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1.
medRxiv ; 2023 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-37873422

RESUMO

Deuterium Metabolic Imaging (DMI) is a novel method that can complement traditional anatomical magnetic resonance imaging (MRI) of the brain. DMI relies on the MR detection of metabolites that become labeled with deuterium (2H) after administration of a deuterated substrate and can provide images with highly specific metabolic information. However, clinical adoption of DMI is complicated by its relatively long scan time. Here, we demonstrate a strategy to interleave DMI data acquisition with MRI that results in a comprehensive neuro-imaging protocol without adding scan time. The interleaved MRI-DMI routine includes four essential clinical MRI scan types, namely T1-weighted MP-RAGE, FLAIR, T2-weighted Imaging (T2W) and susceptibility weighted imaging (SWI), interwoven with DMI data acquisition. Phantom and in vivo human brain data show that MR image quality, DMI sensitivity, as well as information content are preserved in the MRI-DMI acquisition method. The interleaved MRI-DMI technology provides full flexibility to upgrade traditional MRI protocols with DMI, adding unique metabolic information to existing types of anatomical image contrast, without extra scan time.

2.
Magn Reson Med ; 90(3): 1228-1241, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37145035

RESUMO

PURPOSE: To design and implement a multi-coil (MC) array for B0 field generation for image encoding and simultaneous advanced shimming in a novel 1.5T head-only MRI scanner. METHODS: A 31-channel MC array was designed following the unique constraints of this scanner design: The vertically oriented magnet is very short, stopping shortly above the shoulders of a sitting subject, and includes a window for the subject to see through. Key characteristics of the MC hardware, the B0 field generation capabilities, and thermal behavior, were optimized in simulations prior to its construction. The unit was characterized via bench testing. B0 field generation capabilities were validated on a human 4T MR scanner by analysis of experimental B0 fields and by comparing images for several MRI sequences acquired with the MC array to those acquired with the system's linear gradients. RESULTS: The MC system was designed to produce a multitude of linear and nonlinear magnetic fields including linear gradients of up to 10 kHz/cm (23.5 mT/m) with MC currents of 5 A per channel. With water cooling it can be driven with a duty cycle of up to 74% and ramp times of 500 µs. MR imaging experiments encoded with the developed multi-coil hardware were largely artifact-free; residual imperfections were predictable, and correctable. CONCLUSION: The presented compact multi-coil array is capable of generating image encoding fields with amplitudes and quality comparable to clinical systems at very high duty cycles, while additionally enabling high-order B0 shimming capabilities and the potential for nonlinear encoding fields.


Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Humanos , Encéfalo/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas , Campos Magnéticos , Artefatos
3.
J Magn Reson ; 341: 107247, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35691241

RESUMO

Gradient modulated RF pulses, especially gradient offset independent adiabaticity (GOIA) pulses, are increasingly gaining attention for high field clinical magnetic resonance spectroscopy and spectroscopic imaging (MRS/MRSI) due to the lower peak B1 amplitude and associated power demands achievable relative to its non-modulated adiabatic full passage counterparts. In this work we describe the development of two GOIA RF pulses: 1) A power efficient, 3.0 ms wideband uniform rate with smooth truncation (WURST) modulated RF pulse with 15 kHz bandwidth compatible with a clinically feasible peak B1 amplitude of 0.87 kHz (or 20 µT), and 2) A highly selective asymmetric 6.66 ms RF pulse with 20 kHz bandwidth designed to achieve a single-sided, fractional transition width of only 1.7%. Effects of potential asynchrony between RF and gradient-modulated (GM) waveforms for 3 ms GOIA-WURST RF pulses was evaluated by simulation and experimentally. Results demonstrate that a 20+ µs asynchrony between RF and GM functions substantially degrades inversion performance when using large RF offsets to achieve translation. A projection-based method is presented that allows a quick calibration of RF and GM asynchrony on pre-clinical/clinical MR systems. The asymmetric GOIA pulse was implemented within a multi-pulse OVS sequence to achieve power efficient, highly-selective, and B1 and T1-independent signal suppression for extracranial lipid suppression. The developed GOIA pulses were utilized with linear gradient modulation (X, Y, Z gradient fields), and with second-order-field modulations (Z2, X2Y2 gradient fields) to provide elliptically-shaped regions-of-interest for MRS and MRSI acquisitions. Both described GOIA-RF pulses have substantial clinical value; specifically, the 3.0 ms GOIA-WURST pulse is beneficial to realize short TE sLASER localized proton MRS/MRSI sequences, and the asymmetric GOIA RF pulse has applications in highly selective outer volume signal suppression to allow interrogation of tissue proximal to extracranial lipids with full-intensity.


