الفهرس 
Gross Anatomy o? the ?rainOnly 14 pages are availabe for public view
 |  | from | 162 |  |  |
| | | from | 162 | | |
Abstract
Conventional MRI has been the life long established method for evaluating brain tumors both before and after treatment. Perfusion MRI is a diagnostic method that visualizes a blood flow at a microscopic level and thus demonstrates even the angiogenesis that could not be detected on conventional MRI. Blood flow at a microscopic level is visualized via perfusion analysis. Perfusion MRI is valuable as it depict neovascularity of tumor tissue which is directly proportional to the tumor grade. Neovascularization is a key mechanism in glioma growth and represents a key histologic criterion to distinguish low from high grade classification. Perfusion-weighted imaging is currently used to grade gliomas. Perfusion MRI not only valuable for Preoperative diagnosis and characterization of brain tumors, but also has Post-operative value in differentiation tumor recurrence from Treatment induced necrosis (Radiation necrosis). In the current study which was done on 50 cases of variable age and sex (40 cases preoperative and 10 cases postoperative) and all are clinically suspected to have a space occupying lesion & 30 cases were compared with histopathological analysis and we found the following results. Conventional MRI had failed to characterize either primary tumors (high grade glioma) from metastases and primary CNS lymphoma), also it was also unable to differentiate post-operative tumor recurrence from radiation necrosis. Perfusion MRI using T2* dynamic suscibitibility contrast (DSC) Method depending on the max r CBV (cerebral blood volume) as the parameter of choice, not only gave excellent results in grading gliomas & differentiation high grade gliomas (GBM) & metastesis and primary central nervous system lymphoma but also was valuable in differentiation Postoperative tumor recurrence from radiation necrosis as the following: 1- Preoperative cases : • Intralesional max rCBV (cerebral blood volume) could differentiate primary tumor (high grade gliomas) and metasatesis from primary CNS lymphoma, measuring rCBV in tumor core, gave high values in both primary tumors (Gliomas) and metasatesis but low values were detected in primary CNS lymphoma. • Intralesional max rCBV values could not differentiate primary tumors from metastasis since both had high values within tumor core but it was able to grade the primary tumor and differentiate between high and low grade tumors as high grade tumors showed higher values of max rCBV and low grade tumors showed low r CBV values. • Perilesional max rCBV could be able to differentiate primary tumors from metastasis as primary tumors showed higher values of max rCBV in the surrounding perilesional area denoting perilesional infiltration which is absent in metastasis in which there is pure vasogenic edema with no tumor infiltration so showed low level of max rCBV • Total number of preoperative cases underwent perfusion MRI were 40 with the following results: - Fifteen cases were suggested to be GBM (high grade glioma), five of them underwent biopsy, four cases were GBM and only one case was metastesis. - Ten cases were suggested to be Low grade glioma. - Ten cases were suggested to be metastasis, four of them underwent biopsy, three cases were metastasis and only one case was GBM. - Five cases were suggested to be Primary CNS lymphoma; only one case underwent biopsy which was of the same diagnosis. 2- Postoperative cases: Both recurrent tumor and radiation necrosis appeared as enhancing lesion in conventional MRI with contrast, but using perfusion MRI, recurrent tumor showed high max rCBV values as compared to radiation necrosis at which it was low. - Total number of cases were 10, eight of them were suggested to be postoperative recurrence and two cases supposed to be radiation necrosis. Conclusion: from the current study it can be concluded that analysis of perfusion parameters should be used preoperatively to differentiate GBMs, metastases and PCNSLs, which may look similarly on standard MR examinations as strongly enhancing focal brain lesions surrounded by edema. In the clinical practice we recommend a two-step approach based on evaluation of the most important parameter which is max rCBV first within the tumor core to distinguish hyperperfused (GBMs and metastases) from hypoperfused (PCNSLs) tumors, and secondly within the peritumoral zone of the hyperperfused tumors to search for neoplastic infiltration typical for GBM or pure vasogenic edema characteristic for metastases, another value of PWI is preoperative grading of primary brain tumors. Postoperatively, value of perfusion is to differentiate tumor recurrence (high max rCBV) from radiation necrosis (low max r CBV). PWI which is technique easy to perform and fast to post process should be incorporated in the MR protocol of all intracranial tumors.