S2457
Physics - Radiomics, functional and biological imaging, and outcome prediction
ESTRO 2026
hypoxia scores were found centrally within tumours. Mean and median hypoxia scores decreased for all patients after two weeks of radiotherapy. Changes in median hypoxia score ranged from -0.075 (patient 7) to -0.405 (patient 4) indicating large inter-patient variability.
Department of Clinical Sciences Lund, Lund University, Lund, Sweden. 5 Department of Medical Imaging and Physiology, Skåne University Hospital, Lund, Sweden. 6 Medical Radiation Physics, Lund University, Lund, Sweden Purpose/Objective Diffusion-MRI (dMRI) is a functional imaging method that can be used to assess tissue hypoxia [1,2]. In head and neck cancer (HNC), geometric distortions caused by susceptibility differences in tissue-air interfaces introduce large uncertainties in tumour size and location, limiting the use of dMRI in radiotherapy. The aim of this study was to develop a complete workflow, from image acquisition to quantitative hypoxia mapping, optimised for HNC and capable of providing improved geometric accuracy for use in the treatment preparation process. To our knowledge, this study presents the first evaluation of dMRI-based hypoxia mapping in HNC during radiotherapy. Material/Methods Seven patients (n=7) with HNC were scanned using a wide-bore 3.0T GE Signa Architect. Diffusion images were acquired using 3-shot multiplexed sensitivity encoding in four phase-encoding directions (AP, PA, RL, LR) with b-values (0, 50, 200, 800) s/mm 2 , along with T2w images. Scans were acquired prior to treatment and after two weeks of radiotherapy. The GTV was delineated on T2w images by an experienced radiation oncologist. TOPUP and Eddy from the FMRIB Software Library were used for distortion correction [3]. Hypoxia scores were calculated using intravoxel incoherent motion analysis (based on perfusion fraction (f) and diffusion coefficient (D)) [1]. Parameter values were normalised between their 1st and 99th percentiles, as described in [2]. Results Uncorrected dMRI data showed displacement of up to 12 mm in the phase-encoding direction, affecting the position of both tumour and air cavity. Distortion- corrected images show improved alignment with T2w anatomy.
Conclusion Generation of hypoxia maps using dMRI is feasible for head and neck radiotherapy when using distortion- minimising acquisition and distortion-correction, achieving sufficient geometric accuracy. Preliminary results suggest that the reduction in tumour hypoxia after two weeks of radiotherapy varies widely between patients. References [1] Hompland T, Hole KH, Ragnum HB, et al. Combined MR Imaging of Oxygen Consumption and Supply Reveals Tumor Hypoxia and Aggressiveness in Prostate Cancer Patients. Cancer Res. 2018. [2] Mo T, Brandal SHB, Köhn-Luque A, et al. Quantification of Tumor Hypoxia through Unsupervised Modelling of Consumption and Supply Hypoxia MR Imaging in Breast Cancer. Cancers. 2022. [3] Andersson J.L.R, Skare S, Ashburner, J. How to correct susceptibility distortions in spin-echo echo- planar images: application to diffusion tensor imaging. NeuroImage. 2003. Personalizing liver radiotherapy therapy through machine learning-based hypertrophy prediction models Aashish Gupta 1 , Mais Altaie 1 , Austin Castelo 1 , Tien T Tang 1 , Caleb S O'Connor 1 , David B Flint 1 , Sireesha Yedururi 2 , Eugene J Koay 3 , Kristy K Brock 1 1 Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, USA. 2 Abdominal Imaging, The University of Texas MD Anderson Cancer Center, Houston, USA. 3 Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA Purpose/Objective: The objective of this study was to develop and validate predictive models to accurately quantify liver response to radiotherapy, establish clinically relevant dose-response thresholds, and demonstrate the impact of personalized treatment planning for liver Digital Poster Highlight 3026
At baseline, three patients (1, 2, 7) had well- oxygenated peripheral areas with a localised hypoxic sub-volume, whereas others (3, 4, 5) were hypoxic across almost the entire GTV. Patient 6 showed diffuse, moderate hypoxia. For most patients, higher
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