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Evaluation of the Spatial Distribution of γH2AX following Ionizing Radiation
Published on: August 7, 2010
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Comparison of 2D and 3D gamma analyses.
Kiley B Pulliam1, Jessie Y Huang1, Rebecca M Howell1
1Department of Radiation Physics, The University of Texas MD Anderson Cancer Center and The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030.
Medical Physics
|February 11, 2014
Summary
Three-dimensional (3D) gamma analysis for intensity-modulated radiation therapy (IMRT) quality assurance shows better agreement than 2D analysis. This 3D approach can yield up to 2.9% more passing pixels, improving QA accuracy.
Area of Science:
- Medical Physics
- Radiation Oncology
Background:
- Intensity-modulated radiation therapy (IMRT) quality assurance (QA) is increasingly utilizing 3D metrics.
- 3D gamma analysis offers a different search space compared to 2D, potentially leading to different results.
Purpose of the Study:
- To compare the results of 2D and 3D gamma analysis for clinical IMRT treatment plans.
- To evaluate the impact of different parameters on the agreement between 2D and 3D gamma analyses.
Main Methods:
- Fifty IMRT plans were recalculated using Monte Carlo methods.
- 2D and 3D gamma analyses were performed using various dose-difference and distance-to-agreement criteria, low-dose thresholds, and data grid sizes.
- Key metrics evaluated included average gamma, lower 95th percentile gamma, and percentage of passing pixels.
Main Results:
- 3D gamma analysis consistently demonstrated better agreement across all tested acceptance criteria compared to 2D analysis.
- The difference in passing pixels between 2D and 3D analyses ranged from 0.8% to 2.1%, even with low-dose thresholds.
- No significant differences in gamma results were observed with variations in data grid size.
Conclusions:
- 3D gamma analysis resulted in a higher percentage of passing pixels (up to 2.9% more) than 2D analysis.
- Clinical implementation should consider potential differences in dosimeters used for 2D vs. 3D measurements.
- The added dimension in 3D analysis is a crucial factor, alongside potential dosimeter variations, for accurate QA.
