ESTRO 2024 - Abstract Book

S4064

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

Keywords: Registration, Uncertainty, Dose Accumulation

References:

[1] S. Klein, M. Staring, K. Murphy, M.A. Viergever, J.P.W. Pluim, "elastix: a toolbox for intensity based medical image registration," IEEE Transactions on Medical Imaging, vol. 29, no. 1, pp. 196 - 205, January 2010

1911

Poster Discussion

Dose accumulation after online adaptive MR-guided RT compared to CT-based IGRT in prostate cancer.

Martina Murr 1 , Daniel Wegener 2,3 , Arndt-Christian Mueller 2,4 , Daniel Zips 2,5 , David Mönnich 1 , Moritz Schneider 1 , Simon Boeke 2 , Cihan Gani 2 , Maximilian Niyazi 2 , Daniela Thorwarth 6 1 University of Tuebingen, Department of Radiation Oncology, Tuebingen, Germany. 2 University Hospital and Medical Faculty, Department of Radiation Oncology, Tuebingen, Germany. 3 Alb Fils Klinikum, Department of Radiation Oncology, Göppingen, Germany. 4 RKH Kliniken, Clinic of Radiation Oncology and Radiation Therapy, Ludwigsburg, Germany. 5 Universitätsmedizin Berlin, Klinik für Radioonkologie und Strahlentherapie der Charité, Berlin, Germany. 6 University of Tuebingen of Tübingen, Department of Radiation Oncology, Tuebingen, Germany

Purpose/Objective:

Image-guided radiation therapy (IGRT) is standard of care has been used for many years to perform precise irradiation of the target volume and to spare healthy tissue in prostate cancer (PC). The patient position is validated and corrected on the basis of cone-beam computed tomography (CBCT) images acquired on the treatment machine, followed by a rigid registration to the reference anatomy derived from the planning CT. However, this method cannot account for inter-fraction deformations and volume changes, which may be crucial for healthy tissue sparing. Consequently, online adaptive RT techniques, such as magnetic resonance guided radiotherapy (MRgRT) may enable better organ at risk sparing while ensuring high dose coverage of the tumor. The aim of this study was to compare classical IGRT dose delivery using daily imaging to register a reference plan based on pre-treatment planning CT, to online adaptive MRgRT (oa-MRgRT) using deformable dose accumulation techniques in PC. Therefore, a dosimetric comparison of IGRT versus oa-MRgRT was performed.

Material/Methods:

A total of 10 patients with PC, previously treated at a 1.5T MR-Linac (20 x 3 Gy) were enrolled in this retrospective study. Reference treatment plans were generated for each patient based on the planning CT. For each patient, two treatment strategies were compared: classical IGRT and oa-MRgRT. IGRT treatments were simulated by rigidly registering the planning CT to the daily T2w-MRIs of each fraction. Then, the dose of each fraction was deformably registered and accumulated. For oa-MRgRT, the daily adapted plan doses were deformably registered and