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1.
Med Image Comput Comput Assist Interv ; 11(Pt 1): 576-84, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18979793

RESUMO

We present a method for fast and automatic labeling of anatomical structures in MR FastView localizer images, which can be useful for automatic MR examination planning. FastView is a modern MR protocol, that provides larger planning fields of view than previously available with isotropic 3D resolution by scanning during continuous movement of the patient table. Hence, full 3D information is obtained within short acquisition time. Anatomical labeling is done by registering the images to a statistical atlas created from training image data beforehand. The statistical atlas consists of a statistical model of deformation and a statistical model of grey value appearance. It is generated by non-rigid registration and principal component analysis of the resulting deformation fields and registered images. Labeling of an unseen FastView image is done by non-rigid registration of the image to the statistical atlas and propagating the labels from the atlas to the image. In our implementation, the statistical models of deformation and appearance are both implemented on the GPU (graphics processing unit), which permits computing the atlas based labeling using GPU hardware acceleration. The running times of about 10 to 30 seconds are of the same magnitude as the image acquisition itself, which allows for practical usage in clinical MR routine.


Assuntos
Documentação/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Imagem por Ressonância Magnética/métodos , Modelos Biológicos , Reconhecimento Automatizado de Padrão/métodos , Técnica de Subtração , Algoritmos , Inteligência Artificial , Simulação por Computador , Humanos , Aumento da Imagem/métodos , Modelos Estatísticos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Interface Usuário-Computador
2.
Neuroimage ; 35(1): 234-43, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17188900

RESUMO

Echo-planar imaging (EPI) generates considerable acoustic noise by rapidly oscillating gradients. In functional magnetic resonance imaging (FMRI), unshielded EPI sounds activate the auditory system inasmuch as it is responsive. Instead of attenuating EPI noise, our goal was to utilize it for auditory FMRI by omitting read-outs from the pulse sequence's gradient train. Read-out gradient pulses are the primary noise determinant of EPI introducing its peak sound level and fundamental frequency peak which inversely relates to twice the echo spacing. Using model-driven analyses, we demonstrate that withholding read-outs from EPI is suited to reliably evoke hemodynamic blood oxygenation level-dependent (BOLD) signal modulations bilaterally in the auditory cortex of normal hearing subjects (n=60). To investigate the utility of EPI read-out omissions for auditory FMRI at an individual subject's level, we compare traditional Family-Wise-Error-Rate (FWER)-corrected maximum height thresholding to spatial mixture modeling (SMM). With the latter, appropriate bilateral auditory activations were confirmed in 95% of the individuals, whereas FWER-based voxel thresholding detected such activations in up to 72%. We illustrate the applicability of this novel EPI modification for clinical diagnostic purposes and report on a patient with bilateral large vestibular aqueducts (LVAs) and severe binaural sensorineural hearing loss (SNHL). In this particular case, read-out omissions from EPI were used to assert residual audition prior to cochlear implantation (CI). Requiring no specific task compliance or sophisticated stimulation equipment other than the scanner on its own, FMRI by read-out omissions lends itself to auditory investigations and to quickly probe audition.


Assuntos
Imagem Ecoplanar/métodos , Audição/fisiologia , Imagem por Ressonância Magnética/métodos , Estimulação Acústica , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Córtex Auditivo/fisiopatologia , Circulação Cerebrovascular/fisiologia , Criança , Implante Coclear , Interpretação Estatística de Dados , Reações Falso-Negativas , Reações Falso-Positivas , Feminino , Perda Auditiva Neurossensorial/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Oxigênio/sangue , Doenças Vestibulares/fisiopatologia , Vestíbulo do Labirinto/fisiopatologia
3.
Radiology ; 241(2): 528-37, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17005775

RESUMO

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to retrospectively evaluate remote control magnetic resonance (MR) imaging in complex cardiovascular procedures, whereby operational expertise was made available locally from a remote location. Thirty patients underwent cardiac (12 patients) and/or vascular (30 patients) 1.5-T MR imaging with a remote operator by using a personal computer. All patient studies were compared with 30 control studies obtained with conventional local imaging. Cardiac cine, myocardial delayed enhancement, and MR angiograms were assessed for overall image quality and motion artifact. MR angiograms were evaluated for vascular definition. Image quality was excellent in 90% (38 of 42) of remote images versus 60% (25 of 42) of control group images (P < .01). Scores for motion artifact were not significantly different (P = .11). Interactive MR imaging was successfully implemented with remote control in complex cardiovascular cases; diagnostic quality of images was superior to that of images obtained locally.


Assuntos
Doenças Cardiovasculares/diagnóstico , Imagem por Ressonância Magnética/instrumentação , Telemedicina/instrumentação , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Artefatos , Criança , Pré-Escolar , Desenho de Equipamento , Estudos de Viabilidade , Feminino , Humanos , Lactente , Masculino , Microcomputadores , Pessoa de Meia-Idade , Estudos Retrospectivos , Estatísticas não Paramétricas
4.
Artigo em Inglês | MEDLINE | ID: mdl-17354755

RESUMO

Although magnetic resonance imaging is considered to be non-invasive, there is at least one effect on the patient which has to be monitored: The heating which is generated by absorbed radio frequency (RF) power. It is described using the specific absorption rate (SAR). In order to obey legal limits for these SAR values, the scanner's duty cycle has to be adjusted. The limiting factor depends on the patient's position with respect to the scanner. Detection of this position allows a better adjustment of the RF power resulting in an improved scan performance and image quality. In this paper, we propose real-time methods for accurately detecting the patient's position with respect to the scanner. MR data of thirteen test persons acquired using a new "move during scan" protocol which provides low resolution MR data during the initial movement of the patient bed into the scanner, is used to validate the detection algorithm. When being integrated, our results would enable automatic SAR optimization within the usual acquisition workflow at no extra cost.


Assuntos
Interpretação de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Movimento , Reconhecimento Automatizado de Padrão/métodos , Postura , Radiometria/métodos , Imagem Corporal Total/métodos , Algoritmos , Inteligência Artificial , Carga Corporal (Radioterapia) , Humanos , Aumento da Imagem/métodos , Imageamento Tridimensional/métodos , Doses de Radiação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
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