الفهرس 
NTRODUCTION& Aim of the workOnly 14 pages are availabe for public view
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Abstract
Both of radiation necrosis and tumor recurrence may occur simultaneously and within the irradiated area after 1 year or more of brain irradiation and the differentiation between both entities after brain tumor radiotherapy is indispensable for adequate treatment and prognosis. The purpose of this study is to differentiate between radiation necrosis and tumor recurrence by MRS. All patients underwent MR Spectroscopic examination; 23 patients were examined after administration of contrast media. SVS was done for 6 patients& CSI for 24 patients according to homogeneity &size of the lesions. MR Spectra were acquired using TR/TE: 1500/270; to allow metabolites such as Choline, Creatine &NAA to be detected. On the basis of signal intensity ratios of these metabolites; we observed no significant difference between metabolites ratios of MRS diagnosed tumor &normal brain. On the other hand, there was significant reduction of ICho/Itcr &ICho/INAA ratios in MRS diagnosed radiation necrosis compared to normal brain (p=0.018&0.04). Signal intensity ratios of ICho/Itcr & ICho/ INAA allowed diagnosis of lesions as tumor recurrence and radiation necrosis with accuracy 77% & 85% respectively. Sensitivity& Specificity values of MRS in differentiation between tumor recurrence &radiation necrosis were (83.3% &78.6% respectively).MRS can be used to differentiate between tissue areas of tumor recurrence and radiation- therapy changes in patient whose neurodiagnostic interpretation based on CT or MRI is equivocal and it can guide the extent of resection limited to area of recurrence. MRS creates a non invasive technique to neurometabolism as it provides greater information than MRI to differentiate between radiation necrosis and tumor recurrence. It is advisable to add H1MRS to MRI follow up of patients with irradiated brain tumors for better diagnosis.