الفهرس 
Anatomiyof the brainOnly 14 pages are availabe for public view
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Abstract
Intracerebral cysts and cyst appearing intracerebral masses are common findings at routine cerebral imaging examination.
Differentiation of various intracranial cystic lesions usingconventional MRI may sometimes be difficult because of nonspecific clinical findings and a similar appearance on imaging. Using conventionalMR images to discriminate between the lesion types is often a very challenging task, and usually follow-up studies or biopsy procedures are required.
Intracranial cystic mass lesions include true cysts lined by epithelial, ependymal or meningothelial cells, dermoid and epidermoid cysts, parasitic cysts (cysticercosis, hydatid cysts) or may be pseudocystic neoplastic or inflammatory lesions (abscesses) secondary to accumulation of necrotic, intercellular mixed or proteinaceous material.
DWI is based on the irregular diffusion motion of water molecules and provides more detailed information at the cellular level than conventional MRI. It is a quick and practical technique in emergency radiology and is unaffected by size of the lesion. It has high sensitivity and specificity for the differentiation of brain abscess from other non-abscess intracranial cystic mass lesions.
DWI provide a greater degree of confidence in differentiating various intracranial cystic mass lesions in combination with the conventional MRI.
The contents of the lesions are predominantly responsible for the difference in ADC of the cystic cavities of abscesses from tumor cysts.
Arachnoid and Epidermoid cysts show almost the same criteria in conventional MRI. DWI can differentiate between them. Arachnoid show free diffusion because ofits clear CSFcontent, unlike Epidermoid which show restricted diffusion.
Conventional MRIis still a challenge to differentiate infectious abscesses from other ring enhancing lesions, especially cystic glioblastomas. The organized abscess environment containing microorganisms, macromolecules, and intact inflammatory cells so it shows restriction of water molecules in diffusion images. Cystic glioma containing necrotic material so it shows free movement of water molecules in diffusion images.
Metastasis behavior on DWI is much more unpredictable. Well differentiated adenocarcinoma metastases tend to be hypointense (non restricting) whereas more aggressive small and large cell neuroendocrine carcinomas are hyperintense on DWI.
DWI is useful as additional diagnostic modalities in differentiating intracranial cystic lesions, is more accurate, requires less imaging time and is also easier to interpret.