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Dosimetric Evaluation of the Compass Program for Patient Dose Analysis in IMRT Delivery Quality Assurance

J Song*, Chonnam National University Medical School


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: A practical method was designed to verify the accuracy of dose distributions calculated using Compass, which can reconstruct the dose distribution inside a patient’s body during intensity-modulated radiation therapy (IMRT).

Methods: After acquiring CT images of ArcCHECK for IMRT DQA, twelve virtual IMRT plans were made based on the virtual tumor targets and OARs, which were contoured on the CT images, for typical clinical cases. The dosimetric accuracy of Compass was evaluated by analyzing the degree of similarity between the dose distribution by the actual beam delivery measured at the detector array of ArcCHECK, the recalculated dose distribution in Compass, and the reconstructed dose distribution based on the data measured using MatriXX. The validity of Compass for clinical applications was also confirmed through an additional comparison with the results calculated using 3DVH, another dose reconstruction program.

Results: Based on the results of gamma evaluation for the 12 plans, Compass achieved average pass rates higher than 98%, which confirmed proper dosimetric accuracy in the IMRT quality assurance process. In the tumor target, the average pass rate was 98.9±2.1% in the Compass recalculation, 96.5±3.9% in 3DVH, and 92.3±12.5% in the Compass reconstruction. In the OARs, the average pass rate was 99.9±0.3% in the Compass recalculation, 99.6±0.6% in 3DVH, and 99.2±1.0% in the Compass reconstruction, demonstrating no significant difference for the different calculation methods.

Conclusion: It is necessary to verify the accuracy of the calculated dose in advance before the commercialized dose reconstruction program is applied in clinical practice. The method based on the comparative analysis with the actual measured dose values as devised in this study can be applied effectively to analyze the dosimetric accuracy of the dose reconstruction program.


Not Applicable / None Entered.


Not Applicable / None Entered.

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