ESTRO 2022 - Abstract Book

S1402

Abstract book

ESTRO 2022

T2 propeller (a voxel size of 0.39 × 0.39 × 3.29 mm3, a matrix size of 512 × 512 × 51, TR = 5319.7 ms, TE = 95.9 ms, and FA = 140°) (Fig. 1. d, e, f). The tandem and ovoid geometries were projected from the Varian’s library of applicators into the MRI and were positioned manually to their location in the images by the physicist (Fig 1.c). A reference segmentation of the tandem was therefore extracted. The tandem, which appear with low intensities (signal loss), was segmented automatically on the MRI sequences by thresholding. Dice, sensitivity, and Jaccard indices were computed between the reference segmentation and the MRI-based segmentation of the tandem in each MRI sequence. Distances were measured from the tandem tip to the MRI artifact edge in right/left/superior and anterior/posterior directions in the coronal and sagittal views respectively. Eclipse Brachytherapy Planning System (Version 16.1) was used for measurements.

Results Table 1 shows the segmentation indices obtained for each MR sequence type of the brachytherapy protocol. The distances measured for MRI artifacts are displayed in table 1. The sagittal 3D cube T2 MRI presented the smallest average artifacts whereas the highest average artifacts were obtained for the para-axial T2 MRI which is used for the contouring of the OARs and target.

Conclusion In this study, we have characterized artifacts due to titanium brachytherapy applicators in multiple MR sequences at 1.5T. Future work will consist on optimizing the MR sequences to reduce the artifacts while preserving imaging time and contrast.

PO-1615 Evaluation of prostate synthetic CTs from 0.35T MR images using different deep training cohort sizes

J. Nunes 1,3 , L. Macque 1 , S. Tahri 1 , S. Fettem 1 , H. Chourak 1 , A. Barateau 1 , C. Lafond 1 , R. de Crevoisier 1 , O. Acosta 1 , I. Bessieres 2 , L. Marage 2 1 Université de Rennes 1, LTSI (Laboratoire du Traitement du Signal et de l'Image), INSERM UMR 1099, CLCC Eugène Marquis, Rennes, France; 2 CGFL - Centre Georges-François Leclerc, Medical Physics, Dijon, France; 3 Université de Rennes 1, LTSI (Laboratoire du Traitement du Signal et de l'Image), INSERM UMR 1099, CLCC Eugène Marquis , Rennes, France