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Prostate positioning errors associated with two automatic registration based image guidance strategies
D Ryan, C Rivest1,2, Terence A Riauka3,2
1Department of Physics, University of Alberta, Edmonton, Alberta, Canada.
Journal of Applied Clinical Medical Physics
|November 18, 2009
Summary
Bone matching (BM) is more accurate than image matching (IM) for daily prostate positioning in helical tomotherapy. This study quantifies prostate misplacement, recommending BM for improved treatment accuracy and reduced toxicity.
Area of Science:
- Medical Physics
- Radiation Oncology
- Image Guidance
Background:
- Accurate daily prostate positioning is crucial for helical tomotherapy efficacy and toxicity reduction.
- Manual registration without fiducials can lead to inaccurate prostate localization.
- Automatic registration methods require quantitative evaluation for clinical implementation.
Purpose of the Study:
- To quantify prostate misplacement using automatic bone matching (BM) and image matching (IM) registration algorithms.
- To compare the accuracy of BM and IM for daily image guidance in prostate tomotherapy.
- To determine the optimal registration strategy for helical tomotherapy prostate patients.
Main Methods:
- Retrospective analysis of 204 megavoltage CT (MVCT) images from 8 prostate cancer patients undergoing helical tomotherapy.
- Independent registration of MVCT images to planning CT using BM and IM algorithms based on mutual information.
- Automatic prostate localization using a correlation coefficient algorithm with planning CT contour information.
- Calculation of daily 3D prostate positioning errors for both BM and IM algorithms.
Main Results:
- Mean 3D prostate positioning errors were 3.7 +/- 2.1 mm for BM and 4.6 +/- 2.3 mm for IM.
- Maximum 3D positioning errors were 11.8 mm for BM and 11.5 mm for IM.
- Image matching (IM) resulted in positioning errors >= 3 mm in 62% of fractions, compared to 51% for bone matching (BM). Positioning errors >= 5 mm occurred in 29% of fractions for IM versus 17% for BM.
Conclusions:
- Bone matching (BM) demonstrates superior accuracy and reliability compared to image matching (IM) for daily prostate image guidance in helical tomotherapy.
- Automatic daily image guidance for prostate tomotherapy should prioritize bone matching over image matching to minimize positioning errors.
- Implementing bone matching can enhance treatment efficacy and reduce potential toxicity in prostate cancer radiotherapy.
