RESUMO
Tractography (TG) is the only non-invasive technique that enables the fibres of the white substance to be dissected. This technique can study the projection, association, and commissural fibres, and is an improvement and an important complement to conventional MR imaging. TG is an important tool for preoperative sub-cortical mapping, and there is a good correlation between TG and the direct sub-cortical stimulation technique. TG can have false positives in regions infiltrated by the tumour or with a mass effect. Furthermore, a negative TG does not exclude functional fibre persistence. TG is capable of demonstrating changes in other pathologies (congenital malformations, ischaemic disease and demyelinating diseases).
Assuntos
Encefalopatias/diagnóstico , Imagem de Tensor de Difusão , HumanosRESUMO
PURPOSE: To elucidate the possibilities and indications of high-resolution magnetic resonance imaging (MRI) in the study of the orbit and its contents. METHODS: Orbital anatomy was studied in sliced specimens of fifteen fresh frozen cadavers and the results were compared with those obtained in thirty asymptomatic subjects who underwent a magnetic resonance with 1.5 Tesla equipment. The information obtained was used to interpret the findings in twenty-two patients with various orbital diseases. RESULTS: High-resolution MRI allows visualization of structures difficult to assess previously, like the cerebrospinal fluid (CSF) surrounding the optic nerve, the complete intraorbital route and the exit of the third cranial nerve, the ophthalmic artery and the intraorbital relationships of the sixth cranial nerve, which can be clearly differentiated from the lateral rectus muscle. CONCLUSIONS: High-resolution MRI is a very useful tool for the study of the orbit and its content. It provides accurate diagnoses through non-invasive procedures and facilitates the planning of the surgical approaches by improving the visualization of pathologic orbital structures. lcarlos@correo.uniovi.es
