title: Pulmonary ventilation imaging based on 4-dimensional computed tomography: comparison with pulmonary function tests and SPECT ventilation images.
abstract: OBJECTIVE
  4-dimensional computed tomography (4D-CT)-based pulmonary ventilation imaging is an emerging functional imaging modality. The purpose of this study was to investigate the physiological significance of 4D-CT ventilation imaging by comparison with pulmonary function test (PFT) measurements and single-photon emission CT (SPECT) ventilation images, which are the clinical references for global and regional lung function, respectively.
  
  
  METHODS
  In an institutional review board-approved prospective clinical trial, 4D-CT imaging and PFT and/or SPECT ventilation imaging were performed in thoracic cancer patients. Regional ventilation (V4DCT) was calculated by deformable image registration of 4D-CT images and quantitative analysis for regional volume change. V4DCT defect parameters were compared with the PFT measurements (forced expiratory volume in 1 second (FEV1; % predicted) and FEV1/forced vital capacity (FVC; %). V4DCT was also compared with SPECT ventilation (VSPECT) to (1) test whether V4DCT in VSPECT defect regions is significantly lower than in nondefect regions by using the 2-tailed t test; (2) to quantify the spatial overlap between V4DCT and VSPECT defect regions with Dice similarity coefficient (DSC); and (3) to test ventral-to-dorsal gradients by using the 2-tailed t test.
  
  
  RESULTS
  Of 21 patients enrolled in the study, 18 patients for whom 4D-CT and either PFT or SPECT were acquired were included in the analysis. V4DCT defect parameters were found to have significant, moderate correlations with PFT measurements. For example, V4DCT(HU) defect volume increased significantly with decreasing FEV1/FVC (R=-0.65, P<.01). V4DCT in VSPECT defect regions was significantly lower than in nondefect regions (mean V4DCT(HU) 0.049 vs 0.076, P<.01). The average DSCs for the spatial overlap with SPECT ventilation defect regions were only moderate (V4DCT(HU)0.39 ± 0.11). Furthermore, ventral-to-dorsal gradients of V4DCT were strong (V4DCT(HU) R(2) = 0.69, P=.08), which was similar to VSPECT (R(2) = 0.96, P<.01).
  
  
  CONCLUSIONS
  An 18-patient study demonstrated significant correlations between 4D-CT ventilation and PFT measurements as well as SPECT ventilation, providing evidence toward the validation of 4D-CT ventilation imaging.
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California; Department of Radiation Oncology, University of California Davis School of Medicine, Sacramento, California. Electronic address: toyamamoto@ucdavis.edu.
authors.forename: Tokihiro
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Digital Imaging, Philips Research Europe, Hamburg, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Kabus
authors.affiliation: Department of Digital Imaging, Philips Research Europe, Hamburg, Germany.
authors.forename: Cristian
authors.initials: C
authors.lastname: Lorenz
authors.affiliation: Departments of Radiology, Stanford University School of Medicine, Stanford, California.
authors.forename: Erik
authors.initials: E
authors.lastname: Mittra
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Julian C
authors.initials: JC
authors.lastname: Hong
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Melody
authors.initials: M
authors.lastname: Chung
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Neville
authors.initials: N
authors.lastname: Eclov
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: To
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Diehn
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California.
authors.forename: Billy W
authors.initials: BW
authors.lastname: Loo
authors.affiliation: Radiation Physics Laboratory, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Keall
mesh_terms: D000368:Aged; D005260:Female; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008175:Lung Neoplasms / Q000503:physiopathology*; D008297:Male; D011446:Prospective Studies; D012123:Pulmonary Ventilation / Q000502:physiology*; D019275:Radiopharmaceuticals; D012129:Respiratory Function Tests; D016284:Technetium Tc 99m Pentetate; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate
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