Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 15 de 15
Filtrar
Mais filtros










Intervalo de ano de publicação
1.
Adv Exp Med Biol ; 1192: 95-115, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31705491

RESUMO

Cerebral small vessel disease is associated with late-life depression, cognitive impairment, executive dysfunction, distress, and loss of life for older adults. Late-life depression is becoming a substantial public health burden, and a considerable number of older adults presenting to primary care have significant clinical depression. Even though white matter hyperintensities are linked with small vessel disease, white matter hyperintensities are nonspecific to small vessel disease and can co-occur with other brain diseases. Advanced neuroimaging techniques at the ultrahigh field magnetic resonance imaging are enabling improved characterization, identification of cerebral small vessel disease and are elucidating some of the mechanisms that associate small vessel disease with late-life depression.


Assuntos
Envelhecimento , Doenças de Pequenos Vasos Cerebrais/diagnóstico por imagem , Imagem por Ressonância Magnética/métodos , Neuroimagem/métodos , Idoso , Encéfalo , Depressão , Humanos , Substância Branca
2.
Einstein (Sao Paulo) ; 17(2): eAO4156, 2019 Mar 18.
Artigo em Inglês, Português | MEDLINE | ID: mdl-30892376

RESUMO

OBJECTIVE: To develop and test a beat-to-beat blood pressure monitoring device during coronary angiography, and compare it with invasive blood pressure monitoring. METHODS: Twenty-eight patients with an indication for hemodynamic study were selected for this investigation, and kept in supine position. Before starting the coronary angiography, they were instructed about the use of the left radial bracelet for beat-to-beat blood pressure monitoring. RESULTS: There was a significant difference between the time required for the catheterization laboratory team to acquire the first invasive blood pressure reading and the time to obtain the first beat-to-beat reading (11.1±5.1 and 1.5±1.8, respectively; p<0.0001). The intraclass correlation coefficients (95%CI) of systolic and diastolic blood pressures were 0.897 (0.780-0.952) and 0.876 (0.734-0.942), indicating good reproducibility. CONCLUSION: This study showed the process to develop a beat-to-beat blood pressure monitoring device. When compared to invasive blood pressure monitoring, there were no significant differences between the two methods. This technique may play a promising coadjuvant role when combined with invasive monitoring during coronary angiography procedures.


Assuntos
Determinação da Pressão Arterial/instrumentação , Monitores de Pressão Arterial , Angiografia Coronária/métodos , Determinação da Pressão Arterial/métodos , Desenho de Equipamento , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes
3.
PLoS One ; 14(1): e0209663, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30629618

RESUMO

A variety of 7 Tesla RF coil systems have been proposed to produce spin excitation (B1+ field) and MR image acquisition. Different groups have attempted to mitigate the challenges at high and ultra-high field MRI by proposing novel hardware and software solutions to obtain uniformly high spin excitation at acceptable RF absorption levels. In this study, we extensively compare the designs of two distributed-circuit based RF coils: the Tic-Tac-Toe (TTT) head coil and TEM head coil on multiple anatomically detailed head models and in-vivo. Bench measurements of s-parameters and experimental B1+ field distribution were obtained in volunteers and compared with numerical simulations. RF absorption, quantified by both average and peak SAR, and B1+ field intensity and homogeneity, calculated/measured in terms of maximum over minimum and coefficient of variation (CV) in the region of interest (ROI), are presented for both coils. A study of the RF consistency of both coils across multiple head models for different RF excitation strategies is also presented.


Assuntos
Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Simulação por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Cabeça , Humanos , Aumento da Imagem/métodos , Imagens de Fantasmas , Ondas de Rádio , Software
4.
Einstein (Säo Paulo) ; 17(2): eAO4156, 2019. tab, graf
Artigo em Inglês | LILACS-Express | ID: biblio-989777

RESUMO

ABSTRACT Objective To develop and test a beat-to-beat blood pressure monitoring device during coronary angiography, and compare it with invasive blood pressure monitoring. Methods Twenty-eight patients with an indication for hemodynamic study were selected for this investigation, and kept in supine position. Before starting the coronary angiography, they were instructed about the use of the left radial bracelet for beat-to-beat blood pressure monitoring. Results There was a significant difference between the time required for the catheterization laboratory team to acquire the first invasive blood pressure reading and the time to obtain the first beat-to-beat reading (11.1±5.1 and 1.5±1.8, respectively; p<0.0001). The intraclass correlation coefficients (95%CI) of systolic and diastolic blood pressures were 0.897 (0.780-0.952) and 0.876 (0.734-0.942), indicating good reproducibility. Conclusion This study showed the process to develop a beat-to-beat blood pressure monitoring device. When compared to invasive blood pressure monitoring, there were no significant differences between the two methods. This technique may play a promising coadjuvant role when combined with invasive monitoring during coronary angiography procedures.


