title: Background-based Delineation of Internal Tumor Volume in Static Positron Emission Tomography in a Phantom Study.
abstract: OBJECTIVE
  Considering the fact that the standardized uptake value (SUV) of a normal lung tissue is expressed asx±SD,x+3×SDcould be considered as the threshold value to outline the internal tumor volume (ITV) of a lung neoplasm.
  
  
  METHODS
  Three hollow models were filled with 55.0 kBq/mL fluorine-18 fluorodeoxyglucose (18F-FDG) to represent tumors. The models were fixed to a barrel filled with 5.9 kBq/mL18F-FDG to characterize normal lung tissues as a phantom. The PET/CT images of the phantom were acquired at rest. Then, the barrel was moved periodically to simulate breathing while acquiring PET/CT data. Volume recovery coefficient (VRC) was applied to evaluate the accuracy of ITVs. For statistical analysis, paired t-test and analysis of variance were applied.
  
  
  RESULTS
  The VRCs ranged from 0.74 to 0.98 and significantly varied among gross tumor volumes for delineating ITV (P<0.01). In two-dimensional PET scans, the motion distance did not affect VRC (P>0.05), whereas VRC decreased with increasing distance in three-dimensional PET scans (P<0.05).
  
  
  CONCLUSIONS
  The threshold value (x+3×SD) had the potential to delineate the ITV of cancerous tissues, surrounded by lung tissues, particularly in two-dimensional PET images.
authors.affiliation: Department of Nuclear Medicine, Quanzhou First Hospital, Fujian Medical University, Quanzhou, China; The PET-CT Center, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
authors.forename: Yangchun
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Radiology, Quanzhou First Hospital, Fujian Medical University, Quanzhou, China.
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Chen
authors.affiliation: Guangdong Provincial Key Laboratory of Micro-nano Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou, China.
authors.forename: Ji-An
authors.initials: JA
authors.lastname: Liu
authors.affiliation: The PET-CT Center, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
authors.forename: Fanyong
authors.initials: F
authors.lastname: Li
keywords: Gross Tumor Volume; Internal Tumor Volume; Positron Emission Tomography; Standardized Uptake Value