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Constant Dose Rate and Constant Angular Spacing Intensity Modulated Arc Therapy (CDRCASIMAT) Using Multi-Criteria Dose Plan Optimization for Cervical Cancer:Feasibility of Selective Sparing of Organs at Risk

R Zhang1,2 , W Bai2 , Q Zhang2*, Y Feng1 , W Jiang1 , B Zhang2 , Z Zhao2 , (1)Department of Biomedical Engineering,Tianjin University, Tianjin,China (2) The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei,China


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: Patients with cervical cancer treated with CDR‑CAS‑IMAT using conventional Linac Varian 23EX can get equivalent or superior dose distribution compared to those treated with IMRT, while which will increased low‑dose irradiated area. The purpose of this study was to investigate the feasibility of using multi-criteria dose plan optimization (MCO) for CDR‑CAS‑IMAT MCO-based plan futher sparing of organs at risk.

Methods: Twenty patients with cervical cancer previously treated with CDR‑CAS‑IMAT were retreated using multi-criteria optimization CDR‑CAS‑IMAT-MCO plan on Monaco (v5.1.0) TPS. Minimum acceptable target coverage with physician-defined organsparing priorities. Maximum bowel sparing without losing target coverage (if needed at the expense of the bladder). Maximum bladder sparing without losing target coverage (if needed at the expense of the bowel).The quality of the CDR‑CAS‑IMAT-MCO plans was compared to the quality of the non-MCO VMAT plans, and the ability of the MCO module to selectively spare OARs (bladder or bowel) with CDR‑CAS‑IMAT-MCO was evaluated.

Results: All plans satisfies constraints for target coverage (CTV: V95%=100% and PTV: V98%≥95%).Non-MCO plans had higher Conformity Index (CI) compared to CDR‑CAS‑IMAT-MCO(0.75 Vs. 0.71). CDR‑CAS‑IMAT-MCO plans had smaller hotspots in elective volumes, but higher dose volumes to bowel. Time spent on optimization was shorter for Non-MCO due to considerable increase in the calculation and conversion time compared to CDR‑CAS‑IMAT-MCO (16.4 ± 3.5 min vs. 18.6 ± 2.2 min).

Conclusion: This study demonstrates that preference-informed dose planning with CDR‑CAS‑IMAT-MCO is indeed feasible, selective sparing of OARs in CDR‑CAS‑IMAT-MCO can significantly reduced options for dose redistribution. Further investigations will be undertaken to review any clinical benefit of this improved planned dosimetry.


Treatment Verification, Rotational Therapy, Optimization


TH- External beam- photons: VMAT dose optimization algorithms

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