S2088
Physics - Image acquisition and processing
ESTRO 2026
margin while maintaining similar pattern-of-failure, thereby sparing healthy tissue without compromising tumor coverage. References: 1. Niyazi, M., et al., ESTRO-EANO guideline on target delineation and radiotherapy details for glioblastoma. Radiother Oncol, 2023. 184: p. 109663.2. Tang, P.L.Y., Méndez Romero, A., Jaspers, J.P.M. et al. The potential of advanced MR techniques for precision radiotherapy of glioblastoma. Magn Reson Mater Phy35, 127–143 (2022).3. Tang, P.L.Y., Romero, A.M., Nout, R.A. et al. Amide proton transfer-weighted CEST MRI for radiotherapy target delineation of glioblastoma: a prospective pilot study. Eur Radiol Exp8, 123 (2024).4. Gebhardt BJ, Dobelbower MC, Ennis WH, Bag AK, Markert JM, Fiveash JB. Patterns of failure for glioblastoma multiforme following limited-margin radiation and concurrent temozolomide. Radiat Oncol. 2014 Jun 6;9:130. Keywords: Glioblastoma, APT-weighted MRI, target delineation A customized NEMA phantom for PET image quality assessment in sub-centimeter uptake volumes René M Winter 1,2 , Silje Kjærnes Øen 1 , Jin Han 1 , Oddbjørn Sæther 1 , Anna Karlberg 1 1 Department of Radiology and Nuclear Medicine, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway. 2 Department of Oncology, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway Purpose/Objective: Quantitative imaging biomarkers (QIBs) offer great potential to assess treatment response and guide personalized radiotherapy. Recent advances in PET technology have enabled imaging with high sensitivity and spatial resolution, enabling the detection and quantitative evaluation of small lesions. These developments drive the need for new phantom Digital Poster Highlight 4104 designs with smaller volume inserts. This study aimed to design, build and evaluate a novel phantom setup for investigating PET image quality in sub-centimeter uptake volumes. Material/Methods: A customized phantom was developed by integrating in-house 3D-printed sphere holders into a standard NEMA image quality phantom (Fig1). The holders contained four hollow micro-spheres with 4, 5, 6, and 8 mm diameter (DataSpectrum), complementing the six standard NEMA spheres (10--37 mm). First phantom experiments with 18F-FDG and 68Ga- solution were performed on a PET/CT (Siemens
Fig-1: Target volumes and dose to OARs.
Fig-2: Plans of an exemplary patient. Conclusion:
Integrating APT-weighted MRI for GTV delineation in glioblastoma allows reduction of the 15-mm CTV-
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