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1.
Nat Methods ; 20(12): 2048-2057, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-38012321

RESUMO

To increase granularity in human neuroimaging science, we designed and built a next-generation 7 Tesla magnetic resonance imaging scanner to reach ultra-high resolution by implementing several advances in hardware. To improve spatial encoding and increase the image signal-to-noise ratio, we developed a head-only asymmetric gradient coil (200 mT m-1, 900 T m-1s-1) with an additional third layer of windings. We integrated a 128-channel receiver system with 64- and 96-channel receiver coil arrays to boost signal in the cerebral cortex while reducing g-factor noise to enable higher accelerations. A 16-channel transmit system reduced power deposition and improved image uniformity. The scanner routinely performs functional imaging studies at 0.35-0.45 mm isotropic spatial resolution to reveal cortical layer functional activity, achieves high angular resolution in diffusion imaging and reduces acquisition time for both functional and structural imaging.


Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Humanos , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Imageamento por Ressonância Magnética/métodos , Cabeça , Neuroimagem , Razão Sinal-Ruído
2.
Plant Cell ; 35(7): 2527-2551, 2023 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-36976907

RESUMO

Fungi and oomycetes deliver effectors into living plant cells to suppress defenses and control plant processes needed for infection. Little is known about the mechanism by which these pathogens translocate effector proteins across the plasma membrane into the plant cytoplasm. The blast fungus Magnaporthe oryzae secretes cytoplasmic effectors into a specialized biotrophic interfacial complex (BIC) before translocation. Here, we show that cytoplasmic effectors within BICs are packaged into punctate membranous effector compartments that are occasionally observed in the host cytoplasm. Live cell imaging with fluorescently labeled proteins in rice (Oryza sativa) showed that these effector puncta colocalize with the plant plasma membrane and with CLATHRIN LIGHT CHAIN 1, a component of clathrin-mediated endocytosis (CME). Inhibiting CME using virus-induced gene silencing and chemical treatments resulted in cytoplasmic effectors in swollen BICs lacking effector puncta. By contrast, fluorescent marker colocalization, gene silencing, and chemical inhibitor studies failed to support a major role for clathrin-independent endocytosis in effector translocation. Effector localization patterns indicated that cytoplasmic effector translocation occurs underneath appressoria before invasive hyphal growth. Taken together, this study provides evidence that cytoplasmic effector translocation is mediated by CME in BICs and suggests a role for M. oryzae effectors in coopting plant endocytosis.


Assuntos
Ascomicetos , Magnaporthe , Oryza , Oryza/genética , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Ascomicetos/metabolismo , Doenças das Plantas/microbiologia
3.
MAGMA ; 37(2): 169-183, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38197908

RESUMO

OBJECTIVE: To assess the possible influence of third-order shim coils on the behavior of the gradient field and in gradient-magnet interactions at 7 T and above. MATERIALS AND METHODS: Gradient impulse response function measurements were performed at 5 sites spanning field strengths from 7 to 11.7 T, all of them sharing the same exact whole-body gradient coil design. Mechanical fixation and boundary conditions of the gradient coil were altered in several ways at one site to study the impact of mechanical coupling with the magnet on the field perturbations. Vibrations, power deposition in the He bath, and field dynamics were characterized at 11.7 T with the third-order shim coils connected and disconnected inside the Faraday cage. RESULTS: For the same whole-body gradient coil design, all measurements differed greatly based on the third-order shim coil configuration (connected or not). Vibrations and gradient transfer function peaks could be affected by a factor of 2 or more, depending on the resonances. Disconnecting the third-order shim coils at 11.7 T also suppressed almost completely power deposition peaks at some frequencies. DISCUSSION: Third-order shim coil configurations can have major impact in gradient-magnet interactions with consequences on potential hardware damage, magnet heating, and image quality going beyond EPI acquisitions.


Assuntos
Imageamento por Ressonância Magnética , Imãs , Imageamento por Ressonância Magnética/métodos
4.
Magn Reson Med ; 90(6): 2592-2607, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37582214

RESUMO

PURPOSE: A 128-channel receive-only array for brain imaging at 7 T was simulated, designed, constructed, and tested within a high-performance head gradient designed for high-resolution functional imaging. METHODS: The coil used a tight-fitting helmet geometry populated with 128 loop elements and preamplifiers to fit into a 39 cm diameter space inside a built-in gradient. The signal-to-noise ratio (SNR) and parallel imaging performance (1/g) were measured in vivo and simulated using electromagnetic modeling. The histogram of 1/g factors was analyzed to assess the range of performance. The array's performance was compared to the industry-standard 32-channel receive array and a 64-channel research array. RESULTS: It was possible to construct the 128-channel array with body noise-dominated loops producing an average noise correlation of 5.4%. Measurements showed increased sensitivity compared with the 32-channel and 64-channel array through a combination of higher intrinsic SNR and g-factor improvements. For unaccelerated imaging, the 128-channel array showed SNR gains of 17.6% and 9.3% compared to the 32-channel and 64-channel array, respectively, at the center of the brain and 42% and 18% higher SNR in the peripheral brain regions including the cortex. For R = 5 accelerated imaging, these gains were 44.2% and 24.3% at the brain center and 86.7% and 48.7% in the cortex. The 1/g-factor histograms show both an improved mean and a tighter distribution by increasing the channel count, with both effects becoming more pronounced at higher accelerations. CONCLUSION: The experimental results confirm that increasing the channel count to 128 channels is beneficial for 7T brain imaging, both for increasing SNR in peripheral brain regions and for accelerated imaging.


Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Imageamento por Ressonância Magnética/métodos , Encéfalo/diagnóstico por imagem , Razão Sinal-Ruído , Imagens de Fantasmas , Neuroimagem/métodos , Desenho de Equipamento
5.
Chem Res Toxicol ; 36(2): 202-212, 2023 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-36638203

RESUMO

This study examined the variation of benzo[a]pyrene (B[a]P), N'-nitrosonornicotine (NNN), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) levels in 16 smokeless tobacco products from several different product subcategories obtained at two different locations and at two different procurement times. B[a]P quantities range from 0.6 to 160 ng/g on a wet-weight basis, whereas NNN and NNK quantities range from 276 to 10473 ng/g and 79 to 28882 ng/g, respectively. The B[a]P, NNN, and NNK quantities vary widely among various smokeless tobacco product categories and among various brands within each product subcategory. Dry snuff products contain the highest B[a]P, NNN, and NNK quantities, whereas loose and portioned snus products contain the lowest B[a]P, NNN, and NNK levels. In general, variation of B[a]P, NNN, and NNK levels across four sets of each product brand purchased six months apart and at two different locations show statistically significant differences (p < 0.05), although with a much narrower product set-to-set variability.


Assuntos
Nitrosaminas , Produtos do Tabaco , Tabaco sem Fumaça , Benzo(a)pireno , Nicotiana , Carcinógenos/análise
6.
AIDS Care ; 35(6): 818-823, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-36223538

RESUMO

We conducted a retrospective cohort study of pregnancy and infant outcomes in 670 adolescents and young adult women with perinatally acquired HIV (AYAPHIV), aged 15-24 years, in Thailand and Vietnam. Between January 2013 and December 2018, there were 52 pregnancies, for an incidence of 2.49 (95% CI 1.90-3.27) per 100 person-years. The median age at pregnancy was 17.7 years (IQR 16.8-18.9). Pregnant AYAPHIV had been on cART for a lifetime median of 9.8 years (IQR 7.3-12.4). At the time of conception, the median CD4 was 521 cells/mm3 (IQR 213-760), and 76% had HIV RNA ≤400 copies/ml. Of the 51 pregnancies with available outcomes, 90% resulted in live singleton births at a median gestational age of 38 weeks (IQR 37-39); 77% of mothers (n = 27/35) had HIV RNA ≤400 copies/ml at delivery. Among infants with available data, 50% (n = 21/42) were male and 29% (n = 12/42) were reported to be low birthweight (<2,500gm); none (n = 0/41) were breastfed. One infant was diagnosed with HIV. Our findings emphasize that efforts to strengthen reproductive health education, including contraception, pregnancy-related psychosocial support services, and prevention of vertical HIV transmission interventions, in our region are needed for adolescents with perinatally acquired HIV as they transition to young adults.


