title: A study to quantify the effectiveness of daily endorectal balloon for prostate intrafraction motion management.
abstract: OBJECTIVE
  To quantify intrafraction prostate motion between patient groups treated with and without daily endorectal balloon (ERB) employed during prostate radiotherapy and establish the effectiveness of the ERB.
  
  
  METHODS
  Real-time intrafraction prostate motion from 29 non-ERB (1,061 sessions) and 30 ERB (1,008 sessions) patients was evaluated based on three-dimensional (3D), left, right, cranial, caudal, anterior, and posterior displacements. The average percentage of time with 3D and unidirectional prostate displacements >2, 3, 4, 5, 6, 7, 8, 9, and 10 mm in 1-min intervals was calculated for up to 6 min of treatment time. The Kolmogorov-Smirnov method was used to evaluate the intrafraction prostate motion pattern between both groups.
  
  
  RESULTS
  Large 3D motion (up to 1 cm or more) was only observed in the non-ERB group. The motion increased as a function of elapsed time for displacements >2-8 mm for the non-ERB group and >2-4 mm for the ERB group (p < 0.05). The percentage time distributions between the two groups were significantly different for motion >5 mm (p < 0.05). The 3D symmetrical internal margin (IM) can be reduced from 5 to 3 mm (40% reduction), whereas the asymmetrical IM can be reduced from 3 to 2 mm (33% reduction) in cranial, caudal, anterior, and posterior for 6 min of treatment, when ERB is used. Beyond 6 min, the symmetrical 3D and asymmetrical cranial, caudal, anterior, and posterior IMs can be reduced from 9, 4, 7, 7, and 8 to 5, 2, 5, 3, and 4 mm, respectively (up to 57% reduction).
  
  
  CONCLUSIONS
  The percentage of time that the prostate was displaced in any direction was less in the ERB group for almost all magnitudes of motion considered. The directional analysis shows that the ERB reduced IMs in almost all directions, especially the anterior-posterior direction.
authors: Department of Radiation Oncology, Hospital of University of Pennsylvania, Philadelphia, PA 19104, USA. wangken@uphs.upenn.edu
authors: Ken Kang-Hsin
authors: KK
authors: Wang
authors: Neha
authors: N
authors: Vapiwala
authors: Curtiland
authors: C
authors: Deville
authors: John P
authors: JP
authors: Plastaras
authors: Ryan
authors: R
authors: Scheuermann
authors: Haibo
authors: H
authors: Lin
authors: Voika
authors: V
authors: Bar Ad
authors: Zelig
authors: Z
authors: Tochner
authors: Stefan
authors: S
authors: Both
mesh_terms: D003199:Computer Systems; D055590:Electromagnetic Phenomena; D057918:Fiducial Markers; D006801:Humans; D007103:Immobilization / Q000295:instrumentation / Q000379:methods*; D007259:Infrared Rays; D008297:Male; D009068:Movement; D011467:Prostate; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D012007:Rectum; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D013997:Time Factors