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Dosimetric Evaluation of Forwarding-Optimizing-Fluence-Script and Hybrid IMRT Planning Techniques for Whole Left Breast Treatment

D Wang1*, M Weiss1, H Perlingiero1, M Kalman1, Y Hu1,2, A Denittis1,3, (1) Lankenau Hospital, Wynnewood, PA, (2) Bryn Mawr Health Center, Wynnewood, PA, (3) Lankenau Institute For Medical Research

Presentations

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

Room: AAPM ePoster Library

Purpose: IMRT (H-IMRT) is one of the commonly used IMRT techniques for whole left breast treatment. The Forwarding-Optimizing-Fluence-Script (FOFS) is a forward-planning script for a treatment planning system and is deployed to generate optimal fluence for tangential breast plans. It is known that creating a plan with the FOFS is more efficient than with the H-IMRT technique. However, no publication on dosimetric evaluation and delivery efficiency of the plans with the two techniques was found.


Methods: retrospective study including 29 whole left breast cases was performed to evaluate the dosimetric quality of the plans with the two techniques. The 29 H-IMRT plans were clinically delivered in 2019 and a new FOFS plan for each case was created with identical geometry and breast coverage. The following indexes were evaluated: HI (homogeneity Index), Dmean (mean dose to PTV), V105 (percentage of PTV with 105% prescription dose(PD) or higher), Dmax(heart) (maximum dose to heart), Dmean(heart) (mean dose to heart), V5(heart) (percentage of heart with 5Gy or higher), V20(lung) (volume in percentage of left lung with 20Gy or higher), Dmean(lung) (mean dose to lung) and delivery efficiency.


Results: average HI was decreased by (2.1±0.6)% with FOFS technique while the V105 and Dmean was decreased by (229±123)% and (0.8±0.3)%, respectively. The Dmax(heart), Dmean(heart) and V5(heart) were reduced by (23.3±11.3)%, (4.6±1.8)% and (37.2±19)%. The V20(lung) and Dmean(lung) were also decreased by (7.6±4.6)% and (4.2±1.8)%. The typical delivery time for FOFS plan was 50% of that for H-IMRT.


Conclusion: in the whole left breast in the FOFS plan was more uniform while dose to heart and lung were significantly reduced compared that in the H-IMRT plan. The faster delivery for FOFS plan greatly facilitated patient comfort of DIBH (deep inspiration breath hold)/gated treatment.

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Keywords

Breast, Intensity Modulation, Heart

Taxonomy

TH- External Beam- Photons: IMRT/VMAT dose optimization algorithms

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