title: Measurement Variability of Persistent Pulmonary Subsolid Nodules on Same-Day Repeat CT: What Is the Threshold to Determine True Nodule Growth during Follow-Up?
abstract: OBJECTIVE
  To assess the measurement variability of subsolid nodules (SSNs) in follow-up situations and to compare the degree of variability between measurement metrics.
  
  
  METHODS
  Two same-day repeat-CT scans of 69 patients (24 men and 45 women) with 69 SSNs were randomly assigned as initial or follow-up scans and were read by the same (situation 1) or different readers (situation 2). SSN size and solid portion size were measured in both situations. Measurement variability was calculated and coefficients of variation were used for comparisons.
  
  
  RESULTS
  Measurement variability for the longest and average diameter of SSNs was ±1.3 mm (±13.0%) and ±1.3 mm (±14.4%) in situation 1, and ±2.2 mm (±21.0%) and ±2.1 mm (±21.3%) in situation 2, respectively. For solid portion, measurement variability on lung and mediastinal windows was ±1.2 mm (±27.1%) and ±0.8 mm (±24.0%) in situation 1, and ±3.7 mm (±61.0%) and ±1.5 mm (±47.3%) in situation 2, respectively. There were no significant differences in the degree of variability between the longest and average diameters and between the lung and mediastinal window settings (p>0.05). However, measurement variability significantly increased when the follow-up and initial CT readers were different (p<0.001).
  
  
  CONCLUSIONS
  A cutoff of ±2.2 mm can be reliably used to determine true nodule growth on follow-up CT. Solid portion measurements were not reliable in evaluating SSNs' change when readers of initial and follow-up CT were different.
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.|Aerospace Medical Group, Air Force Education and Training Command, Jinju, Korea.
authors: Hyungjin
authors: H
authors: Kim
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.
authors: Chang Min
authors: CM
authors: Park
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.
authors: Yong Sub
authors: YS
authors: Song
authors: Department of Radiology, SMG-SNU Boramae Medical Center, Seoul, Korea.
authors: Leonard
authors: L
authors: Sunwoo
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.|Department of Radiology, SMG-SNU Boramae Medical Center, Seoul, Korea.
authors: Ye Ra
authors: YR
authors: Choi
authors: Department of Radiology, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors: Jung Im
authors: JI
authors: Kim
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.
authors: Jae Hyun
authors: JH
authors: Kim
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.
authors: Jae Seok
authors: JS
authors: Bae
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.
authors: Jong Hyuk
authors: JH
authors: Lee
authors: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.
authors: Jin Mo
authors: JM
authors: Goo
mesh_terms: D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology; D008175:Lung Neoplasms / Q000145:classification / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D055613:Multiple Pulmonary Nodules / Q000145:classification / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000473:pathology; D015588:Observer Variation; D014057:Tomography, X-Ray Computed / Q000523:psychology