Papers by Rafael Valero Rojas
Topics in Magnetic Resonance Imaging, 2005
Topics in Magnetic Resonance Imaging, 2014
Seminars in Roentgenology, 2004
American Journal of Roentgenology, 2012
Emergency Radiology, 2007
Methadone is an opiate used as part of the treatment for heroin abuse; it can be ingested orally.... more Methadone is an opiate used as part of the treatment for heroin abuse; it can be ingested orally. We present the lethal outcome of a 22-month-old child intoxicated after methadone ingestion.
Topics in Magnetic Resonance Imaging, 2014
Neurologic disease in acquired immunodeficiency syndrome (AIDS) patients is related either to opp... more Neurologic disease in acquired immunodeficiency syndrome (AIDS) patients is related either to opportunistic pathogens or to direct central nervous system (CNS) invasion by the human immunodeficiency virus. Despite the increasing availability of antiretroviral therapy, opportunistic infections continue to afflict patients in the developing world and in other populations with limited access to appropriate treatment. Classic CNS infections in the setting of AIDS include toxoplasmosis, cryptococcosis, progressive multifocal leukoencephalopathy, and cytomegalovirus encephalitis. Additionally, AIDS patients are far more susceptible to acquiring CNS tuberculosis and neurosyphilis, both of which exhibit altered disease characteristics in the setting of immunosuppression. Neuroimaging is a crucial component of the diagnostic work-up of these conditions, and findings include, but are not limited to, intracranial mass lesions, white matter disease, meningoencephalitis, vascular complications, and hydrocephalus. Though various disease processes can produce imaging findings that overlap with one another, certain characteristic patterns may suggest a particular pathogen, and advanced imaging techniques and laboratory tests allow for definitive diagnosis. Knowledge of the imaging patterns seen in the setting of AIDS-related CNS disease is vital to the neuroradiologist, whose interpretation may guide decisions related to treatment and further work-up.
Medical Imaging 2000: Image Processing, 2000
ABSTRACT
Medical Imaging 2002: Image Processing, 2002
An adaptive noise filter that can be used in MRI for noise reduction is presented. The algorithm ... more An adaptive noise filter that can be used in MRI for noise reduction is presented. The algorithm is mainly based on the robust estimator, mode. Using the mode as the gray scale value estimator it is possible to differentiate the structures of interest from the background noise. Noise reduction is one of the most common image correction procedures, used in the enhancement of digital images. Wildly used noise reduction filters for digital imaging are based on median estimation, median filters. Eery time noise reduction filters are applied to an image there is a general softening or blurring of it, in particular mean filters are characterized by a strong softening effect for the case of high amplitude noise levels, practically destroying all the fine features in the filtered image. This problem is significantly reduced when median filters are used. The adaptive mode filter proposed in this work have very good noise reduction effect without a strong softening effect and is comparable in CPU time to the median filters. This fine resolution is achieved because the filter changes the mode estimator according to the difference of the deviation of the mode calculated for each the neighborhood of pixels with the global deviation of the mode for each class in the image. We consider it robust, because it uses the mode of gray-scale intensity distribution of the pixels neighborhood and its mode deviation.
European Journal of Pain, 2000
Reports on phantom limb patients concerning neuronal reorganization using non-invasive methods ha... more Reports on phantom limb patients concerning neuronal reorganization using non-invasive methods have focused mainly on the cortical regions and suggest the presence of pain as the cause of this reorganization. The phantom limb, however, includes other somatic and motor sensations other than pain. Here we describe the results of non-painful stimulation in cortical and subcortical lateralization and reorganization and also examine the involvement of subcortical structures in phantom limb telescoping perception. We describe an enlarged contralateral cortical representation of the stump, a cortical and thalamic bilateral representation of the remaining leg, and a neuronal correlate of a telescoping perception of the phantom limb. The missing leg produces an enlarged cortical representation due to abnormal information and the remaining leg has a bilateral SII representation, which could be related to new, compensatory functions. The telescoping perception of a phantom limb by the stimulation of misallocation points was correlated with lenticular nuclei, thalamic and cingulate gyrus activation.
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Papers by Rafael Valero Rojas