title: Treatment planning dosimetric parameters for a (90)Y coil source used in intravascular brachytherapy.
abstract: BACKGROUND
  (90)Y coil sources have been used in animal and clinical trials for treatment of restenosis in intravascular brachytherapy (IVBT). This study aims to determine the American Association of Physicists in Medicine (AAPM) Task Group-60 (TG-60) dosimetric quantities in regions surrounding the balloon wall for use in treatment planning computer systems.
  
  
  METHODS
  The Monte Carlo method was used to determine the dose distribution, using MCNP4B2 code. The coil source was modeled by a hollow cylinder of 2.9 cm length centered in a balloon (2.5 mm diameter) filled with carbon dioxide (CO(2)) at 5 atm. Scoring voxels consisted of contiguous annular disk shells with 0.1 mm spacing in the radial direction and 0.2 mm spacing in the longitudinal direction. The scoring region ranges from the center of the source to 1.0 cm in the longitudinal direction, and from 0.13 to 1 cm in the radial direction. In the plane containing the source axis, the Monte Carlo-generated doses in rectilinear coordinates are converted to polar coordinates.
  
  
  RESULTS
  The dose rate of the source is provided in both Cartesian and polar coordinates. The dose rate constant [D(r(0),theta(0))], anisotropy function [F(r,theta)], and radial dose function [g(r)] were generated from these values and listed in tabular format. At shallow angles and longer distances from the source center, large values of the anisotropy function resulted, deviating two orders of magnitude from unity. CONCLUSIONS The doses given to the intima, media, and adventitia are very crucial quantities in IVBT. The calculated TG-60 dosimetric quantities, used commonly in conventional brachytherapy applications, provide a means for the user to determine the three-dimensional dose surrounding the balloon catheter. These parameters can be used in future treatment planning system for IVBT. We also discuss the need to develop a new formalism specific to longer sources used in IVBT.
authors.affiliation: Department of Radiation Oncology and Cardiology, Beth Israel Medical Center and St. Luke's--Roosevelt Hospital Center, 10 Union Square East, New York, NY 10003, USA.
authors.forename: N S
authors.initials: NS
authors.lastname: Patel
authors.forename: S T
authors.initials: ST
authors.lastname: Chiu-Tsao
authors.forename: P
authors.initials: P
authors.lastname: Fan
authors.forename: E
authors.initials: E
authors.lastname: Ahunbay
authors.forename: K
authors.initials: K
authors.lastname: Ravi
authors.forename: W
authors.initials: W
authors.lastname: Sherman
authors.forename: H
authors.initials: H
authors.lastname: Quon
authors.forename: J
authors.initials: J
authors.lastname: Pisch
authors.forename: H S
authors.initials: HS
authors.lastname: Tsao
authors.forename: L B
authors.initials: LB
authors.lastname: Harrison
mesh_terms: D015906:Angioplasty, Balloon, Coronary; D001918:Brachytherapy / Q000295:instrumentation*; D003327:Coronary Disease / Q000532:radiotherapy*; D006801:Humans; D009010:Monte Carlo Method; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D015021:Yttrium Radioisotopes
chemical_list: D015021:Yttrium Radioisotopes