Assuntos
Imageamento por Ressonância Magnética , Processamento de Sinais Assistido por Computador , Encéfalo/metabolismo , Frequência Cardíaca , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas
4.
Magn Reson Med ; 88(1): 28-37, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35225375

RESUMO

PURPOSE: To integrate deuterium metabolic imaging (DMI) with clinical MRI through an interleaved MRI and DMI acquisition workflow. Interleaved MRI-DMI was enabled with hardware and pulse sequence modifications, and the performance was demonstrated using fluid-attenuated inversion recovery (FLAIR) MRI as an example. METHODS: Interleaved FLAIR-DMI was developed by interleaving the 2 H excitation and acquisition time windows into the intrinsic delay periods presented in the FLAIR method. All 2 H MR signals were up-converted to the 1 H Larmor frequency using a custom-built hardware unit, which also achieved frequency and phase locking of the output signal in real-time. The interleaved measurements were compared with direct measurements both in phantom and in the human brain in vivo. RESULTS: The interleaved MRI-DMI acquisition strategy allowed simultaneous detection of FLAIR MRI and DMI in the same scan time as a FLAIR-only MRI acquisition. Both phantom and in vivo data showed that the MR image quality, DMI sensitivity as well as information content were preserved using interleaved MRI-DMI. CONCLUSION: The interleaved MRI-DMI technology can be used to extend clinical MRI protocols with DMI, thereby offering a metabolic component to the MR imaging contrasts without a penalty on patient comfort or scan time.


Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Encéfalo/diagnóstico por imagem , Meios de Contraste , Deutério , Humanos , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas
5.
J Pharm Pract ; 34(4): 587-591, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31835959

RESUMO

BACKGROUND: Data indicate there are tens of thousands of self-administered medication errors each year in the United States alone. OBJECTIVE: The aim of this study was to determine whether information embedded in Quick Response (QR) codes could reduce self-administered medication errors compared to current medication labeling among older and younger age groups. METHODS: Two population samples (Arizona State University undergraduates and senior citizens over 70; n = 55) were recruited for participation. Participants were randomly assigned to 2 groups: one with access to QR code-based information (graphic and text) and a second group with only bottle label information. Participants were allowed 30 minutes to answer 17 scenario-based questions about administering their medications. RESULTS: Statistically significant main effects of more correct answers when using QR code than current bottle labeling, F 1, 51 = 181.57, P < .001, η2 = 0.78, and for younger adults compared to older, F 1, 51 = 24.4, P < .001, η2 = 0.33. CONCLUSION: The study supports the use of QR code technology to increase patient safety of self-administered medications in both older and younger age groups. Future research is needed to address the technological and usability aspects of implementation (eg, phone app, voice, graphic, and text presentation).


Assuntos
Erros de Medicação , Segurança do Paciente , Adulto , Humanos , Tecnologia , Estados Unidos
6.
NMR Biomed ; 34(1): e4415, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33001485

RESUMO

A multitude of extracranial lipid suppression methods exist for proton MRSI acquisitions. Popular and emerging lipid suppression methods each have their inherent set of advantages and disadvantages related to the achievable level of lipid suppression, RF power deposition, insensitivity to B1+ field and lipid T1 heterogeneity, brain coverage, spatial selectivity, chemical shift displacement (CSD) errors and the reliability of spectroscopic data spanning the observed 0.9-4.7 ppm band. The utility of elliptical localization with pulsed second order fields (ECLIPSE) was previously demonstrated with a greater than 100-fold in extracranial lipid suppression and low power requirements utilizing 3 kHz bandwidth AFP pulses. Like all gradient-based localization methods, ECLIPSE is sensitive to CSD errors, resulting in a modified metabolic profile in edge-of-ROI voxels. In this work, ECLIPSE is extended with 15 kHz bandwidth second order gradient-modulated RF pulses based on the gradient offset-independent adiabaticity (GOIA) algorithm to greatly reduce CSD and improve spatial selectivity. An adiabatic double spin-echo ECLIPSE inner volume selection (TE = 45 ms) MRSI method and an ECLIPSE outer volume suppression (TE = 3.2 ms) FID-MRSI method were implemented. Both GOIA-ECLIPSE MRSI sequences provided artifact-free metabolite spectra in vivo, with a greater than 100-fold in lipid suppression and less than 2.6 mm in-plane CSD and less than 3.3 mm transition width for edge-of-ROI voxels, representing an ~5-fold improvement compared with the parent, nongradient-modulated method. Despite the 5-fold larger bandwidth, GOIA-ECLIPSE only required a 1.9-fold increase in RF power. The highly robust lipid suppression combined with low CSD and sharp ROI edge transitions make GOIA-ECLIPSE an attractive alternative to commonly employed lipid suppression methods. Furthermore, the low RF power deposition demonstrates that GOIA-ECLIPSE is very well suited for high field (≥3 T) MRSI applications.


Assuntos
Algoritmos , Encéfalo/diagnóstico por imagem , Imageamento por Ressonância Magnética , Prótons , Simulação por Computador , Feminino , Humanos , Lipídeos/análise , Masculino , Imagens de Fantasmas , Ondas de Rádio , Água/análise
7.
Magn Reson Med ; 84(6): 2953-2963, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32544274

RESUMO

PURPOSE: Spatial encoding for MRI is generally based on linear x, y, and z magnetic field gradients generated by a set of dedicated gradient coils. We recently introduced the dynamic multicoil technique (DYNAMITE) for B0 field control and demonstrated DYNAMITE MRI in a preclinical MR environment. In this study, we report the first realization of DYNAMITE MRI of the in vivo human head. METHODS: Gradient fields for DYNAMITE MRI were generated with a 28-channel multicoil hardware arranged in 4 rows of 7 coils on a cylindrical surface (length 359 mm, diameter 344 mm, maximum 5 A per coil). DYNAMITE MRIs of a resolution phantom and in vivo human heads were acquired with multislice gradient-echo, multislice spin-echo, and 3D gradient-echo sequences. The resultant image fidelity was compared to that obtained with conventional gradient coil technology. RESULTS: DYNAMITE field control enabled the realization of all imaging sequences with average gradient errors ≤ 1%. DYNAMITE MRI provided image quality and sensitivity comparable to conventional gradient technology without any obvious artifacts. Some minor geometric deformations were noticed primarily in the image periphery as the result of regional field imperfections. The imperfections can be readily approximated theoretically through numerical integration of the Biot-Savart law and removed through image distortion correction. CONCLUSION: The first realization of DYNAMITE MRI of the in vivo human head has been presented. The obtained image fidelity is comparable to MRI with conventional gradient coils, paving the way for full-fledged DYNAMITE MRI and B0 shim systems for human applications.


Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Artefatos , Encéfalo/diagnóstico por imagem , Humanos , Campos Magnéticos , Imagens de Fantasmas
8.
NMR Biomed ; 33(3): e4235, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31879985

