in a treatment regimen as described by gordon in u s pat no 4 106 488 more specifically these fine particles responsive to and interactive with the imposed magnetic field provide more local anomalies in the field and enhance the mapped signal image in much the manner of the enhancement or a television image by increasing the number of 34 lines 34 transmitted and displayed less dispersion is seen in individual peaks i e they are sharper whereby the image is better resolved offering enhanced clarity the particles serve a 34 shadowing 34 function intensifying and contrasting an image generated by the nmr sensitive nuclei more specifically the particles affect particularly spin spin interactions related to the dephasing of nuclei and the transfer of energy between adjacent nuclei hence t 2 values are influenced by the presence of the particles that is the presence of a substance having a certain magnetic susceptibility in a high frequency oscillating field causes a change in frequency as a consequence of a 34 heterodyning 34 phenomenon relative to a fixed frequency signal each magnetically susceptible nucleus when dephased acts as a high frequency oscillator and the presence of the ferromagnetic diamagnetic or paramagnetic particles thus dampens or reinforces the phased precession of the magnetically susceptible muclei affecting the observed frequencies directly and therefore sharpening the resultant nmr peaks reflected in individual plots of signal vs frequency or mapped sample regions collecting such peaks the result is a clearer image of enhanced resolution by reason of the controlled perturbation of the field in a frequency related manner in turn governing the width of the plotted nmr peaks in contradistinction to the above effect the use of paramagnetic salts or radio protective substances as.