title: Daily computed tomography measurement of needle applicator displacement during high-dose-rate interstitial brachytherapy for previously untreated uterine cervical cancer.
abstract: OBJECTIVE
  We investigated daily needle applicator displacement during high-dose-rate interstitial brachytherapy.
  
  
  METHODS
  Ten patients with previously untreated uterine cervical cancer received 30Gy in five fractions during 3 days of high-dose-rate interstitial brachytherapy combined with external beam radiotherapy using our unique ambulatory technique. To analyze displacement, we obtained daily computed tomography (CT) images for 147 flexible needle applicators at 21 and 45h after implantation. The distance was defined as the length between the center of gravity of titanium markers and the needle applicator tips along the daily CT axis. We adapted dwell positions of the treatment source to cover clinical target volume with a 15-mm cranial margin.
  
  
  RESULTS
  The median displacement was 1mm (range, -6 to 12mm) at 21h and 2mm (range, -9 to 14mm) at 45h, respectively. Statistically significant caudal displacement was observed only between the displacement at 0 and 21h (p<0.0001), and not between the displacement at 21 and 45h (p=0.1). In cases with displacement of 3mm or more, we changed dwell positions to correct the treatment plan. We corrected 45 applicators (31%) at 21h and 67 (46%) at 45h.
  
  
  CONCLUSIONS
  We investigated needle applicator displacement in our ambulatory technique using daily CT examination and considered that a 15-mm cranial margin was sufficient to cover clinical target volume.
authors.affiliation: Department of Radiology, National Hospital Organization Osaka National Hospital, Osaka, Japan. mikamim@onh.go.jp
authors.forename: Mari
authors.initials: M
authors.lastname: Mikami
authors.forename: Ken
authors.initials: K
authors.lastname: Yoshida
authors.forename: Tadashi
authors.initials: T
authors.lastname: Takenaka
authors.forename: Hideya
authors.initials: H
authors.lastname: Yamazaki
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Kotsuma
authors.forename: Mineo
authors.initials: M
authors.lastname: Yoshida
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Aramoto
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Yamada
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ban
authors.forename: Eiichi
authors.initials: E
authors.lastname: Tanaka
authors.forename: Kazuya
authors.initials: K
authors.lastname: Honda
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000295:instrumentation*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009339:Needles; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*