title: Mean heart dose variation over a course of breath-holding breast cancer radiotherapy.
abstract: OBJECTIVE
  The purpose of the work was to estimate the dose received by the heart throughout a course of breath-holding breast radiotherapy.
  
  
  METHODS
  113 cone-beam CT (CBCT) scans were acquired for 20 patients treated within the HeartSpare 1A study, in which both an active breathing control (ABC) device and a voluntary breath-hold (VBH) method were used. Predicted mean heart doses were obtained from treatment plans. CBCT scans were imported into a treatment planning system, heart outlines defined, images registered to the CT planning scan and mean heart dose recorded. Two observers outlined two cases three times each to assess interobserver and intraobserver variation.
  
  
  RESULTS
  There were no statistically significant differences between ABC and VBH heart dose data from CT planning scans, or in the CBCT-based estimates of heart dose, and no effect from the order of the breath-hold method. Variation in mean heart dose per fraction over the three imaged fractions was <6 cGy without setup correction, decreasing to 3.3 cGy with setup correction. If scaled to 15 fractions, all differences between predicted and estimated mean heart doses were <0.5 Gy and in 80% of cases, they were <0.25 Gy.
  
  
  CONCLUSIONS
  Variation in mean heart dose was at an acceptable level over the duration of breath-holding radiotherapy and was well predicted by the planning system. Advances in knowledge: Mean heart dose was not adversely affected by fraction-to-fraction variations throughout a course of heart-sparing radiotherapy using two well-established breath-holding methods.
authors: 1 Medical Physics Department Royal Surrey County Hospital, Guildford, UK.
authors: Nicolle
authors: N
authors: Dunkerley
authors: 2 Oncology Department Portsmouth Hospitals NHS Trust, Portsmouth, UK.
authors: Frederick R
authors: FR
authors: Bartlett
authors: 3 Radiotherapy Department The Royal Marsden NHS Foundation Trust, London, UK.
authors: Anna M
authors: AM
authors: Kirby
authors: 4 Centre for Vision, Speech and Signal Processing, University of Surrey, Guildford, UK.
authors: Philip M
authors: PM
authors: Evans
authors: 5 Physics Department, The Royal Marsden NHS Foundation Trust, London, UK.
authors: Ellen M
authors: EM
authors: Donovan
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D062485:Breath Holding; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000528:radiation effects*; D006801:Humans; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided