Ken Kang-Hsin Wang1, Neha Vapiwala2, Viet Bui2, Curtiland Deville2, John P Plastaras2, Voichita Bar-Ad3, Zelig Tochner2, Stefan Both2. 1. Department of Radiation Oncology, University of Pennsylvania, Philadelphia; Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore. Electronic address: kwang27@jhmi.edu. 2. Department of Radiation Oncology, University of Pennsylvania, Philadelphia. 3. Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, USA.
Abstract
PURPOSE: The aim of this study was to quantify the impact of rectal stool/gas volumes on intrafraction prostate motion for patients undergoing prostate radiotherapy with daily endorectal balloon (ERB). METHODS: Total and anterior stool/gas rectal volumes were quantified in 30 patients treated with daily ERB. Real-time intrafraction prostate motion from 494 treatment sessions, at most 6 min in length, was evaluated using Calypso(®) tracking system. RESULTS: The deviation of prostate intrafraction motion distribution was a function of stool/gas volume, especially when stool/gas is located in the anterior part of the rectum. Compared to patients with small anterior stool/gas volumes (<10 cm(3)), those with large volume (10-60 cm(3)) had a twofold increase in 3D prostate motion and interquartile data range within the 6th minute of treatment time. The 10% of the overall CBCT session where large anterior rectal volumes were observed demonstrated larger percentage of time at displacement greater than our proposed internal margin 3 mm. CONCLUSION: Volume and location of stool/gas can directly impact the ERB's intrafraction immobilization ability. Although our patient preparation protocol and the 100 cm(3) daily ERB effectively stabilized prostate motion for 90% of the fractions, a larger-sized ERB may improve prostate fixation for patients with greater and/or variable daily rectal volume.
PURPOSE: The aim of this study was to quantify the impact of rectal stool/gas volumes on intrafraction prostate motion for patients undergoing prostate radiotherapy with daily endorectal balloon (ERB). METHODS: Total and anterior stool/gas rectal volumes were quantified in 30 patients treated with daily ERB. Real-time intrafraction prostate motion from 494 treatment sessions, at most 6 min in length, was evaluated using Calypso(®) tracking system. RESULTS: The deviation of prostate intrafraction motion distribution was a function of stool/gas volume, especially when stool/gas is located in the anterior part of the rectum. Compared to patients with small anterior stool/gas volumes (<10 cm(3)), those with large volume (10-60 cm(3)) had a twofold increase in 3D prostate motion and interquartile data range within the 6th minute of treatment time. The 10% of the overall CBCT session where large anterior rectal volumes were observed demonstrated larger percentage of time at displacement greater than our proposed internal margin 3 mm. CONCLUSION: Volume and location of stool/gas can directly impact the ERB's intrafraction immobilization ability. Although our patient preparation protocol and the 100 cm(3) daily ERB effectively stabilized prostate motion for 90% of the fractions, a larger-sized ERB may improve prostate fixation for patients with greater and/or variable daily rectal volume.
Authors: Sebastian Hild; Christian Graeff; Antoni Rucinski; Klemens Zink; Gregor Habl; Marco Durante; Klaus Herfarth; Christoph Bert Journal: Strahlenther Onkol Date: 2015-11-27 Impact factor: 3.621