[Optimization of obtaining magnetic resonance images in relation to ultra-low fields]

The authors discuss possible approaches to optimization of magnetic resonance images in connection with ultralow fields with consideration for external and internal factors modifying the contrast. Of the internal factors the crucial role is played by protonic density and relaxation time of different tissues; the internal factors significant are magnetic induction, characteristics of the device and programs, radiofrequency sequence and its parameters, as well as use of special contrast agents. Practical measures whose use helps optimize a magnetic resonance image, that is, the choice of an adequate pulse sequence, a greater number of repetitions, a larger imaging field, a thicker section and its better orientation, are described. Standard schemes for obtaining MR images of various organs with due account of the before factors with an ultralow field tomographer have been developed.