http://www.ajnr.org/content/21/1/55.full.pdf

Incidence of Postangiographic Abnormalities Revealed by
Diffusion-Weighted MR Imaging

The changes of diffusion restriction observed
on DW-MR and ADC studies after acute
infarction persist for 1 to 2 weeks (19, 24, 25).

http://www.myesr.org/html/img/pool/I3_Vol_3_Suppl_1_ECR_2012...

Methods and Materials: 176 consecutive stroke patients (within 12 months) demonstrating restricted diffusion at initial MR examination were evaluated. Extension of diffusion restriction was judged both on initial MR as well as on follow‑up after 24 hours. Changes in lesion extension were assessed by two radiologists
independently, as well as overall image quality (4-tier scale).

Conclusion: Our findings prove the existing assumption that diffusion restriction
represents infarct core, which may remain unchanged or increase in volume over
time, indicating an accuracy of almost 98%. Partial or complete resolution of
diffusion-restriction is extremely rare.

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http://www.scribd.com/doc/20984901/Diseases-of-the-Brain-Hea...

; strong hyperintensity due to diffusion restriction of the pus in the a

diffusion-weighted image: no diffusion restriction

such as necrotic metastasis, no diffusion restriction is seen (Figs. 12, 13) [15]. In radione




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Note added at 58 mins (2012-04-23 10:39:55 GMT)
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http://nogginpower.com/docs/Diseases of head neck spine.pdf

Fig. 13 a, b. Ring-enhancing abscess. a Transverse gadolinium-enhanced T1-weighted image; left occipital lesion with peripheral enhancement. b Transverse diffusion-weighted image; strong hyperintensity due to diffusion restriction of the pus in the abscess

Differential Diagnosis of Non-tumoral Lesions
Finally, it is important to note that, in the presence of a
space-occupying lesion in the brain, the differential diagnosis
has to include non-tumoral lesions, such as abscesses,
radionecrosis, aneurysms, multiple sclerosis,
infarction, etc. The clinical presentation of these lesions
differs in each case and can be very confusing.
Abscesses can appear as ring-enhancing lesions on contrast-
enhanced MR. Here, DWI plays a major diagnostic role, since the presence of pus, bacteria, and cellular debris in the center of an abscess leads to strong restriction of diffusion, with very high signal on DWI, whereas in tumors, such as necrotic metastasis, no diffusion restriction is seen (Figs. 12, 13) [15].