groups (susceptibility, P = .21; R2*, P = .24). For the subgroup, the mean interval between the first and last ferumoxytol administration was 14 months ± 8 (range, 1-25 months). Mean susceptibility and R2* values of the dentate (first MRI: 0.06 ppm ± 0.05 and 25.78 sec-1 ± 5.9; last MRI: 0.06 ppm ± 0.02 and 25.55 sec-1 ± 4.71), substantia nigrae (first MRI: 0.06 ppm ± 0.06 and 28.26 sec-1 ± 9.56; last MRI: 0.07 ppm ± 0.06 and 25.65 sec-1 ± 6.37), globus pallidi (first MRI: 0.13 ppm ± 0.07 and 27.53 sec-1 ± 8.88; last MRI: 0.14 ppm ± 0.06 and 29.78 sec-1 ± 6.54), putamina (first MRI: 0.03 ppm ± 0.03 and 19.78 sec-1 ± 3.51; last MRI: 0.03 ppm ± 0.02 and 19.73 sec-1 ± 3.01), caudate (first MRI: -0.09 ppm ± 0.05 and 21.38 sec-1 ± 4.72; last MRI: -0.1 ppm ± 0.05 and 18.75 sec-1 ± 2.68), and thalami (first MRI: 0.01 ppm ± 0.02 and 17.65 sec-1 ± 5.16; last MRI: 0 ppm ± 0.02 and 15.32 sec-1 ± 2.49) did not differ between the first and last MRI examinations (susceptibility, P = .95; R2*, P = .54). Conclusion No overall significant differences were found in susceptibility and R2* values of deep gray structures to suggest retained iron in the brain between ferumoxytol-exposed and unexposed children and young adults with arteriovenous malformations and in those exposed to ferumoxytol over time. © RSNA, 2020.
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Malformações Arteriovenosas/diagnóstico por imagem , Encéfalo/metabolismo , Meios de Contraste/administração & dosagem , Óxido Ferroso-Férrico/administração & dosagem , Ferro/metabolismo , Imageamento por Ressonância Magnética/métodos , Adolescente , Estudos de Casos e Controles , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Estudos Retrospectivos , Adulto JovemRESUMO
BACKGROUND: To maintain cerebral blood flow (CBF), cerebral blood vessels dilate and contract in response to blood supply through cerebrovascular reactivity (CR). PURPOSE: Cardiovascular (CV) disease is associated with increased stroke risk, but which risk factors specifically impact CR is unknown. STUDY TYPE: Prospective longitudinal. SUBJECTS: Fifty-three subjects undergoing carotid endarterectomy or stenting. FIELD STRENGTH/SEQUENCE: 3T, 3D pseudo-continuous arterial spin labeling (PCASL) ASL, and T1 3D fast spoiled gradient echo (FSPGR). ASSESSMENT: We evaluated group differences in CBF changes for multiple cardiovascular risk factors in patients undergoing carotid revascularization surgery. STATISTICAL TESTS: PRE (baseline), POST (48-hour postop), and 6MO (6 months postop) whole-brain CBF measurements, as 129 CBF maps from 53 subjects were modeled as within-subject analysis of variance (ANOVA). To identify CV risk factors associated with CBF change, the CBF change from PRE to POST, POST to 6MO, and PRE to 6MO were modeled as multiple linear regression with each CV risk factor as an independent variable. Statistical models were performed controlling for age on a voxel-by-voxel basis using SPM8. Significant clusters were reported if familywise error (FWE)-corrected cluster-level was P < 0.05, while the voxel-level significance threshold was set for P < 0.001. RESULTS: The entire group showed significant (cluster-level P < 0.001) CBF increase from PRE to POST, decrease from POST to 6MO, and no significant difference (all voxels with P > 0.001) from PRE to 6MO. Of multiple CV risk factors evaluated, only elevated systolic blood pressure (SBP, P = 0.001), chronic renal insufficiency (CRI, P = 0.026), and history of prior stroke (CVA, P < 0.001) predicted lower increases in CBF PRE to POST. Over POST to 6MO, obesity predicted lower (P > 0.001) and cholesterol greater CBF decrease (P > 0.001). DATA CONCLUSION: The CV risk factors of higher SBP, CRI, CVA, BMI, and cholesterol may indicate altered CR, and may warrant different stroke risk mitigation and special consideration for CBF change evaluation. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2020;51:734-747.
