Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 28
Filtrar
1.
Magn Reson Med ; 92(1): 43-56, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38303151

RESUMO

PURPOSE: To introduce universal modes by applying the universal pulse concept to time-interleaved acquisition of modes (TIAMO), thereby achieving calibration-free B 1 + $$ {B}_1^{+} $$ inhomogeneity mitigation for body imaging at ultra-high fields. METHODS: Two databases of different RF arrays were used to demonstrate the feasibility of universal modes. The first comprised 31 cardiac in vivo data sets acquired at 7T while the second consisted of 6 simulated 10.5T pelvic data sets. Subject-specific solutions and universal modes were computed and subsequently evaluated alongside predefined default modes. For the cardiac database, subdivision into subpopulations was investigated. The optimization was performed using least-squares (LS) TIAMO and acquisition modes optimized for refocused echoes (AMORE). Finally, universal modes based on simulated pelvis data were applied in vivo at 10.5T. RESULTS: In all studied cases, the universal modes yield improvements over the predefined default modes of up to 51% (cardiac) and 30% (pelvic) in terms of median excitation error when using two modes. The subpopulation-specific cardiac solutions revealed a further improvement of universal modes at the expense of increased errors when applied outside the appropriate subpopulation. Direct application of simulation-based universal modes in vivo resulted in up to a 14% reduction in excitation error compared to default modes and up to a 34% reduction in peak 10 g local specific absorption rate (SAR) compared to subject-specific solutions. CONCLUSIONS: Universal modes are feasible for calibration-free B 1 + $$ {B}_1^{+} $$ inhomogeneity mitigation at ultra-high fields. In addition, simulation-based solutions can be applied directly in vivo, eliminating the need for large in vivo databases.


Assuntos
Algoritmos , Coração , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Pelve , Humanos , Coração/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Pelve/diagnóstico por imagem , Calibragem , Masculino , Adulto , Simulação por Computador , Imagens de Fantasmas , Feminino , Análise dos Mínimos Quadrados , Bases de Dados Factuais
2.
Magn Reson Med ; 91(2): 513-529, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-37705412

RESUMO

PURPOSE: To increase the RF coil performance and RF management for body imaging at 10.5 T by validating and evaluating a high-density 16-channel transceiver array, implementing virtual observation points (VOPs), and demonstrating specific absorption rate (SAR) constrained imaging in vivo. METHODS: The inaccuracy of the electromagnetic model of the array was quantified based on B1 + and SAR data. Inter-subject variability was estimated using a new approach based on the relative SAR deviation of different RF shims between human body models. The pTx performance of the 16-channel array was assessed in simulation by comparison to a previously demonstrated 10-channel array. In vivo imaging of the prostate was performed demonstrating SAR-constrained static RF shimming and acquisition modes optimized for refocused echoes (AMORE). RESULTS: The model inaccuracy of 29% and the inter-subject variability of 85% resulted in a total safety factor of 1.91 for pelvis studies. For renal and cardiac imaging, inter-subject variabilities of 121% and 141% lead to total safety factors of 2.25 and 2.45, respectively. The shorter wavelength at 10.5 T supported the increased element density of the 16-channel array which in turn outperformed the 10-channel version for all investigated metrics. Peak 10 g local SAR reduction of more than 25% without a loss of image quality was achieved in vivo, allowing a theoretical improvement in measurement efficiency of up to 66%. CONCLUSIONS: By validating and characterizing a 16-channel dipole transceiver array, this work demonstrates, for the first time, a VOP-enabled RF coil for human torso imaging enabling increased pTx performance at 10.5 T.


