title: Delineation gross tumor volume based on positron emission tomography images by a numerical approximation method.
abstract: OBJECTIVE
  A scheme, named SUV_Shape, for the gross tumor volume (GTV) delineation on positron emission tomography (PET) images was designed by a numerical approximation method, and evaluated during this study.
  
  
  METHODS
  Twenty-one vacuous plastic balls of different shapes and sizes, their volumes ranged from 0.56 to 179.50 mL and were confirmed by a BL610 balance (Sartorius, Canada), consisted of four group models. Every group model was filled with a specific activity [18F]-FDG solution (55.1, 38.2, 23.7, and 36.3 kBq/mL) represented tumor, and fixed at the bottom of a barrel which was filled with unlike [18F]-FDG solution (5.4, 6.8, 8.1, and 4.0 kBq/mL, correspondingly) represented the background. The PET data of them were acquired by two-dimensional and three-dimensional mode in a PET/CT scanner (Discovery ST8, GE Healthcare, USA). The volume of each ball was measured by SUV_Shape, and the BL610 balance, labeled as GTVs and GTVt, respectively. Five rabbits implanted VX2 squamous carcinomas were acquired by [18F]-FDG PET/CT. These rabbits were mercy killed within 24 h after PET/CT acquisition. VX2 tumors were surgically removed, and their volumes were measured by SUV_Shape, and caliper, labeled as GTVs and GTVt. The Spearman's ρ between GTVs and GTVt were done.
  
  
  RESULTS
  The tumor-background ratios in four groups of phantom models were 10.3, 5.6, 2.9, and 9.0, respectively. The relationship between GTVt and GTVs for phantom models was significant (Spearman's ρ > 0.95, P < 0.01), regardless of the different acquisition modes. Twelve VX2 tumor nodes or masses were measured; their GTVt ranged from 0.11 to 29.26 mL. The relationship between GTVt and GTVs was significant (Spearman's ρ = 0.893, P < 0.01) for animal tumor models.
  
  
  CONCLUSIONS
  The SUV_Shape scheme could delineate tumors based on their radiopharmaceutical-avid PET images.
authors.affiliation: Nuclear Medicine Department, Quanzhou First Hospital of Fujian Medical University, 248 East street, Licheng District, 362000, Quanzhou, China, 1526797743@qq.com.
authors.forename: Yangchun
authors.initials: Y
authors.lastname: Chen
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Chen
authors.forename: Fanyong
authors.initials: F
authors.lastname: Li
authors.forename: Liu
authors.initials: L
authors.lastname: Ji-An
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D021621:Imaging, Three-Dimensional; D008297:Male; D008954:Models, Biological; D064847:Multimodal Imaging / Q000295:instrumentation / Q000379:methods; D009368:Neoplasm Transplantation; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D011817:Rabbits; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18