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Abstract
Brain tumors present a challenge for radiological diagnosis and therapeutic management. This is partly due to the histological heterogeneity of the lesions, the non-specific pattern of therapeutic response and the wide range of differential diagnosis in a significant number of patients.
Although MR imaging is the most useful radiological technique in the diagnosis and evaluation of common brain tumors, in some instances it is not effective for differentiation of tumor type or detection of tumor grade or even for differentiation between gliomas and other entities.
Diffusion-weighted magnetic resonance (MR) imaging is advanced technique that provides information not available from conventional MR imaging. In particular, it has a number of applications with regard to characterization of tumors and assessment of tumor response to therapy.
The diagnostic importance of DWI and ADC maps are well shown in the differential diagnosis of ring-enhancing cerebral masses. The presence of central hyper-intensity on DWI and very low ADC values (0.5-0.9 X10-3 mm2/sec) is in keeping with pyogenic abscess while a lesion with mostly hypo intense DWI signal and high ADC value is in keeping with necrotic center of tumor.
In addition, ADC values are useful in the grading of malignant tumors, and not for the differentiation of the different tumor types in the same grade.