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Doenças Cardiovasculares , Encéfalo , Doenças Cardiovasculares/diagnóstico por imagem , Circulação Cerebrovascular , Fatores de Risco de Doenças Cardíacas , Humanos , Imageamento por Ressonância Magnética , Estudos Prospectivos , Fatores de Risco , Marcadores de SpinRESUMO
PURPOSE: Amplified magnetic resonance imaging (aMRI) was recently introduced as a new brain motion detection and visualization method. The original aMRI approach used a video-processing algorithm, Eulerian video magnification (EVM), to amplify cardio-ballistic motion in retrospectively cardiac-gated MRI data. Here, we strive to improve aMRI by incorporating a phase-based motion amplification algorithm. METHODS: Phase-based aMRI was developed and tested for correct implementation and ability to amplify sub-voxel motions using digital phantom simulations. The image quality of phase-based aMRI was compared with EVM-based aMRI in healthy volunteers at 3T, and its amplified motion characteristics were compared with phase-contrast MRI. Data were also acquired on a patient with Chiari I malformation, and qualitative displacement maps were produced using free form deformation (FFD) of the aMRI output. RESULTS: Phantom simulations showed that phase-based aMRI has a linear dependence of amplified displacement on true displacement. Amplification was independent of temporal frequency, varying phantom intensity, Rician noise, and partial volume effect. Phase-based aMRI supported larger amplification factors than EVM-based aMRI and was less sensitive to noise and artifacts. Abnormal biomechanics were seen on FFD maps of the Chiari I malformation patient. CONCLUSION: Phase-based aMRI might be used in the future for quantitative analysis of minute changes in brain motion and may reveal subtle physiological variations of the brain as a result of pathology using processing of the fundamental harmonic or by selectively varying temporal harmonics. Preliminary data shows the potential of phase-based aMRI to qualitatively assess abnormal biomechanics in Chiari I malformation.
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Malformação de Arnold-Chiari/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Imageamento por Ressonância Magnética , Adulto , Algoritmos , Ataxia Cerebelar/diagnóstico por imagem , Pré-Escolar , Simulação por Computador , Feminino , Forame Magno/diagnóstico por imagem , Voluntários Saudáveis , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Processamento de Imagem Assistida por Computador/métodos , Masculino , Movimento , Imagens de Fantasmas , Gravação em VídeoRESUMO
While brain connectivity analyses have been demonstrated to identify ill patients for a number of diseases, their ability to predict cognitive impairment after brain injury is not well established. Traditional post brain injury models, such as stroke, are limited for this evaluation because pre-injury brain connectivity patterns are infrequently available. Patients with severe carotid stenosis, in contrast, often undergo non-emergent revascularization surgery, allowing the collection of pre and post-operative imaging, may experience brain insult due to perioperative thrombotic/embolic infarcts or hypoperfusion, and can suffer post-operative cognitive decline. We hypothesized that a distributed function such as memory would be more resilient in patients with brains demonstrating higher degrees of modularity. To test this hypothesis, we analyzed preoperative structural connectivity graphs (using T1 and DWI MRI) for 34 patients that underwent carotid intervention, and evaluated differences in graph metrics using the Brain Connectivity Toolbox. We found that patients with lower binary component number, binary community number and weighted community number prior to surgery were at greater risk for developing cognitive decline. These findings highlight the promise of brain connectivity analyses to predict cognitive decline following brain injury and serve as a clinical decision support tool. Hum Brain Mapp 37:2185-2194, 2016. © 2016 Wiley Periodicals, Inc.
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Encéfalo/diagnóstico por imagem , Estenose das Carótidas/diagnóstico por imagem , Estenose das Carótidas/cirurgia , Disfunção Cognitiva/diagnóstico por imagem , Complicações Pós-Operatórias/diagnóstico por imagem , Idoso , Estudos de Coortes , Humanos , Interpretação de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Testes de Estado Mental e Demência , Vias Neurais/diagnóstico por imagem , Testes Neuropsicológicos , RiscoRESUMO
PURPOSE: This work describes a new method called amplified MRI (aMRI), which uses Eulerian video magnification to amplify the subtle spatial variations in cardiac-gated brain MRI scans and enables better visualization of brain motion. METHODS: The aMRI method takes retrospective cardiac-gated cine MRI data as input, applies a spatial decomposition, followed by temporal filtering and frequency-selective amplification of the MRI cardiac-gated frames before synthesizing a motion-amplified cine data set. RESULTS: This approach reveals deformations of the brain parenchyma and displacements of arteries due to cardiac pulsatility, especially in the brainstem, cerebellum, and spinal cord. CONCLUSION: aMRI has the potential for widespread neuro- and non-neuro clinical use because it can amplify and characterize small, often barely perceptible motion and can visualize the biomechanical response of tissues using the heartbeat as an endogenous mechanical driver. Magn Reson Med 75:2245-2254, 2016. © 2016 Wiley Periodicals, Inc.
