A serial in vivo 7T magnetic resonance phase imaging study of white matter lesions in multiple sclerosis.
BACKGROUND
Magnetic resonance (MR) phase imaging using high field MR scanners has demonstrated excellent contrast in multiple sclerosis (MS) lesions that is thought to be closely correlated to the local iron content. This pilot study acquired serial in vivo MR scans at 7T to track the evolution of phase contrast as MS lesions progress.


METHODS
Five MS patients with relapsing-remitting MS were serially scanned for about 2.5 years at 7T using a high resolution T2*-weighted gradient-echo sequence. Magnitude and phase images were reconstructed for each scan and co-registered to their baseline study.


RESULTS
Five non-enhancing ring and 70 nodular phase lesions were found in the five patients at baseline. None of the baseline phase lesions (including all five ring phase lesions) showed obvious qualitative variation on phase images during the study. Of note, we observed that three magnitude lesions, not initially read as abnormal signal, were either better appreciated using phase contrast imaging (two lesions) or preceded (one lesion) by phase changes.


CONCLUSIONS
The observation that ring phase lesions remained unchanged over 2.5 years of follow-up challenges the notion that such lesions reveal the presence of acute activated iron-rich macrophages. It suggests that either different phenotypes of macrophages persist longer than previously expected or other mechanisms related to tissue injury contribute to the phase contrast.
The UC Berkeley & UCSF Graduate Program in Bioengineering, University of California San Francisco, USA.
Wei
W
Bian
Kristin
K
Harter
Kathryn E
KE
Hammond-Rosenbluth
Janine M
JM
Lupo
Duan
D
Xu
Douglas Ac
DA
Kelley
Daniel B
DB
Vigneron
Sarah J
SJ
Nelson
Daniel
D
Pelletier
D001921:Brain / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000473:pathology*