title: Dose and dose rate effects of beta-particle emitting radioactive stents in a porcine model of restenosis.
abstract: BACKGROUND
  Radioactive stents have been proposed as a means to prevent in-stent restenosis by inhibiting intimal proliferation with continuous low-dose irradiation.
  
  
  OBJECTIVE
  The purpose of this study is to determine the effects of cumulative dose and dose-rate delivery on neointimal formation using 32P and 90Y beta-particle emitting radioactive stents in a porcine coronary model of restenosis.
  
  
  METHODS
  We compared the late histologic results of 0.25 to 32.0 microCi 90Y (half-life 64 hours) (n = 64 stents) and 0.1 to 57.6 microCi 32P (half-life 14.3 days) (n = 55 stents) Beta-particle emitting radioactive stents with non-radioactive (n = 40) stents in a porcine coronary model of restenosis. A computer-based dosimetry modeling program was used to determine the 28 day cumulative dose and dose-rate delivery for the beta-particle emitting radioactive stents at a distance of 0.1 mm from the stent surface.
  
  
  RESULTS
  Continuous low dose-rate (1 to 5 cGy/hr) radiation delivery for > 2 weeks via a 0.1 to 0.5 microCi 32P radioactive stent effectively reduced in-stent neointimal hyperplasia at 90 days. Cumulative doses of > 55 Gy induced severe adventitial fibrosis, microvascular damage and promoted the formation of a matrix-rich neointima. Delayed vascular repair was evident at focal regions within the body of radioactive stents that delivered cumulative doses of > or = 140 Gy at 28 days and cumulative doses of 1,100 Gy at 90 days.
  
  
  CONCLUSIONS
  These data may be useful in predicting safe and effective dose and dose rate delivery for beta-particle emitting radioactive stents.
authors.affiliation: Experimental Coronary Intervention Laboratories, Stanford University Medical Center, California 94305-5218, USA. a_carter@cvmed.stanford.edu
authors.forename: A J
authors.initials: AJ
authors.lastname: Carter
authors.forename: S
authors.initials: S
authors.lastname: Jenkins
authors.forename: W
authors.initials: W
authors.lastname: Sweet
authors.forename: L
authors.initials: L
authors.lastname: Bailey
authors.forename: R
authors.initials: R
authors.lastname: Jones
authors.forename: T A
authors.initials: TA
authors.lastname: Fischell
authors.forename: R
authors.initials: R
authors.lastname: Virmani
mesh_terms: D000818:Animals; D001918:Brachytherapy / Q000379:methods*; D003327:Coronary Disease / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D010761:Phosphorus Radioisotopes / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D015607:Stents; D013552:Swine; D015021:Yttrium Radioisotopes / Q000627:therapeutic use*
chemical_list: D010761:Phosphorus Radioisotopes; D015021:Yttrium Radioisotopes