RESUMO

Deuterium metabolic imaging (DMI) is a novel MR-based method to spatially map metabolism of deuterated substrates such as [6,6'-2 H2 ]-glucose in vivo. Compared with traditional 13 C-MR-based metabolic studies, the MR sensitivity of DMI is high due to the larger 2 H magnetic moment and favorable T1 and T2 relaxation times. Here, the magnetic field dependence of DMI sensitivity and transmit efficiency is studied on phantoms and rat brain postmortem at 4, 9.4 and 11.7 T. The sensitivity and spectral resolution on human brain in vivo are investigated at 4 and 7 T before and after an oral dose of [6,6'-2 H2 ]-glucose. For small animal surface coils (Ø 30 mm), the experimentally measured sensitivity and transmit efficiency scale with the magnetic field to a power of +1.75 and -0.30, respectively. These are in excellent agreement with theoretical predictions made from the principle of reciprocity for a coil noise-dominant regime. For larger human surface coils (Ø 80 mm), the sensitivity scales as a +1.65 power. The spectral resolution increases linearly due to near-constant linewidths. With optimal multireceiver arrays the acquisition of DMI at a nominal 1 mL spatial resolution is feasible at 7 T.


Assuntos
Deutério/metabolismo , Campos Magnéticos , Imageamento por Ressonância Magnética , Animais , Encéfalo/diagnóstico por imagem , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Humanos , Imagens de Fantasmas , Ratos , Razão Sinal-Ruído
9.
Magn Reson Med ; 83(5): 1539-1552, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-31742799

RESUMO

PURPOSE: The robust and reliable utilization of proton magnetic resonance spectroscopic imaging (MRSI) at high fields is hampered by several key technical difficulties, including contamination from extracranial lipids. To that end, this work presents novel lipid suppression sequences for proton MRSI in the human brain utilizing elliptical localization with pulsed second-order fields (ECLIPSE). METHODS: Two lipid suppression methods were implemented with the ECLIPSE gradient insert. One method is a variable power, 4-pulse sequence optimized to achieve outer volume suppression (OVS) and compared against a standard, 8-slice OVS method. The second ECLIPSE method is implemented as an inversion recovery (IR) sequence with elliptical inner volume selection (IVS) and compared against a global IR method. RESULTS: The ECLIPSE-OVS sequence provided a 116-fold mean lipid suppression (range, 104-134), whereas an optimized 8-slice OVS sequence achieved 15-fold suppression (range, 13-18). Furthermore, the superior ECLIPSE-OVS suppression was achieved at 30% of the radiofrequency (RF) power required by 8-slice OVS. The ECLIPSE-based IR sequence suppressed skull lipids by 155-fold (range, 122-257), compared to 16-fold suppression (range, 14-19) achieved with IR. CONCLUSION: OVS and IVS executed with ECLIPSE provide robust and effective lipid suppression at reduced RF power with high immunity to variations in B1 and T1 .


Assuntos
Algoritmos , Prótons , Encéfalo/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Tomografia por Emissão de Pósitrons
10.
Sci Adv ; 4(8): eaat7314, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30140744

RESUMO

Currently, the only widely available metabolic imaging technique in the clinic is positron emission tomography (PET) detection of the radioactive glucose analog 2-18F-fluoro-2-deoxy-d-glucose (18FDG). However, 18FDG-PET does not inform on metabolism downstream of glucose uptake and often provides ambiguous results in organs with intrinsic high glucose uptake, such as the brain. Deuterium metabolic imaging (DMI) is a novel, noninvasive approach that combines deuterium magnetic resonance spectroscopic imaging with oral intake or intravenous infusion of nonradioactive 2H-labeled substrates to generate three-dimensional metabolic maps. DMI can reveal glucose metabolism beyond mere uptake and can be used with other 2H-labeled substrates as well. We demonstrate DMI by mapping metabolism in the brain and liver of animal models and human subjects using [6,6'-2H2]glucose or [2H3]acetate. In a rat glioma model, DMI revealed pronounced metabolic differences between normal brain and tumor tissue, with high-contrast metabolic maps depicting the Warburg effect. We observed similar metabolic patterns and image contrast in two patients with a high-grade brain tumor after oral intake of 2H-labeled glucose. Further, DMI used in rat and human livers showed [6,6'-2H2]glucose stored as labeled glycogen. DMI is a versatile, robust, and easy-to-implement technique that requires minimal modifications to existing clinical magnetic resonance imaging scanners. DMI has great potential to become a widespread method for metabolic imaging in both (pre)clinical research and the clinic.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/patologia , Deutério/metabolismo , Glioma/patologia , Glucose/metabolismo , Imageamento por Ressonância Magnética/métodos , Animais , Encéfalo/metabolismo , Estudos de Casos e Controles , Glioma/metabolismo , Humanos , Processamento de Imagem Assistida por Computador/métodos , Masculino , Pessoa de Meia-Idade , Ratos , Ratos Endogâmicos F344
11.
NMR Biomed ; 31(9): e3949, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29985532