Assuntos
Imageamento por Ressonância Magnética , Próstata , Masculino , Humanos , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas , Desenho de Equipamento , Simulação por Computador , Ondas de Rádio
3.
Small ; 19(45): e2302633, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37232212

RESUMO

Correlating metal-organic framework (MOF) synthesis processes and microwave absorption (MA) enhancement mechanisms is a pioneer project. Nevertheless, the correlation process still relies mainly on empirical doctrine, which hardly corresponds to the specific mechanism of the effect on the dielectric properties. Hereby, after the strategy of modulation of protonation engineering and solvothermal temperature in the synthesis route, the obtained sheet-like self-assembled nanoflowers were constructed. Porous structures with multiple heterointerfaces, abundant defects, and vacancies are obtained by controlled design of the synthesis procedure. The rearrangement of charges and enhanced polarization can be promoted. The designed electromagnetic properties and special nano-microstructures of functional materials have significant impact on their electromagnetic wave energy conversion effects. As a consequence, the MA performance of the samples has been enhanced toward broadband absorption (6.07 GHz), low thickness (2.0 mm), low filling (20%), and efficient loss (-25 dB), as well as being suitable for practical environmental applications. This work establishes the connection between the MOF-derived materials synthesis process and the MA enhancement mechanism, which provides insight into various microscopic microwave loss mechanisms.

4.
Magn Reson Med ; 88(4): 1702-1719, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35692053

RESUMO

PURPOSE: To develop and evaluate a novel RF shimming optimization strategy tailored to improve the transmit efficiency in turbo spin echo imaging when performing time-interleaved acquisition of modes (TIAMO) at ultrahigh fields. THEORY AND METHODS: A nonlocalized efficiency shimming cost function is proposed and extended to perform TIAMO using acquisition modes optimized for refocused echoes (AMORE). The nonlocalized efficiency shimming was demonstrated in brain and knee imaging at 7 Tesla. Phantom and in vivo torso imaging studies were performed to compare the performance between AMORE and previously proposed TIAMO mode optimizations with and without localized constraints in turbo spin echo and gradient echo acquisitions. RESULTS: The proposed nonlocalized efficiency RF shimming produced a circularly polarized-like field with fewer signal dropouts in the brain and knee. For larger targets, AMORE was used and required a significantly lower transmitter voltage to produce a similar contrast to existing TIAMO mode design approaches for turbo spin echo as well as gradient echo acquisitions. In vivo, AMORE effectively reduced signal dropout in the interior torso while providing more uniform contrast with reduced transmit power. A local constraint further improved performance for a target region while maintaining performance in the larger FOV. CONCLUSION: AMORE based on the presented nonlocalized efficiency shimming cost function demonstrated improved contrast and SNR uniformity as well as increased transmit efficiency for both gradient echo and turbo spin echo acquisitions.


Assuntos
Interpretação de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Algoritmos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas
5.
Magn Reson Med ; 88(5): 2311-2325, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35781696

RESUMO

PURPOSE: The purpose of this study is to present a workflow for predicting the radiofrequency (RF) heating around the contacts of a deep brain stimulation (DBS) lead during an MRI scan. METHODS: The induced RF current on the DBS lead accumulates electric charge on the metallic contacts, which may cause a high local specific absorption rate (SAR), and therefore, heating. The accumulated charge was modeled by imposing a voltage boundary condition on the contacts in a quasi-static electromagnetic (EM) simulation allowing thermal simulations to be performed with the resulting SAR distributions. Estimating SAR and temperature increases from a lead in vivo through EM simulation is not practical given anatomic differences and variations in lead geometry. To overcome this limitation, a new parameter, transimpedance, was defined to characterize a given lead. By combining the transimpedance, which can be measured in a single calibration scan, along with MR-based current measurements of the lead in a unique orientation and anatomy, local heating can be estimated. Heating determined with this approach was compared with results from heating studies of a commercial DBS electrode in a gel phantom with different lead configurations to validate the proposed method. RESULTS: Using data from a single calibration experiment, the transimpedance of a commercial DBS electrode (directional lead, Infinity DBS system, Abbott Laboratories, Chicago, IL) was determined to be 88 Ω. Heating predictions using the DBS transimpedance and rapidly acquired MR-based current measurements in 26 different lead configurations resulted in a <23% (on average 11.3%) normalized root-mean-square error compared to experimental heating measurements during RF scans. CONCLUSION: In this study, a workflow consisting of an MR-based current measurement on the DBS lead and simple quasi-static EM/thermal simulations to predict the temperature increase around a DBS electrode undergoing an MRI scan is proposed and validated using a commercial DBS electrode.


