الفهرس 
Introducation and Aim of the workOnly 14 pages are availabe for public view
 |  | from | 170 |  |  |
| | | from | 170 | | |
Abstract
Summary
Brain tumors are the second leading cause of cancer-related deaths in children and adults younger than 39 years old, and they affect adults of all ages
The goal of brain tumor surgery is to maximize the extent of tumor resection while minimizing post-operative neurological deficits resulting from damage to intact, functioning brain. This requires pre-or intra operative mapping of the tumor and its spatial relationship to functional structures, including the cerebral cortex and WM tracts, as brain tumors can often displace, infiltrate, or disrupt WM tracts.
Computed tomography (CT) may be the first modality employed in a patient presenting with a brain tumor but for the most part MRI is the primary imaging modality in brain tumor patients. The role of CT is largely relegated to emergent imaging in the detection of hemorrhage, herniation, and hydrocephalus but mass effect from brain tumors and calcification within brain tumors such as oligodendrogliomas or menigiomas can potentially be detected.
Although qualitative interpretation of basic brain tumor MRI (including T2-weighted images and gadolinium [Gd]-enhanced T1-weighted images), remains the backbone of brain tumor imaging, in a significant number of cases, these techniques fail to allow confident and correct differential diagnosis, grading, and monitoring of brain tumor.
DWI has a sensitivity and specificity of over 90% for distinguishing epidermoid (low ADC) from arachnoid cyst (high ADC) and distinguishing abscess (low ADC) from necrotic tumor (high ADC). The viscous keratin and cholesterol in epidermoid and the viscous and cellular
pus in abscess produce a very low ADC that distinguishes these lesions from increased diffusivity in necrotic tumor and from normal or slightly low diffusivity in demyelinating plaque.
DWI became, and remains, the imaging method of choice for patients suspected of having cerebral infarction or abscessand is also very helpful in grading brain tumors. It is now well known that hypercellular tumors such as glioblastoma and lymphoma have a lower apparent diffusion coefficient (ADC) than do benign masses and that lymphomas show a lower ADC than do gliomas .
DTI is an advanced magnetic resonance technique that allows visualization of white matter tracts, and describes the movement of water molecules by using two parameters, mean diffusivity (MD) and fractional anisotropy (FA), which represent the directionality of water diffusion.
DTI is able to demonstrate structural changes of white matter tracts related to brain tumours, such as the detection of alterations, integrity, or dislocation of individual tracts. Thus, DTI provides other important information that can help distinguish infiltrative grow ing tumours from bounded tumours and, together with assessment of the ADC and conventional MRI with a contrast agent, the grading of tumours can be better specified.