Role of Functional MRI in Liver SBRT: Current Use and Future Directions

SIMPLE SUMMARY: The use of magnetic resonance imaging (MRI) for liver radiation treatment planning, adaptation and response assessment is an active area of clinical research. Particularly, research on the use of functional MRI to optimise radiation dose distribution and perform mid-treatment adaptation has grown in recent times. The aim of this review is to provide the current state of evidence on the most relevant functional MRI methods being investigated for liver radiation therapy applications aimed at the development of individualised, adaptive treatments for patients with liver cancer. ABSTRACT: Stereotactic body radiation therapy (SBRT) is an emerging treatment for liver cancers whereby large doses of radiation can be delivered precisely to target lesions in 3–5 fractions. The target dose is limited by the dose that can be safely delivered to the non-tumour liver, which depends on the baseline liver functional reserve. Current liver SBRT guidelines assume uniform liver function in the non-tumour liver. However, the assumption of uniform liver function is false in liver disease due to the presence of cirrhosis, damage due to previous chemo- or ablative therapies or irradiation, and fatty liver disease. Anatomical information from magnetic resonance imaging (MRI) is increasingly being used for SBRT planning. While its current use is limited to the identification of target location and size, functional MRI techniques also offer the ability to quantify and spatially map liver tissue microstructure and function. This review summarises and discusses the advantages offered by functional MRI methods for SBRT treatment planning and the potential for adaptive SBRT workflows.