Advanced Imaging Strategies in Brain Tumors




Diagnosis   of    tumours  has   improved considerably due to the introduction of new
imaging CT and MRI techniques. These techniques, and the contrast medium in particular, provide anatomical and structural information    about  brain   tumours,        and information about the physiology, metabolism, and haemodynamics of individual tumours. Advanced magnetic resonance techniques in neuroradiology evaluate changes at the microvascular, haemodynamic, and cellular levels of brain tumours, and in addition to structural changes, evaluate changes at the metabolic and biochemical levels DTI is an advanced magnetic resonance technique that allows visualization of white matter tracts, and describes the movement of water molecules by using two parameters, mean diffusivity (MD) and fractional anisotropy (FA), which represent the directionality of water diffusion. With PWI it is possible to determine tumour grading non-invasively. In general, high-grade tumours have higher CBV values than low- grade tumours. PWI is also used for localization of the parts of a tumour with a high degree of vascularity for the purpose of stereotactic biopsy. PWI helps to define the edge of a tumour, which is important in planning surgical treatment radiotherapy. PWI is also used to monitor the effect of treatment on patients. MRS is a non-invasive method and currently is part of the advanced diagnostic protocol in neuroradiology. MRS can determine pathological changes in brain tissue long before conventional techniques. Presently, in tumour imaging, fMRI is used predominantly for the preoperative localization of eloquent cortical regions that may have been displaced, distorted or compressed by the tumour. Neuronavigation is a common method of preoperative localization of brain tumours. It uses imaging materials of preoperative MRI examinations, 3D sequences and DTI and fMRI data, that are transferred to a computer database of a neuronavigation device. DSA is used to detect the blood vessels supplying the brain tumours, and also tocontrol the hypervascular tumour embolization.