title: Imaging of VSOP labeled stem cells in agarose phantoms with susceptibility weighted and T2* weighted MR Imaging at 3T: determination of the detection limit.
abstract: OBJECTIVE
  This study aimed to evaluate the detectability of stem cells labeled with very small iron oxide particles (VSOP) at 3T with susceptibility weighted (SWI) and T2* weighted imaging as a methodological basis for subsequent examinations in a large animal stroke model (sheep).
  
  
  METHODS
  We examined ovine mesenchymal stem cells labeled with VSOP in agarose layer phantoms. The experiments were performed in 2 different groups, with quantities of 0-100,000 labeled cells per layer. 15 different SWI- and T2*-weighted sequences and 3 RF coils were used. All measurements were carried out on a clinical 3T MRI. Images of Group A were analyzed by four radiologists blinded for the number of cells, and rated for detectability according to a four-step scale. Images of Group B were subject to a ROI-based analysis of signal intensities. Signal deviations of more than the 0.95 confidence interval in cell containing layers as compared to the mean of the signal intensity of non cell bearing layers were considered significant.
  
  
  RESULTS
  
  500 or more labeled cells were judged as confidently visible when examined with a SWI-sequence with 0.15 mm slice thickness. Group B: 500 or more labeled cells showed a significant signal reduction in SWI sequences with a slice thickness of 0.25 mm. Slice thickness and cell number per layer had a significant influence on the amount of detected signal reduction.
  
  
  CONCLUSIONS
  500 VSOP labeled stem cells could be detected with SWI imaging at 3 Tesla using an experimental design suitable for large animal models.
authors.affiliation: Department of Neuroradiology, University Hospital Leipzig, Leipzig, Germany. donald.lobsien@medizin.uni-leipzig.de
authors.forename: Donald
authors.initials: D
authors.lastname: Lobsien
authors.forename: Antje Y
authors.initials: AY
authors.lastname: Dreyer
authors.forename: Albrecht
authors.initials: A
authors.lastname: Stroh
authors.forename: Johannes
authors.initials: J
authors.lastname: Boltze
authors.forename: Karl-Titus
authors.initials: KT
authors.lastname: Hoffmann
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005290:Ferric Compounds / Q000378:metabolism*; D057230:Limit of Detection; D008279:Magnetic Resonance Imaging / Q000379:methods*; D059630:Mesenchymal Stem Cells / Q000378:metabolism / Q000648:ultrastructure*; D010316:Particle Size; D019047:Phantoms, Imaging; D012685:Sepharose; D012756:Sheep; D013194:Staining and Labeling / Q000379:methods; D033581:Stem Cell Transplantation / Q000379:methods*; D020521:Stroke / Q000628:therapy*
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide; D012685:Sepharose