Monitoring Locally Induced Hyperthermia with Magnetic Resonance Imaging

Abstract

Magnetic resonance thermometry is a relatively new and unique technology for non-invasive monitoring of (local) therapeutic temperature changes that is not yet in common use. Temperature measurements using magnetic resonance heat thermometry can be performed in several ways. Four common methods are described. Spin-lattice (T1) relaxation thermometry seems robust and viable, but relatively inaccurate. Diffusion thermometry is slightly more accurate at the cost of increased scan time. Chemical shift thermometry is most accurate but inherently slow and therefore impracticable. Its derivative, phase shift thermometry seems most promising for monitoring mild temperature changes. Phase shift imaging is, however, difficult to implement due to motion artifacts and susceptibility effects. Apparently two fields for use of MR thermometry in practical therapeutic applications emerge: high temperature gradients for thermoablation that need not be quantified exactly, and low temperature gradients for heat related biological effects that must be controlled precisely.