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Encéfalo/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Contração Miocárdica/fisiologia , Processamento de Sinais Assistido por Computador , Adulto , Algoritmos , Eletrocardiografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Movimento/fisiologia , Fotopletismografia , Gravação em VídeoRESUMO
BACKGROUND: Susceptibility-weighted imaging (SWI) in neuroimaging can be challenging due to long scan times of three-dimensional (3D) gradient recalled echo (GRE), while faster techniques such as 3D interleaved echo-planar imaging (iEPI) are prone to motion artifacts. Here we outline and implement a 3D short-axis propeller echo-planar imaging (SAP-EPI) trajectory as a faster, motion-correctable approach for SWI. METHODS: Experiments were conducted on a 3T MRI system. The 3D SAP-EPI, 3D iEPI, and 3D GRE SWI scans were acquired on two volunteers. Controlled motion experiments were conducted to test the motion-correction capability of 3D SAP-EPI. The 3D SAP-EPI SWI data were acquired on two pediatric patients as a potential alternative to 2D GRE used clinically. RESULTS: The 3D GRE images had a better target resolution (0.47 × 0.94 × 2 mm, scan time = 5 min), iEPI and SAP-EPI images (resolution = 0.94 × 0.94 × 2 mm) were acquired in a faster scan time (1:52 min) with twice the brain coverage. SAP-EPI showed motion-correction capability and some immunity to undersampling from rejected data. CONCLUSION: While 3D SAP-EPI suffers from some geometric distortion, its short scan time and motion-correction capability suggest that SAP-EPI may be a useful alternative to GRE and iEPI for use in SWI, particularly in uncooperative patients.
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Artefatos , Encéfalo/anatomia & histologia , Imagem de Difusão por Ressonância Magnética/métodos , Imagem Ecoplanar/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Adulto , Algoritmos , Humanos , Aumento da Imagem/métodos , Masculino , Movimento (Física) , Imagem Multimodal/métodos , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
PURPOSE: To investigate if delays in resting-state spontaneous fluctuations of the BOLD (sfBOLD) signal can be used to create maps similar to time-to-maximum of the residue function (Tmax) in Moyamoya patients and to determine whether sfBOLD delays affect the results of brain connectivity mapping. MATERIALS AND METHODS: Ten patients were scanned at 3 Tesla using a gradient-echo echo planar imaging sequence for sfBOLD imaging. Cross correlation analysis was performed between each brain voxel signal and a reference signal comprised of either the superior sagittal sinus (SSS) or whole brain (WB) average time course. sfBOLD delay maps were created based on the time shift necessary to maximize the correlation coefficient, and compared with dynamic susceptibility contrast Tmax maps. Standard and time-shifted resting-state BOLD connectivity analyses of the default mode network were compared. RESULTS: Good linear correlations were found between sfBOLD delays and Tmax using the SSS as reference (r(2) = 0.8, slope = 1.4, intercept = -4.6) or WB (r(2) = 0.7, slope = 0.8, intercept = -3.2). New nodes of connectivity were found in delayed regions when accounting for delays in the analysis. CONCLUSION: Resting-state sfBOLD imaging can create delay maps similar to Tmax maps without the use of contrast agents in Moyamoya patients. Accounting for these delays may affect the results of functional connectivity maps.