Assuntos
Infecções por HIV , Complicações Infecciosas na Gravidez , Gravidez , Lactente , Adulto Jovem , Adolescente , Humanos , Masculino , Feminino , Complicações Infecciosas na Gravidez/epidemiologia , Infecções por HIV/prevenção & controle , Estudos Retrospectivos , Tailândia/epidemiologia , Vietnã/epidemiologia , Transmissão Vertical de Doenças Infecciosas/prevenção & controle , RNA , Resultado da Gravidez/epidemiologia
7.
Pain Med ; 24(Suppl 1): S81-S94, 2023 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-36069660

RESUMO

Management of patients suffering from low back pain (LBP) is challenging and requires development of diagnostic techniques to identify specific patient subgroups and phenotypes in order to customize treatment and predict clinical outcome. The Back Pain Consortium (BACPAC) Research Program Spine Imaging Working Group has developed standard operating procedures (SOPs) for spinal imaging protocols to be used in all BACPAC studies. These SOPs include procedures to conduct spinal imaging assessments with guidelines for standardizing the collection, reading/grading (using structured reporting with semi-quantitative evaluation using ordinal rating scales), and storage of images. This article presents the approach to image acquisition and evaluation recommended by the BACPAC Spine Imaging Working Group. While the approach is specific to BACPAC studies, it is general enough to be applied at other centers performing magnetic resonance imaging (MRI) acquisitions in patients with LBP. The herein presented SOPs are meant to improve understanding of pain mechanisms and facilitate patient phenotyping by codifying MRI-based methods that provide standardized, non-invasive assessments of spinal pathologies. Finally, these recommended procedures may facilitate the integration of better harmonized MRI data of the lumbar spine across studies and sites within and outside of BACPAC studies.


Assuntos
Degeneração do Disco Intervertebral , Dor Lombar , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/patologia , Região Lombossacral , Dor Lombar/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos
8.
Regul Toxicol Pharmacol ; 133: 105199, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35662636

RESUMO

Smokeless tobacco products expose adult and youth tobacco users to various addictive and carcinogenic constituents that can cause long-term nicotine dependence and oral cancers. In this study, nicotine, benzo[a]pyrene (B[a]P), N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), acetaldehyde, crotonaldehyde, formaldehyde, moisture, and pH levels in 16 smokeless tobacco products were measured on a wet-weight basis (wwb). In addition, change in analytical variability with increasing replicate measurements was assessed. Total nicotine in the products varied from 6.2 to 35.5 mg/g. The percentage of total nicotine in the unprotonated form ranged from 0.1 to 62%; whereas, product moisture varied from 7.4 to 57%. The quantities of harmful and potentially harmful constituents (HPHCs) range from 0.46 to 179.9 ng/g for B [a]P, 270-12206 and 81-20716 ng/g for NNN and NNK, respectively, and 0.33-6.85 and 0.13-5.67 µg/g for acetaldehyde and formaldehyde, respectively. This study shows wide variation in smokeless tobacco product HPHC quantities. The results also show that analytical variability stabilizes after seven replicate measurements.


