ESTRO 2024 - Abstract Book

S4759

Physics - Quality assurance and auditing

ESTRO 2024

Denmark. 4 Aalborg University Hospital, Clinical Cancer Research Center, Aalborg, Denmark. 5 Aalborg University Hospital, Department of Clinical Medicine, Aalborg, Denmark

Purpose/Objective:

In advanced lung-radiotherapy, delineation of the Gross Tumor Volume (GTV) is performed on a four-dimensional computed tomography (4D-CT) that is separated into phases of the respiratory cycle. To capture tumor motion related to breathing, the GTV should ideally be delineated on all phases. Subsequently, the GTV from all phases should be integrated into one accumulated GTV structure and projected onto, for instance, a mid-ventilation phase (mv-phase) before further margin delineation and dose calculation. However, delineating the GTV on all phases is time-consuming in clinical practice. Therefore, there is a need for a fast and accurate method of automatically propagating of the GTV from one phase into the remaining phases of the 4D CT to optimize the clinical workflow.

The aim of this study was to evaluate the performance of two systems designed for the automatic deformable propagation of the GTV from one phase to the remaining phases of the 4D-CT.

Material/Methods:

The two systems evaluated in this study were Aria (ver. 16.1) and Velocity (ver. 4.1), both from Varian. Using these systems, deformable propagation was performed on 10 consecutive 4D-CT scanned patients, all referred to stereotactic body radiotherapy of a peripheral lung-tumor. The 4D-CT scans were separated into ten phases, and the GTV was manually delineated on all phases by an experienced radiologist in collaboration with a thoracic oncologist. The manually defined GTVs were considered the Ground Truth and accumulated into the structure GTVacc_GT for each patient. Aria and Velocity were used to automatically propagate the manual GTV-delineation from the mv-phase to the nine remaining phases. Subsequently, all ten GTVs for every patient were accumulated into the structures GTVacc_Ar or GTVacc_Ve on Aria or Velocity, respectively (see Figure 1 ).