الفهرس 
Cross sectional MRI anatomyOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
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.