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Dosimetric Comparison of Single and Dual Isocenters VMAT Planning for Synchronous Bilateral Breast Cancer

T Sun1*, X Lin2 , Y Yin3 , (1) Shandong cancer hospital, Jinan, shandong, (2) Shandong Cancer Hospital, Affiliated to Shandong University, Jinan, 37, (3) Shandong Cancer Hospital Affiliated to Shandong University, Jinan, Shandong


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: To compare the dosimetric differences of single and dual isocenters for VMAT planning in patients with lymph node positive synchronous bilateral breast cancer(SBBC) .

Methods: The research was conducted with 8 SBBC patients.Treatment plans were retrospectively analyzed using two different VMAT planning techniques: dual-isocenter VMAT plans (Iso2) and monoisocenter VMAT plans (Iso1). Plans were designed to achieve 90% coverage of target to a dose of 50 Gy while maximally sparing organs-at-risk.The plans were evaluated based on a dose-volume histogram analysis.

Results: For both techniques the planning aims for PTV coverage and OARs were met.The target coverage between the Iso1 and Iso2 plans was found comparable. No statistical differences were observed on target homogeneity index. Iso2 plans showed better conformity.The mean doses for the total lungs and heart were significantly reduced in Iso2 plans when compared to Iso1 plans. Iso2 plans showed lower values on V5 of total lung and heart. Iso2 plans significantly reduced V20 of total lung. No statistical differences were observed in V30 and V40 of heart. Iso2 plans showed more MUs.

Conclusion: VMAT plans with dual isocenter improved conformity to the target and reduced doses to the lungs and heart.


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