D Le Bihan

Magnetic Resonance Imaging of Perfusion

Recent developments have shown that diffusion and blood microcirculation (perfusion) could be imaged and measured noninvasively by MRI. The purpose of this presentation is to overview the different approaches that use B0 field gradients to monitor diffusion / perfusion. The principles of these different methods are discussed together with their limitations and their potential applications.

Recent Trends in Noninvasive Thermal Control

Owing to its evident possible impact on the development of hyperthermia treatments, noninvasive thermometry (NIT) is in clinical demand, especially for deep-seated and/or large tumors. A recent International Consensus Meeting on Hyperthermia (1989) pointed out that (a) measuring the temperature distribution and (b) comparing it to a specified standard are essential to validate the results obtained from clinical trials. As is well known, these problems cannot yet be considered completely solved. Invasive techniques are now regarded as sufficiently accurate (except for ultrasound), but they only indicate the temperature at a limited number of points and are considered traumatic for patients. For approximately a decade, several noninvasive techniques have been considered and presented as potential candidates for clinical use, but as yet none has achieved a marked impact on clinical practice. For this reason, there is now a need to update previous attempts at a systematic comparison of these techniques (e.g., Bolomey and Hawley 1989; Cetas 1984; Hand 1984; Mizushina 1987).