title: Liver tumors: MR imaging of radioactive holmium microspheres--phantom and rabbit study.
abstract: OBJECTIVE
  To investigate the use of magnetic resonance (MR) imaging in the administration and biodistribution of holmium-loaded poly(L-lactic acid) microspheres (Ho-PLLA-MS) in liver tumors.
  
  
  METHODS
  MR imaging measurements were obtained in phantoms, three ex vivo rabbit livers, and four livers in living rabbits. When applicable, measurements were compared with those on scintigraphic images. The transverse relaxivity R2* of the Ho-PLLA-MS was determined in a phantom study. The in vivo animal experiments were performed by using rabbits with an implanted VX2 tumor. Detection of passing Ho-PLLA-MS to estimate lung shunting was performed in a scaled model of the vena cava.
  
  
  RESULTS
  In the ex vivo liver experiments, the feasibility of real-time MR imaging during administration of microspheres was demonstrated. The in vivo rabbit experiments demonstrated that MR imaging can depict radioactive, nonradioactive, and decayed Ho-PLLA-MS after treatment for as long as they remain in the body. Furthermore, this study showed the ability of dynamic MR imaging to detect single doses of passing Ho-PLLA-MS.
  
  
  CONCLUSIONS
  Ho-PLLA-MS used for internal radionuclide therapy can be imaged clearly in vivo with MR imaging.
authors.affiliation: Department of Nuclear Medicine, University Medical Centre, Heidelberglaan 100, Room E02.222, 3584 CX, Utrecht, The Netherlands. f.nijsen@azu.nl
authors.forename: Johannes F W
authors.initials: JF
authors.lastname: Nijsen
authors.forename: Jan-Henry
authors.initials: JH
authors.lastname: Seppenwoolde
authors.forename: Thomas
authors.initials: T
authors.lastname: Havenith
authors.forename: Clemens
authors.initials: C
authors.lastname: Bos
authors.forename: Chris J G
authors.initials: CJ
authors.lastname: Bakker
authors.forename: Alfred D
authors.initials: AD
authors.lastname: van het Schip
mesh_terms: D000818:Animals; D005260:Female; D006695:Holmium / Q000493:pharmacokinetics; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008863:Microspheres; D019047:Phantoms, Imaging; D011817:Rabbits; D011868:Radioisotopes / Q000493:pharmacokinetics; D011877:Radionuclide Imaging; D014018:Tissue Distribution
chemical_list: D011868:Radioisotopes; D006695:Holmium