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Aperture Area in IMRT Studied Via Accumulated Dose Uncertainty Potential

E Shiba1,2*, A Saito2, M Furumi1, D Kawahara2, K Miki2, Y Murakami2, T Ohguri1, S Ozawa3, M Tsuneda4, K Yahara1, T Nishio4, Y Korogi1, Y Nagata2, (1) University of Occupational and Environmental Health, Fukuoka, JP, (2) Hiroshima University, Hiroshima, JP, (3) Hiroshima High-precision Radiotherapy Cancer Center, Hiroshima, JP, (4) Tokyo Women's Medical University, Tokyo, JP


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: In radiotherapy, it has been reported that the small aperture (AA) area needs careful attention due to the limited accuracy in the dose calculation. In this study, we examined how DUP (dose uncertainty potential), which was developed in our previous study, has a relationship with AA.
Methods: Verification plans on the Delta4 phantom were created for 60 head-and-neck IMRT cases in the XiO treatment planning system. All plans were created using 9 SMLC beams of ONCOR. Segmental MU-weighted mean AA was calculated for each plan. The DUP distribution was generated by our in-house software, and a cumulative histogram was created with a segmental MU-weighting. The DUP values corresponding to 5, 10, 30, 50, 70, and 90% of the calculation voxel (U5%, U10%, U30%, U50%, U70%, and U90%) were extracted from the cumulative DUP histogram. The relationship between these extracted DUP values with the mean AA was analyzed.
Results: It was found that U5% had the strongest correlation with the mean AA. Small U5% values were observed for the cases with a large mean AA. The U5% was widely distributed for the small mean AA cases. This result shows that there is a higher probability of having a large DUP value when the mean AA is small.
Conclusion: We found the correlation between DUP and mean AA. This result is expected to improve the understanding of the plan quality of IMRT.


Penumbra, Quality Assurance, Intensity Modulation


TH- External Beam- Photons: Quality Assurance - IMRT/VMAT

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