Super-paramagnetic iron oxide nanoparticles improve liver tumor visualization throughout online MRI-guided liver stereotactic radiotherapy

Motivation: Can we provide superior liver tumor visualization for online adaptive planning? MRI enables direct visualization of tumor and organs-at-risk (OAR). However, MRI contrast agents are often required to differentiate primary and metastatic liver malignant lesions from functional hepatic parenchyma. Goal(s): We employed super-paramagnetic iron oxide nanoparticles (SPION) as an MRI contrast agent. Approach: SPION enhanced the liver-to-tumor contrast ration for rapid and accurate delineation of tumors and functional hepatic parenchyma throughout the entire treatment course. Results: This study is the first to report the efficiency of a single SPION injection for multi-fractionated MRI-guided liver stereotactic body radiotherapy on a 1.5T Elekta MR-Linac. Impact: A single SPION injection significantly improved the tumor-to-liver contrast, and it was maintained throughout multi-fraction MRI-guided liver SBRT to provide rapid and accurate contouring tumor lesions from functional liver parenchyma for online adaptive planning.