The Impact of Residual Geometric Inaccuracies on Normal Organ Doses in Image Guided-Radiation Therapy of Prostate Cancer Using On-Board Kilovoltage Cone-Beam Computed Tomography

Document Type : Original Paper

Authors

1 Tabriz University of Medical Sciences

2 2. Radiation therapy department, Dokuz Eylul university hospital, Izmir, Turkey

3 3. Medical Physics department, Institute of health sciences, Dokuz Eylul University, Izmir, Turkey

Abstract

Introduction: The aim of this retrospective study was to evaluate the variations in delivered dose to the bladder, rectum, and femoral heads of prostate cancer patients during a course of treatment by image-guided radiation therapy (IGRT).
Materials and Methods: Overall, 15 patients with prostate cancer were selected and. Each week, for each patient five consecutive cone beam computed tomography (CBCT) images were taken after bony anatomy alignment by using two orthogonal radiographic images, as well as CBCT images. Dose distributions and dose volume histograms (DVH) for all the original and CBCT plans were obtained. Maximum, as well as mean doses and volumes of the bladder, rectum, and both femoral heads were recorded for each CBCT plan and compared with the original CT plan. For all the studied body parts, the differences in DVH between CBCT plans and original CT plan were calculated and compared.         
Results: Considering all the 75 CBCT images for the 15 patients, average of changes in mean doses and volumes were 17.8%, 41.8%, 7.1%, and 36.8% for the bladder and rectum, respectively. There was a significant (P<0.05) negative correlation between mean bladder dose and volume, while a weak and positive correlation was found between mean dose and volume of rectum in our patients.
Conclusion: Our results showed that changes in volumes of the bladder and rectum alter their received inter-factional mean doses. Further attention to the volume variations of the bladder and rectum during a radiotherapy course is recommended for more accurate IGRT treatment. 

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Iranian Journal of Medical Physics
Volume 14, Issue 2
May and June 2017
Pages 104-113

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History

  • Receive Date: 05 October 2016
  • Revise Date: 13 March 2017
  • Accept Date: 28 March 2017

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