Magnetic resonance diffusion and perfusion imaging in differentiation and grading the diffuse glial brain neoplasms
- Georgiev, B. Balev, M. Novakova, L. Marinova,S. Andonova, D. Dzhenkov, D. Handzhiev
Gliomas are the most common primary brain tumors. They are heterogenous group of tumors, which have infiltrative growth and relative resistance to radio-and chemotherapy. Gliomas are estimated from the WHO classification by means of grades from I до IV. Grade I (localized, “special” gliomas) and grade II (diffuse gliomas) are considered low-grade, while grade III, IV are high-grade. Although histologically benign, the majority of grade II tumors will transform into malignant grades III and IV during the interval 5-10 years from the initial diagnosis. Glial tumor grading is based on a histo-pathological analysis of the most malignant tumour region, and takes into account the number of mitoses, nuclear atypia, microvascular proliferation and presence of necrosis. These grade are important, because they determine the therapeutic approach and the prognosis in patients with gliomas. Conventional MR images provide important information about contrast-enhancement, oedema, distant tumoral focuses, hemorrhage, necrosis, mass effect and etc, which are very useful in assessment of the tumor aggressiveness and hence tumor grade. Contrast-enhancement reflects the blood-brain-barrier status and could not be a reliable marker of malignancy. Modern physiological MR techniques like MR diffusion and MR perfusion imaging provide information about umor physiology like microvascularity, angiogenesis and cellularity, all of which are also important in defining the tumor grade. Diffusion weighted imaging estimates the tumor structure-cellulariuty and water content. Perfusion weighted imaging shows capillary density and neovascularization.
Key words: DIFFUSE GLIOMAS. GLIOMA GRADE. DIFFUSION WEIGHTED AND PERFUSION WEIGHTED MAGNETIC RESONANCE IMAGING