title: Quantifying the reproducibility of heart position during treatment and corresponding delivered heart dose in voluntary deep inhalation breath hold for left breast cancer patients treated with external beam radiotherapy.
abstract: OBJECTIVE
  Voluntary deep inhalation breath hold (VDIBH) reduces heart dose during left breast irradiation. We present results of the first study performed to quantify reproducibility of breath hold using bony anatomy, heart position, and heart dose for VDIBH patients at treatment table.
  
  
  METHODS
  Data from 10 left breast cancer patients undergoing VDIBH whole-breast irradiation were analyzed. Two computed tomography (CT) scans, free breathing (FB) and VDIBH, were acquired to compare dose to critical structures. Pretreatment weekly kV orthogonal images and tangential ports were acquired. The displacement difference from spinal cord to sternum across the isocenter between coregistered planning Digitally Reconstructed Radiographs (DRRs) and kV imaging of bony thorax is a measure of breath hold reproducibility. The difference between bony coregistration and heart coregistration was the measured heart shift if the patient is aligned to bony anatomy.
  
  
  RESULTS
  Percentage of dose reductions from FB to VDIBH: mean heart dose (48%, SD 19%, p = 0.002), mean LAD dose (43%, SD 19%, p = 0.008), and maximum left anterior descending (LAD) dose (60%, SD 22%, p = 0.008). Average breath hold reproducibility using bony anatomy across the isocenter along the anteroposterior (AP) plane from planning to treatment is 1 (range, 0-3; SD, 1) mm. Average heart shifts with respect to bony anatomy between different breath holds are 2 ± 3 mm inferior, 1 ± 2 mm right, and 1 ± 3 mm posterior. Percentage dose changes from planning to delivery: mean heart dose (7%, SD 6%); mean LAD dose, ((9%, SD 7%)S, and maximum LAD dose, (11%, SD 11%) SD 11%, p = 0.008).
  
  
  CONCLUSIONS
  We observed excellent three-dimensional bony registration between planning and pretreatment imaging. Reduced delivered dose to heart and LAD is maintained throughout VDIBH treatment.
authors.affiliation: Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908-0375, USA.
authors.forename: Alyson
authors.initials: A
authors.lastname: McIntosh
authors.forename: Asal N
authors.initials: AN
authors.lastname: Shoushtari
authors.forename: Stanley H
authors.initials: SH
authors.lastname: Benedict
authors.forename: Paul W
authors.initials: PW
authors.lastname: Read
authors.forename: Krishni
authors.initials: K
authors.lastname: Wijesooriya
mesh_terms: D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D017023:Coronary Angiography; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000528:radiation effects; D006801:Humans; D001239:Inhalation; D058958:Organs at Risk / Q000000981:diagnostic imaging* / Q000528:radiation effects; D056888:Patient Positioning; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control; D013902:Radiography, Thoracic; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed