title: Determination of planning target volume for whole stomach irradiation using daily megavoltage computed tomographic images.
abstract: OBJECTIVE
  Whole stomach radiation therapy is often used in the management of gastric lymphoma. However, very limited data exist with regard to planning target volume requirements for the whole stomach. This study retrospectively analyzed daily megavoltage computed tomographic (CT) scans of gastric lymphoma patients in order to help determine the interfraction variation of the stomach position.
  
  
  METHODS
  Forty-one daily megavoltage CT images from 3 gastric lymphoma patients were used for stomach contouring. Each patient's megavoltage CT images were rigidly registered to their CT simulation data sets, and the margin in each direction that covered at least 95% of the daily stomach volumes was computed using a simple grid search. Patient setup variation was also calculated from the daily patient shifts. The organ motion margin was then added to the setup margin to render the total margin.
  
  
  RESULTS
  A uniform margin of 2.2 cm is required to cover 95% of the stomach over the treatment course. However, direction-specific margins were observed from 1.72, 1.88, 0.92, 2.23, 1.90, and 0.86 cm for the right, left, posterior, anterior, superior, and inferior directions, respectively.
  
  
  CONCLUSIONS
  The results of this study provide helpful 3-dimensional volumetric information to the limited existing data on margin requirements for whole stomach radiation therapy.
authors.affiliation: Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Johnson
authors.affiliation: Department of Radiation Oncology and Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri.
authors.forename: Gisele C
authors.initials: GC
authors.lastname: Pereira
authors.affiliation: Medical Physics Unit, Montreal General Hospital, McGill University, Montreal, QC, Canada.
authors.forename: Issam M
authors.initials: IM
authors.lastname: El Naqa
authors.affiliation: Department of Radiation Oncology and Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri.
authors.forename: S Murty
authors.initials: SM
authors.lastname: Goddu
authors.affiliation: Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Rawan
authors.initials: R
authors.lastname: Al-Lozi
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York.
authors.forename: Aditya
authors.initials: A
authors.lastname: Apte
authors.affiliation: Department of Radiation Oncology and Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri. Electronic address: mansur@radonc.wustl.edu.
authors.forename: David B
authors.initials: DB
authors.lastname: Mansur