title: Volumetric measurement pulmonary ground-glass opacity nodules with multi-detector CT: effect of various tube current on measurement accuracy--a chest CT phantom study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of various tube currents on the accuracy of volumetric measurements of ground-glass opacity (GGO) nodules using a chest phantom.
  
  
  METHODS
  A chest phantom containing 13 artificial GGO nodules with known volumes was scanned using a 64-slice computed tomographic scanner at different tube currents (30, 60, 90, 120, 150, 180, and 210 mA). Volumetric measurements were performed using software. The relative percentage error and the absolute percentage error between the volume measures on computed tomography and the reference-standard volumes were calculated. Correlations between the mean absolute percentage error and the mean attenuation of nodules and between the ratio of solid component and the mean attenuation of nodules were analyzed.
  
  
  RESULTS
  The relative percentage errors showed that there was substantial underestimation of nodule volumes at 30, 60, and 90 mA and substantial overestimation of volumes at 120, 150, 180, and 210 mA, but there was no statistically significant difference in absolute percentage errors (P = .876). Pearson's correlation coefficient of the mean absolute percentage errors of nodules on volumetric measurement versus the mean attenuation value of nodules showed a negative correlation, and the ratio of solid component to whole nodule versus the mean attenuation of nodules showed a positive correlation.
  
  
  CONCLUSIONS
  Volume measurement is a promising method for the quantification of GGO nodule volume. It is important to know that different tube currents can affect the accuracy of volumetric measurements.
authors.affiliation: Department of Radiology, Beijing Friendship Hospital-Affiliated Capital Medical University, 95 YongAn Road, XuanWu District, Beijing, China.
authors.forename: E
authors.initials: E
authors.lastname: Linning
authors.forename: Ma
authors.initials: M
authors.lastname: Daqing
mesh_terms: D000328:Adult; D000465:Algorithms; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D007221:Industry / Q000295:instrumentation; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*