title: 166Ho-labeled hydroxyapatite particles: a possible agent for liver cancer therapy.
abstract: OBJECTIVE
  Intra-arterial administration of particulates labeled with -emitting radionuclides is one of the promising modalities for the treatment of liver cancer. 166Ho [T1/2=26.9 hours, E(max) = 1.85 MeV, Egamma = 81keV (6.4%)] could be envisioned as an attractive radionuclide for use in liver cancer therapy owing to its high energy emission, short half-life, and feasibility of its production with adequately high specific activity and radionuclidic purity. Hydroxyapatite (HA) particles in the size range of 20-60 micros were chosen as the particulate carrier due to their biocompatibility and ease of labeling with lanthanides.
  
  
  METHODS
  166Ho was produced by thermal neutron bombardment on a natural holmium target. HA particles of the desired size range were synthesized, characterized, and radiolabeled with 166Ho. The biologic behavior of166Ho-HA was tested in normal Wistar rats by carrying out biodistribution and imaging studies.
  
  
  RESULTS
  166Ho was produced with a specific activity of 5.55-6.48 TBq/g and radionuclidic purity of approximately 100%. HA particles were labeled with 166Ho with a high radiochemical purity of >99% and good in vitro stability up to 7 days. The biodistribution and imaging studies revealed satisfactory hepatic retention (approximately 89% of injected activity after 2 days) with insignificant uptake in any other major organ/tissue.
  
  
  CONCLUSIONS
  166Ho-HA exhibited promising features as an agent for liver cancer therapy in preliminary studies and warrants further investigation
authors.affiliation: Radiopharmaceuticals Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
authors.forename: Tapas
authors.initials: T
authors.lastname: Das
authors.forename: Sudipta
authors.initials: S
authors.lastname: Chakraborty
authors.forename: Haladhar D
authors.initials: HD
authors.lastname: Sarma
authors.forename: Meera
authors.initials: M
authors.lastname: Venkatesh
authors.forename: Sharmila
authors.initials: S
authors.lastname: Banerjee
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D017886:Durapatite / Q000737:chemistry; D006695:Holmium / Q000737:chemistry / Q000493:pharmacokinetics / Q000627:therapeutic use*; D007270:Injections, Intra-Articular; D008113:Liver Neoplasms / Q000532:radiotherapy*; D010087:Oxides / Q000737:chemistry; D011868:Radioisotopes / Q000032:analysis / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D014018:Tissue Distribution; D051598:Whole Body Imaging
chemical_list: D010087:Oxides; D011868:Radioisotopes; D017886:Durapatite; D006695:Holmium