Assuntos
Nitrosaminas , Produtos do Tabaco , Tabaco sem Fumaça , Acetaldeído , Adolescente , Adulto , Carcinógenos/análise , Formaldeído , Humanos , Concentração de Íons de Hidrogênio , Nicotina , Nicotiana/química , Produtos do Tabaco/efeitos adversos , Tabaco sem Fumaça/efeitos adversos
9.
Chem Res Toxicol ; 34(3): 704-712, 2021 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-33512154

RESUMO

The mainstream smoke yields of five volatile organic compounds (VOCs) were determined from 60 commercial U.S. little cigar products under ISO 3308 and Canadian Intense (CI) smoking regimens on linear smoking machines using a gas sampling bag collection. The five VOCs, 1,3-butadiene, acrylonitrile, benzene, isoprene, and toluene were analyzed using an automated GC/MS analytical method validated for measuring various VOCs in mainstream smoke. The VOCs range in amounts from micrograms to milligrams per little cigar. VOC deliveries vary considerably among the little cigar products under the ISO smoking regimen primarily due to varying filter ventilation. Under the CI smoking regimen where filter ventilation is blocked, the delivery range narrows, although individual and total VOC yields are approximately 2 fold higher than those under the ISO smoking regimen. Correlation analysis reveals strong associations between acrylonitrile and 1,3-butadiene or toluene under the ISO smoking regimen. Compared to cigarettes, little cigars delivered substantially higher VOC mainstream smoke yields under both ISO and CI smoking regimens. Moreover, little cigar smoke also contains higher VOCs than cigarette smoke when adjusted for mass of tobacco.


Assuntos
Fumaça/análise , Produtos do Tabaco/análise , Compostos Orgânicos Voláteis/análise
10.
J Environ Manage ; 261: 110202, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32148272

RESUMO

The importance of faecal sludge management is gaining recognition. However, methods are still lacking to reasonably estimate the quantities and qualities (Q&Q) that need to be managed, which makes the planning for and implementing of management solutions quite difficult. The objective of this study was to collect and analyse Q&Q of faecal sludge at a citywide scale, and to evaluate whether "SPA-DET" data (=> spatially analysable - demographic, environmental and technical) could then be used as predictors of Q&Q of faecal sludge. 60 field samples and questionnaires from Hanoi and 180 from Kampala were analysed. Software tools were used in an iterative process to predict total solids (TS) and emptying frequency in both Hanoi, Vietnam and Kampala, Uganda. City-specific data could be predicted with types of "SPA-DET" data as input variables, and model performance was improved by analysing septic tanks and pit latrines separately. Individual models were built for TS concentrations and emptying frequency. In addition, a model was built across both cities for emptying frequency of septic tanks based on number of users and containment volume, indicating predictive models can be relevant for multiple cities. Number of users, containment volume, truck volume and income level were identified as the most common variables for the correction function. Results confirm the high intrinsic variability of faecal sludge characteristics, and illustrate the importance of moving beyond simple reporting of city-wide average values for estimations of Q&Q. The collected data and developed scripts have been made available for replication in future studies.


Assuntos
Saneamento , Esgotos , Cidades , Uganda , Vietnã
11.
Neuroimage ; 184: 396-408, 2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-30237033

RESUMO

We investigate the utility of radiofrequency (RF) parallel transmission (pTx) for whole-brain resting-state functional MRI (rfMRI) acquisition at 7 Tesla (7T). To this end, Human Connectome Project (HCP)-style data acquisitions were chosen as a showcase example. Five healthy subjects were scanned in pTx and single-channel transmit (1Tx) modes. The pTx data were acquired using a prototype 16-channel transmit system and a commercially available Nova 8-channel transmit 32-channel receive RF head coil. Additionally, pTx single-spoke multiband (MB) pulses were designed to image sagittal slices. HCP-style 7T rfMRI data (1.6-mm isotropic resolution, 5-fold slice and 2-fold in-plane acceleration, 3600 image volumes and ∼ 1-h scan) were acquired with pTx and the results were compared to those acquired with the original 7T HCP rfMRI protocol. The use of pTx significantly improved flip-angle uniformity across the brain, with coefficient of variation (i.e., std/mean) of whole-brain flip-angle distribution reduced on average by ∼39%. This in turn yielded ∼17% increase in group temporal SNR (tSNR) as averaged across the entire brain and ∼10% increase in group functional contrast-to-noise ratio (fCNR) as averaged across the grayordinate space (including cortical surfaces and subcortical voxels). Furthermore, when placing a seed in either the posterior parietal lobe or putamen to estimate seed-based dense connectome, the increase in fCNR was observed to translate into stronger correlation of the seed with the rest of the grayordinate space. We have demonstrated the utility of pTx for slice-accelerated high-resolution whole-brain rfMRI at 7T; as compared to current state-of-the-art, the use of pTx improves flip-angle uniformity, increases tSNR, enhances fCNR and strengthens functional connectivity estimation.


Assuntos
Encéfalo/fisiologia , Conectoma/métodos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ondas de Rádio , Descanso/fisiologia , Adulto Jovem
12.
Pediatr Allergy Immunol ; 30(3): 348-355, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30793379

RESUMO

BACKGROUND: There is a paucity of data on the prevalence of food allergy (FA) in Vietnam. A cross-sectional, population-based study was conducted to evaluate the current prevalence of FA among 2- to 6-year-old children in two different regions in Vietnam. METHOD: A structured, anonymous questionnaire, modified from published FA epidemiologic studies and based on EAACI guidelines, was distributed to parents/guardians of participating children in Hue City (urban area) and Tien Giang Province (rural area). Data collected from the survey were statistically analyzed to generate the prevalence of self-reported and doctor-diagnosed FA and overarching pattern of food allergens. RESULTS: A total of 8620 responses were collected (response rate 81.5%). Children in Tien Giang reported more than twice the food-induced adverse reactions seen in children in Hue (47.8% vs. 20.5%). In contrast, children in Hue showed higher self-reported FA (9.8%) and doctor-diagnosed FA rates (8.4%) than children in Tien Giang (7.9% and 5.0%, respectively). Crustacean was the predominant allergy-inducing food in both areas (330 of 580 cases, 56.9%), followed by fish, mollusk, beef, milk, and egg. However, substantial variations of FA patterns were seen between the study sites. Geographic location and co-morbidities of other allergic diseases were key risk factors for FA (P < 0.001). CONCLUSIONS: The prevalence of FA in Vietnamese children seems to be higher than previously reported from other Asian countries. Crustacean is the predominant allergy-inducing food among participating preschool children in Vietnam. The variation of reported food allergen sources across different socio-economic locations could imply different eating habits or the participation of indoor and outdoor allergen exposure.


Assuntos
Hipersensibilidade Alimentar/epidemiologia , Criança , Pré-Escolar , Estudos Transversais , Feminino , Alimentos , Humanos , Masculino , Prevalência , Fatores de Risco , Fatores Socioeconômicos , Inquéritos e Questionários , Vietnã/epidemiologia
13.
Neuroimage ; 164: 155-163, 2018 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-28213116

RESUMO

Encoding higher spatial resolution in simultaneous multi-slice (SMS) EPI is highly dependent on gradient performance, high density receiver coil arrays and pulse sequence optimization. We simulate gradient amplitude and slew rate determination of EPI imaging performance in terms of minimum TE, echo spacing (ES) and spatial resolution. We discuss the effects of image zooming in pulse sequences that have been used for sub-millimeter resolutions and the trade-offs in using partial Fourier and parallel imaging to reduce TE, PSF and ES. Using optimizations for SMS EPI pulse sequences with available gradient and receiver hardware, experimental results in ultra-high resolution (UHR) (0.45-0.5mm isotropic) SMS-EPI fMRI and mapping ocular dominance columns (ODC) in human brain at 0.5 mm isotropic resolution are demonstrated. We discuss promising future directions of UHR fMRI.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/diagnóstico por imagem , Imagem Ecoplanar/métodos , Processamento de Imagem Assistida por Computador/métodos , Algoritmos , Encéfalo/fisiologia , Dominância Ocular/fisiologia , Humanos , Imageamento Tridimensional/métodos
14.
Neuroimage ; 164: 164-171, 2018 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-28185951

RESUMO

High isotropic resolution fMRI is challenging primarily due to long repetition times (TR) and insufficient SNR, especially at lower field strengths. Recently, Simultaneous Multi-Slice (SMS) imaging with blipped-CAIPI has substantially reduced scan time and improved SNR efficiency of fMRI. Similarly, super-resolution techniques utilizing sub- voxel spatial shifts in the slice direction have increased both resolution and SNR efficiency. Here we demonstrate the synergistic combination of SLIce Dithered Enhanced Resolution (SLIDER) and SMS for high-resolution, high-SNR whole brain fMRI in comparison to standard resolution fMRI data as well as high-resolution data. With SLIDER-SMS, high spatial frequency information is recovered (unaliased) even in absence of super-resolution deblurring algorithms. Additionally we find that BOLD CNR (as measured by t-value in a visual checkerboard paradigm) is improved by as much as 100% relative to traditionally acquired high- resolution data. Using this gain in CNR, we are able to obtain unprecedented nominally isotropic resolutions at 3T (0.66 mm) and 7T (0.45 mm).


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Humanos , Aumento da Imagem/métodos
15.
Neuroimage ; 178: 104-118, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29753105

RESUMO

Diffusion MRI of the cortical gray matter is challenging because the micro-environment probed by water molecules is much more complex than within the white matter. High spatial and angular resolutions are therefore necessary to uncover anisotropic diffusion patterns and laminar structures, which provide complementary (e.g. to anatomical and functional MRI) microstructural information about the cortex architectonic. Several ex-vivo and in-vivo MRI studies have recently addressed this question, however predominantly with an emphasis on specific cortical areas. There is currently no whole brain in-vivo data leveraging multi-shell diffusion MRI acquisition at high spatial resolution, and depth dependent analysis, to characterize the complex organization of cortical fibers. Here, we present unique in-vivo human 7T diffusion MRI data, and a dedicated cortical depth dependent analysis pipeline. We leverage the high spatial (1.05 mm isotropic) and angular (198 diffusion gradient directions) resolution of this whole brain dataset to improve cortical fiber orientations mapping, and study neurites (axons and/or dendrites) trajectories across cortical depths. Tangential fibers in superficial cortical depths and crossing fiber configurations in deep cortical depths are identified. Fibers gradually inserting into the gyral walls are visualized, which contributes to mitigating the gyral bias effect. Quantitative radiality maps and histograms in individual subjects and cortex-based aligned datasets further support our results.


Assuntos
Córtex Cerebral/anatomia & histologia , Imagem de Difusão por Ressonância Magnética/métodos , Processamento de Imagem Assistida por Computador/métodos , Fibras Nervosas , Neuroimagem/métodos , Adulto , Axônios , Córtex Cerebral/diagnóstico por imagem , Dendritos , Humanos , Neuritos
16.
Neuroimage ; 164: 18-31, 2018 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-28373123

