title: Online MRI guidance for healthy tissue sparing in patients with cervical cancer: an IMRT planning study.
abstract: OBJECTIVE
  During cervical cancer treatment, target volumes change position and shape due to organ motion and tumour regression. An MRI-accelerator will provide information on these changes by online magnetic resonance imaging (MRI) guidance throughout each treatment fraction. The purpose of this intensity-modulated radiation therapy (IMRT) planning study is to assess the benefit of online MRI guidance in healthy tissue sparing.
  
  
  METHODS
  Weekly MRI scans of 11 cervical cancer patients were used. We created four IMRT plans per patient, based on these weekly MRI scans, to simulate an online-IMRT approach. We applied a primary and nodal planning target volume (PTV) margin of 4 mm. As reference, we created an IMRT plan based on the pre-treatment MRI scan (pre-IMRT) using a primary and nodal PTV margin of 15 and 10 mm. The weekly defined bladder, rectum, bowel, and sigmoid contours were evaluated on the online-IMRT and pre-IMRT dose distributions at six dose levels (V10(Gy), V20(Gy), V30(Gy), V40(Gy), V42.8(Gy), and V45(Gy)).
  
  
  RESULTS
  Online-IMRT compared to pre-IMRT significantly reduced the volume of healthy tissue irradiated to all dose levels, except V10(Gy).
  
  
  CONCLUSIONS
  Online MRI guidance reduces healthy tissue involvement in patients with cervical cancer.
authors.affiliation: Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands. E.Kerkhof@umcutrecht.nl
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Kerkhof
authors.forename: Bas W
authors.initials: BW
authors.lastname: Raaymakers
authors.forename: Uulke A
authors.initials: UA
authors.lastname: van der Heide
authors.forename: Linda
authors.initials: L
authors.lastname: van de Bunt
authors.forename: Ina M
authors.initials: IM
authors.lastname: Jürgenliemk-Schulz
authors.forename: Jan J W
authors.initials: JJ
authors.lastname: Lagendijk
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007422:Intestines / Q000528:radiation effects; D008279:Magnetic Resonance Imaging; D009038:Motion; D009367:Neoplasm Staging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*