title: Combined Ventilation and Perfusion Imaging Correlates With the Dosimetric Parameters of Radiation Pneumonitis in Radiation Therapy Planning for Lung Cancer.
abstract: OBJECTIVE
  The purpose of this study was to prospectively investigate clinical correlations between dosimetric parameters associated with radiation pneumonitis (RP) and functional lung imaging.
  
  
  METHODS
  Functional lung imaging was performed using four-dimensional computed tomography (4D-CT) for ventilation imaging, single-photon emission computed tomography (SPECT) for perfusion imaging, or both (V/Q-matched region). Using 4D-CT, ventilation imaging was derived from a low attenuation area according to CT numbers below different thresholds (vent-860 and -910). Perfusion imaging at the 10th, 30th, 50th, and 70th percentile perfusion levels (F10-F70) were defined as the top 10%, 30%, 50%, and 70% hyperperfused normal lung, respectively. All imaging data were incorporated into a 3D planning system to evaluate correlations between RP dosimetric parameters (where fV20 is the percentage of functional lung volume irradiated with >20 Gy, or fMLD, the mean dose administered to functional lung) and the percentage of functional lung volume. Radiation pneumonitis was evaluated using Common Terminology Criteria for Adverse Events version 4.0. Statistical significance was defined as a P value of <.05.
  
  
  RESULTS
  Sixty patients who underwent curative radiation therapy were enrolled (48 patients for non-small cell lung cancer, and 12 patients for small cell lung cancer). Grades 1, 2, and ≥3 RP were observed in 16, 44, and 6 patients, respectively. Significant correlations were observed between the percentage of functional lung volume and fV20 (r=0.4475 in vent-860 and 0.3508 in F30) or fMLD (r=0.4701 in vent-860 and 0.3128 in F30) in patients with grade ≥2 RP. F30∩vent-860 results exhibited stronger correlations with fV20 and fMLD in patients with grade ≥2 (r=0.5509 in fV20 and 0.5320 in fMLD) and grade ≥3 RP (r=0.8770 in fV20 and 0.8518 in fMLD).
  
  
  CONCLUSIONS
  RP dosimetric parameters correlated significantly with functional lung imaging.
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan. Electronic address: tkkimura@hiroshima-u.ac.jp.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Kimura
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Doi
authors.affiliation: Department of Radiation Oncology, Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Nakashima
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Nobuki
authors.initials: N
authors.lastname: Imano
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Kawabata
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Ikuno
authors.initials: I
authors.lastname: Nishibuchi
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Okabe
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kenjo
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ozawa
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Murakami
authors.affiliation: Department of Radiation Oncology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nagata
mesh_terms: D000328:Adult; D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009068:Movement; D011446:Prospective Studies; D011829:Radiation Dosage; D017564:Radiation Pneumonitis / Q000000981:diagnostic imaging / Q000209:etiology*; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided / Q000379:methods; D012119:Respiration; D055752:Small Cell Lung Carcinoma / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*; D014797:Vital Capacity