الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
Despite the excellent soft tissue contrast provided by MRI, the sensitivity and specificity with which this modality precisely defines tumor type and grade is limited. Overcoming these problems requires the development of new imaging modalities that highlight functional or physiological properties of the tumor.
Diffusion-weighted imaging (DWI) provides information about physiological properties of the tumor that has been linked to cellularity and structural integrity. DWI has become a powerful, multifaceted tool both for very basic clinical needs and for advanced, specialized diagnosis and treatment planning. Briefly speaking, this approach is based on the measurement of Brownian motion of molecules. This technique can characterize water diffusion properties at each picture element (pixel) of an image.
In different elements, water does not diffuse equally in all directions, a property called anisotropic diffusion. For example, brain water diffuses preferentially along axonal fiber directions. Now it is believed that it is possible to use this diffusion property to study the structure in living organs non-invasively.
The aim of this study is to assess the role of diffusion weighted MRI in evaluation and differentiation of space occupying brain lesions.
This study was conducted on 75 patients with suspected space occupying brain lesions, presented to the out-patient clinic of the neuro-surgery department and referred to two private radiodiagnosis and medical imaging centers for further assessment of their clinical problems.
All patients were subjected to full history taking, thorough clinical and neurological examination. Conventional and Diffusion weighted MRI examinations of the brain were preformed for all patients included in this study. The DWI study was performed on Philips 1.5 T MRI scanner. Isotropic ADC maps were generated for all patients.
Final diagnosis was reached either by surgical findings & histopathological examinations in 53 patients. Post treatment radiological and clinical follow up for 17 patients. The diagnosis in the remaining five patients was confirmed through a consensus of clinical profile and characteristic imaging findings. The studied cases included 40 males (53.3%) and 35 females (46.6%) with their age ranged from 2 and 72 years, with mean age of 35.52. The patients were categorized, according to the final diagnosis, into four main groups:
Group A: Patients with intracranial neoplastic lesions (61.3%).
Group B: Patients with non neoplastic tumor -like lesions (22.6%).
Group C: Patients with intracranial suppuration (9.3%).
Group D: Patients with intracerebral hemorrhage (6.6%).
In the current study, false positive result was encountered in one patient; where conventional MRI and diffusion weighted imaging revealed the diagnosis of high grade glioma (astrocytoma), however, histopathological examination revealed high grade (anaplastic) oligodendroglioma.
In the current study, diffusion weighted MRI added valuable information; it helped in characterization of 61 cases (81.3%) as follows:
- Brain abscesses in five patients differentiating them from necrotic (cystic) gliomas and metastases in eleven patients.
- Subdural empyema in two patients differentiating them from subdural effusion.
- Encephalitis in three patients differentiating them from diffuse or low grade glioma targeting the frontal and temporal lobes in three patients.
- Medulloblastoma in five patients differentiating them from fourth ventricular ependymoma in two patients.
- CNS lymphoma in three patients differentiating them from glioma.
- GII grade glioma including pontine glioma differentiating them from infarctions& inflammatory conditions in eight patients.
- Primary intracranial non neoplastic cysts; epidermoid cysts in six patients differentiating them from arachnoid cysts in four patients.
- Tumefactive MS/ADEM in three patients differentiating them from neoplastic lesions.
- Determination of glioma grade (II-IV) in sixteen patients.
- Determination of chronological age of intracerebral hematoma in five patients.
- Diagnostic confirmation of atypical/malignant meningioma with invasive behavior in two patients, differentiating them from typical/ benign meningiomas.
The role of DWI was controversial in six cases (8%), including two cases of oligodendroglioma and four cases of benign meningiomas.
On the other hand, DWI had no valuable diagnostic yield in 8 cases (10.6%) including four cases of pilocytic astrocytoma, one case of ADEM, one case of supratentorial PNET, one case of hemangioblastoma, and one case of suprasellar &pineal region germinoma.