title: Dosimetric perturbations due to an implanted cardiac pacemaker in MammoSite(®) treatment.
abstract: OBJECTIVE
  To investigate dose perturbations for pacemaker-implanted patients in partial breast irradiation using high dose rate (HDR) balloon brachytherapy.
  
  
  METHODS
  Monte Carlo (MC) simulations were performed to calculate dose distributions involving a pacemaker in Ir-192 HDR balloon brachytherapy. Dose perturbations by varying balloon-to-pacemaker distances (BPD = 50 or 100 mm) and concentrations of iodine contrast medium (2.5%, 5.0%, 7.5%, and 10.0% by volume) in the balloon were investigated for separate parts of the pacemaker (i.e., battery and substrate). Relative measurements using an ion-chamber were also performed to confirm MC results.
  
  
  RESULTS
  The MC and measured results in homogeneous media without a pacemaker agreed with published data within 2% from the balloon surface to 100 mm BPD. Further their dose distributions with a pacemaker were in a comparable agreement. The MC results showed that doses over the battery were increased by a factor of 3, compared to doses without a pacemaker. However, there was no significant dose perturbation in the middle of substrate but up to 70% dose increase in the substrate interface with the titanium capsule. The attenuation by iodine contrast medium lessened doses delivered to the pacemaker by up to 9%.
  
  
  CONCLUSIONS
  Due to inhomogeneity of pacemaker and contrast medium as well as low-energy photons in Ir-192 HDR balloon brachytherapy, the actual dose received in a pacemaker is different from the homogeneous medium-based dose and the external beam-based dose. Therefore, the dose perturbations should be considered for pacemaker-implanted patients when evaluating a safe clinical distance between the balloon and pacemaker.
authors.affiliation: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Wonmo
authors.initials: W
authors.lastname: Sung
authors.forename: Siyong
authors.initials: S
authors.lastname: Kim
authors.forename: Jung-In
authors.initials: JI
authors.lastname: Kim
authors.forename: Jae-Gi
authors.initials: JG
authors.lastname: Lee
authors.forename: Young-Joo
authors.initials: YJ
authors.lastname: Shin
authors.forename: Jae-Yong
authors.initials: JY
authors.lastname: Jung
authors.forename: Sung-Joon
authors.initials: SJ
authors.lastname: Ye
mesh_terms: D016477:Artifacts; D001918:Brachytherapy / Q000379:methods*; D004567:Electrodes, Implanted; D009010:Monte Carlo Method; D010138:Pacemaker, Artificial; D011874:Radiometry; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results