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Mapeamento Encefálico/métodos , Imageamento por Ressonância Magnética/métodos , Doença de Moyamoya/patologia , Adulto , Idoso , Meios de Contraste , Imagem Ecoplanar , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Masculino , Meglumina/análogos & derivados , Pessoa de Meia-Idade , Compostos Organometálicos , Estudos ProspectivosRESUMO
OBJECTIVE: Hydrocephalus is a challenging neurosurgical condition due to nonspecific symptoms and complex brain-fluid pressure dynamics. Typically, the assessment of hydrocephalus in children requires radiographic or invasive pressure monitoring. There is usually a qualitative focus on the ventricular spaces even though stress and shear forces extend across the brain. Here, the authors present an MRI-based vector approach for voxelwise brain and ventricular deformation visualization and analysis. METHODS: Twenty pediatric patients (mean age 7.7 years, range 6 months-18 years; 14 males) with acute, newly diagnosed hydrocephalus requiring surgical intervention for symptomatic relief were randomly identified after retrospective chart review. Selection criteria included acquisition of both pre- and posttherapy paired 3D T1-weighted volumetric MRI (3D T1-MRI) performed on 3T MRI systems. Both pre- and posttherapy 3D T1-MRI pairs were aligned using image registration, and subsequently, voxelwise nonlinear transformations were performed to derive two exemplary visualizations of compliance: 1) a whole-brain vector map projecting the resulting deformation field on baseline axial imaging; and 2) a 3D heat map projecting the volumetric changes along ventricular boundaries and the brain periphery. RESULTS: The patients underwent the following interventions for treatment of hydrocephalus: endoscopic third ventriculostomy (n = 6); external ventricular drain placement and/or tumor resection (n = 10); or ventriculoperitoneal shunt placement (n = 4). The mean time between pre- and postoperative imaging was 36.5 days. Following intervention, the ventricular volumes decreased significantly (mean pre- and posttherapy volumes of 151.9 cm3 and 82.0 cm3, respectively; p < 0.001, paired t-test). The largest degree of deformation vector changes occurred along the lateral ventricular spaces, relative to the genu and splenium. There was a significant correlation between change in deformation vector magnitudes within the cortical layer and age (p = 0.011, Pearson), as well as between the ventricle size and age (p = 0.014, Pearson), suggesting higher compliance among infants and younger children. CONCLUSIONS: This study highlights an approach for deformation analysis and vector mapping that may serve as a topographic visualizer for therapeutic interventions in patients with hydrocephalus. A future study that correlates the degree of cerebroventricular deformation or compliance with intracranial pressures could clarify the potential role of this technique in noninvasive pressure monitoring or in cases of noncompliant ventricles.
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BACKGROUND: Outlining acutely infarcted tissue on non-contrast CT is a challenging task for which human inter-reader agreement is limited. We explored two different methods for training a supervised deep learning algorithm: one that used a segmentation defined by majority vote among experts and another that trained randomly on separate individual expert segmentations. METHODS: The data set consisted of 260 non-contrast CT studies in 233 patients with acute ischemic stroke recruited from the multicenter DEFUSE 3 (Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3) trial. Additional external validation was performed using 33 patients with matched stroke onset times from the University Hospital Lausanne. A benchmark U-Net was trained on the reference annotations of three experienced neuroradiologists to segment ischemic brain tissue using majority vote and random expert sampling training schemes. The median of volume, overlap, and distance segmentation metrics were determined for agreement in lesion segmentations between (1) three experts, (2) the majority model and each expert, and (3) the random model and each expert. The two sided Wilcoxon signed rank test was used to compare performances (1) to 2) and (1) to (3). We further compared volumes with the 24 hour follow-up diffusion weighted imaging (DWI, final infarct core) and correlations with clinical outcome (modified Rankin Scale (mRS) at 90 days) with the Spearman method. RESULTS: The random model outperformed the inter-expert agreement ((1) to (2)) and the majority model ((1) to (3)) (dice 0.51±0.04 vs 0.36±0.05 (P<0.0001) vs 0.45±0.05 (P<0.0001)). The random model predicted volume correlated with clinical outcome (0.19, P<0.05), whereas the median expert volume and majority model volume did not. There was no significant difference when comparing the volume correlations between random model, median expert volume, and majority model to 24 hour follow-up DWI volume (P>0.05, n=51). CONCLUSION: The random model for ischemic injury delineation on non-contrast CT surpassed the inter-expert agreement ((1) to (2)) and the performance of the majority model ((1) to (3)). We showed that the random model volumetric measures of the model were consistent with 24 hour follow-up DWI.
