Neutron activation of holmium poly(L-lactic acid) microspheres for hepatic arterial radio-embolization: a validation study

Biomed Microdevices. 2009 Aug;11(4):763-72. doi: 10.1007/s10544-009-9291-y.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calorimetry, Differential Scanning
  • Embolization, Therapeutic / instrumentation
  • Embolization, Therapeutic / methods*
  • Hepatic Artery*
  • Holmium / chemistry*
  • Holmium / therapeutic use
  • Humans
  • Lactic Acid
  • Liver Neoplasms / radiotherapy*
  • Microscopy, Electron, Scanning
  • Microspheres*
  • Neutrons*
  • Particle Size
  • Polyesters
  • Polymers
  • Time Factors


  • Polyesters
  • Polymers
  • Lactic Acid
  • poly(lactide)
  • Holmium