title: Utrecht Interstitial Applicator Shifts and DVH Parameter Changes in 3D CT-based HDR Brachytherapy of Cervical Cancer.
abstract: BACKGROUND
  For brachytherapy of cervical cancer, applicator shifts can not be avoided. The present investigation concerned Utrecht interstitial applicator shifts and their effects on organ movement and DVH parameters during 3D CT-based HDR brachytherapy of cervical cancer.
  
  
  METHODS
  After the applicator being implanted, CT imaging was achieved for oncologist contouring CTVhr, CTVir, and OAR, including bladder, rectum, sigmoid colon and small intestines. After the treatment, CT imaging was repeated to determine applicator shifts and OARs movements. Two CT images were matched by pelvic structures. In both imaging results, we defined the tandem by the tip and the base as the marker point, and evaluated applicator shift, including X, Y and Z. Based on the repeated CT imaging, oncologist contoured the target volume and OARs again. We combined the treatment plan with the repeated CT imaging and evaluated the change range for the doses of CTVhr D90, D2cc of OARs.
  
  
  RESULTS
  The average applicator shift was -0.16 mm to 0.10 mm for X, 1.49 mm to 2.14 mm for Y, and 1.9 mm to 2.3 mm for Z. The change of average physical doses and EQD2 values in Gyα/β range for CTVhr D90 decreased by 2.55 % and 3.5 %, bladder D2cc decreased by 5.94 % and 8.77 %, rectum D2cc decreased by 2.94 % and 4 %, sigmoid colon D2cc decreased by 3.38 % and 3.72 %, and small intestines D2cc increased by 3.72 % and 10.94 %.
  
  
  CONCLUSIONS
  Applicator shifts and DVH parameter changes induced the total dose inaccurately and could not be ignored. The doses of target volume and OARs varied inevitably.
authors.affiliation: Department of Radiation Oncology, China-Japan Union Hospital of Jilin University, Changchun, China E-mail : chengguanghuifl@163.com.
authors.forename: Dan
authors.initials: D
authors.lastname: Shi
authors.forename: Ming-Yuan
authors.initials: MY
authors.lastname: He
authors.forename: Zhi-Peng
authors.initials: ZP
authors.lastname: Zhao
authors.forename: Ning
authors.initials: N
authors.lastname: Wu
authors.forename: Hong-Fu
authors.initials: HF
authors.lastname: Zhao
authors.forename: Zhi-Jian
authors.initials: ZJ
authors.lastname: Xu
authors.forename: Guang-Hui
authors.initials: GH
authors.lastname: Cheng
mesh_terms: D000328:Adult; D000368:Aged; D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy*; D012809:Colon, Sigmoid / Q000528:radiation effects; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008875:Middle Aged; D058958:Organs at Risk; D011379:Prognosis; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided; D014057:Tomography, X-Ray Computed / Q000379:methods*; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*