Biomedical subjects

Miguel Alonso

Publications and source records attributed to Miguel Alonso.

4 recordsLinked to original sources

PubMed2005

Miliary brain metastases presenting as rapidly progressive dementia.

We report the case of a 79-year-old woman who developed a rapidly progressive dementia (RPD) with severe memory impairment, early visual hallucinations and extrapyramidal signs. Symptoms started suddenly after hip replacement surgery following an accidental fall. Motor epileptic seizures appeared at the end of the illness. Dementia worsened gradually leading to akinetic mutism. She died five and a half months after the onset of symptoms. MRI showed cerebral atrophy but failed to detect any other lesion. Results of all laboratory tests performed were negative. After the most frequent treatable diseases were excluded, the diagnosis of dementia with Lewy bodies was initially considered. CJD was also suggested based on the rapid evolution of the disease and the positivity of 14-3-3 protein in CSF. Neuropathological examination revealed an extensive miliary metastatic dissemination from an unknown primary adenocarcinoma. Pulmonary origin was suggested according to the immunohistochemical profile. Histopathological changes of Alzheimer's disease were also observed in the cerebral cortex and hippocampus. Neither Lewy bodies nor PrP deposits were found. The sudden onset of the dementia just after the hip replacement surgery raises the possibility of a pathological fracture with secondary tumoral microembolic dissemination. Despite its rarity, this entity should be included in the differential diagnosis of RPD. This case illustrates the definite importance of neuropathological post-mortem examination in order to elucidate the different types of dementia.

Aged↗

PubMed2005

A bioinstrumentation system for the identification of EEG correlates of tinnitus.

Tinnitus is the spontaneous 'ringing' sensation within the auditory system reported by many individuals, which currently can only be diagnosed by behavioral response. Studies in this area have yet to identify definite mechanisms or sites associated with the generation of this sensation. The tinnitus sensation is typically reported to be prominent during silence. In addition, the complete withdrawal of auditory stimulus usually precedes the onset of the tinnitus sensation. This paper describes the conceptualization, integration and testing of an experimental instrument, developed to observe Auditory Evoked Potentials (AEPs) in order to identify possible EEG correlates of tinnitus. The instrumental setup permits the study of AEP responses during silence, as well as to observe the transitional nature of the AEP.

Algorithms↗

PubMed2005

Software-based compensation of visual refractive errors of computer users.

For human beings, vision is one of the most important senses in interacting with the surrounding environment, as well as with any tools that require visual communication. As such, the ability to interact effectively with computers through typical graphic user interfaces (GUIs) is greatly affected by any refractive errors present in an individual's visual system. If the refractive errors can be mathematically modeled, a system for overcoming these aberrations can be devised which can increase the effective human-computer interaction for these individuals. Several methods, such as Adaptive Optics, have been proposed that attempt to solve this problem using electro-mechanical devices. These methods are costly and impractical, preventing most visually impaired individuals from benefiting from their use. In contrast, an image-processing method, based on deconvolution techniques, has recently been proposed for the pre-compensation of images to be displayed in a computer. This method is much more practical, being completely implemented in software, and has achieved encouraging results. Previous results have yielded an average 50% increase in visual efficiency in the compensation of a known artificial aberration introduced into the field of vision of experimental subjects. This paper describes the difficulties encountered with the present software-only compensation and proposes several methods for overcoming these obstacles. The difficulties, as well as the proposed solutions, are described theoretically and followed by examples using a lens system showing the improvement over previous methods.

Algorithms↗

PubMed2003

Digital image processing for pre-compensation of high-order aberrations of the human eye.

Human beings rely significantly on their visual capabilities to successfully interact with their environment. In today's technology-based world, one of the most important interaction channels is through computers. Some individuals with severe visual impairments may have difficulty in interacting with computers, even when using traditional means of visual correction (e.g., spectacles, contact lenses). This is, in part, because these correction mechanisms can only compensate for the most regular distortions or aberrations of the image in the eye. This paper proposes an image processing approach that will pre-compensate the images displayed on the computer screen, so as to counter the effect of the eye's aberrations on the image. The characterization of the eye required to perform this customized pre-compensation is the eye's Point Spread Function (PSF). The PSF can now be measured by a new generation of ophthalmic instruments generically called. Wavefront Analyzers.. The characterization provided by these instruments also includes the .higher-order aberration components. and could, therefore, lead to a more comprehensive vision correction than traditional mechanisms. The methods presented here will be explained in terms of their theoretical foundation and illustrated with results from the correction of aberrations introduced by lenses with known and constant PSFs.

Audiovisual Aids↗