Integrated Therapy Delivery Systems

Abstract

Since both the chemical environment and relaxation properties of the nuclei that are thesource of the signal in magnetic resonance (MR) are sensitive to Brownian motion andthe associated molecular tumbling rates, MR imaging (MRI) techniques are intrinsicallysensitive to temperature. Of the many MR parameters that can provide temperature-sensitive contrast, the temperature dependence and sensitivity of several parameters inparticular, have proven useful for monitoring temperature changes in soft tissue duringdelivery of hyperthermia or thermal therapies: the apparent diffusion constant of water(D), the spin-lattice relaxation time (T1), and the water proton resonance frequency (PRF). The temperature sensitivities associated with each of these parameters are largeenough to allow temperature-dependent changes to be observed quantitatively usingeither direct or indirect measurements using standard MRI devices over a range oftemperatures relevant for thermal therapy. The development of these techniques tononinvasively measure temperature changes in tissue has brought renewed interest inusing these techniques to enhance the guidance of thermal therapy treatments.