title: Microspheres with ultrahigh holmium content for radioablation of malignancies.
abstract: OBJECTIVE
  The aim of this study was to develop microspheres with an ultra high holmium content which can be neutron activated for radioablation of malignancies. These microspheres are proposed to be delivered selectively through either intratumoral injections into solid tumors or administered via an intravascularly placed catheter.
  
  
  METHODS
  Microspheres were prepared by solvent evaporation, using holmium acetylacetonate (HoAcAc) crystals as the sole ingredient. Microspheres were characterized using light and scanning electron microscopy, coulter counter, titrimetry, infrared and Raman spectroscopy, differential scanning calorimetry, X-ray powder diffraction, magnetic resonance imaging (MRI), and X-ray computed tomography (CT).
  
  
  RESULTS
  Microspheres, thus prepared displayed a smooth surface. The holmium content of the HoAcAc microspheres (44% (w/w)) was higher than the holmium content of the starting material, HoAcAc crystals (33% (w/w)). This was attributed to the loss of acetylacetonate from the HoAcAc complex, during rearrangement of acetylacetonate around the holmium ion. The increase of the holmium content allows for the detection of (sub)microgram amounts of microspheres using MRI and CT.
  
  
  CONCLUSIONS
  HoAcAc microspheres with an ultra-high holmium content were prepared. These microspheres are suitable for radioablation of tumors by intratumoral injections or treatment of liver tumors through transcatheter administration.
authors.affiliation: Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands. w.bult@umcutrecht.nl
authors.forename: W
authors.initials: W
authors.lastname: Bult
authors.forename: P R
authors.initials: PR
authors.lastname: Seevinck
authors.forename: G C
authors.initials: GC
authors.lastname: Krijger
authors.forename: T
authors.initials: T
authors.lastname: Visser
authors.forename: L M J
authors.initials: LM
authors.lastname: Kroon-Batenburg
authors.forename: C J G
authors.initials: CJ
authors.lastname: Bakker
authors.forename: W E
authors.initials: WE
authors.lastname: Hennink
authors.forename: A D
authors.initials: AD
authors.lastname: van het Schip
authors.forename: J F W
authors.initials: JF
authors.lastname: Nijsen
mesh_terms: D002152:Calorimetry, Differential Scanning; D006695:Holmium / Q000008:administration & dosage* / Q000737:chemistry* / Q000627:therapeutic use; D006801:Humans; D006885:Hydroxybutyrates / Q000008:administration & dosage / Q000737:chemistry; D008113:Liver Neoplasms / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging; D008863:Microspheres; D010316:Particle Size; D010422:Pentanones / Q000008:administration & dosage / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D014057:Tomography, X-Ray Computed; D014961:X-Ray Diffraction
chemical_list: D006885:Hydroxybutyrates; D010422:Pentanones; C049529:acetyl acetonate; D006695:Holmium