title: Variability of target and normal structure delineation using multimodality imaging for radiation therapy of pancreatic cancer.
abstract: OBJECTIVE
  To explore the potential of multimodality imaging (dynamic contrast-enhanced magnetic resonance imaging [DCE-MRI], apparent diffusion-coefficient diffusion-weighted imaging [ADC-DWI], fluorodeoxyglucose positron emission tomography [FDG-PET], and computed tomography) to define the gross tumor volume (GTV) and organs at risk in radiation therapy planning for pancreatic cancer. Delineated volumetric changes of DCE-MRI, ADC-DWI, and FDG-PET were assessed in comparison with the finding on 3-dimensional/4-dimensional CT with and without intravenous contrast, and with pathology specimens for resectable and borderline resectable cases of pancreatic cancer.
  
  
  METHODS
  We studied a total of 19 representative patients, whose DCE-MRI, ADC-DWI, and FDG-PET data were reviewed. Gross tumor volume and tumor burden/active region inside pancreatic head/neck or body were delineated on MRI (denoted GTVDCE, and GTVADC), a standardized uptake value (SUV) of 2.5, 40%SUVmax, and 50%SUVmax on FDG-PET (GTV2.5, GTV40%, and GTV50%). Volumes of the pancreas, duodenum, stomach, liver, and kidneys were contoured according to CT (VCT), T1-weighted MRI (VT1), and T2-weighted MRI (VT2) for 7 patients.
  
  
  RESULTS
  Significant statistical differences were found between the GTVs from DCE-MRI, ADC-DW, and FDG-PET, with a mean and range of 4.73 (1.00-9.79), 14.52 (3.21-25.49), 22.04 (1.00-45.69), 19.10 (4.84-45.59), and 9.80 (0.32-35.21) cm(3) for GTVDCE, GTVADC, GTV2.5, GTV40%, and GTV50%, respectively. The mean difference and range in the measurements of maximum dimension of tumor on DCE-MRI, ADC-DW, SUV2.5, 40%SUVmax, and 50%SUVmax compared with pathologic specimens were -0.84 (-2.24 to 0.9), 0.41 (-0.15 to 2.3), 0.58 (-1.41 to 3.69), 0.66 (-0.67 to 1.32), and 0.15 (-1.53 to 2.38) cm, respectively. The T1- and T2-based volumes for pancreas, duodenum, stomach, and liver were generally smaller compared with those from CT, except for the kidneys.
  
  
  CONCLUSIONS
  Differences exists between DCE-, ADC-, and FDG-PET-defined target volumes for RT of pancreatic cancer. Organ at risk volumes based on MRI are generally smaller than those based on CT. Further studies combined with pathologic specimens are required to identify the optimal imaging modality or sequence to define GTV.
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Entesar
authors.initials: E
authors.lastname: Dalah
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Ion
authors.initials: I
authors.lastname: Moraru
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Radiology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Eric
authors.initials: E
authors.lastname: Paulson
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Beth
authors.initials: B
authors.lastname: Erickson
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin. Electronic address: ali@mcw.edu.
authors.forename: X Allen
authors.initials: XA
authors.lastname: Li
mesh_terms: D003287:Contrast Media; D004386:Duodenum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007668:Kidney / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008099:Liver / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging / Q000379:methods*; D064847:Multimodal Imaging / Q000379:methods*; D009929:Organ Size; D058958:Organs at Risk / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D010179:Pancreas / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D010190:Pancreatic Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D013270:Stomach / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18