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Quantifying intra- and inter-fractional motion in breast radiotherapy
Scott Jones1, Rhys Fitzgerald2, Rebecca Owen1
1Division of Cancer Services, Radiation Oncology Mater Centre, Princess Alexandra Hospital Brisbane, Australia.
Journal of Medical Radiation Sciences
|August 1, 2015
Summary
Intra-fractional motion in breast cancer patients receiving tangential megavoltage photon therapy is minimal. Inter-fractional setup variations are larger but generally within tolerance, supporting advanced radiotherapy techniques.
Area of Science:
- Medical Physics
- Radiation Oncology
Background:
- Investigating setup variations in breast cancer patients undergoing tangential megavoltage photon therapy.
- Utilizing an electronic portal imaging device (EPID) to assess intra- and inter-fractional variations.
Purpose of the Study:
- Quantify patient setup variations during tangential megavoltage photon beam therapy for breast cancer.
- Analyze intra-fractional (respiratory) and inter-fractional (daily setup) motion.
Main Methods:
- Captured daily cine-EPID images for 10 breast cancer patients in the supine position.
- Measured central lung distance (CLD), central flash distance (CFD), superior axial measurement (SAM), and inferior axial measurement (IAM).
- Analyzed variations within and between treatment fractions.
Main Results:
- Respiratory motion (intra-fraction) showed <0.1 cm standard deviation (SD) in the anterior-posterior (AP) direction.
- Inter-fraction setup variations averaged 0.28 cm SD in the AP direction.
- Superior-inferior (SI) measurements were unreliable due to ambiguity in image landmarks.
Conclusions:
- Minimal intra-fractional chest wall motion due to respiration was observed.
- Inter-fractional variations were larger but typically within the 0.5 cm departmental tolerance.
- Findings support the feasibility of advanced radiotherapy techniques like IMRT and VMAT for breast cancer treatment.
