title: Impact of internal metallic ports in temporary tissue expanders on postmastectomy radiation dose distribution.
abstract: OBJECTIVE
  Temporary tissue expanders (TTE) with an internal magnetic metal port (IMP) have been increasingly used for breast reconstruction in post-mastectomy patients who receive radiation therapy (XRT). We evaluated XRT plans of patients with IMP to determine its effect on XRT dose distribution.
  
  
  METHODS
  Original treatment plans with CT simulation scans of 24 consecutive patients who received XRT (ORI), planned without heterogeneity corrections, to a reconstructed breast containing an IMP were used. Two additional treatment plans were then generated: one treatment plan with the IMP assigned the electron density of the rare earth magnet, nickel plated neodymium-iron-boron (HET), and a second treatment plan with the IMP assigned a CT value of 1 to simulate a homogeneous breast without an IMP (BRS). All plans were prescribed 50 Gy to the reconstructed breast (CTV).
  
  
  RESULTS
  CTV coverage by 50 Gy was significantly lower in the HET (mean 87.7% CTV) than in either the ORI (mean 99.7% CTV, P<.001) or BRS plans (mean 95.0% CTV, P<.001). The effect of the port was more pronounced on CT slices containing the IMP with prescription dose coverage of the CTV being less in the HET than in either ORI (mean difference 33.6%, P<.01) or BRS plans (mean difference 30.1%, P<.001). HET had a less homogeneous and conformal dose distribution than BRS or ORI.
  
  
  CONCLUSIONS
  IMPs increase dose heterogeneity and reduce dose to the breast CTV through attenuation of the beam. For optimal XRT treatment, heterogeneity corrections should be used in XRT planning for patients with TTE with IMP, as the IMP impacts dose distribution.
authors.affiliation: Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, Georgia, USA.
authors.forename: Susie A
authors.initials: SA
authors.lastname: Chen
authors.forename: Tomiwa
authors.initials: T
authors.lastname: Ogunleye
authors.forename: Anees
authors.initials: A
authors.lastname: Dhabbaan
authors.forename: Eugene H
authors.initials: EH
authors.lastname: Huang
authors.forename: Albert
authors.initials: A
authors.lastname: Losken
authors.forename: Sheryl
authors.initials: S
authors.lastname: Gabram
authors.forename: Lawrence
authors.initials: L
authors.lastname: Davis
authors.forename: Mylin A
authors.initials: MA
authors.lastname: Torres
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D016462:Mammaplasty / Q000295:instrumentation*; D008408:Mastectomy; D008670:Metals; D008875:Middle Aged; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015625:Tissue Expansion Devices
chemical_list: D008670:Metals