Assuntos
Estimulação Encefálica Profunda , Estimulação Encefálica Profunda/métodos , Eletrodos , Eletrodos Implantados , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas , Ondas de Rádio , Temperatura , Fluxo de Trabalho
6.
Magn Reson Med ; 86(1): 17-32, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33497006

RESUMO

PURPOSE: To develop a 3D composite adiabatic spectral-spatial pulse for refocusing in spin-echo spectroscopy acquisitions and to compare its performance against standard acquisition methods. METHODS: A 3D composite adiabatic pulse was designed by modulating a train of parallel transmit-optimized 2D subpulses with an adiabatic envelope. The spatial and spectral profiles were simulated and validated by experiments to demonstrate the feasibility of the design in both single and double spin-echo spectroscopy acquisitions. Phantom and in vivo studies were performed to evaluate the pulse performance and compared with semi-LASER with respect to localization performance, sequence timing, signal suppression, and specific absorption rate. RESULTS: Simultaneous 2D spatial localization with water and lipid suppression was achieved with the designed refocusing pulse, allowing high-quality spectra to be acquired with shorter minimum TE/TR, reduced SAR, as well as adaptation to spatially varying B0 and B1+ field inhomogeneities in both prostate and brain studies. CONCLUSION: The proposed composite pulse can serve as a more SAR efficient alternative to conventional localization methods such as semi-LASER at ultrahigh field for spin echo-based spectroscopy studies. Subpulse parallel-transmit optimization provides the flexibility to manage the tradeoff among multiple design criteria to accommodate different field strengths and applications.


Assuntos
Algoritmos , Encéfalo , Encéfalo/diagnóstico por imagem , Espectroscopia de Ressonância Magnética , Masculino , Imagens de Fantasmas , Próstata
7.
Magn Reson Med ; 84(1): 289-303, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-31846121

RESUMO

PURPOSE: To investigate the feasibility of imaging the human torso and to evaluate the performance of several radiofrequency (RF) management strategies at 10.5T. METHODS: Healthy volunteers were imaged on a 10.5T whole-body scanner in multiple target anatomies, including the prostate, hip, kidney, liver, and heart. Phase-only shimming and spoke pulses were used to demonstrate their performance in managing the B1+ inhomogeneity present at 447 MHz. Imaging protocols included both qualitative and quantitative acquisitions to show the feasibility of imaging with different contrasts. RESULTS: High-quality images were acquired and demonstrated excellent overall contrast and signal-to-noise ratio. The experimental results matched well with predictions and suggested good translational capabilities of the RF management strategies previously developed at 7T. Phase-only shimming provided increased efficiency, but showed pronounced limitations in homogeneity, demonstrating the need for the increased degrees of freedom made possible through single- and multispoke RF pulse design. CONCLUSION: The first in-vivo human imaging was successfully performed at 10.5T using previously developed RF management strategies. Further improvement in RF coils, transmit chain, and full integration of parallel transmit functionality are needed to fully realize the benefits of 10.5T.


Assuntos
Interpretação de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Coração , Humanos , Masculino , Ondas de Rádio , Razão Sinal-Ruído
8.
Int J Neuropsychopharmacol ; 20(5): 374-382, 2017 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-28177081