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While multiple factors impact disease, artificial intelligence (AI) studies in medicine often use small, non-diverse patient cohorts due to data sharing and privacy issues. Federated learning (FL) has emerged as a solution, enabling training across hospitals without direct data sharing. Here, we present FL-PedBrain, an FL platform for pediatric posterior fossa brain tumors, and evaluate its performance on a diverse, realistic, multi-center cohort. Pediatric brain tumors were targeted due to the scarcity of such datasets, even in tertiary care hospitals. Our platform orchestrates federated training for joint tumor classification and segmentation across 19 international sites. FL-PedBrain exhibits less than a 1.5% decrease in classification and a 3% reduction in segmentation performance compared to centralized data training. FL boosts segmentation performance by 20 to 30% on three external, out-of-network sites. Finally, we explore the sources of data heterogeneity and examine FL robustness in real-world scenarios with data imbalances.
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Inteligência Artificial , Neoplasias Encefálicas , Humanos , Criança , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/patologia , Adolescente , Feminino , Masculino , Pré-Escolar , Disseminação de Informação/métodosRESUMO
Despite the global impact and advances in understanding the pathophysiology of cerebrovascular diseases, the term "stroke" is not consistently defined in clinical practice, in clinical research, or in assessments of the public health. The classic definition is mainly clinical and does not account for advances in science and technology. The Stroke Council of the American Heart Association/American Stroke Association convened a writing group to develop an expert consensus document for an updated definition of stroke for the 21st century. Central nervous system infarction is defined as brain, spinal cord, or retinal cell death attributable to ischemia, based on neuropathological, neuroimaging, and/or clinical evidence of permanent injury. Central nervous system infarction occurs over a clinical spectrum: Ischemic stroke specifically refers to central nervous system infarction accompanied by overt symptoms, while silent infarction by definition causes no known symptoms. Stroke also broadly includes intracerebral hemorrhage and subarachnoid hemorrhage. The updated definition of stroke incorporates clinical and tissue criteria and can be incorporated into practice, research, and assessments of the public health.
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Neurologia/história , Acidente Vascular Cerebral/história , Instituições Filantrópicas de Saúde/história , Instituições Filantrópicas de Saúde/normas , American Heart Association/história , História do Século XXI , Humanos , Acidente Vascular Cerebral/classificação , Acidente Vascular Cerebral/epidemiologia , Estados UnidosRESUMO
Functional MRI (fMRI) brain studies performed in the presence of a steady-state or "blood pool" contrast agent yields activation maps that are weighted for cerebral blood volume (CBV). Previous animal experiments suggest significant contrast-to-noise ratio (CNR) improvements, but these studies have not yet been performed in humans due to the lack of availability of a suitable agent. Here we report the use of the USPIO ferumoxytol (AMAG Pharmaceuticals, Inc., Cambridge, MA) for functional brain activation in humans, termed contrast enhanced functional blood volume imaging (CE-fBVI). Four subjects were scanned during a unilateral finger tapping task with standard blood-oxygen level dependent (BOLD) imaging before contrast and CE-fBVI after contrast injection. The CE-fBVI response showed both a fast (5.8±1.3 s) and a slow (75.3±27.5 s) component of CBV response to stimuli. A significant CNR gain of approximately 2-3 was found for CE-fBVI compared to BOLD fMRI. Interestingly, less susceptibility-related signal dropouts were observed in the inferior frontal and temporal lobes with CE-fBVI. The combination of higher CNR and better spatial specificity, enabled by CE-fBVI using blood pool USPIO contrast agent opens the door to higher resolution brain mapping.
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Determinação do Volume Sanguíneo/métodos , Mapeamento Encefálico/métodos , Encéfalo/fisiologia , Meios de Contraste , Óxido Ferroso-Férrico , Imageamento por Ressonância Magnética/métodos , Adulto , Volume Sanguíneo/fisiologia , Humanos , Interpretação de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Desempenho Psicomotor/fisiologia , Razão Sinal-Ruído , Adulto JovemRESUMO
In this study, a spin- and gradient-echo echo-planar imaging (SAGE EPI) MRI pulse sequence is presented that allows simultaneous measurements of gradient-echo and spin-echo dynamic susceptibility-contrast perfusion-weighted imaging data. Following signal excitation, five readout trains were acquired using spin- and gradient-echo echo-planar imaging, all of them with echo times of less than 100 ms. Contrast agent concentrations in brain tissue were determined based on absolute R2* and R(2) estimates rather than relative changes in the signals of individual echo trains, producing T(1)-independent dynamic susceptibility-contrast perfusion-weighted imaging data. Moreover, this acquisition technique enabled vessel size imaging through the simultaneous quantification of R2* and R(2), without an increase in acquisition time. In this work, the concepts of SAGE EPI pulse sequence and results in stroke and tumor imaging are presented. Overall, SAGE EPI combined the advantages of higher sensitivity to contrast agent passage of gradient-echo perfusion-weighted imaging with better microvascular selectivity of spin-echo perfusion-weighted imaging.
