title: Neutron activation of holmium poly(L-lactic acid) microspheres for hepatic arterial radio-embolization: a validation study.
abstract: Poly(L-lactic acid) microspheres loaded with holmium-166 acetylacetonate (166Ho-PLLA-MS) are a novel microdevice for intra-arterial radio-embolization in patients with unresectable liver malignancies. The neutron activation in a nuclear reactor, in particular the gamma heating, damages the 166Ho-PLLA-MS. The degree of damage is dependent on the irradiation characteristics and irradiation time in a particular reactor facility. The aim of this study was to standardize and objectively validate the activation procedure in a particular reactor. The methods included light- and scanning electron microscopy (SEM), particle size analysis, differential scanning calorimetry, viscometry, thermal neutron flux measurements and energy deposition calculations. Seven hours-neutron irradiation results in sufficient specific activity of the 166Ho-PLLA-MS while structural integrity is preserved. Neutron flux measurements and energy deposition calculations are required in the screening of other nuclear reactors. For the evaluation of microsphere quality, light microscopy, SEM and particle size analysis are appropriate techniques.
authors.affiliation: Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands. m.vente@umcutrecht.nl
authors.forename: M A D
authors.initials: MA
authors.lastname: Vente
authors.forename: J F W
authors.initials: JF
authors.lastname: Nijsen
authors.forename: R
authors.initials: R
authors.lastname: de Roos
authors.forename: M J
authors.initials: MJ
authors.lastname: van Steenbergen
authors.forename: C N J
authors.initials: CN
authors.lastname: Kaaijk
authors.forename: M J J
authors.initials: MJ
authors.lastname: Koster-Ammerlaan
authors.forename: P F A
authors.initials: PF
authors.lastname: de Leege
authors.forename: W E
authors.initials: WE
authors.lastname: Hennink
authors.forename: A D
authors.initials: AD
authors.lastname: van Het Schip
authors.forename: G C
authors.initials: GC
authors.lastname: Krijger
mesh_terms: D000818:Animals; D002152:Calorimetry, Differential Scanning; D004621:Embolization, Therapeutic / Q000295:instrumentation / Q000379:methods*; D006499:Hepatic Artery; D006695:Holmium / Q000737:chemistry* / Q000627:therapeutic use; D006801:Humans; D019344:Lactic Acid; D008113:Liver Neoplasms / Q000532:radiotherapy*; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D009502:Neutrons; D010316:Particle Size; D011091:Polyesters; D011108:Polymers; D013997:Time Factors
chemical_list: D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide); D006695:Holmium