One aspect of the present invention relates to a microsphere impregnated witha radioisotope that emits therapeutic .szlig.-particles and a radioisotopethat emits diagnostic .gamma.-radiation； wherein the atomic number of thefirst radioisotope is not the same as the atomic number of the secondradioisotope. In one preferred embodiment, the microsphere is composed ofglass impregnated with 90Y as the source of the therapeutic .szlig.-emissionsand 198Au as the source of the diagnostic .gamma.-emissions. Another aspect ofthe present invention relates to the preparation of a microsphere impregnatedwith a radioisotope that emits therapeutic .szlig.-particles and aradioisotope that emits diagnostic .gamma.-radiation； wherein the atomicnumber of the first radioisotope is not the same as the atomic number of thesecond radioisotope. In one preferred embodiment, a glass microspherecontaining 90Y and 198Au is prepared by neutron activation of a glassmicrosphere comprising glass, 89Y and 197Au. Another aspect of the presentinvention relates to administration to a mammal of a therapeutically effectiveamount of microspheres impregnated with a .szlig.-emitting radioisotope and a.gamma.-emitting radioisotope； wherein the atomic number of the firstradioisotope is not the same as the atomic number of the second radioisotope.In one preferred embodiment, said microspheres are administered to the patientthrough a catheter.
