Effects of Tissue Coagulative Necrosis on Longitudinal Relaxation Time-Based Magnetic Resonance Thermometry

Real-time monitoring of tissue temperature is required during high intensity focused ultrasound (HIFU) tumor treatment to ensure safety and effectiveness. Magnetic resonance imaging (MRI) can be used to measure tissue temperature non-invasively during HIFU treatment. This paper examined the effects of coagulation necrosis-induced tissue phase transition on magnetic resonance thermometry (MRT) during HIFU tumor treatment. With a two-state rapid exchange model, the relationship between tissue longitudinal relaxation time (T1) and temperature before and after HIFU radiation-induced coagulation necrosis/tissue phase transition were analyzed theoretically. Taking the effects of tissue phase transition into account, the experimental scheme and data processing procedures for MRT were optimized, and better temperature measurements were obtained. The work demonstrated the importance of considering the effects of tissue phase transition in real-time MRT during HIFU treatment.