title: Cardiac dosimetric evaluation of deep inspiration breath-hold level variances using computed tomography scans generated from deformable image registration displacement vectors.
abstract: There is a reduction in cardiac dose for left-sided breast radiotherapy during treatment with deep inspiration breath-hold (DIBH) when compared with treatment with free breathing (FB). Various levels of DIBH may occur for different treatment fractions. Dosimetric effects due to this and other motions are a major component of uncertainty in radiotherapy in this setting. Recent developments in deformable registration techniques allow displacement vectors between various temporal and spatial patient representations to be digitally quantified. We propose a method to evaluate the dosimetric effect to the heart from variable reproducibility of DIBH by using deformable registration to create new anatomical computed tomography (CT) scans. From deformable registration, 3-dimensional deformation vectors are generated with FB and DIBH. The obtained deformation vectors are scaled to 75%, 90%, and 110% and are applied to the reference image to create new CT scans at these inspirational levels. The scans are then imported into the treatment planning system and dose calculations are performed. The average mean dose to the heart was 2.5Gy (0.7 to 9.6Gy) at FB, 1.2Gy (0.6 to 3.8Gy, p < 0.001) at 75% inspiration, 1.1Gy (0.6 to 3.1Gy, p = 0.004) at 90% inspiration, 1.0Gy (0.6 to 3.0Gy) at 100% inspiration or DIBH, and 1.0Gy (0.6 to 2.8Gy, p = 0.019) at 110% inspiration. The average mean dose to the left anterior descending artery (LAD) was 19.9Gy (2.4 to 46.4Gy), 8.6Gy (2.0 to 43.8Gy, p < 0.001), 7.2Gy (1.9 to 40.1Gy, p = 0.035), 6.5Gy (1.8 to 34.7Gy), and 5.3Gy (1.5 to 31.5Gy, p < 0.001), correspondingly. This novel method enables numerous anatomical situations to be mimicked and quantifies the dosimetric effect they have on a treatment plan.
authors.affiliation: Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA; Department of Radiation Medicine, Oregon Health and Science University, Portland, OR; Department of Nuclear Engineering and Radiation Health Physics, Oregon State University, Corvallis, OR.
authors.forename: Taylor
authors.initials: T
authors.lastname: Harry
authors.affiliation: Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA.
authors.forename: Doug
authors.initials: D
authors.lastname: Rahn
authors.affiliation: Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA.
authors.forename: Denis
authors.initials: D
authors.lastname: Semenov
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX.
authors.forename: Xuejun
authors.initials: X
authors.lastname: Gu
authors.affiliation: Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA.
authors.forename: Catheryn
authors.initials: C
authors.lastname: Yashar
authors.affiliation: Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA.
authors.forename: John
authors.initials: J
authors.lastname: Einck
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX.
authors.forename: Steve
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA. Electronic address: lcervino@ucsd.edu.
authors.forename: Laura
authors.initials: L
authors.lastname: Cerviño
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006321:Heart; D006801:Humans; D001239:Inhalation; D008168:Lung; D011829:Radiation Dosage; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed
keywords: Deep inspiration breath-hold; Deformable registration; Demons; Dosimetry; Left-sided breast; Radiation therapy