RESUMO Objetivo Desenvolver e validar um equipamento para monitorização de pressão arterial batimento a batimento, durante a realização de coronariografia, e comparar com as medidas de pressão arterial invasiva obtidas. Métodos Foram selecionados 28 pacientes com indicação de estudo hemodinâmico, que permaneceram em decúbito dorsal horizontal e, antes do início da coronariografia, foram orientados quanto ao uso da pulseira radial esquerda para monitorização da pressão arterial batimento a batimento. Resultados Houve diferença significativa entre o tempo necessário para a equipe de hemodinâmica adquirir a primeira medida da pressão arterial invasiva e o tempo da primeira medida da pressão arterial batimento a batimento (11,1±5,1 e 1,5±1,8, respectivamente; p<0,0001). Os coeficientes de correlação intraclasse (IC95%) da pressão arterial sistólica e da diastólica foram 0,897 (0,780-0,952) e 0,876 (0,734-0,942), indicando boa reprodutibilidade. Conclusão Este estudo demonstrou o processo de desenvolvimento de um equipamento para avaliação da pressão arterial batimento a batimento. Quando comparado com a pressão arterial invasiva, não foram encontradas diferenças significativas entre as duas medidas. Essa técnica pode constituir ferramenta coadjuvante promissora, associada à monitorização invasiva, durante procedimentos de coronariografia.

5.
Artigo em Inglês | MEDLINE | ID: mdl-31892441

RESUMO

OBJECTIVE: We sought to determine whether the aspects of white matter connectivity implicated in major depression also relate to mild depressive symptoms in family dementia caregivers (dCGs). METHODS: Forty-one dCGs (average age=69 years, standard deviation=6.4) underwent a 7 Tesla 64-direction (12-minute) diffusion-weighted imaging sequence. We compared the fractional anisotropy (FA) of 11 white matter features between dCGs with (n=20) and without (n=21) depressive symptoms (Patient Health Questionnaire-9 scores ≥5). RESULTS: Caregivers reporting depression symptoms had lower FA in tracts connecting to the posterior cingulate cortex (Cohen's d = -0.9) and connecting dorsolateral prefrontal with rostral cingulate regions (Cohen's d = -1.2). CONCLUSIONS: Posterior cingulate and dorsolateral prefrontal-to-rostral cingulate white matter, implicated in prior studies of major depression, appear relevant to mild depression in dCGs.

6.
PLoS One ; 13(11): e0206127, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30481187

RESUMO

Radio-frequency (RF) field inhomogeneities and higher levels of specific absorption rate (SAR) still present great challenges in ultrahigh-field (UHF) MRI. In this study, an in-depth analysis of the eigenmodes of a 20-channel transmit Tic-Tac-Toe (TTT) RF array for 7T neuro MRI is presented. The eigenmodes were calculated for five different Z levels (along the static magnetic field direction) of the coil. Four eigenmodes were obtained for each Z level (composed of 4 excitation ports), and they were named based on the characteristics of their field distributions: quadrature, opposite-phase, anti-quadrature, and zero-phase. Corresponding finite-difference time-domain (FDTD) simulations were performed and experimental B1+ field maps were acquired using a homogeneous spherical phantom and human head (in-vivo). The quadrature mode is the most efficient and it excites the central brain regions; the opposite-phase mode excites the brain peripheral regions; anti-quadrature mode excites the head periphery; and the zero-phase mode excites cerebellum and temporal lobes. Using this RF array, up to five eigenmodes (from five different Z levels) can be simultaneously excited. The superposition of these modes has the potential to produce homogeneous excitation with full brain coverage and low levels of SAR at 7T MRI.


Assuntos
Cerebelo/diagnóstico por imagem , Simulação por Computador , Imagem por Ressonância Magnética/métodos , Lobo Temporal/diagnóstico por imagem , Cerebelo/efeitos da radiação , Campos Eletromagnéticos , Cabeça/diagnóstico por imagem , Cabeça/efeitos da radiação , Humanos , Campos Magnéticos , Cavidade Nasal/diagnóstico por imagem , Cavidade Nasal/efeitos da radiação , Imagens de Fantasmas , Ondas de Rádio , Lobo Temporal/efeitos da radiação
7.
Am J Geriatr Psychiatry ; 26(6): 690-699, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29628321

RESUMO

OBJECTIVES: Hippocampal hyperactivation marks preclinical dementia pathophysiology, potentially due to differences in the connectivity of specific medial temporal lobe structures. Our aims were to characterize the resting-state functional connectivity of medial temporal lobe sub-structures in older adults, and evaluate whether specific substructural (rather than global) functional connectivity relates to memory function. METHODS: In 15 adults (mean age: 69 years), we evaluated the resting state functional connectivity of medial temporal lobe substructures: dentate/Cornu Ammonis (CA) 4, CA1, CA2/3, subiculum, the molecular layer, entorhinal cortex, and parahippocampus. We used 7-Tesla susceptibility weighted imaging and magnetization-prepared rapid gradient echo sequences to segment substructures of the hippocampus, which were used as structural seeds for examining functional connectivity in a resting BOLD sequence. We then assessed correlations between functional connectivity with memory performance (short and long delay free recall on the California Verbal Learning Test [CVLT]). RESULTS: All the seed regions had significant connectivity within the temporal lobe (including the fusiform, temporal, and lingual gyri). The left CA1 was the only seed with significant functional connectivity to the amygdala. The left entorhinal cortex was the only seed to have significant functional connectivity with frontal cortex (anterior cingulate and superior frontal gyrus). Only higher left dentate-left lingual connectivity was associated with poorer CVLT performance (Spearman r = -0.81, p = 0.0003, Benjamini-Hochberg false discovery rate: 0.01) after multiple comparison correction. CONCLUSIONS: Rather than global hyper-connectivity of the medial temporal lobe, left dentate-lingual connectivity may provide a specific assay of medial temporal lobe hyper-connectivity relevant to memory in aging.


Assuntos
Mapeamento Encefálico , Hipocampo/fisiopatologia , Memória/fisiologia , Idoso , Feminino , Humanos , Imagem por Ressonância Magnética , Masculino , Rememoração Mental/fisiologia , Vias Neurais/fisiopatologia
8.
9.
Magn Reson Imaging ; 45: 1-6, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28893660

RESUMO

A four-channel Tic-Tac-Toe (TTT) transmit RF coil was designed and constructed for foot and ankle imaging at 7T MRI. Numerical simulations using an in-house developed FDTD package and experimental analyses using a homogenous phantom show an excellent agreement in terms of B1+ field distribution and s-parameters. Simulations performed on an anatomically detailed human lower leg model demonstrated an B1+ field distribution with a coefficient of variation (CV) of 23.9%/15.6%/28.8% and average B1+ of 0.33µT/0.56µT/0.43µT for 1W input power (i.e., 0.25W per channel) in the ankle/calcaneus/mid foot respectively. In-vivo B1+ mapping shows an average B1+ of 0.29µT over the entire foot/ankle. This newly developed RF coil also presents acceptable levels of average SAR (0.07W/kg for 10g per 1W of input power) and peak SAR (0.34W/kg for 10g per 1W of input power) over the whole lower leg. Preliminary in-vivo images in the foot/ankle were acquired using the T2-DESS MRI sequence without the use of a dedicated receive-only array.


Assuntos
Pé/anatomia & histologia , Imagem por Ressonância Magnética/métodos , Imagens de Fantasmas , Tornozelo/anatomia & histologia , Tornozelo/diagnóstico por imagem , Desenho de Equipamento , Pé/diagnóstico por imagem , Humanos , Modelos Biológicos , Ondas de Rádio
10.
PLoS One ; 12(8): e0183168, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28806768

RESUMO

OBJECTIVE: The purpose of this study is to design an anthropomorphic heterogeneous head phantom that can be used for MRI and other electromagnetic applications. MATERIALS AND METHODS: An eight compartment, physical anthropomorphic head phantom was developed from a 3T MRI dataset of a healthy male. The designed phantom was successfully built and preliminarily evaluated through an application that involves electromagnetic-tissue interactions: MRI (due to it being an available resource). The developed phantom was filled with media possessing electromagnetic constitutive parameters that correspond to biological tissues at ~297 MHz. A preliminary comparison between an in-vivo human volunteer (based on whom the anthropomorphic head phantom was created) and various phantoms types, one being the anthropomorphic heterogeneous head phantom, were performed using a 7 Tesla human MRI scanner. RESULTS: Echo planar imaging was performed and minimal ghosting and fluctuations were observed using the proposed anthropomorphic phantom. The magnetic field distributions (during MRI experiments at 7 Tesla) and the scattering parameter (measured using a network analyzer) were most comparable between the anthropomorphic heterogeneous head phantom and an in-vivo human volunteer. CONCLUSION: The developed anthropomorphic heterogeneous head phantom can be used as a resource to various researchers in applications that involve electromagnetic-biological tissue interactions such as MRI.


