title: Phase-based manganese enhanced MRI, a new methodology to enhance brain cytoarchitectural contrast and study manganese uptake.
abstract: OBJECTIVE
  As the magnetic susceptibility induced frequency shift increases linearly with magnetic field strength, the present work evaluates manganese as a phase imaging contrast agent and investigates the dose dependence of brain enhancement in comparison to T(1) -weighted imaging after intravenous administration of MnCl(2).
  
  
  METHODS
  Experiments were carried out on 12 Sprague-Dawley rats. MnCl(2) was infused intravenously with the following doses: 25, 75, 125 mg/kg (n=4). Phase, T(1) -weighted images and T(1) maps were acquired before and 24 h post MnCl(2) administration at 14.1 Tesla.
  
  
  RESULTS
  Manganese enhancement was manifested in phase imaging by an increase in frequency shift differences between regions rich in calcium gated channels and other tissues, together with local increase in signal to noise ratio (from the T(1) reduction). Such contrast improvement allowed a better visualization of brain cytoarchitecture. The measured T(1) decrease observed across different manganese doses and in different brain regions were consistent with the increase in the contrast to noise ratio (CNR) measured by both T(1) -weighted and phase imaging, with the strongest variations being observed in the dentate gyrus and olfactory bulb.
  
  
  CONCLUSIONS
  Overall from its high sensitivity to manganese combined with excellent CNR, phase imaging is a promising alternative imaging protocol to assess manganese enhanced MRI at ultra high field.
authors.affiliation: Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors.forename: Rajika
authors.initials: R
authors.lastname: Maddage
authors.forename: José P
authors.initials: JP
authors.lastname: Marques
authors.forename: Rolf
authors.initials: R
authors.lastname: Gruetter
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D001931:Brain Mapping / Q000379:methods*; D002712:Chlorides / Q000493:pharmacokinetics; D003287:Contrast Media / Q000008:administration & dosage* / Q000493:pharmacokinetics; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D017895:Manganese Compounds / Q000493:pharmacokinetics; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002712:Chlorides; D003287:Contrast Media; D017895:Manganese Compounds; C025340:manganese chloride
keywords: MR phase contrast agent; high field MRI; manganese enhanced MRI; phase imaging