title: Comparison of 1D, 2D, and 3D nodule sizing methods by radiologists for spherical and complex nodules on thoracic CT phantom images.
abstract: OBJECTIVE
  To estimate and statistically compare the bias and variance of radiologists measuring the size of spherical and complex synthetic nodules.
  
  
  METHODS
  This study did not require the institutional review board approval. Six radiologists estimated the size of 10 synthetic nodules embedded within an anthropomorphic thorax phantom from computed tomography scans at 0.8- and 5-mm slice thicknesses. The readers measured the nodule size using unidimensional (1D) longest in-slice dimension, bidimensional (2D) area from longest in-slice and longest perpendicular dimension, and three-dimensional (3D) semiautomated volume. Intercomparisons of bias (difference between average and true size) and variance among methods were performed after converting the 2D and 3D estimates to a compatible 1D scale.
  
  
  RESULTS
  The relative biases of radiologists with the 3D tool were -1.8%, -0.4%, -0.7%, -0.4%, and -1.6% for 10-mm spherical, 20-mm spherical, 20-mm elliptical, 10-mm lobulated, and 10-mm spiculated nodules compared to 1.4%, -0.1%, -26.5%, -7.8%, and -39.8% for 1D. The three-dimensional measurements were significantly less biased than 1D for elliptical, lobulated, and spiculated nodules. The relative standard deviations for 3D were 7.5%, 3.9%, 3.6%, 9.7%, and 8.3% compared to 5.7%, 2.6%, 20.3%, 5.3%, and 16.4% for 1D. Unidimensional sizing was significantly less variable than 3D for the lobulated nodule and significantly more variable for the ellipsoid and spiculated nodules. Three-dimensional bias and variability were smaller for thin 0.8-mm slice data compared to thick 5.0-mm data.
  
  
  CONCLUSIONS
  The study shows that radiologist-controlled 3D volumetric lesion sizing can not only achieve smaller bias but also achieve similar or smaller variability compared to 1D sizing, especially for complex lesion shapes.
authors: Center for Devices and Radiological Health, U.S. Food and Drug Administration, WO62-4118, 10903 New Hampshire Avenue, Silver Spring, MD 20993-0002. Electronic address: nicholas.petrick@fda.hhs.gov.
authors: Nicholas
authors: N
authors: Petrick
authors: Department of Radiological Sciences, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California; Department of Biostatistics, Fielding School of a Public Health at University of California Los Angeles, Los Angeles, California.
authors: Hyun J Grace
authors: HJ
authors: Kim
authors: CoreLab Partners, Inc., Princeton, NJ.
authors: David
authors: D
authors: Clunie
authors: CoreLab Partners, Inc., Princeton, NJ.
authors: Kristin
authors: K
authors: Borradaile
authors: Clinical Trials Imaging Consulting, LLC., Belle Mead, New Jersey.
authors: Robert
authors: R
authors: Ford
authors: Center for Devices and Radiological Health, U.S. Food and Drug Administration, WO62-4118, 10903 New Hampshire Avenue, Silver Spring, MD 20993-0002.
authors: Rongping
authors: R
authors: Zeng
authors: Center for Devices and Radiological Health, U.S. Food and Drug Administration, WO62-4118, 10903 New Hampshire Avenue, Silver Spring, MD 20993-0002.
authors: Marios A
authors: MA
authors: Gavrielides
authors: Department of Radiological Sciences, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California.
authors: Michael F
authors: MF
authors: McNitt-Gray
authors: National Institute of Standards and Technology, Gaithersburg, MD.
authors: Z Q John
authors: ZQ
authors: Lu
authors: National Institute of Standards and Technology, Gaithersburg, MD.
authors: Charles
authors: C
authors: Fenimore
authors: Department of Radiology, Columbia University Medical Center, New York, New York.
authors: Binsheng
authors: B
authors: Zhao
authors: Elucid Bioimaging Inc., Wenham, MA.
authors: Andrew J
authors: AJ
authors: Buckler
mesh_terms: D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D015588:Observer Variation; D019047:Phantoms, Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
keywords: Computer tomography; lung nodules; phantom study; volumetric tumor measurement