Assuntos
Imagem por Ressonância Magnética/métodos , Imagens de Fantasmas , Impressão Tridimensional/instrumentação , Imagem Ecoplanar , Desenho de Equipamento , Cabeça , Humanos , Processamento de Imagem Assistida por Computador
11.
PLoS One ; 12(6): e0175629, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28662061

RESUMO

OBJECTIVE: The purpose of this study was to explore the efficacy of Ultra-high field [UHF] 7 Tesla [T] MRI as compared to 3T MRI in non-contrast enhanced [nCE] imaging of structural anatomy in the elbow, forearm, and hand [upper extremity]. MATERIALS AND METHOD: A wide range of sequences including T1 weighted [T1] volumetric interpolate breath-hold exam [VIBE], T2 weighted [T2] double-echo steady state [DESS], susceptibility weighted imaging [SWI], time-of-flight [TOF], diffusion tensor imaging [DTI], and diffusion spectrum imaging [DSI] were optimized and incorporated with a radiofrequency [RF] coil system composed of a transverse electromagnetic [TEM] transmit coil combined with an 8-channel receive-only array for 7T upper extremity [UE] imaging. In addition, Siemens optimized protocol/sequences were used on a 3T scanner and the resulting images from T1 VIBE and T2 DESS were compared to that obtained at 7T qualitatively and quantitatively [SWI was only qualitatively compared]. DSI studio was utilized to identify nerves based on analysis of diffusion weighted derived fractional anisotropy images. Images of forearm vasculature were extracted using a paint grow manual segmentation method based on MIPAV [Medical Image Processing, Analysis, and Visualization]. RESULTS: High resolution and high quality signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]-images of the hand, forearm, and elbow were acquired with nearly homogeneous 7T excitation. Measured [performed on the T1 VIBE and T2 DESS sequences] SNR and CNR values were almost doubled at 7T vs. 3T. Cartilage, synovial fluid and tendon structures could be seen with higher clarity in the 7T T1 and T2 weighted images. SWI allowed high resolution and better quality imaging of large and medium sized arteries and veins, capillary networks and arteriovenous anastomoses at 7T when compared to 3T. 7T diffusion weighted sequence [not performed at 3T] demonstrates that the forearm nerves are clearly delineated by fiber tractography. The proper digital palmar arteries and superficial palmar arch could also be clearly visualized using TOF nCE 7T MRI. CONCLUSION: Ultra-high resolution neurovascular imaging in upper extremities is possible at 7T without use of renal toxic intravenous contrast. 7T MRI can provide superior peripheral nerve [based on fiber anisotropy and diffusion coefficient parameters derived from diffusion tensor/spectrum imaging] and vascular [nCE MRA and vessel segmentation] imaging.


Assuntos
Imagem de Tensor de Difusão/métodos , Nervos Periféricos/diagnóstico por imagem , Feminino , Humanos , Masculino
12.
NMR Biomed ; 30(1)2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27859861

RESUMO

In ultrahigh-field MRI, such as 7 T, the signal-to-noise ratio (SNR) increases while transmit (Tx) field (B1+ ) can be degraded due to inhomogeneity and elevated specific absorption rate (SAR). By applying new array coil concepts to both Tx and receive (Rx) coils, the B1+ homogeneity and SNR can be improved. In this study, we developed and tested in vivo a new RF coil system for 7 T breast MRI. An RF coil system composed of an eight-channel Tx-only array based on a tic-tac-toe design (can be combined to operate in single-Tx mode) in conjunction with an eight-channel Rx-only insert was developed. Characterizations of the B1+ field and associated SAR generated by the developed RF coil system were numerically calculated and empirically measured using an anatomically detailed breast model, phantom and human breasts. In vivo comparisons between 3 T (using standard commercial solutions) and 7 T (using the newly developed coil system) breast imaging were made. At 7 T, about 20% B1+ inhomogeneity (standard deviation over the mean) was measured within the breast tissue for both the RF simulations and 7 T experiments. The addition of the Rx-only array enhances the SNR by a factor of about three. High-quality MR images of human breast were acquired in vivo at 7 T. For the in vivo comparisons between 3 T and 7 T, an approximately fourfold increase of SNR was measured with 7 T imaging. The B1+ field distributions in the breast model, phantom and in vivo were in reasonable agreement. High-quality 7 T in vivo breast MRI was successfully acquired at 0.6 mm isotropic resolution using the newly developed RF coil system.