Assuntos
Algoritmos , Encéfalo/anatomia & histologia , Gadolínio DTPA , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Angiografia por Ressonância Magnética/métodos , Meios de Contraste , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Marcadores de SpinRESUMO
PURPOSE: To test the theory that velocity-selective arterial spin labeling (VSASL) is insensitive to transit delay. MATERIALS AND METHODS: Cerebral blood flow (CBF) was measured in ten Moyamoya disease patients using xenon computed tomography (xeCT) and magnetic resonance imaging (MRI), which included multiple pseudo-continuous ASL (pcASL) with different postlabel delays, VSASL, and dynamic susceptibility contrast (DSC) imaging. Correlation coefficient, root-mean-square difference, mean CBF error between ASL, and gold-standard xeCT CBF measurements as well the dependence of this error on transit delay (TD) as estimated by DSC time-to-peak of the residue function (Tmax) were determined. RESULTS: For pcASL with different postlabel delay time (PLD), CBF measurement with short PLD (1.5-2 sec) had the strongest correlations with xeCT; VSASL had a lower but still significant correlation with a mean coefficient of 0.55. We noted the theoretically predicted dependence of CBF error on Tmax and on PLD for pcASL; VSASL CBF measurements had the least dependence of the error on TD. We also noted effects suggesting that the location of the label decay (blood vs. tissue) impacted the measurement, which was worse for pcASL than for VSASL. CONCLUSION: We conclude that VSASL is less sensitive to TD than conventional ASL techniques and holds promise for CBF measurements in cerebrovascular diseases with slow flow.
Assuntos
Circulação Cerebrovascular , Angiografia por Ressonância Magnética/métodos , Doença de Moyamoya/patologia , Doença de Moyamoya/fisiopatologia , Tomografia Computadorizada por Raios X/métodos , Xenônio , Adulto , Velocidade do Fluxo Sanguíneo , Meios de Contraste , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Marcadores de SpinRESUMO
Between approximately 5,800 and 3,600 cal B.P. the biggest architectural monuments and largest settlements in the Western Hemisphere flourished in the Supe Valley and adjacent desert drainages of the arid Peruvian coast. Intensive net fishing, irrigated orchards, and fields of cotton with scant comestibles successfully sustained centuries of increasingly complex societies that did not use ceramics or loom-based weaving. This unique socioeconomic adaptation was abruptly abandoned and gradually replaced by societies more reliant on food crops, pottery, and weaving. Here, we review evidence and arguments for a severe cycle of natural disasters-earthquakes, El Niño flooding, beach ridge formation, and sand dune incursion-at approximately 3,800 B.P. and hypothesize that ensuing physical changes to marine and terrestrial environments contributed to the demise of early Supe settlements.
Assuntos
Economia , Meio Ambiente , Agricultura , Desastres , História Antiga , Humanos , Peru , Fatores SocioeconômicosRESUMO
Cerebrovascular reactivity (CVR), the capacity of the brain to increase cerebral blood flow (CBF) to meet changes in physiological demand, is an important biomarker to evaluate brain health. Typically, this brain "stress test" is performed by using a medical imaging modality to measure the CBF change between two states: at baseline and after vasodilation. However, since there are many imaging modalities and many ways to augment CBF, a wide range of CVR values have been reported. An understanding of CVR reproducibility is critical to determine the most reliable methods to measure CVR as a clinical biomarker. This review focuses on CVR reproducibility studies using neuroimaging techniques in 32 articles comprising 427 total subjects. The literature search was performed in PubMed, Embase, and Scopus. The review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We identified 5 factors of the experimental subjects (such as sex, blood characteristics, and smoking) and 9 factors of the measuring technique (such as the imaging modality, the type of the vasodilator, and the quantification method) that have strong effects on CVR reproducibility. Based on this review, we recommend several best practices to improve the reproducibility of CVR quantification in neuroimaging studies.