RESUMO

Proton MRSI has great clinical potential for metabolic mapping of the healthy and pathological human brain. Unfortunately, the promise has not yet been fully achieved due to numerous technical challenges related to insufficient spectral quality caused by magnetic field inhomogeneity, insufficient RF transmit power and incomplete lipid suppression. Here a robust, novel method for lipid suppression in 1 H MRSI is presented. The method is based on 2D spatial localization of an elliptical region of interest using pulsed second-order spherical harmonic (SH) magnetic fields. A dedicated, high-amplitude second-order SH gradient setup was designed and constructed, containing coils to generate Z2, X2Y2 and XY magnetic fields. Simulations and phantom MRI results are used to demonstrate the principles of the method and illustrate the manifestation of chemical shift displacement. 1 H MRSI on human brain in vivo demonstrates high quality, robust suppression of extracranial lipids. The method allows a wide range of inner or outer volume selection or suppression and should find application in MRSI, reduced-field-of-view MRI and single-volume MRS.


Assuntos
Algoritmos , Lipídeos/química , Imageamento por Ressonância Magnética , Imagens de Fantasmas , Espectroscopia de Prótons por Ressonância Magnética , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Humanos
12.
J Occup Health Psychol ; 21(4): 403-414, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26652265

RESUMO

There is a lack of comprehensive research on Ecological Momentary Assessment (EMA) feasibility to study occupational stress, especially its long-term sustainability. EMA application in education contexts has also been sparse. This study investigated the feasibility of using EMA to study teacher stress over 2 years using both objective compliance data and a self-reported feasibility survey. It also examined the influence of individual and school factors on EMA feasibility. Participants were 202 sixth through eighth grade teachers from 22 urban middle schools in the southern United States. EMA was implemented via an iPod-based Teacher Stress Diary (TSD). Teachers recorded demands, stress responses, and resources during 12 days (6 waves) over 2 years. Feasibility was assessed via compliance data generated by the TSD (e.g., entry completion) and an EMA Feasibility Survey of self-reported user-friendliness and EMA interference. The results showed high compliance regarding entry and item completion, and completion time, which was sustained over time. User-friendliness was appraised as very high and EMA interference as low. Initial difficulties regarding timing and length of assessments were addressed via EMA method refinement, resulting in improved feasibility. Teachers' ethnicity, age, marital status, grade/course taught, class size, class load, and daily workload impacted feasibility. The results supported the feasibility of using EMA to study work stress longitudinally and the value of continued feasibility monitoring. They also support EMA use to study teacher stress and inform EMA implementation in schools. Some teacher and school factors need to be taken into consideration when deciding on EMA implementation in education contexts. (PsycINFO Database Record


Assuntos
Comportamento Cooperativo , Avaliação Momentânea Ecológica , Professores Escolares/psicologia , Autorrelato , Estresse Psicológico/psicologia , Adulto , Avaliação Momentânea Ecológica/estatística & dados numéricos , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Análise de Regressão , Professores Escolares/estatística & dados numéricos , Instituições Acadêmicas , Estados Unidos , População Urbana , Local de Trabalho/psicologia , Adulto Jovem
13.
Hum Factors ; 56(6): 1021-35, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25277014

RESUMO

OBJECTIVE: We investigated whether intelligent advanced warnings of the end of green traffic signals help drivers negotiate the dilemma zone (DZ) at signalized intersections and sought to identify behavioral mechanisms for any warning-related benefits. BACKGROUND: Prior research suggested that warnings of end of green can increase slowing and stopping frequency given the DZ, but drivers may sometimes respond to warnings by speeding up. METHOD: In two simulator studies, we compared six types of roadway or in-vehicle warnings with a no-warning control condition. Using multilevel modeling, we tested mediation models of the behavioral mechanisms underlying the effects of warnings. RESULTS: In both studies, warnings led to more stopping at DZ intersections and milder decelerations when stopping compared with no warning. Drivers' predominant response to warnings was anticipatory slowing on approaching the intersection, not speeding up. The increased stopping with warning was mediated by increased slowing. In Study I, anticipatory slowing given warnings generalized to green-light intersections where no warning was given. In Study 2, we found that lane-specific warnings (e.g., LED lights embedded in each lane) sometimes led to fewer unsafe emergency stops than did non-lane-specific roadside warnings. CONCLUSION: End-of-green warnings led to safer behavior in the DZ and on the early approach to intersections. The main mechanism for the benefits of warnings was drivers' increased anticipatory slowing on approaching an intersection. Lane-specific warnings may have some benefits over roadside warnings. APPLICATION: Applications include performance models of how drivers use end-of-green warnings, control algorithms and warning displays for intelligent intersections, and statistical methodology in human factors research.


Assuntos
Prevenção de Acidentes/instrumentação , Acidentes de Trânsito/prevenção & controle , Condução de Veículo/psicologia , Comportamento de Escolha , Interface Usuário-Computador , Adulto , Simulação por Computador , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Equipamentos de Proteção , Tempo de Reação , Adulto Jovem
14.
NMR Biomed ; 27(8): 897-906, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24839167

RESUMO

The in vivo rat model is a workhorse in neuroscience research, preclinical studies and drug development. A repertoire of MR tools has been developed for its investigation; however, high levels of B0 magnetic field homogeneity are required for meaningful results. The homogenization of magnetic fields in the rat brain, i.e. shimming, is a difficult task because of a multitude of complex, susceptibility-induced field distortions. Conventional shimming with spherical harmonic (SH) functions is capable of compensating for shallow field distortions in limited areas, e.g. in the cortex, but performs poorly in difficult-to-shim subcortical structures or for the entire brain. Based on the recently introduced multi-coil approach for magnetic field modeling, the DYNAmic Multi-coIl TEchnique (DYNAMITE) is introduced for magnetic field shimming of the in vivo rat brain and its benefits for gradient-echo echo-planar imaging (EPI) are demonstrated. An integrated multi-coil/radiofrequency (MC/RF) system comprising 48 individual localized DC coils for B0 shimming and a surface transceive RF coil has been developed that allows MR investigations of the anesthetized rat brain in vivo. DYNAMITE shimming with this MC/RF set-up is shown to reduce the B0 standard deviation to a third of that achieved with current shim technology employing static first- through third-order SH shapes. The EPI signal over the rat brain increased by 31%, and a 24% gain in usable EPI voxels could be realized. DYNAMITE shimming is expected to critically benefit a wide range of preclinical and neuroscientific MR research. Improved magnetic field homogeneity, together with the achievable large brain coverage of this method, will be crucial when signal pathways, cortical circuitry or the brain's default network are studied. Together with the efficiency gains of MC-based shimming compared with SH approaches demonstrated recently, DYNAMITE shimming has the potential to replace conventional SH shim systems in small-bore animal scanners.


