title: Dosimetric Advantages of Midventilation Compared With Internal Target Volume for Radiation Therapy of Pancreatic Cancer.
abstract: OBJECTIVE
  The midventilation (midV) approach can be used to take respiratory-induced pancreatic tumor motion into account during radiation therapy. In this study, the dosimetric consequences for organs at risk and tumor coverage of using a midV approach compared with using an internal target volume (ITV) were investigated.
  
  
  METHODS
  For each of the 18 patients, 2 treatment plans (25 × 2.0 Gy) were created, 1 using an ITV and 1 using a midV approach. The midV dose distribution was blurred using the respiratory-induced motion from 4-dimensional computed tomography. The resulting planning target volume (PTV) coverage for this blurred dose distribution was analyzed; PTV coverage was required to be at least V95% >98%. In addition, the change in PTV size and the changes in V10Gy, V20Gy, V30Gy, V40Gy, Dmean and D2cc for the stomach and for the duodenum were analyzed; differences were tested for significance using the Wilcoxon signed-rank test.
  
  
  RESULTS
  Using a midV approach resulted in sufficient target coverage. A highly significant PTV size reduction of 13.9% (P<.001) was observed. Also, all dose parameters for the stomach and duodenum, except the D2cc of the duodenum, improved significantly (P≤.002).
  
  
  CONCLUSIONS
  By using the midV approach to account for respiratory-induced tumor motion, a significant PTV reduction and significant dose reductions to the stomach and to the duodenum can be achieved when irradiating pancreatic tumors.
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: e.lens@amc.uva.nl.
authors.forename: Eelco
authors.initials: E
authors.lastname: Lens
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Astrid
authors.initials: A
authors.lastname: van der Horst
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Eva
authors.initials: E
authors.lastname: Versteijne
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Geertjan
authors.initials: G
authors.lastname: van Tienhoven
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Bel
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004386:Duodenum / Q000000981:diagnostic imaging / Q000528:radiation effects; D005260:Female; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D058958:Organs at Risk / Q000000981:diagnostic imaging* / Q000528:radiation effects; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012119:Respiration; D013270:Stomach / Q000000981:diagnostic imaging / Q000528:radiation effects