title: Evaluation of intrafraction motion of the organs at risk in image-based brachytherapy of cervical cancer.
abstract: OBJECTIVE
  To assess the variation in the doses received by the organs at risk (OARs) that can occur during treatment planning of cervical cancer by image-based brachytherapy.
  
  
  METHODS
  After intracavitary application, two sets of images-CT and MRI-were obtained. The two sets of images were fused together with respect to the applicator. Contouring was done separately on CT and MR images. Dose received by the OARs on CT images with respect to the plans made on the MR images was estimated and compared with those on the MR images.
  
  
  RESULTS
  Although there was always a difference between the dose received by the OARs based on the CT and MRI contours, it was not significant for the bladder and rectum; 2 cc doses differed by 0.49 Gy (±0.44) p = 0.28 for the bladder and 0.30 Gy (±0.29) p = 0.16 for the rectum. The 1 cc and 0.1 cc differences were also not significant. However for the sigmoid colon, there was significant intrafraction variation in the 2 cc doses 0.61 (±0.6) p = 0.001, 1 cc doses 0.73 (±0.67) Gy p = 0.00, and 0.1 cc dose 0.97 (±0.93) Gy p = 0.009.
  
  
  CONCLUSIONS
  The variation in the doses to the OARs must be considered while weighing target coverage against overdose to the OARs. Although not significant for the bladder and rectum, it was significant for the sigmoid colon. Estimated doses to OARs on the planning system may not be the same dose delivered at the time of treatment.
authors.affiliation: Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. Electronic address: vijaiaditya1985@gmail.com.
authors.forename: Vijai
authors.initials: V
authors.lastname: Simha
authors.affiliation: Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India.
authors.forename: Firuza Darius
authors.initials: FD
authors.lastname: Patel
authors.affiliation: Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India.
authors.forename: Suresh Chander
authors.initials: SC
authors.lastname: Sharma
authors.affiliation: Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India.
authors.forename: Bhavana
authors.initials: B
authors.lastname: Rai
authors.affiliation: Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India.
authors.forename: Arun Singh
authors.initials: AS
authors.lastname: Oinam
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: krishnatry
authors.affiliation: Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India.
authors.forename: Bhaswanth
authors.initials: B
authors.lastname: Dhanireddy
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D012809:Colon, Sigmoid / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D058958:Organs at Risk / Q000502:physiology*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012007:Rectum / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
keywords: Image-based brachytherapy; Intrafraction changes; Intrafraction motion; Optimization; Organ motion; Organs at risk