RESUMO

Background: Tamoxifen is the most widely used drug for treating patients with estrogen receptor-sensitive breast cancer. There is evidence that breast cancer patients treated with tamoxifen exhibit cognitive dysfunction. However, the underlying neural mechanism remains unclear. The present study aimed to investigate the neural mechanisms underlying working memory deficits in combination with functional connectivity changes in premenopausal women with breast cancer who received long-term tamoxifen treatment. Methods: A total of 31 premenopausal women with breast cancer who received tamoxifen and 32 matched healthy control participants were included. The participants completed n-back tasks and underwent resting-state functional magnetic resonance imaging, which measure working memory performance and brain functional connectivity, respectively. A seed-based functional connectivity analysis within the whole brain was conducted, for which the dorsolateral prefrontal cortex was chosen as the seed region. Results: Our results indicated that the tamoxifen group had significant deficits in working memory and general executive function performance and significantly lower functional connectivity of the right dorsolateral prefrontal cortex with the right hippocampus compared with the healthy controls. There were no significant changes in functional connectivity in the left dorsolateral prefrontal cortex within the whole brain between the tamoxifen group and healthy controls. Moreover, significant correlations were found in the tamoxifen group between the functional connectivity strength of the dorsolateral prefrontal cortex with the right hippocampus and decreased working memory performance. Conclusion: This study demonstrates that the prefrontal cortex and hippocampus may be affected by tamoxifen treatment, supporting an antagonistic role of tamoxifen in the long-term treatment of breast cancer patients.


Assuntos
Neoplasias da Mama/tratamento farmacológico , Transtornos da Memória/tratamento farmacológico , Memória de Curto Prazo/efeitos dos fármacos , Vias Neurais/fisiopatologia , Córtex Pré-Frontal/fisiopatologia , Tamoxifeno/farmacologia , Tamoxifeno/uso terapêutico , Adulto , Antineoplásicos Hormonais/farmacologia , Antineoplásicos Hormonais/uso terapêutico , Mapeamento Encefálico , Neoplasias da Mama/complicações , Neoplasias da Mama/patologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Transtornos da Memória/etiologia , Pessoa de Meia-Idade , Vias Neurais/efeitos dos fármacos , Testes Neuropsicológicos , Oxigênio/sangue , Córtex Pré-Frontal/efeitos dos fármacos
9.
Neuroradiology ; 58(9): 921-8, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27278455

RESUMO

INTRODUCTION: Complaint about attention disorders is common among breast cancer patients who have undergone chemotherapy, which may be associated with the default mode network (DMN). To validate this hypothesis, we investigated the DMN functional connectivity (FC) change and its relationship with the attention function in breast cancer patients (BC) using resting-state functional magnetic resonance imaging (rs-fMRI). METHODS: Twenty-two BC treated with chemotherapy and 22 healthy controls (HC) were recruited into this study. The FC between the DMN's hubs and regions of the dorsal medial prefrontal cortex (dMPFC) and medial temporal lobe (MTL) subsystems was respectively calculated for each participant. RESULTS: The statistical result showed significantly lower connectivity in dMPFC and MTL subsystems in the BC group. In addition, the partial correlation analysis result indicated that the low connectivity of some brain regions in MTL subsystem was correlated with attention dysfunction following BC chemotherapy. CONCLUSION: These results suggest that the functional disconnection in MTL subsystem of the DMN may have association with attention function of BC after chemotherapy.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Atenção/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/fisiopatologia , Adulto , Antineoplásicos/administração & dosagem , Conectoma/métodos , Ciclofosfamida/administração & dosagem , Doxorrubicina/administração & dosagem , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Rede Nervosa/efeitos dos fármacos , Rede Nervosa/fisiopatologia , Descanso , Taxoides/administração & dosagem , Resultado do Tratamento
10.
Am J Respir Crit Care Med ; 191(10): 1116-25, 2015 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-25763605

