title: The effect of lung volume on nodule size on CT.
abstract: OBJECTIVE
  We sought to determine how measures of nodule diameter and volume on computed tomography (CT) vary with changes in inspiratory level.
  
  
  METHODS
  CT scans were performed with inspiration suspended at total lung capacity (TLC) and then at residual volume (RV) in 41 subjects, in whom 75 indeterminate lung nodules were detected. A fully automated contouring program was used to segment the lungs; followed by segmentation of all nodules and the corresponding lobe using semiautomated contouring in both TLC and RV scans. The percent changes in lung and lobar volumes between TLC and RV were correlated with percent changes in nodule diameters and volumes.
  
  
  RESULTS
  Both nodule diameter and volume varied nonuniformly from TLC to RV-some nodules decreased in size, while others increased. There was a 16.8% mean change in absolute volume across all nodules. Stratified by size, the mean value of the absolute percent volume changes for nodules > or =5 mm and <5 mm were not significantly different (P = .26). Stratified by maximum attenuation, the mean value of the absolute percent volume changes between the TLC and RV series for noncalcified (17.7%, SD = 13.1) and completely calcified nodules (8.6% SD = 5.7) were significantly different (P < .05).
  
  
  CONCLUSIONS
  Significant differences in nodule size were measured between TLC and RV scans. This has important implications for standardizing acquisition protocols in any setting where size and, more important, size change are being used for purposes of lung cancer staging, nodule characterization, or treatment response assessment.
authors: Thoracic Imaging Research Group, Department of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, 924 Westwood Blvd., Suite 650, Box 957319, Los Angeles, CA 90095-7319, USA. ipetkovska@mednet.ucla.edu
authors: Iva
authors: I
authors: Petkovska
authors: Matthew S
authors: MS
authors: Brown
authors: Jonathan G
authors: JG
authors: Goldin
authors: Hyun J
authors: HJ
authors: Kim
authors: Michael F
authors: MF
authors: McNitt-Gray
authors: Fereidoun G
authors: FG
authors: Abtin
authors: Raffi J
authors: RJ
authors: Ghurabi
authors: Denise R
authors: DR
authors: Aberle
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008176:Lung Volume Measurements; D009367:Neoplasm Staging; D012044:Regression Analysis; D015203:Reproducibility of Results; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods*