title: Comparison of the effects of high-energy photon beam irradiation (10 and 18 MV) on 2 types of implantable cardioverter-defibrillators.
abstract: OBJECTIVE
  Radiation therapy for cancer may be required for patients with implantable cardiac devices. However, the influence of secondary neutrons or scattered irradiation from high-energy photons (≥10 MV) on implantable cardioverter-defibrillators (ICDs) is unclear. This study was performed to examine this issue in 2 ICD models.
  
  
  METHODS
  ICDs were positioned around a water phantom under conditions simulating clinical radiation therapy. The ICDs were not irradiated directly. A control ICD was positioned 140 cm from the irradiation isocenter. Fractional irradiation was performed with 18-MV and 10-MV photon beams to give cumulative in-field doses of 600 Gy and 1600 Gy, respectively. Errors were checked after each fraction. Soft errors were defined as severe (change to safety back-up mode), moderate (memory interference, no changes in device parameters), and minor (slight memory change, undetectable by computer).
  
  
  RESULTS
  Hard errors were not observed. For the older ICD model, the incidences of severe, moderate, and minor soft errors at 18 MV were 0.75, 0.5, and 0.83/50 Gy at the isocenter. The corresponding data for 10 MV were 0.094, 0.063, and 0 /50 Gy. For the newer ICD model at 18 MV, these data were 0.083, 2.3, and 5.8 /50 Gy. Moderate and minor errors occurred at 18 MV in control ICDs placed 140 cm from the isocenter. The error incidences were 0, 1, and 0 /600 Gy at the isocenter for the newer model, and 0, 1, and 6 /600Gy for the older model. At 10 MV, no errors occurred in control ICDs.
  
  
  CONCLUSIONS
  ICD errors occurred more frequently at 18 MV irradiation, which suggests that the errors were mainly caused by secondary neutrons. Soft errors of ICDs were observed with high energy photon beams, but most were not critical in the newer model. These errors may occur even when the device is far from the irradiation field.
authors: Department of Radiation Oncology, University of Tsukuba, Tsukuba, Ibaraki, Japan. haruko@pmrc.tsukuba.ac.jp
authors: Haruko
authors: H
authors: Hashii
authors: Takayuki
authors: T
authors: Hashimoto
authors: Ayako
authors: A
authors: Okawa
authors: Koichi
authors: K
authors: Shida
authors: Tomonori
authors: T
authors: Isobe
authors: Masahiro
authors: M
authors: Hanmura
authors: Tetsuo
authors: T
authors: Nishimura
authors: Kazutaka
authors: K
authors: Aonuma
authors: Takeji
authors: T
authors: Sakae
authors: Hideyuki
authors: H
authors: Sakurai
mesh_terms: D017147:Defibrillators, Implantable; D019544:Equipment Failure Analysis; D006801:Humans; D009502:Neutrons; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D017785:Photons / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000379:methods*; D012542:Scattering, Radiation