RESUMO

RATIONALE: The airway transcriptome includes genes that contribute to the pathophysiologic heterogeneity seen in individuals with asthma. OBJECTIVES: We analyzed sputum gene expression for transcriptomic endotypes of asthma (TEA), gene signatures that discriminate phenotypes of disease. METHODS: Gene expression in the sputum and blood of patients with asthma was measured using Affymetrix microarrays. Unsupervised clustering analysis based on pathways from the Kyoto Encyclopedia of Genes and Genomes was used to identify TEA clusters. Logistic regression analysis of matched blood samples defined an expression profile in the circulation to determine the TEA cluster assignment in a cohort of children with asthma to replicate clinical phenotypes. MEASUREMENTS AND MAIN RESULTS: Three TEA clusters were identified. TEA cluster 1 had the most subjects with a history of intubation (P = 0.05), a lower prebronchodilator FEV1 (P = 0.006), a higher bronchodilator response (P = 0.03), and higher exhaled nitric oxide levels (P = 0.04) compared with the other TEA clusters. TEA cluster 2, the smallest cluster, had the most subjects that were hospitalized for asthma (P = 0.04). TEA cluster 3, the largest cluster, had normal lung function, low exhaled nitric oxide levels, and lower inhaled steroid requirements. Evaluation of TEA clusters in children confirmed that TEA clusters 1 and 2 are associated with a history of intubation (P = 5.58 × 10(-6)) and hospitalization (P = 0.01), respectively. CONCLUSIONS: There are common patterns of gene expression in the sputum and blood of children and adults that are associated with near-fatal, severe, and milder asthma.


Assuntos
Asma/genética , Perfilação da Expressão Gênica , Escarro , Transcriptoma/genética , Adolescente , Adulto , Idade de Início , Asma/sangue , Asma/fisiopatologia , Análise Química do Sangue , Estudos de Casos e Controles , Criança , Estudos Transversais , Feminino , Marcadores Genéticos , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Fenótipo , RNA/sangue , RNA/genética , Inquéritos e Questionários , Adulto Jovem
11.
Pediatr Res ; 75(3): 403-8, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24452590

RESUMO

BACKGROUND: Observational studies suggest that asthma control improves after adenotonsillectomy, but longitudinal studies that correlate the effect of the procedure on the levels of biomarkers associated with airway inflammation are limited. METHODS: We conducted a longitudinal, observational study on pediatric patients, both with and without asthma, undergoing adenotonsillectomy. Asthma control test (ACT) scores and chitinase activity in the circulation were measured at time of surgery and at 6-mo follow-up. RESULTS: Sixty-six children with asthma and 64 control subjects were enrolled. Mean ACT scores improved by three points (P < 0.001) after 6 mo. 85% of children with poorly controlled asthma demonstrated an increase in ACT score of at least three points or a decrease in emergency department/urgent care visits, oral corticosteroid courses, or rescue short acting bronchodilator usage. Chitinase activity decreased significantly in asthmatics who improved (P < 0.01). Higher chitinase activity levels at baseline were associated with improved asthma control following surgery (P < 0.01). CONCLUSION: In children with high preoperative circulating chitinase activity levels, asthma control and healthcare utilization were significantly improved after adenotonsillecotmy. Chitinase activity decreased after surgery in children with improved control. This suggests that adenotonsillectomy modulates chitinase activity, affecting airway inflammation and improving airway disease.


Assuntos
Adenoidectomia , Asma/prevenção & controle , Asma/fisiopatologia , Tonsilectomia , Adolescente , Criança , Pré-Escolar , Quitinases/sangue , Ensaio de Imunoadsorção Enzimática , Fluorometria , Humanos , Estudos Longitudinais , Estatísticas não Paramétricas , Inquéritos e Questionários
12.
Hemoglobin ; 38(2): 146-8, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24471736

RESUMO

We have identified four Chinese individuals from three unrelated families with raised Hb A2 levels. The anti-Lepore hybrid hemoglobin (Hb) variant was amplified using a pair of primers, 5' to the ß-globin gene Cap site and 3' to the δ-globin gene polyadenylation site (polyA) region, respectively. Direct sequencing of the ßδ fusion products confirmed the anti-Lepore Hong Kong (NG_000007.3: g.63154_70565dup) variant. We found that this anti-Lepore variant is positioned in zone 3 on the capillary electrophoresis system. It may help in differential diagnosis of Hb variants and providing better information in clinical counseling.


Assuntos
Hemoglobina A2/genética , Hemoglobinas Anormais/genética , Mutação , Proteínas Recombinantes de Fusão/genética , Adulto , China , Análise Mutacional de DNA , Eletroforese Capilar , Saúde da Família , Feminino , Hemoglobinas Anormais/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Proteínas Recombinantes de Fusão/metabolismo , Adulto Jovem , Globinas beta/genética , Globinas delta/genética
13.
Mol Med Rep ; 30(3)2024 09.
Artigo em Inglês | MEDLINE | ID: mdl-38963039

RESUMO

The incidence of Alzheimer's disease (AD) is rising globally, yet its treatment and prediction of this condition remain challenging due to the complex pathophysiological mechanisms associated with it. Consequently, the objective of the present study was to analyze and characterize the molecular mechanisms underlying ferroptosis­related genes (FEGs) in the pathogenesis of AD, as well as to construct a prognostic model. The findings will provide new insights for the future diagnosis and treatment of AD. First, the AD dataset GSE33000 from the Gene Expression Omnibus database and the FEGs from FerrDB were obtained. Next, unsupervised cluster analysis was used to obtain the FEGs that were most relevant to AD. Subsequently, enrichment analyses were performed on the FEGs to explore biological functions. Subsequently, the role of these genes in the immune microenvironment was elucidated through CIBERSORT. Then, the optimal machine learning was selected by comparing the performance of different machine learning models. To validate the prediction efficiency, the models were validated using nomograms, calibration curves, decision curve analysis and external datasets. Furthermore, the expression of FEGs between different groups was verified using reverse transcription quantitative PCR and western blot analysis. In AD, alterations in the expression of FEGs affect the aggregation and infiltration of certain immune cells. This indicated that the occurrence of AD is strongly associated with immune infiltration. Finally, the most appropriate machine learning models were selected, and AD diagnostic models and nomograms were built. The present study provided novel insights that enhance understanding with regard to the molecular mechanism of action of FEGs in AD. Moreover, the present study provided biomarkers that may facilitate the diagnosis of AD.


Assuntos
Doença de Alzheimer , Ferroptose , Doença de Alzheimer/genética , Doença de Alzheimer/imunologia , Ferroptose/genética , Humanos , Aprendizado de Máquina , Bases de Dados Genéticas , Perfilação da Expressão Gênica , Biomarcadores , Prognóstico , Regulação da Expressão Gênica , Biologia Computacional/métodos
14.
Nephron ; 147(6): 362-372, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36649683

RESUMO

BACKGROUND: Obtaining sufficient renal tubular epithelial cells (RTCs) and maintaining the functions of RTCs are vital for developing a bioartificial renal tubule-assisted device for continuous renal replacement therapy. METHODS: We established an optimal Transwell coculture system using human primary renal proximal tubule epithelial cells (RPTECs) and bone marrow mesenchymal stem cells at different cell ratios to investigate morphological and functional changes in RTCs. Changes in cell proliferation, megalin expression, cell cycle, apoptosis, and levels of insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein-7 (BMP-7) after cell culture were investigated. RESULTS: RPTEC/BMMSC coculture at a cell ratio of 3:1 resulted in optimal morphology, function, and growth of RPTECs, in which, viability, proliferation, cytochrome P450 activity, and megalin expression in RPTECs were significantly increased compared to those in other cocultures or RPTECs alone. Additionally, IGF-1 and BMP-7 levels were significantly higher in the 3:1 RPTEC/BMMSC coculture than in the RPTECs alone. CONCLUSION: Our results demonstrate that coculture with RPTECs has great potential for use in renal replacement therapy, thereby providing fundamental information for manufacturing a bioartificial kidney.


Assuntos
Proteína Morfogenética Óssea 7 , Fator de Crescimento Insulin-Like I , Humanos , Técnicas de Cocultura , Fator de Crescimento Insulin-Like I/metabolismo , Proteína-2 Relacionada a Receptor de Lipoproteína de Baixa Densidade/metabolismo , Células Epiteliais/metabolismo , Túbulos Renais Proximais/metabolismo
15.
IEEE Trans Med Imaging ; 42(2): 467-480, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36378797

RESUMO

Accurately delineating individual teeth and the gingiva in the three-dimension (3D) intraoral scanned (IOS) mesh data plays a pivotal role in many digital dental applications, e.g., orthodontics. Recent research shows that deep learning based methods can achieve promising results for 3D tooth segmentation, however, most of them rely on high-quality labeled dataset which is usually of small scales as annotating IOS meshes requires intensive human efforts. In this paper, we propose a novel self-supervised learning framework, named STSNet, to boost the performance of 3D tooth segmentation leveraging on large-scale unlabeled IOS data. The framework follows two-stage training, i.e., pre-training and fine-tuning. In pre-training, three hierarchical-level, i.e., point-level, region-level, cross-level, contrastive losses are proposed for unsupervised representation learning on a set of predefined matched points from different augmented views. The pretrained segmentation backbone is further fine-tuned in a supervised manner with a small number of labeled IOS meshes. With the same amount of annotated samples, our method can achieve an mIoU of 89.88%, significantly outperforming the supervised counterparts. The performance gain becomes more remarkable when only a small amount of labeled samples are available. Furthermore, STSNet can achieve better performance with only 40% of the annotated samples as compared to the fully supervised baselines. To the best of our knowledge, we present the first attempt of unsupervised pre-training for 3D tooth segmentation, demonstrating its strong potential in reducing human efforts for annotation and verification.


Assuntos
Próteses e Implantes , Telas Cirúrgicas , Humanos , Processamento de Imagem Assistida por Computador , Cintilografia , Aprendizado de Máquina Supervisionado
16.
ACS Omega ; 7(29): 25443-25457, 2022 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-35910180

RESUMO

A variety of gaseous products are formed when mine fires and coal and gas outbursts occur in mines. On the one hand, these gas products affect the normal production of mines and the occupational health of miners; on the other hand, the gaseous products can also provide much important information to prevent mine disasters. Thus, the rapid and accurate determination of the component content of multicomponent mixed gases is of great significance. However, the distortion of gas chromatography measurement results, which deviate from the true values, has a serious impact on gas composition determination in mines. To reduce the influence of distortion, an Agilent 490 portable gas chromatograph is used to measure the component content of 11 groups of standard multicomponent mixed gases. It is found that the error rate of the measured result is highly related to the concentration of the selected reference component and the component to be measured. Besides, the key point of each gas concentration is determined according to the scatter diagram of the error rate. Each gas is divided into a high and a low concentration group by the key points, and each gas is selected as the reference component to measure the corresponding component concentration in other gases with multiple-point external standards. Researchers have used the least-squares method to fit univariate linear regression analysis between the measured values and true values of mixed gases. Then, the optimal analysis function and the optimal reference component concentration of each gas can be determined by comparing the regression analysis parameters. Finally, it is found that the error rate of measured values corrected by the optimal analysis function is significantly reduced. It is proved that this method can effectively alleviate the measurement results' distortion, which solves the problem of gas composition determination in underground areas.

17.
J Colloid Interface Sci ; 626: 123-135, 2022 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-35780546

RESUMO

Magnetoelectric coupling is a key strategy to obtain high-performance microwave absorption materials. Especially for carbon matrix composites, the absorbing capacity can be optimized via the tuning of the graphitization degree and the content ratio of the magnetic and dielectric components. Based on this theory, a simple strategy, consisting of the solvothermal method and annealing in an inert atmosphere, is adopted in this study to combine CoNi magnetic alloys with graphitized carbon into micron-scale composite spherical particles. Additionally, special attention is paid to the correlation among the graphitization degree of carbon matrix, component proportion, and dielectric response ability, so as to achieve a flexible micromorphology design and a tunable microwave absorption performance. When the pyrolysis temperature is offset to the best of 700 â„ƒ, a broadband absorption of 6.61 GHz (reflection loss <  - 10 dB) is achieved at an ultrathin matching thickness of 1.9 mm. Adjusting the carbon content can further optimize the impedance matching and realize a high-intensity absorption with a reflection loss of - 72.7 dB. Our work proposes a useful strategy to realize the effective combination of the magnetic and dielectric loss mechanisms and boost the microwave absorption capacity toward achieving the desired broadband and a high-efficiency absorption performance.

18.
Magn Reson Imaging Clin N Am ; 29(1): e1-e19, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33237019

RESUMO

Especially after the launch of 7 T, the ultrahigh magnetic field (UHF) imaging community achieved critically important strides in our understanding of the physics of radiofrequency interactions in the human body, which in turn has led to solutions for the challenges posed by such UHFs. As a result, the originally obtained poor image quality has progressed to the high-quality and high-resolution images obtained at 7 T and now at 10.5 T in the human torso. Despite these tremendous advances, work still remains to further improve the image quality and fully capitalize on the potential advantages UHF has to offer.


Assuntos
Imageamento por Ressonância Magnética/métodos , Tronco/diagnóstico por imagem , Humanos
19.
Prev Vet Med ; 147: 50-52, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-29254726

RESUMO

Clinicians can evaluate the relevance of an outbreak based on its basic reproductive number (R0). So far there has been no report on the R0 of Mycoplasma conjunctivae which is a major cause of goats' conjunctivitis in Taiwan. The present study sought to investigate an outbreak of infectious keratoconjunctivitis (IKC) by Mycoplasma conjunctivae (MC) in an indoor dairy goat barn. The epidemiological curve was recorded to build a susceptible-infected-recovered model and to estimate the R0 by three methods In the investigated goat barn, 60% (31/55) goats showed degrees of IKC signs. The number of infected animals increased quickly after 15days, but slowed down after 41days. The sick goats began to recover after 30days. The epidemic fully stopped after 81days. The estimated R0 ranged from 1.35 to 4.46. In summary, this is the first MC report in Taiwan, and the first one to estimate the R0 of MC.


Assuntos
Número Básico de Reprodução , Surtos de Doenças/veterinária , Doenças das Cabras/epidemiologia , Ceratoconjuntivite Infecciosa/epidemiologia , Infecções por Mycoplasma/veterinária , Mycoplasma conjunctivae/fisiologia , Animais , Doenças das Cabras/microbiologia , Cabras , Ceratoconjuntivite Infecciosa/microbiologia , Infecções por Mycoplasma/epidemiologia , Infecções por Mycoplasma/microbiologia , Prevalência , Taiwan/epidemiologia
20.
Psychoneuroendocrinology ; 75: 116-123, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27815995

RESUMO

Tamoxifen (TAM) is most commonly prescribed for patients with hormone-sensitive breast cancer and exerts agonistic/antagonistic effects on estrogen receptors throughout the body. Accumulating evidence has revealed that breast cancer patients receiving TAM manifest cognitive dysfunction. However, whether these patients have a global attention deficit or a more selective impairment of specific attention networks remains unknown. In the present study, we sought to explore the attention function of premenopausal women with hormone receptor-positive breast cancer treated with TAM using the attention network test (ANT). The subjects included breast cancer patients receiving TAM (TAM, N=43), breast cancer patients not receiving TAM (non-TAM, N=41), and matched healthy controls (HC, N=46). The subjects completed the ANT and neuropsychological tests, which measure three independent attention networks and executive function performance, respectively. Our results indicated that patients in the TAM group had significant deficits in their executive control component but not in the alerting or orienting components. Moreover, the patients showed poor executive function performance in the neuropsychological tests. Additionally, in the TAM group, significant correlations were found between the decreased efficiency of the executive control component and their reduced performance in executive function tests. This study demonstrates that premenopausal women with hormone receptor-positive breast cancer treated with TAM have impairment of the executive attention network and that this impairment was associated with differences in executive function performance.


Assuntos
Atenção/efeitos dos fármacos , Neoplasias da Mama/tratamento farmacológico , Disfunção Cognitiva/induzido quimicamente , Antagonistas de Estrogênios/efeitos adversos , Função Executiva/efeitos dos fármacos , Neoplasias Hormônio-Dependentes/tratamento farmacológico , Pré-Menopausa/efeitos dos fármacos , Tamoxifeno/efeitos adversos , Adulto , Feminino , Humanos , Pessoa de Meia-Idade
SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa