Temperature measurements by nuclear magnetic resonance and its possible use as a means of in vivo noninvasive temperature measurement and for hyperthermia treatment assessment.

In the foregoing we have tried to give a broad survey of the parameters which are of importance for irradiation experiments and which can be measured by NMR. Since it is the temperature change during irradiation that is of immediate interest, we have tried to emphasize the ways in which this quantity can be measured. This has shown that temperature measurement by means of the chemical shift has experimental limits as well as the fact that overlapping signals may cause problems. Hence, more experiments must be carried out in order to clarify the possibilities of its use. Although experimentally this is no easy task, it is feasible. In particular, the possibility of determining the temperature by external markers introduced into the tissue should be studied. The development of new nontoxic thermometric compounds with greater sensitivity would be a great step forward. The possibility of determining the temperature through the relaxation times of water represents a real alternative, especially since this can be carried out by low-resolution NMR. Additional experiments are necessary in order to see whether the sensitivity attainable is satisfactory. Chemical exchange processes and changes in metabolite concentration could also be used to measure the temperature or the effect of an irradiation experiment. In conclusion, one can say that the measurement of control parameters (especially for irradiation experiments by means of NMR) represents a difficult experimental problem. It does not promise success in all cases but probably represents the only noninvasive measurement possibility. For this reason, wide-ranging experiments should be initiated in order to obtain definitive results.