MAGNETIC-RESONANCE THERMOMETRY DURING HYPERTHERMIA FOR HUMAN HIGH-GRADE SARCOMA

Purpose: To determine the feasibility of measuring temperature noninva sively with magnetic resonance imaging during hyperthermia treatment o f human tumors. Methods: The proton chemical shift detected using phas e-difference magnetic resonance imaging (MRI) was used to measure temp erature in phantoms and human tumors during treatment with hyperthermi a. Four adult patients having high-grade primary sarcoma tumors of the lower leg received 5 hyperthermia treatments in the MR scanner using an MRI-compatible radiofrequency heating applicator. Prior to each tre atment, an average of 3 fiberoptic temperature probes mere invasively placed into the tumor (or phantom). Hyperthermia was applied concurren t with MR thermometry. Following completion of the treatment, regions of interest (ROT) were defined on MR phase images at each temperature probe location, in bone marrow, and in gel standards placed outside th e heated region. The median phase difference (compared to pretreatment baseline images) was calculated for each ROI. This phase difference w as corrected for phase drift observed in standards and bone marrow. Th e observed phase difference, with and without corrections, was correla ted with the fiberoptic temperature measurements. Results: The phase d ifference observed with MRI was found to correlate with temperature. P hantom measurements demonstrated a linear regression coefficient of 4. 70 degrees phase difference per degrees Celsius, with an R-2 = 0.998. After human images with artifact were excluded, the linear regression demonstrated a correlation coefficient of 5.5 degrees phase difference per degrees Celsius, with an R-2 = 0.84. In both phantom and human tr eatments, temperature measured via corrected phase difference closely tracked measurements obtained with fiberoptic probes during the hypert hermia treatments. Conclusions: Proton chemical shift imaging with cur rent MRI and hyperthermia technology can be used to monitor and contro l temperature during treatment of large tumors in the distal lower ext remity. (C) 1998 Elsevier Science Inc.