Assuntos
Mama/anatomia & histologia , Mama/diagnóstico por imagem , Aumento da Imagem/instrumentação , Imagem por Ressonância Magnética/instrumentação , Magnetismo/instrumentação , Transdutores , Adulto , Desenho de Equipamento , Análise de Falha de Equipamento , Feminino , Humanos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/instrumentação , Interpretação de Imagem Assistida por Computador/métodos , Campos Magnéticos , Imagens de Fantasmas , Doses de Radiação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
13.
NMR Biomed ; 29(12): 1768-1779, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27809383

RESUMO

The purpose of this study is to develop and evaluate a custom-designed 7  T MRI coil and explore its use for upper extremity applications. An RF system composed of a transverse electromagnetic transmit coil and an eight-channel receive-only array was developed for 7  T upper extremity applications. The RF system was characterized and evaluated using scattering parameters and B1+ mapping. Finite difference time domain simulations were performed to evaluate the B1+ field distribution and specific absorption rate for the forearm region of the upper extremity. High-resolution 7  T images were acquired and compared with those at 3 T. The simulation and experimental results show very good B1+ field homogeneity across the forearm. High-resolution images of musculotendinous, osseocartilaginous, and neurovascular structures in the upper extremity are presented with T1 volumetric interpolated breath-hold examination, T2 double-echo steady state, T2 * susceptibility weighted imaging (SWI), diffusion tensor imaging, and time-of-flight sequences. Comparison between 3  T and 7  T is shown. Intricate contextual anatomy can be delineated in synovial, fibrocartilaginous, interosseous, and intraosseous trabecular structures of the forearm, as well as palmar and digital vascular anatomy (including microvascular detail in SWI). Ultra-high-field 7  T imaging holds great potential in improving the sensitivity and specificity of upper extremity imaging, especially in wrist and hand pathology secondary to bone, ligament, nerve, vascular, and other soft or hard tissue etiology.


Assuntos
Aumento da Imagem/instrumentação , Imagem por Ressonância Magnética/instrumentação , Magnetismo/instrumentação , Transdutores , Extremidade Superior/anatomia & histologia , Projeto Auxiliado por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
14.
J Magn Reson ; 269: 55-64, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27240143

RESUMO

Developing a radiofrequency (RF) coil system that produces a uniform B1(+) field (circularly polarized component of the transverse magnetic field responsible for excitation) and low specific absorption rate (SAR) is critical for high performance ultrahigh field human imaging. In this study, we provide the design of a new eight channel radiofrequency (RF) transmit (Tx) array for breast MRI at 7T. A numerical analysis utilizing an in-house finite difference time domain (FDTD) package was carried out in (1) four breast models, (2) homogeneous spherical model and (3) full body model to calculate the B1(+) intensity (µT) and homogeneity represented by coefficient of variation (CoV=standard deviation/mean) in the proposed RF array design. The numerical results were compared with that measured in breast phantom (Bphantom) and homogeneous spherical phantom at 7T MRI and showed very good agreement. Average and peak SARs were also calculated in the four breast models and the temperature rises due to the operation of the RF array were also measured in the Bphantom. The proposed RF array; which can operate in a single or multi transmit modes, demonstrates homogeneous RF field excitation with acceptable local/average SAR levels for breast MRI at 7T.


Assuntos
Mama/diagnóstico por imagem , Imagem por Ressonância Magnética , Humanos , Campos Magnéticos , Imagens de Fantasmas , Ondas de Rádio
15.
Am J Infect Control ; 42(11): 1188-92, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25234045

RESUMO

BACKGROUND: Monitoring of hand hygiene is an important part of the improvement of hospital quality indicators. METHODS: This study was prospectively performed over a 14-week (electronic observer) period from December 3, 2013-March 9, 2014, to evaluate hand hygiene compliance in an adult step-down unit. We compared electronic handwash counters with the application of radiofrequency identification (RFID - ZigBee; i-Healthsys, São Carlos, Brazil) (electronic observer), which counts each activation of the alcohol gel dispenser to direct observation (human observer) using the iScrub application. RESULTS: For the overall time period of simultaneous electronic and human observation, we found that the electronic observer identified 414 hand hygiene episodes, whereas the human observers identified 448 episodes. Therefore, we found 92% (95% confidence interval [CI], 90%-95%) overall concordance (414/448), with an intraclass correlation coefficient of .87 (95% CI, 0.77-0.92). CONCLUSION: Our RFID (ZigBee) system showed good accuracy (92%) and is a useful method to monitor hand hygiene compliance.


Assuntos
Monitoramento Epidemiológico , Fidelidade a Diretrizes/estatística & dados numéricos , Fidelidade a Diretrizes/normas , Higiene das Mãos/estatística & dados numéricos , Higiene das Mãos/normas , Adulto , Brasil , Humanos , Estudos Prospectivos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA