title: Gradient-based delineation of the primary GTV on FLT PET in squamous cell cancer of the thoracic esophagus and impact on radiotherapy planning.
abstract: BACKGROUND
  To validate a gradient-based segmentation method for gross tumor volume(GTV) delineation on (8)F-fluorothymidine (FLT)positron emission tomography (PET)/ computer tomography (CT) in esophageal squamous cell cancer through pathologic specimen, in comparison with standardized uptake values (SUV) threshold-based methods and CT. The corresponding impact of this GTV delineation method on treatment planning was evaluated.
  
  
  METHODS
  Ten patients with esophageal squamous cell cancer were enrolled. Before radical surgery, all patients underwent FLT-PET/CT. GTVs were delineated by using four methods. GTVGRAD, GTV1.4 and GTV30%max were segmented on FLT PET using a gradient-based method, a fixed threshold of 1.4 SUV and 30% of SUVmax, respectively. GTVCT was based on CT data alone. The maximum longitudinal tumor length of each segmented GTV was compared with the measured tumor length of the pathologic gross tumor length (LPath). GTVGRAD, GTV1.4 and GTV30%max were compared with GTVCT by overlap index. Two radiotherapy plannings (planGRAD) and (planCT) were designed for each patient based on GTVGRAD and GTVCT. The dose-volume parameters for target volume and normal tissues, CI and HI of planGRAD and planCT were compared.
  
  
  RESULTS
  The mean ± standard deviation of LPath was 6.47 ± 2.70 cm. The mean ± standard deviation of LGRAD,L1.4, L30%max and LCT were 6.22 ± 2.61, 6.23 ± 2.80, 5.95 ± 2.50,7.17 ± 2.28 cm, respectively. The Pearson correlation coefficients between LPath and each segmentation method were 0.989, 0.920, 0.920 and 0.862, respectively. The overlap indices of GTVGRAD, GTV1.4, GTV30%max when compared with GTVCT were 0.75 ± 0.12, 0.71 ± 0.12, 0.57 ± 0.10, respectively. The V5, V10, V20, V30 and mean dose of total-lung,V30 and mean dose of heart of planGRAD were significantly lower than planCT.
  
  
  CONCLUSIONS
  The gradient-based method provided the closest estimation of target length. The radiotherapy plannings based on the gradient-based segmentation method reduced the irradiated volume of lung, heart in comparison to CT.
authors.affiliation: Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jiyan Road 440, Jinan, 250117, Shandong Province, P. R. China. zhangguifang2620@sina.com.
authors.forename: Guifang
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jinan, China. dalihan2008@163.com.
authors.forename: Dali
authors.initials: D
authors.lastname: Han
authors.affiliation: Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jiyan Road 440, Jinan, 250117, Shandong Province, P. R. China. machangsheng_2000@126.com.
authors.forename: Changsheng
authors.initials: C
authors.lastname: Ma
authors.affiliation: Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jiyan Road 440, Jinan, 250117, Shandong Province, P. R. China. 119487955@qq.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jiyan Road 440, Jinan, 250117, Shandong Province, P. R. China. freeww82@163.com.
authors.forename: Tao
authors.initials: T
authors.lastname: Sun
authors.affiliation: Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jiyan Road 440, Jinan, 250117, Shandong Province, P. R. China. lthsdu@163.com.
authors.forename: Tonghai
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jiyan Road 440, Jinan, 250117, Shandong Province, P. R. China. zhujian.cn@163.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Department of Radiology, Shandong Cancer Hospital and Institute, Jinan, 250117, Shandong Province, P. R. China. 490225252@qq.com.
authors.forename: Jingwei
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong's Key Laboratory of Radiation Oncology, Jiyan Road 440, Jinan, 250117, Shandong Province, P. R. China. yongyinsd@126.com.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yin
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D015224:Dideoxynucleosides; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D013899:Thoracic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D014018:Tissue Distribution
chemical_list: D015224:Dideoxynucleosides; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals