Thermal therapy can be divided into two regimes. However, it is the ability of MRI to construct maps of in vivo body temperature that make it particularly well suited for guiding and monitoring minimally invasive thermal therapy. In part, this is due to the attractive properties of MRI, such as its non-invasiveness, lack of ionizing radiation, and the ability to image in any scan orientation with good spatial and temporal resolution. Minimally invasive thermal therapy of benign and malignant diseases benefits from near real-time MR image guidance. Special attention is paid to acquisition and reconstruction methods for reducing temperature measurement artifacts introduced by tissue motion, which is often unavoidable during in vivo applications. ![]() Accelerated MRI imaging techniques for real-time monitoring with the PRF method will be discussed. The excellent linearity and temperature dependence of the PRF and its near independence of tissue type have made PRF based phase mapping methods the preferred choice for many in vivo applications. Whereas most measurements give a temperature change relative to a baseline condition, temperature sensitive contrast agents and spectroscopic imaging can provide absolute temperature measurements. In this paper, the principles of temperature measurements with these methods will be reviewed and their usefulness for monitoring in vivo procedures will be discussed. ![]() Noninvasive temperature monitoring is feasible with magnetic resonance (MR) imaging based on temperature sensitive MR parameters such as the proton resonance frequency (PRF), the diffusion coefficient (D), T 1 and T 2 relaxation times, magnetization transfer, the proton density, as well as temperature sensitive contrast agents. Safety and efficacy of the treatment require accurate temperature measurement throughout the thermal procedure. Minimally invasive thermal therapy as local treatment of benign and malignant diseases has received increasing interest in recent years.
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