title: Dosimetric impact of 4-dimensional computed tomography ventilation imaging-based functional treatment planning for stereotactic body radiation therapy with 3-dimensional conformal radiation therapy.
abstract: OBJECTIVE
  The purpose of this study was to clarify the dosimetric impact of 4-dimensional computed tomography (4D-CT)-derived, ventilation-guided functional avoidance for stereotactic body radiation therapy (SBRT) with 3-dimensional conformal radiation therapy.
  
  
  METHODS
  Eleven lung cancer patients with peripheral tumors no greater than 5 cm in size were studied (average planning target volume, 42.4 ± 32.5 cm(3)). Four-dimensional-CT ventilation imaging was performed using deformable image registration for spatial mapping of the peak-exhale 4D-CT image to the peak-inhale 4D-CT image and computation of the Jacobian-based ventilation metric. For each patient, anatomical and functional plans were created using 7 to 9 noncoplanar beams for SBRT (40-56 Gy/4-8 fractions). The anatomical plan was generated without incorporating ventilation information. In the functional plan, functional dose-volume constraints were applied in planning to spare the high-functional lung that was defined as the 90th percentile functional volume. The beam directions of the 2 plans were automatically determined by beam angle optimization.
  
  
  RESULTS
  The percentage of volume receiving a dose of ≥5 Gy (V5), V10, V20, and mean dose to the high-functional lung were 20.5%, 15.6%, 7.8%, and 4.6 Gy, respectively, for the anatomical plan, whereas they were 12.3%, 8.2%, 4.6%, and 3.2 Gy, respectively, for the functional plan. No significant differences in minimum dose, maximum dose, and conformity index of the planning target volume and in all dosimetric parameters for normal tissues between the anatomical and functional plans were seen.
  
  
  CONCLUSIONS
  We compared anatomical and functional plans for SBRT with 3-dimensional conformal radiation therapy for the first time. Our results demonstrated that a functional plan for SBRT reduced the dose in the high-functional regions without a significant change in the total lung or planning target volume even if the radiation technique cannot modulate beam intensity. Thus, this technique can be safely used in functional planning for SBRT.
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan. Electronic address: kadoya.n@rad.med.tohoku.ac.jp.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kadoya
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Sang Yong
authors.initials: SY
authors.lastname: Cho
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kanai
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Onozato
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Ito
authors.affiliation: Department of Radiological Technology, School of Health Sciences, Faculty of Medicine, Tohoku University, Sendai, Japan.
authors.forename: Suguru
authors.initials: S
authors.lastname: Dobashi
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Takaya
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Rei
authors.initials: R
authors.lastname: Umezawa
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Haruo
authors.initials: H
authors.lastname: Matsushita
authors.affiliation: Department of Radiological Technology, School of Health Sciences, Faculty of Medicine, Tohoku University, Sendai, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Takeda
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Jingu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*