Assuntos
Encéfalo/fisiologia , Imageamento por Ressonância Magnética/instrumentação , Imageamento por Ressonância Magnética/métodos , Animais , Imagem Ecoplanar , Eletrodos , Campos Magnéticos , Masculino , Ondas de Rádio , Ratos Sprague-Dawley , Vibrissas
15.
Accid Anal Prev ; 67: 40-8, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24607593

RESUMO

This field experiment takes a novel approach in applying methodologies and theories of visual search to the subject of conspicuity in automobile rear lighting. Traditional rear lighting research has not used the visual search paradigm in experimental design. It is our claim that the visual search design uniquely uncovers visual attention processes operating when drivers search the visual field that current designs fail to capture. This experiment is a validation and extension of previous simulator research on this same topic and demonstrates that detection of red automobile brake lamps will be improved if tail lamps are another color (in this test, amber) rather than the currently mandated red. Results indicate that when drivers miss brake lamp onset in low ambient light, RT and error are reduced in detecting the presence and absence of red brake lamps with multiple lead vehicles when tail lamps are not red compared to current rear lighting which mandates red tail lamps. This performance improvement is attributed to efficient visual processing that automatically segregates tail (amber) and brake (red) lamp colors into distractors and targets respectively.


Assuntos
Acidentes de Trânsito/prevenção & controle , Atenção , Condução de Veículo/psicologia , Automóveis , Iluminação , Segurança , Percepção Visual , Adulto , Cor , Feminino , Humanos , Masculino , Campos Visuais
16.
Accid Anal Prev ; 45: 588-99, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22269546

RESUMO

Worldwide, both brake lamps and tail lamps on motor vehicles are required to be red. Previous studies have not examined the effect of this confound in a complex, high-traffic scenario in a driving simulator or on visuomotor behavior. In the first experiment, drivers detected brake lamps on nine lead vehicles and lane changes on two rear vehicles in a 15 min simulated night time highway drive. A second experiment was used to examine the findings in the context of pre-attentive visual processing research. A third experiment analyzed visuomotor behavior and subjective workload during a vigilance task to further evaluate this hypothesis. For all studies, tail lamp color was manipulated, resulting in two conditions: the currently mandated red tail lamps and red brake lamps vs. yellow tail lamps and red brake lamps. Compared to current rear lighting, employing yellow tail lamps with red brake lamps reduced RT, error, subjective workload, improved performance in detecting lane changes and also changed visuomotor behavior. It is suggested that the mechanism allowing better performance is pre-attentive, parallel visual processing.


Assuntos
Atenção , Condução de Veículo/psicologia , Automóveis , Percepção de Cores , Desaceleração , Área de Dependência-Independência , Iluminação , Reconhecimento Visual de Modelos , Adolescente , Simulação por Computador , Discriminação Psicológica , Movimentos Oculares , Feminino , Humanos , Masculino , Tempo de Reação , Carga de Trabalho/psicologia , Adulto Jovem
17.
J Magn Reson ; 212(2): 280-8, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21824794

RESUMO

High quality magnetic field homogenization of the human brain (i.e. shimming) for MR imaging and spectroscopy is a demanding task. The susceptibility differences between air and tissue are a longstanding problem as they induce complex field distortions in the prefrontal cortex and the temporal lobes. To date, the theoretical gains of high field MR have only been realized partially in the human brain due to limited magnetic field homogeneity. A novel shimming technique for the human brain is presented that is based on the combination of non-orthogonal basis fields from 48 individual, circular coils. Custom-built amplifier electronics enabled the dynamic application of the multi-coil shim fields in a slice-specific fashion. Dynamic multi-coil (DMC) shimming is shown to eliminate most of the magnetic field inhomogeneity apparent in the human brain at 7 T and provided improved performance compared to state-of-the-art dynamic shim updating with zero through third order spherical harmonic functions. The novel technique paves the way for high field MR applications of the human brain for which excellent magnetic field homogeneity is a prerequisite.


Assuntos
Encéfalo/anatomia & histologia , Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Adulto , Algoritmos , Animais , Campos Eletromagnéticos , Desenho de Equipamento , Feminino , Humanos , Imageamento por Ressonância Magnética/instrumentação , Masculino , Ondas de Rádio , Ratos , Especificidade da Espécie
18.
Magn Reson Med ; 66(3): 893-900, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21442653

RESUMO

MR imaging and spectroscopy allow the noninvasive measurement of brain function and physiology, but excellent magnetic field homogeneity is required for meaningful results. The homogenization of the magnetic field distribution in the mouse brain (i.e., shimming) is a difficult task due to complex susceptibility-induced field distortions combined with the small size of the object. To date, the achievement of satisfactory whole brain shimming in the mouse remains a major challenge. The magnetic fields generated by a set of 48 circular coils (diameter 13 mm) that were arranged in a cylinder-shaped pattern of 32 mm diameter and driven with individual dynamic current ranges of ±1 A are shown to be capable of substantially reducing the field distortions encountered in the mouse brain at 9.4 Tesla. Static multicoil shim fields allowed the reduction of the standard deviation of Larmor frequencies by 31% compared to second order spherical harmonics shimming and a 66% narrowing was achieved with the slice-specific application of the multicoil shimming with a dynamic approach. For gradient echo imaging, multicoil shimming minimized shim-related signal voids in the brain periphery and allowed overall signal gains of up to 51% compared to spherical harmonics shimming.


Assuntos
Mapeamento Encefálico/métodos , Imageamento por Ressonância Magnética/instrumentação , Animais , Aumento da Imagem/instrumentação , Processamento de Imagem Assistida por Computador/instrumentação , Modelos Lineares , Camundongos , Modelos Animais
19.
J Magn Reson ; 204(2): 281-9, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20347360

RESUMO

A set of generic, circular individual coils is shown to be capable of generating highly complex magnetic field distributions in a flexible fashion. Arbitrarily oriented linear field gradients can be generated in three-dimensional as well as sliced volumes at amplitudes that allow imaging applications. The multi-coil approach permits the simultaneous generation of linear MRI encoding fields and complex shim fields by the same setup, thereby reducing system complexity. The choice of the sensitive volume over which the magnetic fields are optimized remains temporally and spatially variable at all times. The restriction of the field synthesis to experimentally relevant, smaller volumes such as single slices directly translates into improved efficiency, i.e. higher magnetic field amplitudes and/or reduced coil currents. For applications like arterial spin labeling, signal spoiling and diffusion weighting, perfect linearity of the gradient fields is not required and reduced demands on accuracy can also be readily translated into improved efficiency. The first experimental realization was achieved for mouse head MRI with 24 coils that were mounted on the surface of a cylindrical former. Oblique linear field gradients of 20 kHz/cm (47 mT/m) were generated with a maximum current of 1.4A which allowed radial imaging of a mouse head. The potential of the new approach for generating arbitrary magnetic field shapes is demonstrated by synthesizing the more complex, higher order spherical harmonic magnetic field distributions X2-Y2, Z2 and Z2X. The new multi-coil approach provides the framework for the integration of conventional imaging and shim coils into a single multi-coil system in which shape, strength, accuracy and spatial coverage of the magnetic field can be specifically optimized for the application at hand.


Assuntos
Imageamento por Ressonância Magnética/instrumentação , Magnetismo/instrumentação , Modelos Teóricos , Transdutores , Simulação por Computador , Desenho Assistido por Computador , Campos Eletromagnéticos , Desenho de Equipamento , Análise de Falha de Equipamento
20.
Magn Reson Med ; 63(1): 171-80, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19918909

RESUMO

The prefrontal cortex is a common target brain structure in psychiatry and neuroscience due to its role in working memory and cognitive control. Large differences in magnetic susceptibility between the air-filled sinuses and the tissue/bone in the frontal part of the human head cause a strong and highly localized magnetic field focus in the prefrontal cortex. As a result, image distortion and signal dropout are observed in MR imaging. A set of external electrical coils is presented that provides localized and high-amplitude shim fields in the prefrontal cortex, with minimum impact on the rest of the brain when combined with regular zero- to second-order spherical harmonics shimming. The experimental realization of the new shim method strongly minimized or even eliminated signal dropout in gradient-echo images acquired at settings typically used in functional magnetic resonance at 4 T.


Assuntos
Aumento da Imagem/instrumentação , Interpretação de Imagem Assistida por Computador/instrumentação , Imageamento por Ressonância Magnética/instrumentação , Magnetismo/instrumentação , Córtex Pré-Frontal/anatomia & histologia , Transdutores , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
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