الفهرس | Only 14 pages are availabe for public view |
Abstract Diffusion weighted imaging (DWI) is a relatively new method in which the images are formed by the contrast produced by the random microscopic motion of water molecules in different tissues, although it was introduced into clinical practice in the middle 1990s, but because of its demanding MR engineering requirements—primarily high-performance magnetic field gradients—it has only recently undergone widespread dissemination. Diffusion-weighted magnetic resonance (MR) imaging provides image contrast that is different from that provided by conventional MR techniques. It is particularly sensitive for detection of acute ischemic stroke and differentiation of acute stroke from other processes that manifest with sudden neurologic deficits. Diffusion weighted MR imaging also provides adjunctive information for other cerebral diseases including neoplasms, intracranial infections, traumatic brain injury, and demyelinating processes. This study included 100 patients with different brain lesions other than infarctions (37 males & 63 females) who were further classified into 6 groups. These are intracranial infarctions, intracranial hemorrhage, intracranial masses (which is further subdivided into extra-axial and intra-axial masses), traumatic brain lesions, demyelinating diseases and others (encephalopathies and leukodystrophies). All patients underwent detailed history taking, contrast enhanced MRI examination of the brain and diffusion weighted MRI imaging. Further study of the diffusion characteristics and ADC value of different pathologies in each group was done. Seven patients with intra-cranial infections were encountered with diffusion restriction evident in 6 patients (85.7%). Those were found to have brain abscess, tuberculoma, viral encephalitis and subdural empyema. The calculated ADC values showed a mean of 0.63±0.2 x 10-3 mm2/sec. Statistical significance between the calculated ADC values and the NAWM was detected. Eight patients with intracranial hemorrhage were identified with diffusion restriction observed in 6 of them (75%) with subacute hematomas the most encountered type with diffusion restriction found in those of the late subacute stage (n= 4/5). The calculated ADC values in those showing diffusion restriction showed a mean of 0.71±0.33 x 10-3 mm2/sec. Twenty two extra-axial masses was detected with meningioma being the most encountered pathology (n= 10/22). Diffusion restriction was identified in 16 lesions in this group (72.7%) with mean calculated ADC value of 0.75±0.33 x 10-3 mm2/sec. Forty two patients with intra-axial masses were identified with diffusion restriction identified in 32 of them (76.2 %) with mean calculated ADC value of 0.82±0.2 x 10-3 mm2/sec. Diffusion analysis was of great importance in differentiating degenerated cystic intra-axial masses from abscesses, where the former showed central facilitated diffusion (no restriction) and restricted walls, in contrary to abscess cavities which show central restricted diffusion. Further study of high grade and low grade gliomas showed restricted diffusion to be more with high grade gliomas (n= 13/17, 76.5 %) than low grade gliomas (n= 4/8, 50%); however the calculated ADC values of both showed statistical significance when compared to the NAWM. Twelve patients with demyelinating diseases where studied with multiple sclerosis being the most encountered pathology (n= 11/12). Diffusion restriction was only detected in active lesions, where non-acute plaques showed T2 shine through effect. Diffusion restriction was identified in all lesions encountered in the groups of traumatic brain lesions, encephalopathies and leukodystrophies. |