الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Diffusion magnetic resonance imaging includes: diffusion weighted
imaging that shows possible areas of increased or decreased signal,
reflecting restricted and facilitated diffusion , respectively and the
apparent diffusion coefficient in which the T2-weighted of the diffusion
sequence is cancelled out, and produces numerical evaluation of interest.
Diffusion weighted MR imaging characterized by markedly
decreased imaging time and increased sensitivity to signal changes due to
molecular motion but having the disadvantages of decreased spatial
resolution of the images and magnetic field inhomogeneities which are
partially prominent in anatomic regions with air-tissue interfaces, such as
the base of the skull.
The widest application of diffusion weighted imaging has been
evaluation of cerebral ischemia. However it gives useful clinical
information in several brain disorders besides acute stroke.
In cerebral neoplasms, ADC values have been correlated with the
degree of tumor cellularity. Thus, the lowest ADC value should indicate
the region of greatest cellularity which is helpful in selecting biopsy
targets. DWI helps distinguish low grade gliomas (low ADC values) from
cerebral infarcts (high ADC values). Tumor cellularity was inversely
correlated with tumor ADC value in various grades of astrocytomas.
DWI is useful technique to distinguish areas of predominantly nonenhancing
tumor (low ADC) from areas of predominantly peritumoral
edema (high ADC) when the abnormality was located in the white matter
aligned in the direction of the diffusion weighted gradients. The ADC has also been used to distinguish peritumoral edema and
tumor infiltration to monitor early responses to treatment, to distinguish
tumor recurrence from radiation necrosis.
The signal intensity on DWI may predict the histology of metastases
and their apparent diffusion coefficient values may reflect tumor
cellularity.
In epidermoid tumors, DWI shows best tumor conspicuity, helps
avoid confusing the tumors with arachnoid cysts, and in particular, it
greatly aided in evaluation of postoperative patients.
Statistically significant differences in ADC between the cerebral
lymphoma and GBM. However, the GBM with restricted water diffusion,
that is, hyperintense on DW images and hypointense on ADC maps, has
also been reported. Therefore; discrimination of lymphoma from some
GBMs may be difficult.
DWI is useful, with few exceptions, in distinguishing a brain abscess
from a necrotic or cystic tumor (High signal intensity on DWI and low
ADC value in brain abscesses, in contrast to low signal intensity on DWI
and high ADC value in the tumors).
In AIDS patients, DWI can distinguish toxoplasmosis (unrestricted
diffusion) from lymphoma (restricted diffusion).
In subdural empyema, DWI detects its occurrence as well as the
resolution of infection when treated, earlier than post contrast T1WI.