Contributed Talk

Combined magnetic resonance elastography and 3D MRI deformation mapping for in vivo solid stress assessment in glioblastoma

Noah Jaitner, Tom Meyer, Mehrgan Shahryari, Ingolf Sack

Department of Radiology, Charité-Universitätsmedizin, 10117 Berlin, Germany

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The microenvironment and biomechanical properties surrounding cancer cells play an important role in tumor progression, immune evasion, and cancer treatment response [1]. Glioblastoma, an aggressive brain tumor, disrupts the structure of the surrounding tissue and alters its biomechanical niche. Ismail et al. showed that highly aggressive tumors tend to grow uncontrollably, causing severe tissue deformation and biomechanical changes in the tumor environment [2]. The biomechanical response of tissue to a deformation is quantified by strain and stress. However, while magnetic resonance elastography (MRE) can measure shear stiffness, solid stress has never been addressed by in vivo imaging methods. In this preliminary study we combine MRE with 3D MRI deformation mapping for correlating volumetric strain and octahedral shear strain (OSS) with biomechanical properties.

Eight patients (7 men, 1 woman, 55±5 years) with glioblastoma were studied with MRE and volumetric MRI. Imaging examinations were performed in a 3T MRI scanner (Magnetom Lumina, Siemens, Erlangen, Germany) using a 32-channel head coil. T1 images and MRE at four vibration frequencies (20, 25, 30 and 40 Hz) were acquired. Shear wave speed maps (SWS) were generated using the k-MDEV inversion method [3]. Deformation fields were determined by 3D image registration to the standard brain atlas. Volumetric strain and OSS were then further quantified by calculating the gradient of the deformation field.

Registration of tumor images to standard maps resulted in a compression of all lesions from 6 to 77% independent of tumor size suggesting that the inverse volumetric strain has caused the deformation of brain anatomy due to tumor growth. Spatially resolved volumetric strain and OSS in the tumor environment correlated with tumor compression (R²=0.77, p=0.004 for OSS).

This preliminary study demonstrates that the combination of MRE and 3D MRI deformation mapping is sensitive to solid stress exerted on brain tissue by progressing glioblastoma. The results show there is a significant correlation between mechanical strain and changes in tumor size based on image registration. This suggests that the tumor exerts shear deformation and compression on the surrounding tissue when growing. Tumors with higher stiffness were associated with higher surrounding volumetric strain, possibly reflecting the invasive and compressive nature of aggressive glioblastomas that disrupt normal brain anatomy. Overall, the integration of MRE and MRI deformation mapping provides a novel approach to better understand the biomechanical landscape of glioblastoma and offers potential biomarkers for tumor characterization and progression.