title: 4D-Listmode-PET-CT and 4D-CT for optimizing PTV margins in gastric lymphoma : Determination of intra- and interfractional gastric motion.
abstract: OBJECTIVE
  New imaging protocols for radiotherapy in localized gastric lymphoma were evaluated to optimize planning target volume (PTV) margin and determine intra-/interfractional variation of the stomach.
  
  
  METHODS
  Imaging of 6 patients was explored prospectively. Intensity-modulated radiotherapy (IMRT) planning was based on 4D/3D imaging of computed tomography (CT) and positron-emission tomography (PET)-CT. Static and motion gross tumor volume (sGTV and mGTV, respectively) were distinguished by defining GTV (empty stomach), clinical target volume (CTV = GTV + 5 mm margin), PTV (GTV + 10/15/20/25 mm margins)  plus paraaortic lymph nodes and proximal duodenum. Overlap of 4D-Listmode-PET-based mCTV with 3D-CT-based PTV (increasing margins) and V95/D95 of mCTV were evaluated. Gastric shifts were determined using online cone-beam CT. Dose contribution to organs at risk was assessed.
  
  
  RESULTS
  The 4D data demonstrate considerable intra-/interfractional variation of the stomach, especially along the vertical axis. Conventional 3D-CT planning utilizing advancing PTV margins of 10/15/20/25 mm resulted in rising dose coverage of mCTV (4D-Listmode-PET-Summation-CT) and rising D95 and V95 of mCTV. A PTV margin of 15 mm was adequate in 3 of 6 patients, a PTV margin of 20 mm was adequate in 4 of 6 patients, and a PTV margin of 25 mm was adequate in 5 of 6 patients.
  
  
  CONCLUSIONS
  IMRT planning based on 4D-PET-CT/4D-CT together with online cone-beam CT is advisable to individualize the PTV margin and optimize target coverage in gastric lymphoma.
authors.affiliation: Department of Radiation Oncology, University Hospital Muenster, Albert-Schweitzer Campus 1, Gebäude 1A, 48419, Muenster, Germany. gabriele.reinartz@ukmuenster.de.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Reinartz
authors.affiliation: Department of Radiation Oncology, University Hospital Muenster, Albert-Schweitzer Campus 1, Gebäude 1A, 48419, Muenster, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Haverkamp
authors.affiliation: Department of Radiation Oncology, University Hospital Muenster, Albert-Schweitzer Campus 1, Gebäude 1A, 48419, Muenster, Germany.
authors.forename: Ramona
authors.initials: R
authors.lastname: Wullenkord
authors.affiliation: Department of Radiation Oncology, University Hospital Muenster, Albert-Schweitzer Campus 1, Gebäude 1A, 48419, Muenster, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Lehrich
authors.affiliation: Department of Radiation Oncology, University Hospital Muenster, Albert-Schweitzer Campus 1, Gebäude 1A, 48419, Muenster, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Kriz
authors.affiliation: European Institute for Molecular Imaging (EIMI), University of Muenster, Muenster, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Büther
authors.affiliation: European Institute for Molecular Imaging (EIMI), University of Muenster, Muenster, Germany.|DFG EXC 1003, Cluster of Excellence 'Cells in Motion', Muenster, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Schäfers
authors.affiliation: European Institute for Molecular Imaging (EIMI), University of Muenster, Muenster, Germany.|Department of Nuclear Medicine, University Hospital Muenster, Muenster, Germany.|DFG EXC 1003, Cluster of Excellence 'Cells in Motion', Muenster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schäfers
authors.affiliation: Department of Radiation Oncology, University Hospital Muenster, Albert-Schweitzer Campus 1, Gebäude 1A, 48419, Muenster, Germany.
authors.forename: Hans Theodor
authors.initials: HT
authors.lastname: Eich
mesh_terms: D000328:Adult; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008228:Lymphoma, Non-Hodgkin / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D000072662:Margins of Excision; D008875:Middle Aged; D009038:Motion; D058958:Organs at Risk / Q000528:radiation effects*; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D013382:Subtraction Technique; D016896:Treatment Outcome
keywords: 4D computed tomography; Cone-beam computed tomography; Gastric lymphoma; Intensity-modulated radiotherapy; Planning target volume margin; Positron-emission tomography