title: Assessing changes to the brachytherapy target for cervical cancer using a single MRI and serial ultrasound.
abstract: OBJECTIVE
  To assess changes to the brachytherapy target over the course of treatment and the impact of these changes on planning and resources.
  
  
  METHODS
  Patients undergoing curative treatment with radiotherapy between January 2007 and March 2012 were included in the study. Intrauterine applicators were positioned in the uterine canal while patients were under anesthesia. Images were obtained by MRI and ultrasound at Fraction 1 and ultrasound alone at Fractions 2, 3, and 4. Cervix and uterine dimensions were measured on MRI and ultrasound and compared using Bland-Altman plots and repeated measures one-way analysis of variance.
  
  
  RESULTS
  Of 192 patients who underwent three fractions of brachytherapy, 141 of them received four fractions. Mean differences and standard error of differences between MRI at Fraction 1 and ultrasound at Fraction 4 for anterior cervix measurements were 2.9 (0.31), 3.5 (0.25), and 4.2 (0.27) mm and for posterior cervix 0.8 (0.3), 0.3 (0.3), and 0.9 (0.3) mm. All differences were within clinically acceptable limits. The mean differences in the cervix over the course of brachytherapy were less than 1 mm at all measurement points on the posterior surface. Replanning occurred in 11 of 192 (5.7%) patients, although changes to the cervix dimensions were not outside clinical limits.
  
  
  CONCLUSIONS
  There were small changes to the cervix and uterus over the course of brachytherapy that were not clinically significant. Use of intraoperative ultrasound as a verification aid accurately assesses the target at each insertion, reduces uncertainties in treatment delivery, and improves efficiency of the procedure benefiting both the patient and staff.
authors.affiliation: Radiation Therapy Services, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia. Electronic address: sylvia.vandyk@petermac.org.
authors.forename: Sylvia
authors.initials: S
authors.lastname: van Dyk
authors.affiliation: Rural Clinical School, University of Queensland, Toowoomba, Queensland, Australia.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Kondalsamy-Chennakesavan
authors.affiliation: Department of Medical Imaging and Radiation Science, Monash University, Clayton, Victoria, Australia.
authors.forename: Michal
authors.initials: M
authors.lastname: Schneider
authors.affiliation: Division of Radiation Oncology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Bernshaw
authors.affiliation: Division of Radiation Oncology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia; Department of Obstetrics and Gynaecology, Melbourne University, Melbourne, Victoria, Australia.
authors.forename: Kailash
authors.initials: K
authors.lastname: Narayan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D058958:Organs at Risk / Q000000981:diagnostic imaging*; D016896:Treatment Outcome; D014463:Ultrasonography; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D055815:Young Adult
keywords: Brachytherapy; Cervical cancer; MRI; Ultrasound