AUTHOR=Schweser Ferdinand , Dwyer Michael G., Deistung Andreas , Reichenbach Jürgen R., Zivadinov Robert TITLE=Impact of tissue atrophy on high-pass filtered MRI signal phase-based assessment in large-scale group-comparison studies: a simulation study JOURNAL=Frontiers in Physics VOLUME=1 YEAR=2013 URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2013.00014 DOI=10.3389/fphy.2013.00014 ISSN=2296-424X ABSTRACT=

The assessment of abnormal accumulation of tissue iron in the basal ganglia nuclei and in white matter (WM) plaques using the gradient echo magnetic resonance signal phase has become a research focus in many neurodegenerative diseases such as multiple sclerosis (MS) or Parkinson's disease. A common and natural approach is to calculate the mean high-pass-filtered phase of previously delineated brain structures. Unfortunately, the interpretation of such an analysis requires caution: in this paper we demonstrate that regional gray matter (GM) atrophy, which is concomitant with many neurodegenerative diseases, may itself directly result in a phase shift seemingly indicative of increased iron concentration even without any real change in the tissue iron concentration. Although this effect is relatively small results of large-scale group comparisons may be driven by anatomical changes rather than by changes of the iron concentration.