Abstract: The image diagnosis apparatus of the present invention is equipped with means for automatically determining a window level and a window width for image displaying in accordance with the value of reconstructed image data. With this window level/window width calculating means (13), the window level is obtained with respect to each reconstructed image on the basis of the virtual average value of its pixel data and the window width is also obtained which has a certain relationship with that window level. When displaying each reconstructed image, a display is made in accordance with each window level and each window width thus obtained. Instead of the obtained window level and window width, those set by a manual setting section (23) may be used by a changeover operation when necessary.

Abstract: An NMR data processing method for use with an NMR tomograph, wherein signals, located in a period before and after an NMR signal to be sampled and containing substantially none of the NMR signal component, are measured as offset data for each view, so that even the offset slightly fluctuating in the view can be corrected for the NMR signal, on the basis of that data.

Abstract: After spins in a subject being examined have been selectively excited, the application of gradient magnetic fields is interrupted to produce an FID signal. The intensity of the primary magnetic field is determined based on the central frequency of the Fourier spectrum of the FID signal, i.e., the Larmor frequency. The primary magnetic field is controlled or the observed data is corrected, according to the measured value of the primary magnetic field intensity.

Abstract: In preparing fine and plate-shaped particles of a ferrite having the magnetoplumbite structure by hydrothermal treatment of a powder of .gamma.-Fe.sub.2 O.sub.3 or (FeO).sub.x.Fe.sub.2 O.sub.3, where O<x.ltoreq.1, and a compound of Ba, Sr or Pb in an aqueous alkali solution, Sn.sup.4+, or Sn.sup.4+ and M.sup.2+ such as Fe.sup.2+, Cu.sup.2+ or Zn.sup.2+, are introduced into the reaction system of the hydrothermal treatment such that Fe.sup.3+ in the obtained ferrite are partly substituted by Sn.sup.4+ or M.sup.2+ -Sn.sup.4'. The substitution has the effect of lowering the coercive force of the ferrite powder to a level suitable for use in magnetic recording media of the perpendicularly magnetizing recording type. By using an iron oxide powder having a mean particle size not larger than 500 .ANG. with addition of a surface-active agent, the particle size of the ferrite powder can be reduced to about 0.2 .mu.m.