title: Evaluating 99mTc Auger electrons for targeted tumor radiotherapy by computational methods.
abstract: OBJECTIVE
  Technetium-99m (99mTc) has been widely used as an imaging agent but only recently has been considered for therapeutic applications. This study aims to analyze the potential use of 99mTc Auger electrons for targeted tumor radiotherapy by evaluating the DNA damage and its probability of correct repair and by studying the cellular kinetics, following 99mTc Auger electron irradiation in comparison to iodine-131 (131I) beta minus particles and astatine-211 (211At) alpha particle irradiation.
  
  
  METHODS
  Computational models were used to estimate the yield of DNA damage (fast Monte Carlo damage algorithm), the probability of correct repair (Monte Carlo excision repair algorithm), and cell kinetic effects (virtual cell radiobiology algorithm) after irradiation with the selected particles.
  
  
  RESULTS
  The results obtained with the algorithms used suggested that 99mTc CKMMX (all M-shell Coster-Kroning--CK--and super-CK transitions) electrons and Auger MXY (all M-shell Auger transitions) have a therapeutic potential comparable to high linear energy transfer 211At alpha particles and higher than 131I beta minus particles. All the other 99mTc electrons had a therapeutic potential similar to 131I beta minus particles.
  
  
  CONCLUSIONS
  99mTc CKMMX electrons and Auger MXY presented a higher probability to induce apoptosis than 131I beta minus particles and a probability similar to 211At alpha particles. Based on the results here, 99mTc CKMMX electrons and Auger MXY are useful electrons for targeted tumor radiotherapy.
authors.affiliation: Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal. adriana_tavares@msn.com
authors.forename: Adriana Alexandre S
authors.initials: AA
authors.lastname: Tavares
authors.forename: João Manuel R S
authors.initials: JM
authors.lastname: Tavares
mesh_terms: D001246:Astatine / Q000627:therapeutic use; D003198:Computer Simulation; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects; D004583:Electrons / Q000627:therapeutic use*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D007700:Kinetics; D008954:Models, Biological; D009010:Monte Carlo Method; D009369:Neoplasms / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D015609:Organotechnetium Compounds / Q000627:therapeutic use*; D011336:Probability
chemical_list: D007457:Iodine Radioisotopes; D015609:Organotechnetium Compounds; D001246:Astatine