title: Cardiac dose reduction during tangential breast irradiation using deep inspiration breath hold: a dose comparison study based on deformable image registration.
abstract: BACKGROUND
  Radiation therapy (RT) for a left-sided breast cancer often involves some incidental exposure of the heart and increase in the rate of major coronary events. One method to reduce the dose to the heart during a tangential breast irradiation is the deep inspiration breath hold (DIBH) technique. Our department adopted DIBH for selected left breast cancer patients with a maximum cardiac distance ≥ 10 mm. We evaluated the effect of the DIBH on cardiac dose compared to normal free breathing (FB). The secondary objective of our present study was to use modeled risk estimates to quantify the risk of coronary events after RT with DIBH.
  
  
  METHODS
  Thirty-two patients who underwent RT with DIBH at our hospital were retrospectively analyzed. For each patient, two computed tomography (CT) scans were acquired, FB-CT and DIBH-CT. Using a deformable image registration tool, the target volume was deformed from DIBH-CT to FB-CT, and conventional tangential treatment planning was performed, focusing on the equality of target coverage between the two plans. Doses to the heart, left anterior descending (LAD) artery, and ipsilateral lung were assessed.
  
  
  RESULTS
  By using DIBH, the average mean heart dose was reduced from 724.1 cGy to 279.3 (p < 0.001). The relative heart volume irradiated with 10 Gy-50 Gy was consistently reduced. The mean dose to the LAD coronary artery was reduced from 4079.1 cGy to 2368.9 cGy (p < 0.001). The ipsilateral lung volume receiving 20 Gy or more and 40 Gy or more was reduced by 2.2 % in both cases. Estimated risks of coronary events at 10 years were 4.03 and 2.55 % for RT with FB and DIBH, respectively (p < 0.001).
  
  
  CONCLUSIONS
  The use of DIBH during RT of the left-sided breast considerably reduces the doses delivered to the heart and LAD artery with similar target coverage. For the current study patients, the probability of major coronary events was reduced with DIBH.
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Republic of Korea. hi_juji@daum.net.
authors.forename: Ji Hyeon
authors.initials: JH
authors.lastname: Joo
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Republic of Korea. watermountain@hanmail.net.
authors.forename: Su Ssan
authors.initials: SS
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Republic of Korea. sdahn@amc.seoul.kr.
authors.forename: Seung Do
authors.initials: SD
authors.lastname: Ahn
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Republic of Korea. jwkwak1101@gmail.com.
authors.forename: Jungwon
authors.initials: J
authors.lastname: Kwak
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Republic of Korea. chiyoung.jeong@gmail.com.
authors.forename: Chiyoung
authors.initials: C
authors.lastname: Jeong
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. shahn2@amc.seoul.kr.
authors.forename: Sei-Hyun
authors.initials: SH
authors.lastname: Ahn
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. brdrson@amc.seoul.kr.
authors.forename: Byung-Ho
authors.initials: BH
authors.lastname: Son
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. jjjongwr@hanmail.net.
authors.forename: Jong Won
authors.initials: JW
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000532:radiotherapy*; D062485:Breath Holding; D005260:Female; D006321:Heart / Q000528:radiation effects*; D006801:Humans; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed