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SU-E-J-30: Using Shifting Planned Dose Matrix to Evaluate Daily Dose Changes for IMRT Prostate Treatment
Medical Physics
|May 19, 2017
Summary
Shifting the planned dose matrix effectively estimates daily dose changes for prostate and pelvic lymph node IMRT, offering a common frame for composite dose distributions. This method shows high accuracy within a 5% dose difference.
Area of Science:
- Radiation Oncology
- Medical Physics
- Image-Guided Radiation Therapy
Background:
- Summating daily dose-volume histograms (DVHs) from kV-cone beam CT (KV-CBCT) for composite DVH calculation is complex.
- Directly translating planned dose matrices based on daily prostate displacements offers a potential solution for composite DVH generation.
Purpose of the Study:
- To evaluate the accuracy of the shifting planned dose matrix method for composite DVH calculation.
- To compare the dose recalculation method using daily KV-CBCT with the dose matrix shifting method.
Main Methods:
- Six patients undergoing concurrent IMRT for prostate and pelvic lymph nodes were analyzed, using 124 daily CBCTs.
- Dose recalculations were performed on CBCTs after shifting to corrected isocenters using planning beam configurations.
- An in-house MATLAB program integrated with CERR software facilitated the planned dose matrix translation and DVH generation.
Main Results:
- For prostate displacements <1.5 cm, the dose matrix shifting method achieved 93% and 98% agreement within 5% difference compared to recalculation for prostate and pelvic lymph node D95, respectively.
- Agreement decreased to 58% and 71% when a stricter 2% dose difference criterion was applied.
Conclusions:
- The shifting planned dose matrix method is an effective tool for assessing daily dose variations in concurrent IMRT for prostate and pelvic lymph nodes, within a 5% daily dose difference.
- This method establishes a common coordinate frame, simplifying the creation of composite dose distributions from daily DVHs.
Keywords:
CancerComputer softwareDosimetryIntensity modulated radiation therapyMatrix methodsRadiation therapyTissuesMore Related Videos
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