title: Specific identification of iron oxide-labeled stem cells using magnetic field hyperthermia and MR thermometry.
abstract: Cell-based therapies represent important novel strategies for the improved treatment of various diseases. To monitor the progress of therapy and cell migration, noninvasive imaging methods are needed. MRI represents such a modality, allowing, for example, for the tracking of cells labeled with superparamagnetic iron oxide nanoparticles. Unfortunately, the labeled cells cannot always be identified nonambiguously in the MR images. In this article, we present the combination of two different types of MR experiment to identify iron oxide-labeled cells nonambiguously. The labeled cells appear as hypointense spots on standard T(2)*-weighted MR images. Furthermore, they can be heated magnetically and subsequently identified by MR thermometry as a result of their heat dissipation. Other hypointense regions in the MR images are not heated and do not show heat dissipation. A proof-of-principle study was successfully performed in vitro and in vivo. The positive identification of the iron oxide-labeled cells was demonstrated in collagen type I hydrogel phantoms and in living mice with high spatial and temporal accuracy. The motion of the in vitro samples was corrected in order to improve the specificity of the identification of labeled cells. Therefore, this method possesses the potential for cell tracking without prior knowledge about the cells, and thus allows the noninvasive monitoring of cell-based therapies, as long as the cells contain a sufficient amount of iron oxide for detection in MR thermometry and imaging.
authors.affiliation: MRB Research Center Magnetic-Resonance-Bavaria, Wuerzburg, Germany. haddad@mr-bavaria.de
authors.forename: Daniel
authors.initials: D
authors.lastname: Haddad
authors.forename: Markus F
authors.initials: MF
authors.lastname: Hildenbrand
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Hiller
authors.forename: Meike
authors.initials: M
authors.lastname: Haddad-Weber
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jakob
mesh_terms: D000818:Animals; D002465:Cell Movement; D058948:Cell Tracking / Q000379:methods*; D005290:Ferric Compounds / Q000378:metabolism*; D006614:Hindlimb / Q000033:anatomy & histology; D006358:Hot Temperature; D006801:Humans; D006979:Hyperthermia, Induced; D008279:Magnetic Resonance Imaging / Q000379:methods*; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000502:physiology; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide