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Inter-fraction prostate motion during intensity-modulated radiotherapy for prostate cancer
1Department of Radiation Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610. siow.tian.rui@singhealth.com.sg
Singapore Medical Journal
|July 7, 2011
Summary
Inter-fraction prostate motion and setup errors during intensity-modulated radiotherapy were analyzed using gold seeds. Results show small errors, validating gold seed implantation for prostate position verification.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Intensity-modulated radiotherapy (IMRT) is a common treatment for prostate cancer.
- Accurate patient setup and minimizing inter-fraction motion are crucial for effective IMRT delivery.
- Fiducial markers can aid in verifying prostate position during treatment.
Purpose of the Study:
- To analyze inter-fraction prostate motion and setup errors in IMRT for prostate cancer.
- To evaluate the feasibility and efficacy of gold seed implantation for prostate position verification.
Main Methods:
- Gold seeds were implanted as fiducial markers in patients undergoing IMRT for prostate cancer.
- Daily portal films were acquired to record gold seed displacements from the isocenter.
- Random and systematic errors were calculated to derive margin recipes using the van Herk formula.
Main Results:
- Analysis of 1,077 fractions from 36 patients revealed small setup errors.
- 83.6% to 89.8% of setup errors were within +/- 2 mm across the right-left, superior-inferior, and anterior-posterior axes.
- Derived van Herk margin recipes ranged from 2.69 mm to 3.37 mm for the respective axes.
Conclusions:
- Inter-fraction prostate movements and setup errors during IMRT are minimal.
- Gold seed implantation is a practical and straightforward method for verifying prostate position in radiotherapy.
