ESTRO 2024 - Abstract Book

S3545

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

Conclusion:

The obtained results of the ipsilateral lung transferability and dose/statistical prediction support the possibility to use LWB-TF FB models for the prediction of LWB-TF DBHI candidates. Heart transferability and dose/statistical prediction should be considered with caution, with most free breathing models showing only moderate transferability. A good transferability and relatively low inter-institute variability was found between LWB-TF DIBH models of INST1, INST2 and INST10. Starting with these results, next steps will be devoted to the identification of geometry/anatomic parameters in order to select patients who might benefit from DIBH technique.

Keywords: Knowledge-based, breast cancer, breath-hold

References:

The current study was performed within the MIKAPOCo project, supported by AIRC Grant (IG23150, 248/2021)

1279

Poster Discussion

Study on the dosimetric accuracy of synthetic CT-based treatment plans for lung cancer patients

Min Liu, Bin Tang, Xiongfei Liao, Xianliang Wang, Da Zhang, Feng Yang, Lucia Clara Orlandini

Sichuan Cancer Hospital & Institute, Radiation Oncology, Chengdu, China

Purpose/Objective:

Unity MR-Linac allows daily plan adaptation according to the new patient anatomy; the contours of the structures are adjusted based on the patient's daily MRI, and in the adapt to shape (ATS) workflow, the adapted plan is recalculated on the MRI-based synthetic CT (sCT) generated by bulk density assignment[1]. The accuracy of this calculation is strongly dependent on how the sCT has been generated, and for sites where there is a high electronic density gradient between the target and surrounding tissues, such as in lung cancer treatments, the assignment of an average electronic density (ED) may not be able to reproduce an exact dose calculation[2, 3]. This study aims to evaluate the accuracy of sCT calculation in this type of situation mainly encountered in lung cancer treatments assessing separately tumor sites in different electronic density gradient areas.

Material/Methods:

A total of 42 lung cancer patients who underwent stereotactic body radiation therapy (SBRT) were included in this retrospective study. For each patient 3D-free breathing computed tomography (CT) scan and 4D-CT scan at ten respiratory phases were acquired and exported to MIM Maestro for delineation. Target volumes were defined using all ten respiratory phases, while organs at risk (OARs) were defined using the 3D-CT scan. Patients were divided into three groups Gc, GL, GM, following the location of the tumor in the central (14 patients), lateral (13 patients), and middle (15 patients) areas of the lung, respectively. A representative scheme of the different tumor site areas is shown in Figure 1. The 3D-CT images and delineated structures were imported into Monaco v. 5.4