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Comparing Dosimetry in Prostate VMAT Plans Optimized by the PO and PRO Algorithm Using the Dose Distribution Index

J Chow1*, R Jiang2 , L Xu2 , (1) Princess Margaret Cancer Centre, Toronto, ON, (2) Grand River Regional Cancer Centre, Kitchener, ON


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: Treatment planning dosimetry of prostate volumetric modulated arc therapy (VMAT), optimized by the newer photon optimization (PO) algorithm, was compared to that optimized by the conventional progressive resolution optimization (PRO) algorithm. Dose distribution index (DDI), which considers the dose coverage at the target while sparing all organs-at-risk (OARs) in one single parameter, was used in this study.

Methods: Prostate VMAT plans of 10 patients were created using the PO and PRO algorithm in the Eclipseᵀᴹ treatment planning system. The 6 MV dual-arc technique with prescription equal to 78 Gy/39 fractions was used in treatment planning. Dose-volume histograms (DVHs) of the planning target volume (PTV), rectum, bladder, left and right femur were determined in each plan. DDIs were calculated for all plans considering DVHs of the PTV and all OARs.

Results: The mean DDI value of prostate VMAT plans optimized by the PO algorithm was equal to 0.788, while plans optimized by the PRO algorithm was equal to 0.807. It is seen that the DDI value of the PO algorithm was very similar (only 2.4% less) to the PRO. The dose coverage of the target and/or the sparing of the OARs in the plan optimized by the PRO algorithm was slightly better than the PO. However, considering the lower monitor unit and less complex beam segment in the plan optimized by the PO algorithm, this newer optimizer can generate a more accurate VMAT plan with simpler beam segmentation than the PRO.

Conclusion: For the very small deviation of DDI values determined by the prostate plans optimized by the PO and PRO algorithm, it is concluded that the PO algorithm is a good successor of the PRO which produced better beam segmentation than the former.


Prostate Therapy, Treatment Planning, Inverse Planning


TH- External beam- photons: VMAT dose optimization algorithms

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