title: Evaluation of internal target volume in patients undergoing image-guided intensity modulated adjuvant radiation for gastric cancers.
abstract: OBJECTIVE
  To evaluate three-dimensional (3D) displacements of gastric remnant during adjuvant radiation.
  
  
  METHODS
  From January 2011 to September 2012, patients undergoing adjuvant image-guided intensity-modulated radiation on tomotherapy were included. Megavoltage CT (MVCT) data sets from daily treatment were coregistered with Day 1 MVCT. Residual stomach remnant was delineated on the data set, while the remaining were blinded to previous day contours. Gastric volume and centre of mass (COM) were determined for all data sets. The 3D deviation of COM was calculated for each fraction. Mean 3D and standard deviation (SD) were calculated for each patient and study population, and a 95% confidence interval (CI) was determined. Also, systematic and random errors for patient population and internal target volume (ITV) margin were calculated using the van Herk formula.
  
  
  RESULTS
  There were 119 images available for 15 patients. Mean volume of remnant was 319 cm(3) (146-454 cm(3)). Gastric remnant expanded in different directions with no specific directional expansion. Average deviations in mediolateral, superoinferior and anteroposterior directions were 9 mm (3-25 mm; SD, 5 mm), 6 mm (3-16 mm; SD, 4 mm) and 5 mm (1-10 mm; SD, 3 mm), respectively, with 95% CI of 18, 15 and 11 mm, and ITV margins of 19.2, 13.5 and 7.8 mm, respectively.
  
  
  CONCLUSIONS
  There is large variation in gastric remnant volume during the course of radiation. Large displacements observed in the present study necessitate the need to investigate adaptive techniques for optimizing intensity-modulated radiotherapy (IMRT) delivery.
  
  
  CONCLUSIONS
  An adaptive strategy needs to be developed to optimize IMRT delivery for adjuvant gastric irradiation.
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital, Tata Memorial Centre, Mumbai, India.
authors.forename: A
authors.initials: A
authors.lastname: Aggarwal
authors.forename: S
authors.initials: S
authors.lastname: Chopra
authors.forename: S N
authors.initials: SN
authors.lastname: Paul
authors.forename: R
authors.initials: R
authors.lastname: Engineer
authors.forename: S K
authors.initials: SK
authors.lastname: Srivastava
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000532:radiotherapy; D018279:Carcinoma, Signet Ring Cell / Q000473:pathology / Q000532:radiotherapy; D005260:Female; D018530:Gastric Stump / Q000473:pathology*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D009367:Neoplasm Staging; D018318:Neurofibroma, Plexiform; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D018714:Radiotherapy, Adjuvant / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013274:Stomach Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D047368:Tumor Burden / Q000528:radiation effects*