RESUMO

Following rapid technological advances, ultra-high field functional MRI (fMRI) enables exploring correlates of neuronal population activity at an increasing spatial resolution. However, as the fMRI blood-oxygenation-level-dependent (BOLD) contrast is a vascular signal, the spatial specificity of fMRI data is ultimately determined by the characteristics of the underlying vasculature. At 7T, fMRI measurement parameters determine the relative contribution of the macro- and microvasculature to the acquired signal. Here we investigate how these parameters affect relevant high-end fMRI analyses such as encoding, decoding, and submillimeter mapping of voxel preferences in the human auditory cortex. Specifically, we compare a T2* weighted fMRI dataset, obtained with 2D gradient echo (GE) EPI, to a predominantly T2 weighted dataset obtained with 3D GRASE. We first investigated the decoding accuracy based on two encoding models that represented different hypotheses about auditory cortical processing. This encoding/decoding analysis profited from the large spatial coverage and sensitivity of the T2* weighted acquisitions, as evidenced by a significantly higher prediction accuracy in the GE-EPI dataset compared to the 3D GRASE dataset for both encoding models. The main disadvantage of the T2* weighted GE-EPI dataset for encoding/decoding analyses was that the prediction accuracy exhibited cortical depth dependent vascular biases. However, we propose that the comparison of prediction accuracy across the different encoding models may be used as a post processing technique to salvage the spatial interpretability of the GE-EPI cortical depth-dependent prediction accuracy. Second, we explored the mapping of voxel preferences. Large-scale maps of frequency preference (i.e., tonotopy) were similar across datasets, yet the GE-EPI dataset was preferable due to its larger spatial coverage and sensitivity. However, submillimeter tonotopy maps revealed biases in assigned frequency preference and selectivity for the GE-EPI dataset, but not for the 3D GRASE dataset. Thus, a T2 weighted acquisition is recommended if high specificity in tonotopic maps is required. In conclusion, different fMRI acquisitions were better suited for different analyses. It is therefore critical that any sequence parameter optimization considers the eventual intended fMRI analyses and the nature of the neuroscience questions being asked.


Assuntos
Córtex Auditivo/diagnóstico por imagem , Mapeamento Encefálico/métodos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Algoritmos , Humanos , Sensibilidade e Especificidade
17.
Magn Reson Med ; 80(5): 1857-1870, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-29603381

RESUMO

PURPOSE: Investigating the utility of RF parallel transmission (pTx) for Human Connectome Project (HCP)-style whole-brain diffusion MRI (dMRI) data at 7 Tesla (7T). METHODS: Healthy subjects were scanned in pTx and single-transmit (1Tx) modes. Multiband (MB), single-spoke pTx pulses were designed to image sagittal slices. HCP-style dMRI data (i.e., 1.05-mm resolutions, MB2, b-values = 1000/2000 s/mm2 , 286 images and 40-min scan) and data with higher accelerations (MB3 and MB4) were acquired with pTx. RESULTS: pTx significantly improved flip-angle detected signal uniformity across the brain, yielding ∼19% increase in temporal SNR (tSNR) averaged over the brain relative to 1Tx. This allowed significantly enhanced estimation of multiple fiber orientations (with ∼21% decrease in dispersion) in HCP-style 7T dMRI datasets. Additionally, pTx pulses achieved substantially lower power deposition, permitting higher accelerations, enabling collection of the same data in 2/3 and 1/2 the scan time or of more data in the same scan time. CONCLUSION: pTx provides a solution to two major limitations for slice-accelerated high-resolution whole-brain dMRI at 7T; it improves flip-angle uniformity, and enables higher slice acceleration relative to current state-of-the-art. As such, pTx provides significant advantages for rapid acquisition of high-quality, high-resolution truly whole-brain dMRI data.


Assuntos
Encéfalo/diagnóstico por imagem , Imagem de Difusão por Ressonância Magnética/métodos , Processamento de Imagem Assistida por Computador/métodos , Adolescente , Adulto , Idoso , Algoritmos , Conectoma , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
18.
J Vis ; 18(13): 23, 2018 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-30593068

RESUMO

About a quarter of human cerebral cortex is dedicated mainly to visual processing. The large-scale spatial organization of visual cortex can be measured with functional magnetic resonance imaging (fMRI) while subjects view spatially modulated visual stimuli, also known as "retinotopic mapping." One of the datasets collected by the Human Connectome Project involved ultrahigh-field (7 Tesla) fMRI retinotopic mapping in 181 healthy young adults (1.6-mm resolution), yielding the largest freely available collection of retinotopy data. Here, we describe the experimental paradigm and the results of model-based analysis of the fMRI data. These results provide estimates of population receptive field position and size. Our analyses include both results from individual subjects as well as results obtained by averaging fMRI time series across subjects at each cortical and subcortical location and then fitting models. Both the group-average and individual-subject results reveal robust signals across much of the brain, including occipital, temporal, parietal, and frontal cortex as well as subcortical areas. The group-average results agree well with previously published parcellations of visual areas. In addition, split-half analyses show strong within-subject reliability, further demonstrating the high quality of the data. We make publicly available the analysis results for individual subjects and the group average, as well as associated stimuli and analysis code. These resources provide an opportunity for studying fine-scale individual variability in cortical and subcortical organization and the properties of high-resolution fMRI. In addition, they provide a set of observations that can be compared with other Human Connectome Project measures acquired in these same participants.


Assuntos
Conectoma , Conjuntos de Dados como Assunto , Retina/fisiologia , Córtex Visual/fisiologia , Mapeamento Encefálico , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Reprodutibilidade dos Testes , Adulto Jovem
19.
J Infect Dis ; 215(8): 1188-1196, 2017 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-28077730

RESUMO

Background: Children in Guinea-Bissau receive measles vaccine (MV) at 9 months of age, but studies have shown that an additional dose before 9 months of age might have beneficial nonspecific effects. Within a randomized trial designed to examine nonspecific effects of early MV receipt on mortality, we conducted a substudy to investigate the effect of early MV receipt on morbidity. Methods: Children were randomly assigned at a ratio of 2:1 to receive 2 doses of MV at 18 weeks and age 9 months (intervention group) or 1 dose of MV at age 9 months, in accordance with current practice (control group). Children were visited weekly from enrollment to age 9 months; the mother reported morbidity, and the field assistants examined the children. Using Cox and binomial regression models, we compared the 2 randomization groups. Results: Among the 1592 children, early measles vaccination was not associated with a higher risk of the well-known adverse events of fever, rash, and convulsions within the first 14 days. From 15 days after randomization to age 9 months, early measles vaccination was associated with reductions in maternally reported diarrhea (hazard ratio [HR], 0.89; 95% confidence interval [CI], .82-.97), vomiting (HR, 0.86; 95% CI, .75-.98), and fever (HR, 0.93; 95% CI, .87-1.00). Conclusion: Early MV receipt was associated with reduced general morbidity in the following months, supporting that early MV receipt may improve the general health of children.


Assuntos
Diarreia/epidemiologia , Imunidade Heteróloga , Vacina contra Sarampo/administração & dosagem , Sarampo/prevenção & controle , Vômito/epidemiologia , Feminino , Guiné-Bissau/epidemiologia , Visita Domiciliar/estatística & dados numéricos , Humanos , Esquemas de Imunização , Lactente , Masculino , Morbidade , Modelos de Riscos Proporcionais , Vacinação
20.
Neuroimage ; 154: 23-32, 2017 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-27894889

RESUMO

Whole-brain functional magnetic resonance imaging (fMRI), in conjunction with multiband acceleration, has played an important role in mapping the functional connectivity throughout the entire brain with both high temporal and spatial resolution. Ultrahigh magnetic field strengths (7T and above) allow functional imaging with even higher functional contrast-to-noise ratios for improved spatial resolution and specificity compared to traditional field strengths (1.5T and 3T). High-resolution 7T fMRI, however, has primarily been constrained to smaller brain regions given the amount of time it takes to acquire the number of slices necessary for high resolution whole brain imaging. Here we evaluate a range of whole-brain high-resolution resting state fMRI protocols (0.9, 1.25, 1.5, 1.6 and 2mm isotropic voxels) at 7T, obtained with both in-plane and slice acceleration parallel imaging techniques to maintain the temporal resolution and brain coverage typically acquired at 3T. Using the processing pipeline developed by the Human Connectome Project, we demonstrate that high resolution images acquired at 7T provide increased functional contrast to noise ratios with significantly less partial volume effects and more distinct spatial features, potentially allowing for robust individual subject parcellations and descriptions of fine-scaled patterns, such as visuotopic organization.


Assuntos
Conectoma/métodos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Humanos
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