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Abstract
Objective: We investigated the evolution of new multiple sclerosis (MS) lesions over time using frequency shifts of the magnetic resonance (MR) signal.
Methods: Twenty patients with relapsing-remitting MS were serially scanned for 6 months at 1-month intervals. Maps of MR frequency shifts were acquired using susceptibility-weighted imaging. New lesions were identified by enhancement with gadolinium (Gd).
Results: Forty new lesions were identified as areas of signal increase on Gd-enhanced scans. Up to 3 months before lesion appearance, the frequency in areas of future Gd enhancement was not detectably different from the frequency in normal-appearing white matter. Rapid increase in MR frequency was observed between 1 month before and 1 month after Gd enhancement. Two months postenhancement and later, the frequency stabilized and remained at a constantly increased level.
Conclusions: These findings suggest that an increase in MR frequency does not simply reflect blood-brain barrier disruption or edema; rather, it reflects a change of tissue architecture as a consequence of new lesion formation. The data demonstrate that the MR frequency of focal MS lesions is increased before the lesions appear on conventional MRI. Unlike many other advanced imaging techniques, the images for frequency mapping can be rapidly acquired at high spatial resolution and standardized on most clinical scanners.
GLOSSARY
- DAWM=
- diffusely abnormal white matter;
- FLAIR=
- fluid-attenuated inversion recovery;
- FOV=
- field of view;
- Gd=
- gadolinium;
- GM=
- gray matter;
- MR=
- magnetic resonance;
- MS=
- multiple sclerosis;
- MT=
- magnetization transfer;
- NAWM=
- normal-appearing white matter;
- NWM=
- normal white matter;
- ROI=
- region of interest;
- TE=
- echo time;
- TR=
- repetition time;
- WM=
- white matter;
- WM(D)=
- normal WM that corresponds to areas of DAWM in patients
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
See page 206
Editorial, page 202
- Received August 9, 2012.
- Accepted in final form April 4, 2013.
- © 2013 American Academy of Neurology
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