[Magnet resonance spectroscopy of tumor-bearing rat livers: magnetite particles as an aid in volume selection]. 
Magnetite, an RES-specific contrast medium, has been used in animal experiments and in a few patients for MRI of the liver.  We examined the use of magnetite particles for 31P-MR spectroscopy using a phantom, and perfused tumour-bearing rat livers and liver tumours in living rats.  As expected, there is homogeneous uptake of the magnetite in normal liver leading to extinction of the signal when one uses suitable spectroscopic parameters.  Since the ferrite particles do not penetrate non-hepatic tissue, such as metastases, a signal remains uniquely from the tumour and this can be used, for instance, for following the effect of cytostatic therapy.  The use of magnetite produces a selective effect and interference from normal liver is thereby avoided.  Multiple lesions with irregular configuration can be examined simultaneously by this method.  It remains to be seen how useful the application of magnetite will be for avoiding motion artifacts during spectroscopy.