Observation by MR imaging of in vivo temperature changes induced by radio frequency hyperthermia

Volunteers have undergone radio frequency hyperthermia in a magnetic resonance (MR) imaging system to investigate which of several possible MR parameters would be most convenient and sensitive to use to observe in vivo temperature changes. Measurements were made for T1, T2, and perfusion and diffusion variations, although the number of sequences needed at each temperature meant that the number of data points obtainable was limited. However, in the temperature range studied (around 28-42 degrees C), changes in both T1 and the diffusion coefficient were observed that agreed quite well with those predicted theoretically (respectively around 1.3%/degrees C and 2.4/degrees C).