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Published on: February 6, 2019
Motion and shape change when using an endorectal balloon during prostate radiation therapy
Laurence E Court1, Anthony V D'Amico, Dnyanesh Kadam
1Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Boston, MA 02115, USA. lcourt@lroc.harvard.edu
Summary
Endorectal balloon (ERB) use in prostate cancer radiotherapy shows significant posterior motion and shape changes. These findings suggest a waiting period after ERB insertion may reduce motion during treatment.
Area of Science:
- Radiation Oncology
- Medical Physics
- Prostate Cancer Treatment
Background:
- Endorectal balloons (ERBs) are used to improve positioning accuracy in prostate cancer radiotherapy.
- Understanding ERB motion and shape changes is crucial for precise radiation delivery.
Purpose of the Study:
- To quantify motion and shape alterations of an endorectal balloon (ERB) during prostate cancer radiotherapy.
- To assess inter-imaging and inter-fraction changes in ERB position and form.
Main Methods:
- Nine prostate cancer patients treated with an ERB were analyzed.
- The ERB's anterior wall was contoured on lateral images taken before and after irradiation.
- Inter-imaging motion, inter-fraction shape change, and inter-imaging shape change were calculated.
Main Results:
- 86% of inter-imaging shifts were posterior (mean 1.8 mm).
- Inter-fraction shape change averaged 2.5-5.7 degrees (range 8-20 degrees).
- Inter-imaging shape changes were comparable in magnitude to inter-fraction changes.
Conclusions:
- Patient relaxation post-ERB insertion likely causes motion and shape changes.
- A waiting period after ERB insertion may minimize these variations.
- Image-guided strategies must account for intra- and inter-fraction motion and shape changes.
