الفهرس 
AcknowledgementsOnly 14 pages are availabe for public view
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Abstract
Preoperative grading of gliomas based on conventional MR imaging is often unreliable. Cho/Cr and Cho/NAA ratios can significantly improve the sensitivity and predictive values of preoperative glioma grading.
This is extremely important for determining the most optimal therapy regimen and the regularity and aggressiveness of postoperative follow-up and treatment. At our institution, perfusion MR imaging and MR spectroscopy not only have become a routine part of glioma imaging, but also have become an important adjunctive tool in providing information in gliomas and regions of the brain that may have eluded histopathologic assessment. Perfusion MR imaging and MR spectroscopy can potentially overcome the limitation of sampling error with histopathologic grading of tumor by the ability to sample the entire lesion noninvasively in vivo. Ongoing data collection from longitudinal studies is crucial to determine if metabolite ratios can, in the long run, be comparable to histopathologic examination in predicting tumor behavior and patient prognosis.
Diffusion-weighted imaging and 1H-MRS are useful as additional imaging techniques for establishing the differential diagnosis between brain abscesses and cystic or necrotic brain tumors. Diffusion-weighted imaging in the discrimination between brain abscesses and necrotic tumors requires less imaging time and is more accurate than 1H-MRS. however, some conflicting reports in the literature regarding diffusion-weighted imaging, so the combination of 1H-MRS and diffusion-weighted imaging may improve results compared with the use of only a single technique to differentiate between brain abscesses and cystic or necrotic brain tumors.
MRS cannot reliably differentiate typical intracranial meningiomas from atypical meningiomas preoperatively.
SVS showed a limited value in tumor grading. On the other hand, multi voxel MRI showed higher overall diagnostic accuracy. In term of the echo time, Intermediate TE showed better sensitivity, specificity and accuracy compared to those with short TE. Yet, Combination of both short and intermediate TEs provided higher sensitivity ,specificity and accuracy compared to those of each TE separately.
Recommendations
In using MRS as a complementary tool for discriminating low and high grade tumors:-
*We recommended the use of multi voxel chemical shift imaging,by which spectra from numerous small voxels can be acquired, to enable great coverage of large tumors. It would also added the benefit of measuring the metabolite ratios in the edema, as it has recently been shown that peri-tumoral edema can be more valuable in detecting tumor grade(Kousi et al., 2012). This could be due to the infilterative pattern of high grade tumors which is not typical of low grade tumors.
*We could recommend the combination of both short and intermediate TEs to achieve better sensitivity, specificity and accuracy.